Search found 123 matches

by David
Thu Dec 21, 2017 3:16 pm
Forum: Valves
Topic: Feedback with Battery Bias
Replies: 24
Views: 19362

Re: Feedback with Battery Bias

That's a very good point! I'll check those Black Gates too.......
by David
Mon Dec 18, 2017 4:08 pm
Forum: Valves
Topic: Feedback with Battery Bias
Replies: 24
Views: 19362

Re: Feedback with Battery Bias

Hi Nick,
The resistors were Arcol metal-cased wirewound attached to the chassis and rated at 50 watts. So the 100 watts current seems consistent with failure and the failed transformer.
David
by David
Mon Dec 18, 2017 1:53 pm
Forum: Valves
Topic: Feedback with Battery Bias
Replies: 24
Views: 19362

Re: Feedback with Battery Bias

Hi Mike, Unfortunately there is no evidence of a 300 fault. There was no change in the music output before the bang, eg the usual crackle or pop you get with 300b failure, nor any sign of redplating or other sign of failure. All four valves still work perfectly. It seems to point more to an output t...
by David
Sun Dec 17, 2017 11:50 am
Forum: Valves
Topic: Feedback with Battery Bias
Replies: 24
Views: 19362

Re: Feedback with Battery Bias

So, I checked everything out and the casualties are the two large Arcol wire wound resistors and one half of the output transformer on one channel which has gone open circuit. I'm pretty sure the blow up occurred when the feedback was connected the correct way round as the amp was working with no fe...
by David
Sun Dec 10, 2017 6:33 pm
Forum: Valves
Topic: Feedback with Battery Bias
Replies: 24
Views: 19362

Re: Feedback with Battery Bias

Hi All, There was nothing strange that a photo would have revealed about the way battery bias had been installed. It was in the standard way as was the resistor put in in place of the battery bias as described. The amp is a clone but uses exactly the same circuit as the kit. The only mod done was to...
by David
Fri Dec 08, 2017 5:17 pm
Forum: Valves
Topic: Feedback with Battery Bias
Replies: 24
Views: 19362

Re: Feedback with Battery Bias

Hi All, The amp has worked perfectly for 5 years. Over that time I’ve tried cathode bypass capacitor, no bypass capacitor and then landed on battery bias with no issues and glorious sound. The only issue now and all connections are correct is the feedback squeal which occurs when using battery bias ...
by David
Mon Dec 04, 2017 7:57 pm
Forum: Valves
Topic: Feedback with Battery Bias
Replies: 24
Views: 19362

Re: Feedback with Battery Bias

1-300Bcircuit.pdf Hi Nick, here's the circuit. The amp wrks perfectly with or without cathode bypass cap, some preferring the sound without and also with battery bias. I used the original circuit values and all I get is feedback with the switch in the feedback on position, the amp behaving perfectl...
by David
Sun Dec 03, 2017 6:56 pm
Forum: Valves
Topic: Feedback with Battery Bias
Replies: 24
Views: 19362

Re: Feedback with Battery Bias

Hmm, I get screaming feedback connected like this.............
by David
Thu Nov 23, 2017 7:55 am
Forum: Valves
Topic: Feedback with Battery Bias
Replies: 24
Views: 19362

Re: Feedback with Battery Bias

Thanks Nick
by David
Wed Nov 22, 2017 9:06 pm
Forum: Valves
Topic: Feedback with Battery Bias
Replies: 24
Views: 19362

Feedback with Battery Bias

Hi All,
on the WAD300b pp the cathode resistor is 1k and feedback is applied at the cathode end of a 33r lift resistor. If I'm using battery bias does anyone know if I can connect the battery minus to the 33r lift resistor and apply feedback in the same way?
Thanks
by David
Sun Jan 31, 2016 1:27 pm
Forum: Everyones Projects
Topic: Calling All WAD 300b Stereo Owners
Replies: 3
Views: 4247

Re: Calling All WAD 300b Stereo Owners

Ok, the information given me that a transformer set supplied for a WAD 300b stereo clone was that from a WAD 5881 amp was unfortunately incorrect. I contacted Geoff from SP Wound the supplier and he stated that WAD changed the supplier at some stage, and obviously the spec, but Geoff had supplied to...
by David
Thu Jan 28, 2016 10:50 am
Forum: Buying and Selling
Topic: Rare Amplifon 6C33 40 watts per channel amp
Replies: 2
Views: 4191

Re: Rare Amplifon 6C33 40 watts per channel amp

Now Phillip for one whose changes in amps nearly equals one's changes of underwear that's a strange question :D There's more than one gourmet meal out there and my house was stacked full of some fine food in the shape of 845 DSEs and a WAD 300b stereo. The poor old Amplify was being under-utilised. ...
by David
Thu Jan 28, 2016 10:45 am
Forum: Everyones Projects
Topic: Calling All WAD 300b Stereo Owners
Replies: 3
Views: 4247

Calling All WAD 300b Stereo Owners

Hi Guys, I have started a new London-based business servicing, upgrading and doing new builds of mainly valve amps, although I am also doing Dacs, CD players and the odd solid state amp too. But that’s not why I am writing. I have serviced several WAD 300b clones, some of which I have sourced, and n...
by David
Sun Dec 13, 2015 12:43 pm
Forum: Buying and Selling
Topic: Rare Amplifon 6C33 40 watts per channel amp
Replies: 2
Views: 4191

Rare Amplifon 6C33 40 watts per channel amp

For sale very rare Polish made Valve Amplifier Amplifon Audio WT-40 in full working order and great condition .RRP was around 3000 euro .This amp uses a quartet of 4 x 6C33 triodes on the output stage. The amp was serviced in April 2014 but did not meet my high standards of service so the following ...
by David
Wed Jun 11, 2014 1:18 pm
Forum: Assorted Stuff
Topic: Adding sub out rca sockets to valve amp
Replies: 9
Views: 5873

As I said on another forum to you, I wouldn't connect what is 6.8kohms on my sub across a valve amp input with somewhere around 100k resistance (without a buffer). Easy enough to patch up before going permanent to do a reality check and see what the sonic results are.......