[bpiotrow13]

Yes, increased soundstage and improved imaging, detail retrieval and bass definition. Absolutely you can build a cathode follower OTL using one 6SN7 and 6AS7G, not unlike a Darkvoice or Bottlehead Crack. Those designs could be improved upon though, particularly their power supplies. The Apex Teton is a "high end" OTL using these tubes, although I think it is very overpriced for what it is.

Many thanks! It is tempting to have an amp with one tube each. I have not known Apex. So I guess the answer is not that simple. Two tubes are better than one, but it is ultimately up to the particular design.

 

[Tjj226 Angel]

Many thanks! It is tempting to have an amp with one tube each. I have not known Apex. So I guess the answer is not that simple. Two tubes are better than one, but it is ultimately up to the particular design.

Since you live in Poland, why not use the 6c33c tube? They should be very cheap and plentiful in your country and you could easily build an OTL with 1 triode output.

 

[L0rdGwyn]

No problem, @bpiotrow13 . Yes, it's never so simple, but I would say in general the designs I have heard using a pair of tubes are better. No doubt though you can make a very good sounding amplifier using a single 6AS7G and a 6SN7 though. You certainly could commission someone to build a "premium" OTL amplifier for your Verite using those tubes. Given it should be a low parts count amplifier, I don't think it would be too expensive. You could reach out to the Head-Fier Paladin79, he makes an OTL amplifier using those tubes, I have not heard it, but @bcowen has one. Not sure if he builds for anyone who inquires, but you could ask him. Another less expensive option would be to build or commission a Bottlehead Crack + Speedball build, many are very happy using that amplifier with their high impedance ZMFs. I would avoid the Darkvoice.

I'll be working on the 45 amp some more today, last night I rewired the input sockets for 5687. I like the change and will most likely be keeping it that way, parts for the 12.6VDC heater regulator are on the way. That means the input tube options would include 5687, E182CC, 7119, 7044, and Bendix 6900 if Zach wants to take out a loan. I will be doing some other tweaks today as well, will post some photos assuming I get everything squared away from a cosmetic standpoint.

 

[bpiotrow13]

Since you live in Poland, why not use the 6c33c tube? They should be very cheap and plentiful in your country and you could easily build an OTL with 1 triode output.

I think this is not a big difference nowadays where You live. I have a stock of 6as7 tubes already and it is much easier to tube roll with this family. But 6c33 may be a nice option, thanks

 

[Tjj226 Angel]

I think this is not a big difference nowadays where You live. I have a stock of 6as7 tubes already and it is much easier to tube roll with this family. But 6c33 may be a nice option, thanks

Russian surplus tubes are a different story. There are warehouses of those tubes strooned throughout eastern europe. If you know where to look and who to ask, you should be able to find some for free.

 

[bpiotrow13]

No problem, @bpiotrow13 . Yes, it's never so simple, but I would say in general the designs I have heard using a pair of tubes are better. No doubt though you can make a very good sounding amplifier using a single 6AS7G and a 6SN7 though. You certainly could commission someone to build a "premium" OTL amplifier for your Verite using those tubes. Given it should be a low parts count amplifier, I don't think it would be too expensive. You could reach out to the Head-Fier Paladin79, he makes an OTL amplifier using those tubes, I have not heard it, but @bcowen has one. Not sure if he builds for anyone who inquires, but you could reach out to him. Another less expensive option would be to build or commission a Bottlehead Crack + Speedball build, many are very happy using that amplifier with their high impedance ZMFs. I would avoid the Darkvoice.

I'll be working on the 45 amp some more today

Thanks again. There are at least two recognised producers of OTL amps here in Polan so no problem with finding someone. Probably the most difficult part is to determine what one wants Your thread is really helpful with this regard

I (basically) currently have two headphone amps: Woo wa2 and Ayon Ha 3 (using 45 type tubes) that I use with ZMF Verite. To me 45 type tubes are too neutral and I have just put Ayon for sale. I really enjoy OTL design with Verite. However Woo wa2 uses ecc88 driver tubes and I tend to like ecc82 or 6sn7 more. This is the reason I am contemplating custom project.

Can't wait for more pictures of Your 45 amp

 

[triod750]

No problem, @bpiotrow13 . Yes, it's never so simple, but I would say in general the designs I have heard using a pair of tubes are better. No doubt though you can make a very good sounding amplifier using a single 6AS7G and a 6SN7 though. You certainly could commission someone to build a "premium" OTL amplifier for your Verite using those tubes. Given it should be a low parts count amplifier, I don't think it would be too expensive. You could reach out to the Head-Fier Paladin79, he makes an OTL amplifier using those tubes, I have not heard it, but @bcowen has one. Not sure if he builds for anyone who inquires, but you could ask him. Another less expensive option would be to build or commission a Bottlehead Crack + Speedball build, many are very happy using that amplifier with their high impedance ZMFs. I would avoid the Darkvoice.

I'll be working on the 45 amp some more today, last night I rewired the input sockets for 5687. I like the change and will most likely be keeping it that way, parts for the 12.6VDC heater regulator are on the way. That means the input tube options would include 5687, E182CC, 7119, 7044, and Bendix 6900 if Zach wants to take out a loan. I will be doing some other tweaks today as well, will post some photos assuming I get everything squared away from a cosmetic standpoint.

I guess he could use Melz 6N12S too. That is my favourite tube, but I don't use it for input. It is close to the parameters of 5687 (I think - what do I know about electricity)?

 

[L0rdGwyn]

Wow busy day, spent the entirety of it working on this 45 amp. The amp is done enough to show some pictures, but first I am going to tell you what I did.

