[L0rdGwyn]

Hi AC,

I am new to the forum, but wanted to share a project I recently completed.

Back in December I decided to take on my first serious DIY project, a full from-scratch, design-to-build tube amp. It was a pretty enormous undertaking, for me anyway, considering it was my first time doing it. It is a 3WPC SET build with a switchable headphone output.

Before working on this project, I had done a few Bottlehead builds, restored a vintage tube tester, modified existing circuits, among other tube-oriented DIY things, but this was on another level.  My first degree is in the physical sciences so I’m somewhat used to being self-taught in this kind of technical stuff, but I certainly leaned on those with more experience along the way to discuss concepts, circuit design, etc. I could not have done it without their help.

The amp features quite a few oddball tubes that you aren’t likely to find in commercial tube amplifiers, 4V peri-WWII drivers, including MH4, REN904, E424N, and quite a few others. These driver tubes are SS cascode constant current source loaded. Outputs are an indirectly-heated cousin of the 2A3, the 6A5G. Tube rectifier has a combo socket, so either 4V European B4 base tubes (U18/20, FW4-500) or 5V 5Z3 rectifiers can be used. Mains and output transformers are made by Lundahl. I’ll leave it there as far as components go unless asked.

So how does it sound? It is incredible. The soundstage is expansive, highs are detailed, airy, non-fatiguing, midrange is full and warm, bass is thick, tight and very deep. Frequency response measurements show it flat from 20Hz to 18kHz, it is down ~2dB at 20kHz, something I might go back in and investigate (but I mean, I can't hear that high anyway!).

I have been listening on headphones mostly so far, but did hook it up to my pair of NHT C3 bookshelves (6ohm nominal, 87dB efficient), since this amp will eventually live in my stereo. Despite it being pushed to its max output, the NHTs sound incredible, definitely getting better sound out of them than with my Rogue Audio Sphinx V2. The stereo imaging and staging are outstanding, center image is much more precise with these speakers 7-8ft apart with a slight tow-in.

I will be getting a pair of high-efficiency speakers to pair with this amp in the near future.  I am currently in contact with Louis from Omega (what led me to AC actually), so looking into getting a pair of his beautiful speakers, I can't wait.

Here are some photos, thanks for checking it out!

[borism]

I've also built a few Bottlehead kits. This amplifier, however, is something else. Absolutely stunning!
Congratulations! Hope you find the right speakers to match.

[jmolsberg]

Looks great. Bet it will sound magical w omega speakers!

[happyrabbit]

Those 4P CAPS LOOK LOVELY ! 

[Jon L]

Wow, Duelund CAST-PIO coupling caps and ClairtyCap TC film caps for power supply caps?!  Other parts look lovely as well.   

[jmpsmash]

very nice! top notch workmanship plus top notch quality parts!

[FullRangeMan]

Congratulations! really first class job.
What wire gauge do you have used?

[L0rdGwyn]

Thanks for the compliments everyone!  The coupling caps look just like Duelunds but they are actually Miflex KPCU-02.  The wiring is all silver plated copper from Apex Jr., 18 AWG for the power supply and heaters, 20 AWG for most of the signal wiring, except for the input wiring, which is shielded 24 AWG

Working with Louis now to figure out what speakers to order.  Contenders at the moment are the Junior 8 XRS and his Custom shop 8 high output monitor (not on the site, but in his Instagram).

[ArthurDent]

Very nice looking unit. Well done ! 

[Steidl Guitars]

Beautiful work.

[jmolsberg]

Can’t lose with the junior 8. I love the XRS cause that wide baffle sounds killer!

[L0rdGwyn]

Thanks, Louis suggested the high output 8 monitor based on my music preferences since it has the second woofer, but said the J8 XRS is great too.  I listen to just about everything, from acoustic, to jazz, to classical, to edm/techno.  He thought the high output monitor might be better with the more complex bass-centric stuff.  I've gotta head over to the Omega forum and get some opinions!  This is going to be a tough choice.

[Tyson]

Exceptional!!

[jmolsberg]

I went with the 3xrs HO because that’s what he recommended and I wanted the second woofer too. Wonder if he can do the monitor HO in wide baffle?

[L0rdGwyn]

Those cabinets are stunning.  Is that the walnut?  That is likely the veneer I will be going with, very classy.  I really want to go with the Customshop 8 HO, just need to figure out if those deep cabinets are going to work where these babies will go in my room.  They are quite chunky, similar dimensions to the SAM.

[poseidonsvoice]

As a fellow diy’er myself, your build is clean, neat, exceptional in quality and puts other high end tube companies to shame! No rats nest wiring here folks! Kudos!

Best,
Anand.

[timind]

Excellent work L0rdGwyn. Another DIYer here, and I appreciate the care you've taken to get it so precise. 

[FullRangeMan]

Thanks for the compliments everyone!  The coupling caps look just like Duelunds but they are actually Miflex KPCU-02.  The wiring is all silver plated copper from Apex Jr., 18 AWG for the power supply and heaters, 20 AWG for most of the signal wiring, except for the input wiring, which is shielded 24 AWG

Working with Louis now to figure out what speakers to order.  Contenders at the moment are the Junior 8 XRS and his Custom shop 8 high output monitor (not on the site, but in his Instagram).

Thanks for inform.

[L0rdGwyn]

Thank you all again for the kind words, I really do appreciate it many long hours went into this build, so I am glad that it turned out as well as it did.  I am working on a 45 parafeed headphone amplifier next, input tubes are 6J5, both stages are SS cascode CCS loaded, parafeed transformers will be Sowter.  Won't have the parts for some time given the virus outbreak, but should be a nice little headphone amp I think.

[FullRangeMan]

Sowter are great sound trafos, do you know if they have C cores for output?