Aum AcousticsSingle Triode Tube Buffer – 2nd Order Harmonics Generator

Replaces An Active Preamp With About 5-6db of Gain.Incredible Sound Quality Through The Addition of the Best 2nd Order Harmonics Using the Most Linear Portion Of The Single 6922 Family Triode Tube.

Volume control should be done using a passive device (LDR, autoformer, or transformer based). A carbon pot or resistor attenuator will provide a good solution but not as high a quality as the 3 methods listed above. I can provide a solution should you need an external passive volume control device to use with this tube buffer.

(The 6N23p or Any Other 6922 Family Tube In This Buffer Is Operated At 30 Volts Instead of the Normal 300 Volts! Consequently, the tube will play in its most linear area and will last a long time.)

I’m building and selling a very unique “high level” audio component. It’s a circuit using a single 9 pin triode tube that is an excellent replacement for a 20k+ active preamp.

Check This Link For Why I Used The 6N23P, 1975, Reflector, Silver Shield, Single Getter Tube This Review Found To Be #1 Even Over The Expensive Siemens Cca Tube:

https://www.head-fi.org/threads/6922-tube-review-17-top-6922-6n23p-e88cc-cca-7308-e188cc-tubes.761078/

This component started out many years ago as a tube buffer and it has gradually morphed into the cleanest 2nd harmonics generator that I’ve ever heard. I’ve spent over a year working on trying out various ways to identify the best parts to use while sampling numerous wire types as well as capacitors and resistors. I’ve cleaned up the circuit design and how this unit is put together. The end result is stunning and is too good not to share with other audiophiles looking to improve their own sound quality and is the main reason I’ve decided to build a few for sale.

The main purpose of this component is to create clean 2nd order harmonics that generate a 3 dimensionality and provides for a wider and deeper soundstage for an already high quality audio system. Our human hearing craves 2nd order harmonics and this requires a tube to generate the most authentic quality. Tubes generate 2nd order harmonics but also, unfortunately, bloat the bass or midrange and decrease high frequencies along with adding other undesirable distortion. This component doesn’t do that and instead lets the 2nd order harmonics through while minimizing any “nasty” distortion affects. It operates the single tube in its most linear area. Typically, the most expensive tube preamplifiers also do this but their complexity and super high cost (20k-30k) make them unobtainable for most audiophiles.

A Little Bit Of History

The design for this single tube buffer/harmonizer began a long time ago as a product originally designed by Gary Dodd. Gary is no longer with us but one of his best friends (who also lived close and helped support him), Trung Tran, continued on to further develop Gary’s original circuit. I met Trung when I first purchased one of Gary’s tube buffer kits about 10 years ago and we’ve both explored many of the experiments I’ve gone through in my own efforts to improve audio sound quality.

After Gary passed on, Trung had the idea that he could operate a 300 volt high quality single triode tube using only 30 volts and then further expanded this idea that Gary was working on when he died. Trung chose the NOS 6H30p tube to focus on. At the time, this approach was quite unusual but Trung just kept trying until he finally came up with a circuit design that worked. Along the way, Trung asked Vinnie Rossi and Jeff Golowki (the engineer that designed the SonicCap capacitors) and others for guidance while he kept working on finding a solution that worked. I didn’t accompany Trung at the beginning of this quest and joined him when his circuit design was already working well and was a few years old.

Trung shared his design with Morten Sissener at Tortuga Audio hoping that he would take it and perfect it as a single tube single ended design. Trung didn’t want to offer this product commercially but felt it should be shared and was hoping that Morten would build it. Morten, unfortunately, took Trung’s original design in another direction and created his own balanced approach and didn’t accomplish what Trung was looking for. He also didn’t credit Trung, Gary, or Trung’s friends Mark and Rich who also took the initial journey with Trung with this design. Eventually, I asked Trung to share his circuit design with me and I headed off on my own to further perfect his design and to create the best possible sound quality improvements that I could. I ended up accomplishing that goal!

I spent over a year and a huge amount of money using my own experience and knowledge to further improve Trung’s design. Trung was so excited about the high quality that he was able to get from this circuit that he really wanted Morten Sissener at Tortuga Audio to perfect it. It took quite awhile for Morten to consider using this circuit (since he didn’t originally know that it sounded as good as it did) but eventually he did listen and it became obvious that this was something really worthwhile. However, his concept was to create a balanced commercial version and not to further perfect the concept that Trung wanted him to use. In spite of this different approach, Morten found that by combining a pair of tubes in this circuit with his LDR based volume control product he could create the best sound quality he has been able to come up with to date. This ultimately resulted in his recently releasing a new tube buffer integrated with his LDR volume control product. I was working on my own “tweaked” design for at least a year prior.

