Impressions of Ron Welbornes DRD amps

[bumpy]

Has anybody owned or have an impression of Ron Welborne's DRD 45 or 300B valve amplifiers. I believe his Company has now folded, but what are the amps like? In particular, is it a robust technology?

[bumpy]

So I guess they're not very popular round here.

[hifi_dave]

Never heard of them.

[topoxforddoc]

Quite popular in the US, but I haven't heard one here

[IslandPink]

Can't offer hand-on comment, but just had a look at the circuit to remind myself of the details.
http://www.enjoythemusic.com/magazine/equipment/0206/welborne_laboratories_300b.htm
The plus-point is the direct-coupling of the driver to the output valve, which should improve transparency & tone at low signal levels and remove one high-pass filter (typically 5Hz or lower ) from the coupling cap & grid-leak.
On the downside, you get another high-pass filter from the limited inductance of the choke. So sound quality ( in the bass more than elsewhere ) would depend on the inductance of that choke in his implementation. Also for 300B circuit, I would say ( from experience ) than a 6N1P with about 10ma is marginal for properly driving a 300B grid. I have found 17 or 18ma to be necessary to get full treble transparency from a 300B, although removing a coupling cap should help quite a bit.
In this respect it's not the worst offender out there - I have seen much worse drivers for 300B's in commercial amps. On the 45 I'm sure it works very well - if it's the same driver - you can drive a 45 with a bit of wet string.
Try Audio Asylum 'Tubes' or 'Tube DIY' sections for some user comment - should be something over there.

[SteveTheShadow]

As far as I am aware Ron Welborne ceased trading a while ago.
I and a few others have, however built our own DRD amplifiers and it has to be said that they do sound very good; having a nice direct sound quality about them. If you are looking to buy a Welborne Labs amp off someone, then it would be a good buy.

Here is the one I built around 8 years ago. It's long gone now, since I moved onto push-pull pentode amps that give more power but the DRD concept is fine.

https://dl.dropboxusercontent.com/u/7181882/drdlegs.jpg

here is a link to Jack Elliano's Electraprint site, where you can find a few schematics for DRD amps.

http://electra-print.com/300bdrd.php
The link leads to a 300b amp but he also has a 2A3 and a 45 schematic.

[RobsterD]

Hi
I had both the 45 and the 300B ...I bought them both off Greg at Gpoint Audio,both nice amps :-) He knows lots about them

http://i886.photobucket.com/albums/ac68/RobsterD/CIMG1507_zps648fd01c.jpg

These rocked with 'em

http://i886.photobucket.com/albums/ac68/RobsterD/9b0195b4a4086d0d7e6be357be1d4b3a_zps8110cdfb.jpg

http://i886.photobucket.com/albums/ac68/RobsterD/CIMG1329_zps07f3ff0f.jpg
http://i886.photobucket.com/albums/ac68/RobsterD/CIMG1323_zps9c2a491b.jpg

[CornishPasty]

Seeing those pics made me think I have a write up of the DRD bought as a kit, HFN I think. I'll see if I can find it if you're interested.

[Clive]

Seeing those pics made me think I have a write up of the DRD bought as a kit, HFN I think. I'll see if I can find it if you're interested.
Probably that's my article from 2004. They were very nice amps and well thought out in terms of build. It's such a shame Ron went...what can I say....down on his luck I suppose.

[bumpy]

Probably that's my article from 2004. They were very nice amps and well thought out in terms of build. It's such a shame Ron went...what can I say....down on his luck I suppose.

Allegedly he left a lot of very disappointed customers out of pocket

[6L6]

Has anybody owned or have an impression of Ron Welborne's DRD 45 or 300B valve amplifiers. In particular, is it a robust technology?

I assembled a handful of them back in the day for Ron, and they are very nice indeed.

As for "robust technology", yes, of course it's robust, as the pieces that make the DRD circuit are a large resistor, a large capacitor, and a choke. It's the arrangement and balance of those (common) pieces that makes the circuit, not any particular, proprietary, or unique widget.

If you have a chance to get the amps, and have speakers that are appropriate, by all means do. :D

[bumpy]

Thanks guys for your help.

OK, just got back after a 4 hour round trip, and I have in my possession a pair of DRD 45's :) They auditioned beautifully.

On the top of each is a potentiometer like that shown in the picture (not mine). I was told the 45 valves are self biasing, is that the case? If so, is that a hum pot and how do you adjust it?

http://i1208.photobucket.com/albums/cc362/gregdee/Welborne%20amps/_D3_2678_zps729f82df.jpg

[bumpy]

X

[6L6]

I doubt it's a hum pot, that wouldn't be cricket with modern mains codes. Can you pop the bottom plate off and take a couple well-lit, in-focus photos and post them?

[bumpy]

I doubt it's a hum pot, that wouldn't be cricket with modern mains codes. Can you pop the bottom plate off and take a couple well-lit, in-focus photos and post them?

OK, will do that this morning.

[bumpy]

Here you go. Pictures of the workings my 'new' amp.

[Firebottle]

Yes it's a hum pot. Or a 'humbucker' as they are sometimes known.

Just adjust it for minimum hum on the output. It won't necessarily get rid of all the hum, just put your ear to the speaker and adjust for min.

:)

[bumpy]

Yes it's a hum pot. Or a 'humbucker' as they are sometimes known.

Just adjust it for minimum hum on the output. It won't necessarily get rid of all the hum, just put your ear to the speaker and adjust for min.

:)

Thanks
Am I right in thinking it will have a null point when adjusting it?

[Firebottle]

Null maybe not, but here should be a minimum.

[bumpy]

Null maybe not, but here should be a minimum.

Thank you Alan

All on and playing nicely. At minimum there is a tiny/tiny amount of hum, but all is well