[Monsterzero]

I finished six sockets on @Monsterzero 's GOTL. I'm usually much faster, but this COVID booster really knocked me on my ass! I feel horrible lol. 6J5 sockets are next. Fortunately, I think the chassis cutouts for the loctal sockets will support the new octal sockets so I won't have to widen them with that giant step bit.



I think that's it for today though. In between sockets, I've been listening to the Airmid with PCM56 DAC, MOV L63 inputs and Tung-Sol 7802 outputs. The 7802 sounds amazing in this circuit, really great tubes. It's been fun listening to the Airmid again after its little road trip, can be hard to critically evaluate something you've made when you have been listening to it nonstop every day like a robot. Nice now to just kick back and enjoy it.

Looking forward to hearing my amp after you work your magic on it!

 

[bcowen]

You're talented. Can make almost anything. What's an LCR? A tube phono stage sounds interesting. For both mm & mc? Stepping into vinyl is just as bad as stepping into tubes. I'm thinking of upgrading the cartridge to Denon DL 103R.

Get the Zu modded 103R (or even the 103). Hugely worth it.

https://www.zuaudio.com/turntable

 

[bcowen]

Yeah, vinyl is a endless money pit and rabbit hole. But if you commit, its great! My phono stage is for MC, it uses Lundahl MC step up transformers. Actually the phono stage input is wired for balanced and my tonearm was rewired for balanced, the input transformers convert from balanced to single-ended. This keep the noise pickup between the turntable and phono stage low.

LCR phono stage is one that uses a passive RIAA equalization network made up of choke / resistors / capacitors, as opposed to more typical passive RIAA that only uses resistors / capacitors. The idea is that using a low impedance passive RIAA network gets the best sound, and that is achieved using LCR. But tubes in an LCR phono must have specific characteristics to make the whole thing work, and specific chokes are required as well. Basically it is expensive to make one lol but the sound is considered the best. @leftside has a custom LCR phono, so I'm sure he could shed some light on how it sounds.

You mean not everyone has a tube phono stage? That's like an insult to vinyl itself.

 

[UntilThen]

Get the Zu modded 103R (or even the 103). Hugely worth it.

https://www.zuaudio.com/turntable

Hello compatriot, how about just the standard Denon DL 103R. Why do I have to pay Zu a few dollars more?

 

[bcowen]

Hello compatriot, how about just the standard Denon DL 103R. Why do I have to pay Zu a few dollars more?

Um, 'cause it sounds better? Yeah, that's it.

Seriously, the 103 has been around for, like, ever. Very nice cartridge for the money in stock form, but the plastic body hinders what it's really capable of. Zu went about fixing some of the weak points without disturbing its voicing or overall character. More detail, better bass heft and punch, less stridency on marginal recordings, and much larger soundstage. Of course that's only my opinion (if I had one ).

 

[L0rdGwyn]

Here's @Monsterzero 's modded GOTL.

I swapped out all of the sockets, that was fun, and replaced all with QQQ octal sockets except for the loctal C3g sockets which were replaced with Beltons due to the wider mounting hole centers. The two Belton sockets are now set up for 6J5, the switchable heater circuit now controls the 6SN7 and 6J5 sockets, so 12J5 can also be used in place of 6J5.

I added CCS loads to the input tubes and changed the biasing scheme from resistor / capacitor cathode bias to LED bias. Also adjusted the B+ voltage at the top of the CCS.





Here it is with some tubes, have a GZ34 rectifier in with some Sylvania 6J5GT and Toshiba 6BX7GT.

 

[whirlwind]

Here's @Monsterzero 's modded GOTL.

I swapped out all of the sockets, that was fun, and replaced all with QQQ octal sockets except for the loctal C3g sockets which were replaced with Beltons due to the wider mounting hole centers. The two Belton sockets are now set up for 6J5, the switchable heater circuit now controls the 6SN7 and 6J5 sockets, so 12J5 can also be used in place of 6J5.

I added CCS loads to the input tubes and changed the biasing scheme from resistor / capacitor cathode bias to LED bias. Also adjusted the B+ voltage at the top of the CCS.





Here it is with some tubes, have a GZ34 rectifier in with some Sylvania 6J5GT and Toshiba 6BX7GT.