Initially, Morten understood the value of a buffer so he tried to create a buffer without a tube and built a solid state buffer device. He thought this would be the buffer concept that would provide the best sound. In reality, it was really the tube adding 2nd order harmonics that was the key and not the buffer concept that made this a stellar device. Gradually, he came back to using a pair of tubes since it was the tube harmonics that ruled and not the solid state buffer concept.

The tube is what’s magical with this concept and its inclusion is the reason to build this component. Not just any tube, however, but the best sounding one out of a very large selection if you consider the variety of the 6922 tube family. The 6H30p tube only has the one NOS version and not much else to select from. The 6922 family, however, has many different manufacturers, years, and varying sound quality – a huge array of possible tubes to use. That’s where my work has finally been focused – obtaining the most linear yet beautiful sound quality possible from the best tube in the 6922 tube family.

I’m sure that what Tortuga offers sounds really good. In fact, I’m sure it’s an excellent combination when used with a high quality volume control approach like his LDR based product. However, by using an even more transparent volume control method (like the Slagle autoformer) you can expand sound quality even further and that’s what I recommend if you’re willing to compromise a bit and use the Slagle copper version without remote control features. Slage’s silver version with remote volume control is quite expensive and only a well monied audiophile would probably consider using it. Yet . . . it is the best if you’re looking for the highest level of transparency with the least amount of possible distortion artifacts.

After my considerable work on my own single ended approach (expanding Trung’s concept further), I found that using a pair of 2.0 uF V-Cap CuTF coupling caps was the ultimate key and critical ingredient for this product. It took a large amount of time and a huge amount of money to discover this since I already was using expensive high-end audiophile film capacitors along the way. I eventually found the ultimate capacitors that increased the sound quality of Trung’s power supplies and further improved the signal design through designing my own printed circuit signal board and connecting these exotic capacitors.

Morten must have read my website postings (where I shared that the V-Cap CuTF was the best with nothing even close) and eventually he tried the CuTF V-Caps in his own test unit and ended up with the same conclusion that I did – THESE ARE SUBSTANTIALLY BETTER than any other capacitor that could be used. However, with his balanced approach, his design requires twice the number of parts and that increases the cost (particularly at the higher level cost I’m using ) beyond what normally is commercially acceptable. Plus his design is too general and can operate both the 6H30p as well as the 6922 tubes.

I’ve used Morten’s LDR volume control DIY printed circuit boards in my own volume control designs ever since he first started out offering this as a DIY product. I really like his work. This is still one of my favorite ways to control volume in a high quality audio system even though it’s not the ultimate. It does inject 3rd order harmonics into the signal path and the autoformer and transformer volume controls I also use do sound better. Prior to using Tortuga’s LDR boards, I was using the Warpspeed LDR volume control and prior to that was hard wiring my own individual LDR’s. I like this solution and don’t mind losing some of the transparency over the autoformer approach. The reason is the nice user interface that Tortuga provides with the inclusion of their OLED display. If it wasn’t for that microprocessor interface, I wouldn’t be using the Tortuga product.

However, I like the user interface of the Tortuga OLED display and the Apple remote and don’t mind the slight mismatch between the 2nd order harmonics I get from the buffer/harmonizer and the 3rd order harmonics from the LDR unit. It still sounds good particularly when compared to a carbon pot or resistor attenuator. Yes, the autoformers and transformers do sound more transparent but they also cost more. Vinnie Rossi uses the Slagle autoformers with remote volume control in his amps and this is the best sounding implementation of the Slagel audoformer approach I’ve used to date in my own Vinnie Rossi Amp. Vinnie’s work is beautiful and I highly recommend his products! But . . . the price is really high and I feel that my approach makes a whole lot more sense. If money is no object, purchase the power amp and preamp from Vinnie Rossi.

