SET 45 Amps

[jcmusic]

Who here is now using or in the past used one of these amps? Which one did you have? Do you still use it? If not why?

Jay

[Coytee]

I believe Cut-Throat uses a 45 SET amp on his Khorns

[Cut-Throat]

Yup, I use Welborne StarChief 45 Monoblocks - I have used a 45 amp for about 8 years now. I also own 2A3 Moondogs and Welborne 300b Laurels. The 45 is my preferred amp. Previously to the Star Chiefs I had Welborne DRD45s. Very similar to what I have currently. Here is a picture of the Welborne DRD45s that I built. The Star Chiefs that I have now have Bubinga Wood Bases and the DRD45s had Paduak Bases. After I got 'into' SET amps, I heard a lot of audiophiles raving about the 45 SET. I built a pair and in one evening, I was a believer.

[jcmusic]

Cut-Throat do you know anything about the Yamamoto 45, or Jeff Korneff's?

Jay

[Cody_Mack]

Yup, I use Welborne StarChief 45 Monoblocks - I have used a 45 amp for about 8 years now. I also own 2A3 Moondogs and Welborne 300b Laurels. The 45 is my preferred amp. Previously to the Star Chiefs I had Welborne DRD45s. Very similar to what I have currently. Here is a picture of the Welborne DRD45s that I built. The Star Chiefs that I have now have Bubinga Wood Bases and the DRD45s had Paduak Bases. After I got 'into' SET amps, I heard a lot of audiophiles raving about the 45 SET. I built a pair and in one evening, I was a believer.

I have heard the DRD designs by Jack Elliano of Electra-Print give the Welbornes a good race. Jack provides the schematics and the iron and friendly support. Any experience with these?

Rick

[Cut-Throat]

Cut-Throat do you know anything about the Yamamoto 45, or Jeff Korneff's?

Jay

They are highly regarded amps. I have not heard them myself.

[Cut-Throat]

I have heard the DRD designs by Jack Elliano of Electra-Print give the Welbornes a good race. Jack provides the schematics and the iron and friendly support. Any experience with these?

Rick

I am thinking they are very similar amps to the Welborne, as the Welborne amps have Electra-Print iron and I believe the schematics may be the same as what Welborne was using. Welborne worked closely with Electa-Print.

[jcmusic]

Which tubes are you using in the pic's?

Jay

[Cut-Throat]

Which tubes are you using in the pic's?

Jay

Those were the TJ Meshplate 45s - Mostly I use the Old RCA UX-245 Globes. From the 1930's

[mike stehr]

Homebrew 45 with James 6123HS OPT's.

There is something to be said about the sound of 45's.

[Erik Mandaville]

Jay:

There is a ton of history behind this. The amp in question is actually rather different from the others mentioned, the most obvious of which is probably the fact the Tucker's circuit incorporates a parallel-feed (shunt) output stage. However, like Eliano's DRD, it also uses direct-coupling between the two stages, as well as a different plate-load approach for the input (as opposed to the ubiquitous plate resistor).

In other words, both the DRD and JT45 lack the also-more-common interstage coupling capacitor between input and output. Many, including me, have found the direct coupling, either between plate and grid between each half of the input and driver stage, or between the input plate and output grid (note the absence of a grid leak resistor on both the JT45 and DRD) translates into apparently improved frequency response (we can also call that 'speed' or transient response), clarity, presence, immediacy -- or however one might subjectively choose to describe a stronger illusion of listening to live music.

John Tucker's design, as far as the one I'm familiar with, also does not use vacuum-tube rectification, which, despite the strong tie many hold for vacuum tube rectifiers, may also contribute to the tightly controlled B+, which may in turn contribute to evidently very good frequency response at both poles. The JT also has a rather large bypass capacitor across the bias resistor on the 45 cathode. Larger caps in that locations can effect the low frequency cut-off point of the bandwidth of the circuit, and may contribute to this amp's apparent strong and controlled bass response in light of its comparatively small output power.

