Badcat Hotcat Preamp

[TIMBO]

Hi guy's, Have any of you used this preamp, I read that the circled components may be wrong:-
The 5.1M and 1M resistors may need to be swapped
The 68k incorrect position
The cathode cap not required if the grid leak resistors are right
The .0015 caps are adequate for this application

I would like to use this preamp and I just want to confirm that this schem is correct and if anyone can comment on the delivered sound.Thanks

[Tone Junkie]

Tim put it up in gif. or pdf. i could look, sch. doesnt work here at work (LOL).
Thanks Bill

[PRR]

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[TIMBO]

Thanks PRR. 

[PRR]

0.0015uFd driving the Gain pot area is a 260Hz bass-rolloff. That's awful gutless. If that's what you wanted, you could also shorten the axe's neck and move to much smaller speakers. While it may be useful for screamin'-solos, I suspect it could be 0.015u with a switch-option for the teeny value.

0.0015uFd after the Gain pot gives a treble roll-off varying from 1,260Hz at full-up to 444Hz at half-volume. This seems awful brutal, and the variation with pot-set does not seem to make musical sense.

The position of the 68K is not real important. When in doubt, put it AT the tube grid-pin, after all the other stuff. BTW, the Fender value is 34K (two 68K parallel).

What cathode cap?? You don't have a cathode bias resistor to cap-bypass.

Yes, for *small* signals you can omit cathode bias. This may run better with a grid capacitor and large grid resistor. 1Meg is rather low. 5Meg would be better. FWIW, this type bias was used in guitar amps into the late 1950s, then vanished. I suspect improved (stronger) pickups were overloading the gridleak bias, so designers went to cathode bias. Gridleak "can" give a wee bit more voltage gain, and "can" give a self-debiasing compressor action on slight-overload.... but the trend away from it was very strong.

[TIMBO]

Thanks PRR. Yeah, cathode resistor, that's it  I see that these boutique amp builders will try every trick in the book to make there amps SEEM to be better and push the boundary's to make them unique.The positions of these components placement on the circuit board are easily changed if the circuit is incorrect or not functional.

The demos I have listen to sound fine so i'll have to trust the schem  Thanks

[tubenit]

Timbo,

Take a look at the Stray Cat on Ceriatone:
http://www.ceriatone.com/images/layoutPic/matchlessLayout/StrayCat30Ceriatone.jpg

With respect, Tubenit

[TIMBO]

Thanks T, That clears it up and PRR you got it right again   So not a good idea   Something to shy away from or go for it

The overall circuit has a very Marshall flavour to it and the plan was to use the GAIN circuit http://www.el34world.com/charts/Schematics/files/Misc/badcat_hotcat_30.pdf[/url] as the OD for the JTM30 type build and keep the CLEAN as per my schem

I like to do the same switching as the JTM and have the inputs connected to the one input jack

But I do like the Bogner Ecstasy OD channel, very Marshall,NICE

[SILVERGUN]

But I do like the Bogner Ecstasy OD channel

Timbo, last week I held a bit of an amp shootout here because a guy brought me in a JCM800 4212 to modify for him,,,and he wanted to hear what I had laying around here for options, and to explore the "tonal pallette"
The amps I had were:
1) My TurboWreck
2) Mesa Single Rectoverb 50
3) The Bogner/Sovtek hybrid that I had made for another guy over a year ago (kind of accidental that it came out so well, because I was just starting)...it's back for comparison
4) His 4212

We tried each one,, and all 3 of us that were here agreed that the Bogner sounded the best -BY FAR,,,,,,which I'm not too happy about.....but it's the truth,,,,and I've known it for a while,,,,,, I thought I could get the T-wreck there BUT 

Wanna build the best sounding hi-gain preamp? BOGNER.....I wouldn't steer you wrong
http://www.el34world.com/charts/Schematics/files/Misc/bogner_ecstacy.pdf

[silverfox]

I'm think-n I have to agree SG. Is this the preamp schematic in questions speaking for itself?

Bogner Ecstasy amp - A Sonic Journey

Silverfox.

[TIMBO]

Yeah, I listen to that clip a few times and if that schem is that sound, I think that i'm sold. Thanks guy's