I can assure you, however, that the single ended tube buffer that I build and am offering will sound better than anything anyone else has come up with to date when used with a really good passive volume control solution. It is focused solely on one goal and has been developed to provide that goal at the highest level – the best 3 dimensional soundstage with an expanded width and depth with the least level of undesirable distortion. I’ve tuned this unit only for the 6922 family of tubes and especially for one rare 1975 6n23P Russian tube that also is in the 6922 family.

I have to thank Trung Tran (as well as Mark and Rich) for continuing forward to get this component into a few people’s hands who could take it further and beyond their own hard work. All 3 have shared what they’re doing with Trung’s design. I also thank Trung for being a good friend who has always been willing to share and to do so without the concern to make money or to get anything back for his generosity. You won’t find any reference to Trung’s contribution in Tortuga Audio’s tube buffer design marketing literature. However, I can assure you, that without Trung, Mark, and Rich, Tortuga would never have had this product design and would not have been able to offer it as a new commercial product.

I’m very biased (due to my exhaustive work and willingness to try anything at the highest level) and consider what I’ve put together to produce a better sound quality than the unit offered by Tortuga. I don’t build for a profit or easy implementation nor do I compromise in any way and offer lower cost options to make what I produce more marketable. My goal always is (and has been) to create the absolutely best that I can at whatever cost is required. In the beginning, I have no idea what level of expense will be required. In the end, I select what is the absolute best without regard for the required cost. The chassis design I use for this product (1/8″ thick custom CNC’d aircraft quality aluminum) is the same that I’ve been using for many years. It is the absolute best approach in my opinion sonically and from a longevity viewpoint. It looks really good but doesn’t waste money through unnecessary industrial design. Yes, I really love good looking designs. But . . . these audio components already cost a huge amount of money and I don’t feel a need to go beyond what I find is the best to actually use.

If you have the money, you’ll probably find that the Slagle autoformer solution is sonically the best to use. If you’re trying to save money, however, Tortuga’s LDR board will work well (either with their passive commercial unit, in your own DIY chassis using their DIY PCB for the build, or in the really small chassis that I will be glad to build to accompany the sale of a new triode tube buffer/2nd order harmonics generator).

I like the Tortuga DIY unit (built my own way). However, the Slagle unit with his remote control is the best. That’s what Vinnie Rossi uses in his LIO. I will not build a Slagle based unit for you since I don’t want to spend more money and time on R&D and perfecting yet another person’s product. That work is beyond my control so I really don’t want to get involved  My expertise is with the triode tube buffer/2nd order harmonics component and that’s what I’ll focus on in the future – just this one device.

Designed For The 6922 Tube FamilyAnd Specifically For The 1975 Reflector 6n23p SWGP Silver Shield Tube

The tube used in my component is operated at 30 volts where its sonic curve is most linear. The two power supplies that are used are some of the best available and incorporate two Belleson regulators (6.3vdc for the tube heaters and 30vdc for the buffer board power using Mundorf TubeCap Capacitors, Mundorf Gold/Silver/Oil Film Bypass Caps and other fine parts).

Belleson SPX Regulator

The printed circuit board for the signal input and output uses only naked Vishay resistors (providing an incredible improvement over normal film or carbon resistors). The toroidal power transformer is a custom design created for me by an engineer at toroid.com and is designed specifically for this component. I shared the schematic and operational points with the engineer at toroid.com and he designed the absolute best transformer for the two power supplies plus included an electrostatic shield to lower any potential background noise.

Vishay Naked Resistors

Aum Acoustics Gold Pad Signal PCB

The two stellar DC power supplies make a noticeable and substantial sound quality improvement over normal ones. The blacker the background, the more detail that can rise to the surface “untouched” by distortion and other artifacts. This super black background is one of the things that makes this component really special. These power supplies sending super clean voltage into a superb circuit design that uses all naked Vishay resistors help to create the cleanest 2nd order harmonics I’ve ever heard.

Aum Acoustics Gold Pad Power Supply PCB

However, its the pair of large 2.0uF V-Cap CuTF coupling capacitors that provide the texture and 3 dimensional sound quality and the musical beauty of this superb buffer/harmonizer. Without these incredible capacitors, the sound quality is good but not addictive and any where near as beautiful. With these capacitors installed, you have one of the best sound qualities possible while providing the ultimate benefits of using a stunning sounding tube in your audio circuit.