Congrats Monster....enjoy those 6/12 J5 tubes.....great way to get great drivers at less price than top of line SN7 tubes...especially since NOS tubes are far more easily found.

 

[Monsterzero]

Here's @Monsterzero 's modded GOTL.

I swapped out all of the sockets, that was fun, and replaced all with QQQ octal sockets except for the loctal C3g sockets which were replaced with Beltons due to the wider mounting hole centers. The two Belton sockets are now set up for 6J5, the switchable heater circuit now controls the 6SN7 and 6J5 sockets, so 12J5 can also be used in place of 6J5.

I added CCS loads to the input tubes and changed the biasing scheme from resistor / capacitor cathode bias to LED bias. Also adjusted the B+ voltage at the top of the CCS.





Here it is with some tubes, have a GZ34 rectifier in with some Sylvania 6J5GT and Toshiba 6BX7GT.

Looks great, Keenan!!! Drop me an email when you can so we can get it back home. Ive been making due with a solid state amp/DAC in the interim, which will remain un-named. I miss my tubes!

Congrats Monster....enjoy those 6/12 J5 tubes.....great way to get great drivers at less price than top of line SN7 tubes...especially since NOS tubes are far more easily found.

Thank you sir! Ive been on the j5 hype train since the get-go, but im looking forward to ditching the adapters!

 

[UntilThen]

Here's @Monsterzero 's modded GOTL.

Looks a million bucks now.

 

[L0rdGwyn]

I got my big box of HY69 tubes and the quad of globe 45. The pair of RCA 45 test well and are well-matched, the other two not so well but are still usable. No big deal though as I was most interested in the matched pair. The test label on them is from 1933.



Sound pretty good in my little 45 amp. Will try them out in the 45 headphone amp when it's done.



And the 30 HY69 tubes, don't know where I'm going to store all of these yet lol. Here is one of the ceramic base tubes while tracing curves.



Here are the A1 curves for this one. As I pointed out before, they make very good triodes.



Also got two Airmid chassis in today. Not the greatest photo but here are the top plates, left is Chromy Bronze, right is Anthracite Gray.



Had planned to work on Zach's 45 amp first, but I made some last minute changes on the chassis which delayed the order, so I will likely get it next week some time. Will get started on these in the interim.

 

[UntilThen]

Nice looking 45 amp you got there.

 

[L0rdGwyn]

Nice looking 45 amp you got there.

Thank you!

Spinning some Combat Rock this Friday evening. Happy listening everyone

 

[L0rdGwyn]

So I have some bad news - I've decided I cannot build and sell amplifiers publicly on Head-Fi.

I know this might come as a shock considering I only just recently announced the Airmid OTL and had discussed plans for future headphone amplifiers, but after thinking it over and discussing it with my partner, it just isn't going to work for a few different reasons.

First off, I am a critical care healthcare provider and my profession is pretty demanding. Given the current state of affairs in the critical care world and recent develops in my professional life, I don't have the time and energy to essentially work two jobs, which is what building amplifiers feels like it will become. Also, there is a certain degree of legal liability when selling high voltage audio equipment and to fully protect myself would require a commitment to small business ownership that I am not willing to make. I wanted to keep building amps "casual", but when there is 200V+ inside the chassis and the possibility of electrocution, it cannot be done casually without taking on some degree of risk. And without going into great detail, doing it would make me unhappy, ultimately.

So I will withdraw the Airmid OTL from Head-Fi. I will finish the orders that have been placed and provide future service and support for those amplifiers, but I will not be taking any new orders. I'm sorry to have led anyone on, I hesitated in the past at the idea of selling amplifiers, but thought I should try it out and see if it was going to work - I now know without question that it won't. I'll continue this thread if people are still interested in learning about tube audio design and potentially working on their own projects, but I won't be offering anything I show here for sale.

 

[L0rdGwyn]

On a more positive note, Zach's 45 amplifier chassis looks very nice in Distant Blue. I will have it later this week.

 

[UntilThen]

Totally understandable Keenan. Building amps for others is a lot of work. Although you could do like what Glenn did. Make it a selectively small scale. Boutique amp builders are a cherished lot and they should not disappear. Boutique amp builders are spurred on by their love of tube amps and that's what drives them. Profit is secondary.