I built a 45 amp with two vintage globe 45s a family member sent me, and I agree it can sound exceptional, though to my ears its strength is in the midrange and upper frequencies -- that's a good thing since the vast majority of music I listen to lives in that particular area.

Also: Jack Eliano largely designed the Welborne DRDs. Eliano's first DRD design was a published schematic using the 300B triode, solid state rectifiers (which can sound superb, by the way).

There are those who have incorporated elements of both the DRD output stage (bypass capacitor common lift to B+) and parallel-feed coupling to the speaker -- both I and another forum member have done that with good results (IMO). However, the actual current path of that arrangement has been perplexing at times. What it boiled down to for me was a sound that had superb clarity and 'presence' without glare and etch that's painful to listen to for long periods.

Parallel-feed outputs have been around for such a long, long while. People like Dan Schmalle, John Tucker, Gordan Rankin, John Camille, and others have helped revive these antique-but-still-very-valid circuits for others. The Bottlehead parafeed amps are loved by many, and having built both the 2A3 and 45 DRD amps from Welborne Labs, I can say they are all quite good. One's 'cup-of-tea' sort of thing -- like everything in audio. I just recently finished a pair of 300B monoblocks using the Sophia Electric 300B and very old but wonderful sounding Philco 6SN7s. Superb sound with our Heresies and Lowthers, alike.

I appreciate and really enjoy the picture of the DIY breadboard, which may have battery bias or filaments, perhaps? Very cool.

Have fun,

Erik

[jcmusic]

Hi Erik,

Thanks so very much for the info in your post, it does shed some light on this subject. When you say you just finished some Sophia 300B's what exactly do you mean? You are using their tubes or their design or something else? My current amp is a Sophia Electric 300B MKII that I have been using since 2006, lovely amp really nice sound and looks really nice to boot!!!

Jay

[mike stehr]

I appreciate and really enjoy the picture of the DIY breadboard, which may have battery bias or filaments, perhaps?

Thanks. The filaments are AC heated, with the bias resistor and bypass cap from each filament transformer center tap to ground. A simple way around a null pot, and filament hum is non-objectionable with my Cornwalls. The LaScalas might be a different story...

B+ and the 6.3 volt heater tap is from a Heathkit DC tube supply. It's a 6SL7 SRPP, R/C coupled to the 45's. Coupling caps are Russian telfon military caps. Bypass caps for 6SL7 are Nichicon Muse 330uF. Decoupling caps for 6SL7 are Nichicon 100uF.

The 45 cathode bypass caps are 10uF Sprague Clorinal oil caps with 22uF Solen's bridged arcoss them. 45's are RCA ST's. The primary tap on the James OPT's used is 5K.

With 1500 ohm cathode resistors, the circuit seems to sound best at around 255 volts DC plate voltage. Seems low with tube dissipation at little over 5 watts, but sounds best to my ears over trying the plate voltage 275 volts DC.

I have no problem with low bass, but it's the midrange the 45 excells at.

[Erik Mandaville]

Jay:

It's a reasonably common design using Sophia Electric 300Bs. This amp is really outstanding, and I love the sound of the 300B in general. I also own the Sophia Electric Baby amp, and for the money is a superb value, very well built, etc. I was shocked at what they did with our Klipschorns -- the match was better than virtually every other amp I've used with them. The Transcendent SE OTL and T-16 were also really, really fabulous.

I have no doubt the Sophia Electric 300B MKII is outstanding. They're OPTs are worth the cost -- I know, that's what I got for these most recent amps.

Erik

[jcmusic]

The Transcendent SE OTL and T-16 were also really, really fabulous.

Erik,

Funny you should mention the Transcendent SE OTL amp, it is another I've always wanted to try in my system!!!

Jay

[Clipped and Shorn]

Hi Mike,

What is the deal with the plastic bags (transformers?).

-Sad Drench Poplin

[mike stehr]

Hi Mike,

What is the deal with the plastic bags (transformers?).

-Sad Drench Poplin

To keep from getting them scuffed and scratched.