2.0uF CuTF V-Caps That I Use For Musical Beauty

The Bypass Caps I Use In The Power Supply To Obtain The Cleanest Black Background For The Input/Output Signals

The Electrolytic Caps I Use In The Power Supply That Also Contribute To Providing The Cleanest Black Background

I Use A Custom Instrument Grade Transformer From Toroid.Com – This Transformer Is Custom Designed For This Unit And Provides The Best AC/DC Conversion That Also Contributes Toward Providing The Cleanest Blackest Background

I Use An Audio Note Silver Plated Ceramic Tube Socket On The Signal PCB. I found that these make better contact than the expensive teflon pin style sockets that I used to use. They also sound the best and form the best long-term solder joint on a printed circuit board.

This buffer is as transparent and clean as is possible and uses only one single 9 pin triode tube. The goal that I accomplished was to reduce any distortion as much as possible and to obtain the 3 dimensionality that only a tube provides with as clean a 2nd order harmonic quality as is possible. I also didn’t want to require the use of two expensive matched NOS tubes. As a result, by using only one good tube, I was able to explore the entire realm of the 6922 tube family – it’s huge and a lot of fun to tube roll since there are many varieties! I’m very pleased with the results and I’m sure you will be too if you end up with one of this units.

The Tube

The 6N23p tube I’ve used for tuning this buffer is the most linear of all the substantial number of NOS tubes I’ve tested. It provides the most beautiful 3 dimensional shimmer that expands the sound stage and dimensionality of a really good audio system.

1975 “Holy Grail” Reflector SWGP Silver Shield

This buffer/harmonizer doesn’t require the use of 2 expensive tubes since it uses 1/2 of each side of a single triode tube for the left and right channels. A balanced unit would require twice as many parts and be twice as expensive to build and then it would need two matched tubes. You only need one tube and it doesn’t have to be from a matched pair.

The end result is that you can have the absolute finest musical sound quality at the least possible cost without having to compromise along the way. With this unit, you can afford to use the most expensive and sought after 6922 family tubes until you find one that suits your needs. Once I found the superb tube that I’m now using, my focus turned to improving the sound quality of this single ended circuit rather than attempting to create a balanced circuit that further increased the cost. As a result, I didn’t have to compromise on quality (sound or build quality) and was able to “fine tune” for what I found to be the best sounding tube and the absolute best combination of parts.

This unit wouldn’t sound better if I had used a balanced design. It instead would have allowed the use of longer cable options in place of the typical 1 meter interconnects and 6-8 foot speaker cables most of us use for single ended 2 channel audio. Most audiophiles don’t need to use longer cables than these so it made good sense to spend my money and time perfecting a single ended circuit design using only one triode tube.

Imagine a balanced buffer of this quality requiring over $5,000 just for the parts cost plus a pair of matched NOS tubes every time you wanted to explore changing your sound quality. It doesn’t make any financial sense or allow for easy modeling! What’s interesting is that a single tube using a single-ended circuit design does create the highest possible sound quality at the lowest possible cost even if your output is to a balanced power amplifier. You just need to pay attention to “dressing” your cables so power and signal don’t cross in a way where noise is generated into the single ended design. You also need to use reasonable lengths. That’s not difficult and only requires some common sense and a little bit of time.

I’m running my own buffer singled ended out into a pair of balanced power amps and it works extremely well. The only requirement is that I use a shorter cable and that I watch my cable “dressing”. The cable between my buffer/harmonizer and power amp consists of a high quality 6 foot pair of cables that don’t pick up any extraneous noise. The power amp is built into the back of my floor standing speakers. My approach is still expensive (since I’m using very expensive balanced/se XLR custom cables) but it’s still affordable.

I couldn’t afford to do this if the cable run was 25 feet. At around $5-6k for a stellar balanced unit (the way I build it) plus labor and allocated R&D costs, two NOS tubes, and longer cables, no one would consider purchasing this buffer/harmonizer unit! At around 1/2 that cost, they would and it would leave room for purchasing many single rare NOS 6922 family tubes to try out. Sound quality exploration would then be relatively easy since finding a single rare NOS tube is a whole lot easier than a matched pair and definitely is more affordable.

The 6H30p Tube Isn’t The Best Tube

This buffer circuit was originally designed for a 6H30p tube (beginning with Gary’s and Trung’s work) but that tube doesn’t sound that good after I tried sampling it with the best NOS 6H30p tubes I could find.

