Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: frank57 on March 31, 2021, 01:02:04 pm

Title: Here is the Hiwatt t20 schematic
Post by: frank57 on March 31, 2021, 01:02:04 pm

Well many years later I found this Hiwatt t20 schematic.People were looking for it with little success.

There was a topic I started here with fuzzy photos:https://el34world.com/Forum/index.php?topic=13795.0
Doesn't seem to have much in common with a classic Hiwatt at all.The buzzy hummy Hiwatt Custom 20 tube I have is way closer.
Hiwatt call the T20  "the original pedal amp" in their Hiwatt manual.Looks like the gain is some kind of pedal design?
I guess it's DC power on the filaments with a bridge and 3300uf cap?

Title: Re: Here is the Hiwatt t20 schematic
Post by: Willabe on March 31, 2021, 01:24:21 pm

Thanks for posting this.  :icon_biggrin:

I let Doug know and he'll put it in his schematic library.

Title: Re: Here is the Hiwatt t20 schematic
Post by: frank57 on March 31, 2021, 02:55:07 pm

I redrew the Hiwatt Custom 20 Tube schematic too. I might have posted it before, but  I think this one is a bit more finished and makes a lot more sense now for someone who might want to build it.The Hiwatt lead 20 is also very similar to it.

I redrew it using the dr504 schematic by M.Huss.

Title: Re: Here is the Hiwatt t20 schematic
Post by: Craftyjam on January 03, 2025, 12:37:07 am

Quote from: frank57 on March 31, 2021, 02:55:07 pm

I redrew the Hiwatt Custom 20 Tube schematic too. I might have posted it before, but  I think this one is a bit more finished and makes a lot more sense now for someone who might want to build it.The Hiwatt lead 20 is also very similar to it.

I redrew it using the dr504 schematic by M.Huss.

Hi there, quick question about this schematic.

All the descriptions of the custom 20 say that it only has 3 12ax7, your schematic shows 3 & 1/2.

Would the requlator triode for the LTP something you added the the schematic to make it just like a dr504?

Thanks!