[Erik Mandaville]

Clipped and Shorn

" What is the deal with the plastic bags (transformers?)."

I've done the same thing with plastic wrap. As described, it keeps them from getting damaged during the process of building.

Jay: The Transcendent OTLs have been responsible for the most obvious difference we have heard among those we've used. It's honestly a bit surprising that we don't have one yet, though I have put together a dozen or so kits for others. I completely rebuilt a T-16 for someone and it seemed to have much greater power than its specs would suggest. Even the SE OTL, with an output in the range of the 45 triode we've been discussing, is capable of pretty amazing LF response. In the case of both the Transcendent OTLs, it wasn't only the extension of bass that's impressive. Those things seem to have a really uncanny sense of grip and control in the low end, while balancing that very well with extended mids and highs.

While we don't yet have a Transcendent amp in our system, I can say without hesitation that they are among the very best we have heard. There have been some small ground loop issues that in the case of the T-16 is resolved very well with a small value resistor, and with the SE OTL an adjustment of the shield connections to ground on the inputs. However, having built several of those, I think I've stumbled on a cure that 'might' work well.

Like passive crossovers in multi-driver loudspeaker systems, output transformers are a sort of necessary compromise: The parallel-feed we've talked about is an improvement on that, IMO, and there is no doubt that transformer coupling can sound incredibly good. OTLs just sound quite different, to me, in a positive way. I have also tried the so-called 'upgrade' with more expensive capacitors, and found very little, if any whatsoever, change in sound character. Common metel film resistors, electrolytic capacitors, and PP capacitors work just fine, though of course one should use what one prefers. I suspect that's one of the nice things about the fact that there are so many brands of passive parts to choose from!

The SE OTL may not perform at its best with high order passive crossovers or where really high SPLs are needed/wanted. Wired for monoblock use, a pair of them on Klipschorns with play very loud.

Erik -- trying to figure out how to make paragraph breaks here!

[Cut-Throat]

Clipped and Shorn
" What is the deal with the plastic bags (transformers?)."

I've done the same thing with plastic wrap. As described, it keeps them from getting damaged during the process of building.

Jay: The Transcendent OTLs have been responsible for the most obvious difference we have heard among those we've used. It's honestly a bit surprising that we don't have one yet, though I have put together a dozen or so kits for others. I completely rebuilt a T-16 for someone and it seemed to have much greater power than its specs would suggest. Even the SE OTL, with an output in the range of the 45 triode we've been discussing, is capable of pretty amazing LF response.

In the case of both the Transcendent OTLs, it wasn't only the extension of bass that's impressive. Those things seem to have a really uncanny sense of grip and control in the low end, while balancing that very well with extended mids and highs.


While we don't yet have a Transcendent amp in our system, I can say without hesitation that they are among the very best we have heard.

There have been some small ground loop issues that in the case of the T-16 is resolved very well with a small value resistor, and with the SE OTL an adjustment of the shield connections to ground on the inputs. However, having built several of those, I think I've stumbled on a cure that 'might' work well.

Like passive crossovers in multi-driver loudspeaker systems, output transformers are a sort of necessary compromise: The parallel-feed we've talked about is an improvement on that, IMO, and there is no doubt that transformer coupling can sound incredibly good. OTLs just sound quite different, to me, in a positive way.

I have also tried the so-called 'upgrade' with more expensive capacitors, and found very little, if any whatsoever, change in sound character. Common metel film resistors, electrolytic capacitors, and PP capacitors work just fine, though of course one should use what one prefers. I suspect that's one of the nice things about the fact that there are so many brands of passive parts to choose from!

The SE OTL may not perform at its best with high order passive crossovers or where really high SPLs are needed/wanted. Wired for monoblock use, a pair of them on Klipschorns with play very loud.

Erik -- trying to figure out how to make paragraph breaks here!

For Paragraph breaks, just hit your 'Enter' Key. Or Cut and Paste my Quote of your Quote.

[Erik Mandaville]

Kevin:

I've been doing, but for some reason when I post it looks like one large paragraph.