(By the way, a commercial new production 6922 tube sounds horrible in comparision so I wouldn’t recommend ever using one of those in this circuit. I also wouldn’t use a commercial new production 6H30p tube. Not in this circuit the way I build it.)

The 6H30p (NOS or new production) has way too much gain and provides too much boost to the midrange area. More important, it doesn’t provide a delicacy that I require when placing any tube in my audio circuit. When you perfect the audio circuit as I’ve done, it’s easy to tell the difference between tube types. Without a doubt, the 6N23p tube I’m using is the absolute best of all the tubes in the 6922 tube family. The early 60s Siemens CCA 6922 is my 2nd best favorite. Then a bunch of 6922 NOS tubes. The NOS 6H30p end up toward the bottom with no need to use it anymore.

I’ve spent over a year working on and perfecting this buffer circuit and have gone through all of the best NOS tubes I own, bought or could borrow from my friend Dave (a huge array). I’ve also used up and have thrown away a very large number of custom naked Vishay resistor pairs and wire types. As a result, I have finally put together the best combination I could find and I’m very pleased with the results.

My prototype workhorse that I used to perfect this component has been retired and I have just completed the build for two, brand new, fully finished triode tube buffers. This project is finally “complete” and I’m really excited to share this work with a couple of prospective purchasers. During my exhaustive R&D, I’ve listened to every single connection point and have eliminated connections where possible. I’ve also modeled many different wire metalurgies and gauges as well as all other parts used. In the end, I feel that I’ve perfected this circuit as much as is possible and I now know how to tune this buffer to perfection.

It’s not possible to design this buffer/harmonizer to use both the 6H30 tube type as well as the 6922 tube family and end up with the best sonic result. Operating points and gain settings are just too different! If done that way resistor and part values and types would need to be compromised to get both tube types to sound good. Sound quality wouldn’t be the best for either tube even though both tubes would work well. Instead of designing this buffer to accept both tube types, I went through an exhaustive trial using the best NOS tubes while looking for the best sounding tube I could find. I located that tube and then used it to “fine tune” this component.

During my testing, I found the 6922 tube family to be better sounding and more realistic than the NOS 6H30 tube type so I made a decision to only use the 6922 tube family. This circuit is now tuned for the operating points of the 6922 style tube.

I then eventually discovered that the Reflector 1975 SWSG silver shield tube that I ended up using to further fine tune this component was the absolute best of all the 6922 type tubes I tried. It even bettered the very expensive Siemens 6922 Cca tube that originally was one of my favorites. I ended up choosing a specific NOS 6N23p tube (out of a large array) for this circuit and all resistors and circuit values have been perfected while using this tube.

Even the cathode resistor value makes a huge difference (probably the biggest difference) in the final sonic results of the tube used and it’s value isn’t something I’ll share with anyone. A 250 ohm resistance difference in the value of this resistor pair changes the sound quality considerably and it’s taken quite awhile to move slowly through an almost endless chain of custom ordered naked Vishay resistors while I listened to the sound quality of each pair.. It cost me way too much money (the naked Vishay resistors are expensive) to arrive at this destination value (about $35 per resistor pair and I’ve thrown away many many pairs along the way).

It’s not possible now to go back to the 6H30 tube type and achieve the really great sound quality that I have after all of these careful and minute adjustments. Even though this buffer will easily power the 6H30 tube, and the sonic quality is good for that tube, superior sound quality is no longer there.

The 6N23p tube that I’m using, on the other hand, is unbelievably superb! The other 6922 family tubes also are also fun to explore and there are many you can use. Don’t take my word for it. Try the many 6922 type tubes and come to your own conclusion. I’m including one of my rare “Holy Grail” tubes with every buffer/harmonizer that I build so its owner can use this as a reference. If you work at it, you’ll find that this is the most linear and ultimately the best tube to use in a really good audio system.

A Selection Of The Ultimate Parts

I’ve gone through a huge number of Vishay naked resistors until the combination of values that I now use is as perfect as I could obtain both for the cathode resistors as well as all of the other resistors and elements used on the signal board as well as the power supplies. I’ve also used many different gauges of Neotech teflon coated copper and silver wire (power, ground, input and output) and have experimented with placing wire inside solid copper tubes for ultimate shielding and then removing them (one by one) to find the best sonic combination. In the end, I’m only shielding the solid silver input wires (to eliminate any noise) and have removed the experimental copper tubes from all other wires. I’ve used this wire with and without the teflon jacket and have experimented considerably.

