advice on more bass and treble from "Micro Champ"

[dmartn149]

I built this SE 6aq5 amp pretty much like the Adam Alpern Micro ChampMicro-Champ-R2B.pdf
It works fine, but I'd like to get more bass and treble out of it. I think I can get more bass by changing the coupling caps and for the treble I'm looking at c11 just ahead of the OT.
So my question is, Should I change it's value? if so to what? or should I add a resistor in series? and how much resistance?
Thanks

[eschertron]

If you don't want the tweed 5F1 midrangey 'growl', then insert a tone stack, which tends to remove some mids at any setting. With or without any panel controls - I'm thinking the Champion 600 RI amp here. The fixed filter stack functions as a notch.

The best results I've gotten out of the 'smaller' amps is to ditch the 6" or 8" speaker and play through a 2x12 cab. That's the only way to really move the air for the lower freqs

[dmartn149]

It's already playing through a 12" speaker and it's way more midrangey that my Epiphone Pacemaker (gibson champ) I don't really want to add any more controls. I just want to get more bass and treble and keep just the one tone control

[eschertron]

C11 should be way above the audible range as is. You could put a high power resistor in series with C11, somewhere from 3k to 10k if analysis determines C11 is actually rolling off your HF.

I've changed out coupling cap C9 for a much *smaller* value to eliminate fartiness. You don't get that much bass?

What tone control are you referring to? I don't see one in the schem posted.

[dmartn149]

What tone control are you referring to? I don't see one in the schem posted.

Oops, I forgot that the original didn't have a tone control. I lifted the tone circuit from a 5c2 princeton.
Here is my actual schem that I cut & pasted together.

[eschertron]

So the tone control you have allows you to (kinda) adjust between Highs or Lows but not emphasize them both by cutting mids. I played a little with that at one time, did not prefer it to other options. Changing the value of the caps (maybe clip in another cap parallel to the 500p HF "bright" cap) might bring you some joy.

If you think the amp should sound different than it does now, check component values, solder joints, etc. Something may be amiss.

But, if you simply don't want the 50's mid-rangey sound, then a modification to the circuit - or a different circuit - may be indicated. If the tone ain't what you want, first look at the tone circuit before looking for subtle changes elsewhere. JM2C

[dmartn149]

Okay thanks. I'll experiment with that tone control

[Enzo]

How many other speakers have you played it through. Nothing changes the tone of an amp more than a speaker does.

[dmartn149]

I've only played it through this speaker. I'll try a 12" celestion g65 somthinorother.

[eschertron]

I've only played it through this speaker. I'll try a 12" celestion g65 somthinorother.

What do other amps sound like though this speaker/cabinet? That's kind of why I suggested a 2x12, to reduce the 'boxiness' that comes with the smaller cabinet sizes. Can you try any other cabs, just to see? Enzo's right. The experiment can be enlightening.

[dmartn149]

I bought this speaker specifically for this amp and never tried either with anything else. It's a 12" peavey scorpion. It's in a pretty small box too. I guess I should do some experimenting. Tomorrow morning I'll hook the amp up to another speaker. All my other speakers are 8 ohm though. Should I hook up 2 to keep it @ 4 ohms like the peavey? The old recorder that I got my transformers out of had a 4 ohm speaker.

[J M Fahey]

The Peavey Scorpion is a VERY good speaker, and was offered as an upgrade in some Bandits and other guitar amps.
But itīs not your typical "guitar" speaker by any means.
Itīs a "mini EV" with its large edgewound aluminum ribbon voice coil, cast frame, tightly machined voice coil gap, but mainly relatively thick , non ribbed, curvilinear paper cone.
What the Doctor ordered ... for a PA speaker.
Very flat response, which might "seem" mid heavy compered to Guitar speakers, which are scooped and have huge high mid peaks, some 10dB or so.
Many find Tweeds "midrangey" ... but they use them with modern heavier speakers, while this is old Alnico Jensen response.
As you see, itīs already "equalized" with "bass and treble on full, midrange down" , thatīs why old , practically no EQ amps were actually usable, and very good at that.
Enter the Jensen P12Q:

Read that frequency response curve:
* 100dB on the lowest octave (from, say, 80 to 160 Hz)
* 91dB, or 9dB down at 400Hz, smack in the mids zone
* whopping 108 dB at ear piercing 2 kHz
Who needs tone controls with such "natural" boost and cut at important frequencies?

EDIT: this is Jensen P8R , what an 8" Champ would use, an even more exaggerated "V shape" :


a true "fender tone stack EQ" without *electrical* EQ whatsoever .

FWIW I had to build my own speakers to get that kind of response.

[dmartn149]

Once again, the forum has saved me from lots of useless tinkering. I hooked the amp up to 2 12" Celestions, ea. in their own cab, and it sounds great. A much bigger full freq sound.
Thanks!