Search found 136 matches

by ACPEN
Sat Jan 13, 2024 7:28 pm
Forum: Valves
Topic: PP3521 idht
Replies: 95
Views: 19636

Re: PP3521 idht

How do you power them? I've used ac from a transformer or full wave dc doubler from 7.5v transformer. Neither caused hum problems.
by ACPEN
Sat Jan 13, 2024 5:33 pm
Forum: Valves
Topic: PP3521 idht
Replies: 95
Views: 19636

Re: PP3521 idht

Await resultswith interest- never tried doubling up with PP3521.
I see Langrex still have some ( unless you've just bought them up!)
by ACPEN
Sun Jan 07, 2024 7:46 am
Forum: Valves
Topic: PP3521 idht
Replies: 95
Views: 19636

Re: PP3521 idht

Hi Paul
See you're back onto this ( disguised as GM70)
Just to say I persevered with it and via trying AC/SP3's, settled on the later SP61's as a good option, being MAZDA and good spec.
270 R bias, 50k load. 105v screen.
Worth a try...and very cheap - £4.00 @ Langrex!
by ACPEN
Sat Sep 23, 2023 5:50 pm
Forum: Valves
Topic: PP3521 idht
Replies: 95
Views: 19636

Re: PP3521 idht

Ooops!
E810F or E180F pin compatible if you leave pin 6 disconnected.
by ACPEN
Sat Sep 23, 2023 5:44 pm
Forum: Valves
Topic: PP3521 idht
Replies: 95
Views: 19636

Re: PP3521 idht

Just to say that have broken with tradition (my own) and have tried a 'modern' approach as a driver - an E810E ! in pentode mode - 10k load, 150v S.G, 100R bias. 200v ht, runs at approx 14mA - sounds Good, certainly worth a try if anyone is still looking for driver options for the PP3521 triode. To ...
by ACPEN
Sun Aug 27, 2023 4:01 pm
Forum: Everyones Projects
Topic: SE output Xfrmr as anode load?
Replies: 5
Views: 2880

Re: SE output Xfrmr as anode load?

Thanks Greg,
Didn't know that...
by ACPEN
Sun Aug 27, 2023 2:38 pm
Forum: Everyones Projects
Topic: SE output Xfrmr as anode load?
Replies: 5
Views: 2880

Re: SE output Xfrmr as anode load?

Since the replies to this post I have been playing with a Hammond 20H 20mA choke as anode load for an ML4 driving a KT8c - surprisingly good results but as expected being rather challenged at low audio frequencies.... Wondered if anyone might know of a pair of Hammond 156C chokes looking for a new h...
by ACPEN
Wed Aug 23, 2023 5:57 pm
Forum: Everyones Projects
Topic: SE output Xfrmr as anode load?
Replies: 5
Views: 2880

Re: SE output Xfrmr as anode load?

Thanks Paul,
Yes of course, I actually checked the inductance after sending the email....

CCS it is then!

Thanks.
by ACPEN
Wed Aug 23, 2023 9:18 am
Forum: Everyones Projects
Topic: SE output Xfrmr as anode load?
Replies: 5
Views: 2880

SE output Xfrmr as anode load?

Any one tried using Hammond 125BSE output's as load for driver stage at around 20mA.....any practical experience?
Or, waste of time...
Thanks.
by ACPEN
Wed Apr 26, 2023 7:45 am
Forum: Everyones Projects
Topic: The Newton 300B
Replies: 242
Views: 106775

Re: The Newton 300B

Haven't built a PP amp since 1962 - but have you thought of the 6Y6, a very capable driver......
by ACPEN
Sat Apr 22, 2023 10:09 am
Forum: Valves
Topic: PP3521 idht
Replies: 95
Views: 19636

Re: PP3521 idht

Yes, I like the PP3521 and have done for some time, also the PEN3520 which although a pentode makes a reasonable sub and can be a direct plug in. I too have used the USA types, UY-227 and UY- 224 (tetrode) but came back to the British types of the same period, MH4 being also from the 30's. Be intere...
by ACPEN
Fri Apr 21, 2023 2:11 pm
Forum: Valves
Topic: PP3521 idht
Replies: 95
Views: 19636

Re: PP3521 idht

Hi - I too have tried the PP3521 in SE using drivers recommended to drive PX4's but was never happy with the results - these were the H42 and AC/S2PEN types. Since seeing this thread I decided to try again using MH4's as drivers- good, but slightly low gain, I then tried MH4's in mu follower configu...
by ACPEN
Fri Mar 03, 2023 12:25 pm
Forum: Everyones Projects
Topic: PT15 se A2 operation
Replies: 4
Views: 4254

Re: PT15 se A2 operation

Sketch of cct - told you it wasn't anything special!

Valves are 6SJ7 6Y6 PT15
by ACPEN
Thu Mar 02, 2023 4:53 pm
Forum: Everyones Projects
Topic: PT15 se A2 operation
Replies: 4
Views: 4254

Re: PT15 se A2 operation

Hello Mike It is a long time Tonbridge I think.....Danbury was a loss, still have transformers working! I'll do a sketch (sorry no cgi here!) It's basically just the usual A2 format but using +ve drive to g1 + g2 strapped - works with most transmitter pentodes to varying degrees. Nothing new or spec...
by ACPEN
Thu Mar 02, 2023 11:44 am
Forum: Everyones Projects
Topic: PT15 se A2 operation
Replies: 4
Views: 4254

PT15 se A2 operation

Recently cobbled a 2E22 se A2 amp (g1+g2 driven) - excellent results. On a whim I substituted PT15's - now like many, I've used PT15's in class A with good results but not A2. Taking care not to overrun g1, results are comparable to the 2E22. Also careful to connect g3 to filament mid point or can o...