What’s really interesting is that I found that by only changing the gauge of my ground wire from the signal board to chassis star ground that I could change the musical tone considerably. It was extremely noticeable as well as every single item I’ve installed in this unit. Even the high quality custom transformer sounds better than the typical torrid transformers that I started out using. Consequently, every change I could come up with has been tried and improved upon until I was able to come up with the optimum combination.

During my testing, I’ve burned through a huge number of coupling cap brands and many expensive high-end bypass caps like the Dueland silver and Dueland copper/tin to name a few. In the end, I found that one pair of V-Cap 2.0uF caps was the absolute best BY A HUGE MARGIN. Nothing else came even close and I ended up justifying the use of these very expensive coupling caps because of the excellent sound quality that they provide. I wasn’t able to get this sound quality with any other capacitor brand or smaller bypass caps. I won’t build this buffer without the V-Cap CuTF coupling caps and no longer have an interest in trying other capacitors and definitely no bypass caps no matter what their cost (never did work). That’s how important and critical these V-Caps really are in this circuit and that’s how sensitive this circuit actually is. It’s ideal for the kind of fine tuning that I do and is better than any other component (power amp, preamp, etc that I’ve built in the past).

The combination of parts that I now use have the ultimate blend of connection metals and types, wire gauge and type, simplified high quality circuit designs, the highest quality parts, and the most stunning cathode resistor match I’ve been able to come up with. I’ve gone through in excess of 20 different pairs of naked Vishay resistor values just to discover the best cathode resistor values and other positions, and I kept ordering new values until I found the ultimate combination for the 6922 tube family and specifically for my favorite triode tube, the 1975 Reflector, silver shield, SWSG tube. This buffer has been optimally tuned for this tube and I cannot imagine a better sonic combination. I’m very pleased.

The Stunning FP-901 Rhodium Chassis Jacks In This Unit – YES they make a positive improvement in sound quality compared to Cardas or other alternative RCA chassis jacks. These are definitely worth the added expense!

I Use A Furutech Rhodium Plated IEC Chassis Inlet In This Unit – I’ve tried all of the other Furutech inlets and found this to be the best sounding for the money spent.

I Include A Furutech Rhodium Plated Fuse . . . Yes – A really good fuse does make a positive difference. Try it yourself and you’ll end up agreeing. Use the wrong fuse and you’ll lose sound quality even though it might cost more than cheap hardware brands. This fuse works well for this buffer, but unfortunately is no longer for sale and has been discontinued by Furutech. I’ll save you the aggravation and expense required to chase one of these discontinued fuses down. It’s included.

This Is The Incredible 1/8″ Aluminum Custom Chassis Material That I Use! I design the chassis and send the CNC computer files to a custom CNC manufacturer. I have the aluminum parts they send me hard anodized locally and then assemble them to build the finished unit. Without a doubt, a solid chassis like this does make a positive sound quality contribution – and It can be driven over by a truck and won’t bend. That’s how strong it is. It definitely will last a very long time plus it looks really good!

The Expensive Silver Contact On/Off Switch I Source From The UK Costs Me Over $40 But Again, Makes A Positive Sound Quality Contribution.

The original 6H30p tube that was used in this circuit is just too heavy sounding. The midrange is out of balance and music quality is good but not natural. The low end is good but the treble isn’t delicate. It has a more “in your face” sound quality than one that resembles real live music. The 1975 Reflector tube that I ended up using is the absolute best and most linear of all tubes I tried. This also was confirmed by an extensive tube rolling test done in the Grand Tube Review you’ll find on head-fi.org by rb2013.

Here’s a link to that review:

https://www.head-fi.org/threads/6922-tube-review-17-top-6922-6n23p-e88cc-cca-7308-e188cc-tubes.761078/

This review’s conclusion ended up the same as mine: The ultimate 6922 tube was the Reflektor Holy Grail ’75 6N23P SWGP Silver Shield . . . and this is the tube that I’ve used to perfect this buffer. I’ll include one with every build that I create. It’s that important!