Last night I rewired the input sockets for 5687 to run on AC while I wait for heater regulator parts / PCBs, so that was done fortunately.

Next I wired up the impedance switch that will be on the front panel. Again, the transformers are tapped for 300ohm, 120ohm, and 32ohm.

Here is the wired switch. It is a three-position toggle, up (300ohm), middle (120ohm), down (32ohm).



Next I put some feet on the bottom panel, but I'm not going to show that because it's boring.

Okay, here was the real doozy...

For the original build and prototype, I used the Hammond 167 series transformers for the filament supply. What was not obvious during the prototype and blatantly obvious after building the amp is that these transformers SUCK!!!

Up to this point I have always used Hammond 166 or 266 open bracket dual bobbin transformers for dedicated filament supplies. The 167 series is fully enclosed rather than open bracket. I though "well, fully closed looks better, I wonder if I can get away with leaving them unshielded for the black transformer swag". I quickly learned that was a mistake, as these transformers emit a massive magnetic field audible even with shielding and have horrendous primary-to-secondary coupling. Every bit of mains noise was coupled into the filament supply - noise from my PC (squeeky sounds while moving the mouse), noise from every light dimmer in my house, everything. I actually opened one up afterward thinking perhaps that I had been duped and they weren't really dual bobbin as advertised. They appear to be, but regardless, the coupling and magnetic field were a massive noise problem.

So I ordered an equivalent pair of 166 series open bracket transformers, which I know to be good, and went to work today to make the swap. This was a true joy to work on.

I had to remove the mains transformer as well, then tape everything up for protection including the output transformers, then go through the tedious process of marking everything up for drilling, then out to the garage for machining.



Here are the 166 series transformers in place before I affixed the shields. I had to trim a bit off of the ends of the brackets to fit the shields overtop.



Then put everything back together. Wooooh. Started working on this at around 7AM and just finished. But all of my noise woes are taken care of and the amp sounds great.

The amp isn't completely done as I am running the 5687 on AC at the moment, but it is done enough for pics, will post some shortly.

 

[L0rdGwyn]

Here are some pics. Not color accurate, but close enough.







And one in operation, again the color is off given it is a dark photo with long exposure. Green lighting is the biasing LEDs.

 

[jgwtriode]

Impressive....love those globe 45's and all that iron has gotta be good for the music. Just like for proper blood flow!

Happy listening,

jgwtriode

 

[Mr Trev]

Wow busy day, spent the entirety of it working on this 45 amp. The amp is done enough to show some pictures, but first I am going to tell you what I did.

Last night I rewired the input sockets for 5687 to run on AC while I wait for heater regulator parts / PCBs, so that was done fortunately.

Next I wired up the impedance switch that will be on the front panel. Again, the transformers are tapped for 300ohm, 120ohm, and 32ohm.

Here is the wired switch. It is a three-position toggle, up (300ohm), middle (120ohm), down (32ohm).



Next I put some feet on the bottom panel, but I'm not going to show that because it's boring.

Okay, here was the real doozy...

For the original build and prototype, I used the Hammond 167 series transformers for the filament supply. What was not obvious during the prototype and blatantly obvious after building the amp is that these transformers SUCK!!!

Up to this point I have always used Hammond 166 or 266 open bracket dual bobbin transformers for dedicated filament supplies. The 167 series is fully enclosed rather than open bracket. I though "well, fully closed looks better, I wonder if I can get away with leaving them unshielded for the black transformer swag". I quickly learned that was a mistake, as these transformers emit a massive magnetic field audible even with shielding and have horrendous primary-to-secondary coupling. Every bit of mains noise was coupled into the filament supply - noise from my PC (squeeky sounds while moving the mouse), noise from every light dimmer in my house, everything. I actually opened one up afterward thinking perhaps that I had been duped and they weren't really dual bobbin as advertised. They appear to be, but regardless, the coupling and magnetic field were a massive noise problem.

So I ordered an equivalent pair of 166 series open bracket transformers, which I know to be good, and went to work today to make the swap. This was a true joy to work on.

I had to remove the mains transformer as well, then tape everything up for protection including the output transformers, then go through the tedious process of marking everything up for drilling, then out to the garage for machining.



Here are the 166 series transformers in place before I affixed the shields. I had to trim a bit off of the ends of the brackets to fit the shields overtop.



Then put everything back together. Wooooh. Started working on this at around 7AM and just finished. But all of my noise woes are taken care of and the amp sounds great.

The amp isn't completely done as I am running the 5487 on AC at the moment, but it is done enough for pics, will post some shortly.

Ironic that moving your mouse made squeeky sounds

 

[bcowen]

Here are some pics. Not color accurate, but close enough.







And one in operation, again the color is off given it is a dark photo with long exposure. Green lighting is the biasing LEDs.

Love it!!!

 

[triod750]

For the original build and prototype, I used the Hammond 167 series transformers for the filament supply. What was not obvious during the prototype and blatantly obvious after building the amp is that these transformers SUCK!!!

My Lord, just what I expected from you! You could have asked - I'm here for you...!

 

[Mr Trev]

Here are some pics. Not color accurate, but close enough.







And one in operation, again the color is off given it is a dark photo with long exposure. Green lighting is the biasing LEDs.

At the risk of further inflaming my amp-envy…
Does the 32ohm tap mean it'll play nicely with iems?

 

[L0rdGwyn]

At the risk of further inflaming my amp-envy…
Does the 32ohm tap mean it'll play nicely with iems?

Hmmm think it would depend on the IEM, output impedance on that tap is likely around 10ohm, but very sensitive IEMs will be prone to an audible noise floor. So I don't know! Something like the ER4XR would probably work well, maybe Zach can give it a shot and let us know. I am IEM-less at the moment -_-