Has anyone built a DRD Amp

one example at DRD developer Jack Eliano's home, but IIRC in might have also had some weird driver tube as well?

Generally, the DRD idea makes for a quieter Single Ended Directly Heated Triode Amp. Helps to get the Power Supply OUT of the signal path (or so it is said).

DRD cap becomes the critical element.

Downside, for me at least, and I have done a 'DRD Mod' of sorts to my 300B single ended amps by removing the resistor bypass cap on the 300B and replacing it with a HUGE vintage oil cap from the directly heated cathode of the 300B to B+, is that amps built by Jack Eliano tend to be clean, clear but lacking in the 'SET Magic', whatever that might be.

Maybe SET Magic is just distortion?

First they came for the dumb-asses
And I did not speak out
Because I was not a dumb-ass

RE: No, but I have heard more than one of them..., posted on October 4, 2020 at 07:08:01

panheadchopper
Audiophile

Posts: 12
Location: Pittsburgh
Joined: February 1, 2015

I have this 2A3 DRD amp I built years ago.. It's a little different... I'll draw up the schematic and post it.. It uses a J52P voltage/driver tube.. I didn't expect it to be this good.. It sounds amazing and is very powerful for a 2A3.. I've been trying countless circuits and tube arrangements to beat this thing.. The only ones that come very close is other 2 stage amps.. I'm not sure about the "magic" SE sound being distortion because the 2 stage amplifiers sound very natural, clean, detailed, transparent, and dynamic.. Any of the 3 stages I've tried with various voltage amps and drives sound somewhat opaque, colored, and fatiguing.. Some of the tubes I've tried in countless differnt arrangements are 76, 6SN7, 6350, 3687, 7110, 6N6, 6H30, 7308.. They always sound ok but not "magic"

Yes 2 pairs - A pair of DRD45s and a pair of DRD45 Starchiefs .............., posted on October 4, 2020 at 07:48:22

Cut-Throat
Audiophile

Posts: 18285
Location: Minneapolis - St.Paul Area
Joined: September 2, 2000
Contributor
Since: May 16, 2021

I built a pair of DRD45s when they first came out about 20 years ago. I loved the sound! --- I had a pair of Welborne 2a3 Moondogs at that time, and the new DRD45s were superior in terms of 'SET Magic' and much quieter. Probably the 45 tube was the Reason.

I liked the DRD45s enough that when Welborne announced his 'No Holds Barred' DRD45 amps called the Star Chiefs, I built those also. The main difference in this design was the PS10 Voltage Regulator. I am still running these Amps after 17 years. -- I have not thought about upgrading Amplifiers since owning these. Here are some Pics of my Star Chief DRD45s in various stages of building.

RE: Yes 2 pairs - A pair of DRD45s and a pair of DRD45 Starchiefs .............., posted on October 4, 2020 at 08:04:35
panheadchopper Audiophile Posts: 12 Location: Pittsburgh Joined: February 1, 2015	Whoa, that's beautiful.!! I'll have to take some pics of mine.. It's more industrial looking.. lol

Thanks! And here is the Finished Product, which are my Main Amps Today........, posted on October 4, 2020 at 08:10:21

Cut-Throat
Audiophile

Posts: 18285
Location: Minneapolis - St.Paul Area
Joined: September 2, 2000
Contributor
Since: May 16, 2021

Bubinga Wood Bases. -- Those 1930s Globe RCAs last for Decades. Even with Daily Use.

RE: No, but I have heard more than one of them..., posted on October 4, 2020 at 08:25:03
panheadchopper Audiophile Posts: 12 Location: Pittsburgh Joined: February 1, 2015	Here's the schematic of my build

RE: No, but I have heard more than one of them..., posted on October 4, 2020 at 09:20:13
panheadchopper Audiophile Posts: 12 Location: Pittsburgh Joined: February 1, 2015	Ham show chassis

RE: No, but I have heard more than one of them..., posted on October 4, 2020 at 09:21:15
panheadchopper Audiophile Posts: 12 Location: Pittsburgh Joined: February 1, 2015	Underside

RE: Yes 2 pairs - A pair of DRD45s and a pair of DRD45 Starchiefs .............., posted on October 4, 2020 at 21:42:34
Sidewinder Audiophile Posts: 254 Joined: April 13, 2001	Hi, Nice amp. Can you share the schematic to your Star Chief amp? Regards, David

RE: No, but I have heard more than one of them..., posted on October 4, 2020 at 21:49:19

91derlust
Audiophile

Posts: 1101
Joined: December 25, 2014

A little clarification. The "Ultrapath" element of the DRD design changes the current path and apparently removes some of the PS and cathode bypass capacitor flavour. The ultrapath capacitor is important and the amp stage has less, not more, PSRR because PS noise is injected into the cathode then amplified. If your PS has sufficiently low noise and you can find a good-sounding ultrapath capacitor of sufficiently high voltage, go for it. A partial ultrapath (or WE connection) type arrangement with correctly-size ultrapath capacitor can improve PSRR and apparently can sound rather nice. Or just use the traditional approach with a high-quality cathode bypass capacitor (does not need to be high voltage) and a decent PS cap.

The main benefit, as I see it, of DRD - and most monkey-style - amps is the direct-coupling with protection of the output tube from failure of the input tube.

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

Here you go .................., posted on October 5, 2020 at 05:33:54
Cut-Throat Audiophile Posts: 18285 Location: Minneapolis - St.Paul Area Joined: September 2, 2000 Contributor Since: May 16, 2021	Schematic

RE: Yes, posted on October 9, 2020 at 11:11:57
deafbykhorns Audiophile Posts: 1067 Location: Florida Joined: October 17, 2003	Didn't like the sound but it may of been the cheap iron I purchased from a guy up North off Ebay....

RE: Yes, posted on October 9, 2020 at 17:05:33

drummerwill
Audiophile

Posts: 965
Location: St Louis Mo.
Joined: January 7, 2003

What made you think , "the Iron was Cheap " ?

Willie

RE: Yes, posted on October 12, 2020 at 12:48:36
deafbykhorns Audiophile Posts: 1067 Location: Florida Joined: October 17, 2003	I built another amp later with the same tubes (except DRD) using Dave Slagles iron and it was night and day difference.

SET Asylum

Has anyone built a DRD Amp

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