Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: DummyLoad on July 06, 2014, 05:42:44 pm

Title: good clean fun...
Post by: DummyLoad on July 06, 2014, 05:42:44 pm: this is on one of the breadboards. very nice sounding alternative to a twin reverb, sans reverb, of course.

i'm driving a custom built closed back 15" & 12" cabinet loaded with a EVM-15L and a EVM-12L.

--pete
Title: Re: good clean fun...
Post by: kagliostro on July 07, 2014, 02:50:43 am: Hi DummyLoad

Nice Standel divagation

Please, can you explain what is happening between V2b and V3a, I'm not able to follow the path of the signal

I have a lack of memory and don't remember how that part of the circuit acts

Franco

Quote
EDIT: OK, now I remembered something, some time ago I asked about the 25L15 schematic draw by Napkin in this tread

http://el34world.com/Forum/index.php?topic=14263.msg148981#msg148981 (http://el34world.com/Forum/index.php?topic=14263.msg148981#msg148981)

and Sluckey and HotBluePlates give me answers about
Title: Re: good clean fun...
Post by: HotBluePlates on July 07, 2014, 02:55:34 pm: Quote from: DummyLoad on July 06, 2014, 05:42:44 pm
this is on one of the breadboards. very nice sounding alternative to a twin reverb, sans reverb, of course.

That looks familiar! I don't know if you get the same ultra-clean with that, but I imagine you could...

Quote from: kagliostro on July 07, 2014, 02:50:43 am
Please, can you explain what is happening between V2b and V3a, I'm not able to follow the path of the signal

V2a output goes to V3a input.
V3a has 2 outputs; the main output goes to V3b.
The other V3a output goes left to the tone circuit and V2b, and is a feedback loop.
V2b alters V2a's response due to the shared cathode resistor.
Title: Re: good clean fun...
Post by: kagliostro on July 07, 2014, 03:07:27 pm: Thanks HotBluePlates

I remembered your previous explanation, this may be useful for those who give a look to the schematic for the first time

and are not able to follow the path of the signal as I wasn't

Franco
Title: Re: good clean fun...
Post by: DummyLoad on July 07, 2014, 03:25:56 pm: That looks familiar! I don't know if you get the same ultra-clean with that, but I imagine you could...

somewhat: mostly same as the hand drawn preamp schema floating around in cyberspace. many mods, PS, PI, no countour control, no cut control, fixed bias, NFB added, 100W of EL34 LOUD.

i was tempted to use 4 x KT88 in cathode bias, pentode mode, but the hassle of the PS requirements took precedent, so the easy_to_drive EL34 won in the end because i had the parts to make it happen.

--pete
Title: Re: good clean fun...
Post by: kagliostro on October 13, 2014, 11:10:28 am: Ciao Pete

Have you a Layout for this beauty ?

Franco
Title: Re: good clean fun...
Post by: DummyLoad on October 13, 2014, 04:25:06 pm: Quote from: kagliostro on October 13, 2014, 11:10:28 am
Ciao Pete

Have you a Layout for this beauty ?

Franco

ciao franco, i started one but the interested party lost interest when gave him a price. i'll finish it for you: give me a day or two...

--pete
Title: Re: good clean fun...
Post by: kagliostro on October 13, 2014, 05:10:27 pm: Oh, many thanks Pete

Thank you for the offer to complete the job you have available, I would not give you too much trouble

Franco