Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bnwitt on October 22, 2014, 11:56:30 am

Title: Bad Cat Hot Cat 15 Schematic
Post by: bnwitt on October 22, 2014, 11:56:30 am

Does anyone in here have a schematic and/or other details on the Bad Cat Hot Cat 15 amplifier?  I just picked up one of the Chinese made Bad Cat Cougar 15 amps that I want to gut and change to the Hot Cat 15 or the Vox Handwired AC 15.  Thanks in advance
Barry

Title: Re: Bad Cat Hot Cat 15 Schematic
Post by: tubenit on October 22, 2014, 12:06:50 pm

Maybe this with only 2 EL84's ??

http://el34world.com/charts/Schematics/files/_Miscellaneous/badcat_hotcat_30.pdf (http://el34world.com/charts/Schematics/files/_Miscellaneous/badcat_hotcat_30.pdf)

With respect, Tubenit

Title: Re: Bad Cat Hot Cat 15 Schematic
Post by: bnwitt on October 22, 2014, 05:58:45 pm

Thanks Tubenit.  I do appreciate it.  I've got that one.  I'm sure the two amps are similar.  I was hoping to find the 15 schematic to make sure.  I'm assuming the 15 has EL84 power tubes though

Title: Re: Bad Cat Hot Cat 15 Schematic
Post by: bnwitt on October 23, 2014, 10:16:01 am

Is it just me or does the PI and MV in that schematic look odd?

Title: Re: Bad Cat Hot Cat 15 Schematic
Post by: sluckey on October 23, 2014, 11:24:03 am

Quote from: bnwitt on October 23, 2014, 10:16:01 am

Is it just me or does the PI and MV in that schematic look odd?

The PI is just a standard garden variety LTP. The MV is a bit odd. It will not vary the signal very much and won't even get close to zero volume.

Title: Re: Bad Cat Hot Cat 15 Schematic
Post by: shooter on October 23, 2014, 11:29:14 am

I'll 2nd odd on the pi, the MV is one I've seen a couple times.  by other threads it appears this type is "less liked".

Title: Re: Bad Cat Hot Cat 15 Schematic
Post by: sluckey on October 23, 2014, 03:44:52 pm

Quote from: shooter on October 23, 2014, 11:29:14 am

I'll 2nd odd on the pi...

What's odd about it? I'm looking at the schematic posted by tubenit. Maybe I'm looking at the wrong schematic?

Title: Re: Bad Cat Hot Cat 15 Schematic
Post by: 2deaf on October 23, 2014, 10:39:11 pm

Quote

Is it just me or does the PI and MV in that schematic look odd?

The four-stage pre-amp, the 10K screen resistors, and the additional 100uf for the plates on SS rectifier all clearly indicate an amp designed for extreme overdrive.  A master volume that doesn't work fits right in.  Or maybe he meant for the 220K to go to the 100K pot and the wiper to go to "F".

Title: Re: Bad Cat Hot Cat 15 Schematic
Post by: shooter on October 24, 2014, 08:50:02 am

You "fixed" the odd for me by stating the obvious that I missed, LTP.  I got hung up on each side of the PI being fed by 2 dif channels n missed what the PI actually was.
thanks again

Title: Re: Bad Cat Hot Cat 15 Schematic
Post by: sluckey on October 24, 2014, 09:12:59 am

Quote

...each side of the PI being fed by 2 dif channels...

That's fairly common in amps with a LTP if they don't use one input for NFB. Marshall 1974 (commonly called 18 Watt), Vox AC-15, and some AC-30s do it. And the Matchless Chieftain even uses the second input to mix reverb back into the dry signal. That second grid on the LTP is up for grabs for a lot of ideas, but it it's not going to be used for anything, it should sit at AC ground, usually via a cap to ground.

Title: Re: Bad Cat Hot Cat 15 Schematic
Post by: bnwitt on October 26, 2014, 10:09:35 am

Steve,
Thanks for that explanation.  I did not know that. :smiley:

Title: Re: Bad Cat Hot Cat 15 Schematic
Post by: bnwitt on October 28, 2014, 10:33:23 am

Ok so I guess I'm stuck with the 30 watt schematic for this amp but evidently there are some errors in that schematic.  Below is a link to a thread that has user Loudthud pointing this out:

http://music-electronics-forum.com/t19757/ (http://music-electronics-forum.com/t19757/)

Barry