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View Full Version : World Audio Designs 300b push-pull (original)


petrat
08-04-2016, 15:37
This is the original 300b push-pull power amplifier, offered by WAD as a kit ... the one with inter-stage transformers ... and written about in HiFi World here:
http://www.hi-fiworld.co.uk/index.php/world-audio-design/333-300b-amplifier-part-2.html?showall=1

This amplifier has two switchable modes, with and without feedback ... the latter providing the best sound imo.

I bought this last year, but found it had a few problems which needed sorting. It has now been professionally restored to a high standard, and is offered with a good set of TJ 300b Mesh-Plate valves, together with new 5687 and 6072 input/drivers. Also included are a set of old JJ 300b valves, which are still serviceable. The amplifier is currently set-up for 8 ohm speakers, but also has 4 ohm taps on the output transformers (reconfigurable).

Selling price £1250, incl. delivery / meet up within reasonable distance of Northampton (sorry, will not ship)

http://i1233.photobucket.com/albums/ff384/petrat56/Mobile%20Uploads/20160408_140522_zpsj5jgnfl5.jpg (http://s1233.photobucket.com/user/petrat56/media/Mobile%20Uploads/20160408_140522_zpsj5jgnfl5.jpg.html)

Work done on the amplifier includes:
* set to correct operating point / dissipation for TJ300b valves of 24Watts/valve ... not stressed / no mesh hotspots (previously set at 32 W, design norm is 28W)
* 11dB input attenuators fitted (Audio Note tantalums) to work better with active preamps (and also passives)
* replacement of old capacitors, incl. Mundorf ZNs coupling and Elna Silmics on cathode bypass
* hum reduction via: re-configuration of earthing arrangements; fitted DC supply on input/driver valves; shielded wire on input and feedback wires; etc.
* noisy humbucker potentiometers replaced
* cracked speaker sockets replaced with silver-plated, heavy-duty Audio Notes
After all that (and more!), the amp owes me £1500, but is now functioning beautifully. PM me with questions ...
walpurgis
08-04-2016, 15:50
That looks really nice Peter. Bet it sounds great.
Ali Tait
08-04-2016, 16:34
This is a very very good amp indeed - a total bargain at the price given the SQ on offer IMHO.
lordmortlock
09-04-2016, 09:16
Nice. Who did the work Peter?
petrat
09-04-2016, 09:32
Deco Audio fitted attenuators and DC supply for the input stage, then David Coe did everything else.
NRG
09-04-2016, 13:22
These are outstanding amplifiers, well worth the money especially with all the upgrade work! Goog luck with the sale!
montesquieu
09-04-2016, 15:07
You'll be unsurprised to know Peter that I had one of these for a while ... was superb with Tannoy 15in MGs - that sweet but punchy 24w should be bang on perfect for MGs all round.

I doubt you could buy the bits these days for an amp like this without really breaking the bank. Mine was John Caswell's personal amp for many years and he had built it without feedback after coming to the same conclusions as you.

Lovely bit of kit and surely will find a home among the Tannoy fraternity here. (Shoud also be stellar with Quad ESLs).
petrat
09-04-2016, 20:55
Now you mention it, Tom, it'd be really interesting to hear it with some Quad ESLs. Likely be a great match, as the amp gives a lovely, deep soundstage, with excellent transparency and tonality.

I've also been using it with my Harbeth P3ESRs, and they really gell superbly.
Ninanina
09-04-2016, 20:59
Now you mention it, Tom, it'd be really interesting to hear it with some Quad ESLs. Likely be a great match, as the amp gives a lovely, deep soundstage, with excellent transparency and tonality.

I've also been using it with my Harbeth P3ESRs, and they really gell superbly.

I'd be very interested in the amp if I wasn't so strapped for cash at the moment... :doh:
Marco
09-04-2016, 21:08
Well, if you gave up your cucumber fetish.... :eyebrows: ;)

Marco.
Ninanina
09-04-2016, 21:10
Well, if you gave up your cucumber fetish.... :eyebrows: ;)

Marco.

That will never happen Marco... I love cucumbers and spend a lot of cash on them :eek::eek:
Marco
09-04-2016, 21:14
:lolsign:

Marco.
petrat
12-04-2016, 08:38
http://i1233.photobucket.com/albums/ff384/petrat56/Mobile%20Uploads/20160412_092422_zpszsraeo88.jpg (http://s1233.photobucket.com/user/petrat56/media/Mobile%20Uploads/20160412_092422_zpszsraeo88.jpg.html)

http://i1233.photobucket.com/albums/ff384/petrat56/Mobile%20Uploads/20160412_092501_zpsvx5kxvdo.jpg (http://s1233.photobucket.com/user/petrat56/media/Mobile%20Uploads/20160412_092501_zpsvx5kxvdo.jpg.html)

http://i1233.photobucket.com/albums/ff384/petrat56/Mobile%20Uploads/20160412_092756_zps3vtmoeve.jpg (http://s1233.photobucket.com/user/petrat56/media/Mobile%20Uploads/20160412_092756_zps3vtmoeve.jpg.html)
WESTLOWER
15-04-2016, 12:43
Peter you have PM
petrat
16-04-2016, 16:56
Bump
petrat
17-04-2016, 19:18
NOW SOLD.
montesquieu
17-04-2016, 19:42
NOW SOLD.


Who's the lucky fella?
petrat
17-04-2016, 20:58
Adam (post 14). He brought his Kudos C2 speakers over, which turned out to be an excellent match with the 300b. About half way through the evening, I almost decided to keep the amp and make him an offer for the speakers instead :lol:
montesquieu
17-04-2016, 21:36
Adam (post 14). He brought his Kudos C2 speakers over, which turned out to be an excellent match with the 300b. About half way through the evening, I almost decided to keep the amp and make him an offer for the speakers instead :lol:

Nice. It's cool when stuff works out :)
WESTLOWER
17-04-2016, 23:21
Peter, many thanks for such an accommodating Demo of the Amp, it's getting late and I still can't pull myself from the music his sweet amp if pushing through the Kudos C2s..i have to be up at 6am..I thinks i could still be here! The amp is wonderful, the detail in the presentation, especially with the Vinyl is simply Jaw dropping. I don't really have words for it. Again thanks for the opportunity of owning a great thing. I'll PM you tomorrow am..
Damn this is sweet!..Nice Rat BTW!
petrat
18-04-2016, 22:50
..Nice Rat BTW!

http://i1233.photobucket.com/albums/ff384/petrat56/Mobile%20Uploads/20160405_064820_zpsyhir76v7.jpg (http://s1233.photobucket.com/user/petrat56/media/Mobile%20Uploads/20160405_064820_zpsyhir76v7.jpg.html)
WESTLOWER
19-04-2016, 10:12
It has a certain Character I give you that!!
struth
19-04-2016, 16:14
Not really my favourite animal that. Guess he or she has a cute side though for you Peter.
petrat
19-04-2016, 16:59
Actually, she's not a rat ... she's a Degu ... a Chilean ground-squirrel, related to the Chinchilla ... and she's eight years old, and absolutely delightful.