I have spent a huge amount of time and money finding the absolute best sounding and most linear tube. There’s nothing that touches the beautiful sound quality of this tube. The closest competitor is the exotic and very expensive Siemens CCA tube but it is even surpassed by the sonics of this particular tube. No other year, manufacturer, or alternative tube (6n23p or 6922) works anywhere near as well. Even other tubes made during 1975 don’t compete. It has to be this specific tube and these are getting extremely rare and very difficult to find. I’ve purchased a stash of these tubes (it takes close to 2 months to get them from Russia and then they have to be tested to find the good ones) and will include one with the purchase of any buffer that I build and sell. Because I’m running this tube at 30V instead of the usual 300V, it should last a very long time. I’m expecting at least 10 years of use before needing replacement.

The key to the beauty of the sonics of this tube buffer (a very expensive preamp alternative) really belong to the coupling capacitors I’m using – the V-Cap CuTF. The circuit, parts, power supplies, naked vishay resistors all contribute to providing the least amount of nasty distortion while these coupling caps, the 2.0 uF V-Cap CuTF, provide the incredible sonic beauty that we’ve all been searching for. Everything in this circuit is about providing linearity, transparency, and a correct 3 dimensional sound quality. The body and textural tone comes from these coupling caps. They are key to creating the sound quality and are ultimately the most important element for gaining the incredible sound quality this circuit is capable of. I’ve spent a huge amount of money and time modeling Jupiter copper foil, Jantzen foil and other high-end audiophile coupling capacitors. They all sounded weak and uninteresting (suprisingly) except for the V-Cap CuTF.

The Stunning V-Cap CuTF Coupling Capacitors!

Unfortunately, these 2.0uF V-Cap CuTF coupling capacitors cost $1,151.96 a pair. I’ve tried lower cost V-Caps (OIMP and ODAM) and there is no comparison – not even close. I’ve tried the Jupiter copper foil capacitors as well as other highly regarded and expesive capacitors. The only caps that sound superb and provide a stunning sound quality in this circuit are these CuTF copper foil teflon caps. Their inclusion really adds to the total parts cost but, in all honesty, they are what create the actual final sound quality that competes with 20k+ active preamps. They are what generates the beauty that I love through using this component in my audio system.

The volume control that I recommend (if cost is of concern) is a custom unit where I (or you) purchase the LDR printed circuit board from Tortuga Audio and then use my own parts, chassis and connection methods to build it. I build these with superb parts to gain another level of transparency that this buffer desires (even wire type used is important here to gain the synergy that is possible). I definitely do not want to degrade the sound quality by using a carbon pot or resistor attenuator. These two units (the buffer and ultimate selection for a volume control) are beautiful when combined with a good DAC, a good power amp, and superb speakers. When I use my Slagle autoformer volume control, the quality is absolutely superb and stunning.

The LDR based volume control solution I also use is good, but on its own it sounds relatively “flat” and “uninteresting” until it’s combined with this 6N23p triode tube buffer circuit. The triode tube buffer circuit adds the most beautiful and linear 2nd order harmonics using the Reflector tube I’ve found. The 3D spacial-ness and sound quality provided by this single small triode 9 pin tube is huge, beautiful, and does the least harm to the sound quality. Bass has slam, midrange is textured full with body, and the treble remains super transparent yet incredibly beautiful and not harsh.

I’m really impressed by the sound quality of this buffer even with a LDR volume control add to the system. If I wasn’t, I wouldn’t recommend this combination nor have used it during my lengthy and costly fine tuning process and instead would have moved on. In the end, this buffer is “too good” not to share with other people and is why I’m now offering it as a custom order product. Its up to you wether you want to initially use an LDR based volume control, one with an autoformer, or one that uses a transformer or some other passive volume control device. They all work well. However, I do feel it’s important to keep this passive device outside the buffer chassis to allow the most flexibility. Eventually, you might want to change your initial lower cost solution to an even better one.

Cost & Parts Used

Parts cost for this buffer is close to $3,000. I can’t lower that any more without giving up the substantial positive sound quality I’ve obtained, and this does not include the cost of the single exotic 9 pin triode tube ($150 if you can even find one) or my time and research costs (easily well over 5k just on parts used and abandoned along the way).

I’ve just completed building two of these units and am just finishing completion of a 3rd unit. I will sell each for parts cost only without markup for my time (considerable) or the R&D costs involved (very high). My selling cost for each of these buffers will be $2,950 plus any selling and shipping costs involved.

I’ll also include one of my rare “Holy Grail” 1975 6n23p tubes and an excellent Furutech fuse at no cost. At the price I’m asking, I lose the cost of this tube (about $150 if you can find one) and the cost of the fuse (no longer available) but at least I’ll pay for the raw parts used for each unit. Beyond these three units, I plan on adding labor cost, a reasonable prorated R&D amount, and a proper value for the included tube. I won’t be including the fuse I’m currently using since I can’t get them anymore. The selling price I will need to charge for future units will be much higher than these first two units.

Non-Monetary Payment

As a non-monetary payment for my work involved in perfecting these two introductory units, I’m asking that whoever buys one of these two unique buffers to provide an honest review that I can include on my website. All sales beyond these three units will include the cost for my time and a reasonable proration of R&D costs so this is a one time opportunity for three people to work with me during my initial introduction phase.

The price beyond these 3 units will be considerably higher than what I’m offering right now. Plus, wait time will be fairly long (up to 2 to 3 months per order). All future triode tube buffers will be made to order and will not be a stock inventory item. Parts will be purchased at current prevailing prices only after the initial payment has been received (the full parts cost of $3,000+ adjusted for any higher costs for parts will be the initial down payment). Unless I can operate at a reasonable profit level, I won’t compromise this buffer in any way nor give away my time, money, or efforts.

To Summarize

I have just completed two single ended, single triode (6922 tube family) units, sold them, and am just finishing the build for the 3rd unit. It will be ready to ship very soon. Each unit yields about 5-6db of gain and provides the most linear tube component I’ve ever heard.

This tube buffer/harmonizer should be connected between your passive volume control (using RCA inputs and outputs) and then connected to your power amp (via the RCA outputs on the back of the buffer).

You can connect this unit to a balanced only power amp but you’ll need to use a custom built RCA to XLR cable (to make the conversion). If you do this, make sure the cable you have made isn’t too long to pick up noise along the way. I’ll be glad to make recommendations if you need help.

I can help you with if you have a balanced only power amp. Most really good power amps are singled ended Class A types and this is my preference. A pair of 6′ cables (RCA to XLR) would be totally adequate and useable if you need to convert from RCA singled ended on this buffer to XLR balanced inputs on your power amp. I wouldn’t use a longer cable length for this purpose. I know from experience that 6 foot conversion cables work. I have a high quality 6 foot pair in my system and like them a lot. They work well and sound great without any issues.

Passive Volume Control Solution

If you need a passive volume control (to use with this buffer), I can build an LDR based single input single output (or optionally 2 inputs and one pair of output jacks) small unit and I’ll be glad to discuss your possible needs with you. Two alternative volume control solutions that work extremely well are the Slagle autoformers and the Stevens and Billington transformers. The Slagle autoformer solution is my favorite.

However, the OLED display that is designed for the Tortuga based LDR and the Apple Remote provides 100 attenuation steps (not 24 or 48) and the ability to change output impedance. Sound quality for all three volume control methods is excellent and all three would work well as a good “front end” volume control for this triode buffer.

You should not use an active preamp when using this triode tube buffer in your system. Unless it’s of the highest quality you’ll defeat the purpose of maintaining a pristine yet ideal clean circuit that I’ve designed. If it’s high enough in quality, then it probably costs between $10k = $20k and you really don’t need my help. A passive volume control works best with this single tube.

Dimensions

This unit measures: 13″ wide x 10″ deep x 3.25″ tall (plus an added 1/2″ height for the included feet)

I’ll include a free “Holy Grail” 1975 Reflector Tube And A Discontinued Rhodium Plated Furutech Fuse. I want each new owner to hear this buffer at its best and use these two items as a reference for future tube and fuse rolling.

I’m not including a power cable. You will need to use a decent (but not super expensive) audiophile quality power cable of your own selection so I’m not going to include a cheap one that come with most low cost units since it won’t sound good.

2 Are Now Sold & There Is Only 1 Remaining And Ready To Ship(Orders Beyond These 3 Will Be At A Normal PriceOnce This Last One Is Sold!)

Your Price For This 3rd Unit = $2,950 (parts cost only)PlusYou Pay Actual UPS Ground Shipping CostAndYou Pay the PayPal Fee If Using PayPal

Let me know if you have any questions. Use the contact page on this website to reach me:

http://aumacoustics.com/contact-form

Thanks for checking out my website,Richard BeckerAum Acoustics