More bottom, please. Kalamazoo Model One.

[Boy Howdy]

I'm working on my Model One. It's starting to sound pretty good. It's got a nice spankiness to it, great for strummy stuff, but I sure would love some more bottom end (said the ass man).

I left the .01 coupling caps in place and I added 1mf and a 2mf cathode bypass caps to stage 1 and 2, respectively. I don't like big caps in the preamp. So I'm hoping you guys have a trick or two to get more bottom out of the 6bq5. I did add a 22mf cathode bypass cap there for hum reduction. I didn't really notice a change in tone (but I wasn't looking for one either, really). Could I possibly get a little more low end if I doubled that to 44mf? Anything to be gained from messing with that 150 resistor? I changed out the power sply. caps some time ago, put bigger ones in (all 30mf if memory serves - that's what I could get locally).

Any ideas, guys? I'm thinking about trying to figure out some sort of midrange rolloff circuit to at least give the illusion of more bottom. Any recommendations there?

Schematic below:

http://www.rru.com/~meo/Guitar/Amps/...ages/schem.gif

[doldrumdesign]

I'd love to find this out too! Just got one for X-mas. Love the sound as is, but it definitely needs a boost down there.

[Chuck H]

A bigger bypass cap will technically help stabilize the bias and give better bottom end when the tube is clipping. The difference will be pretty subtle though. I think with an amp like that the speaker would be the most important factor. The amp is already clipping, so more bottom end could just mean more mud and flab. Once the amp is clipping, and the bottom end of the coupling caps has been tuned to give best results without flabbiness, all that's left for EQ adjustment is the speaker. Maybe try plugging the amp into another cabinet to see how it sounds. There's a good reason a lot of Champ owners "upgrade" to a ten inch speaker.

[Steve Conner]

Yes, a small amp will be deliberately tuned for a lack of bass. The speaker can't handle it, and even if it could, the wimpy SE output stage can't. So it's a common design choice to focus the power into the midrange, allowing the amp to go louder without getting "farty".

If you only ever play it quietly, you can revoice it for more bass. (put it in the corner of the room, no soldering required )

[Boy Howdy]

!

If you only ever play it quietly, you can revoice it for more bass. (put it in the corner of the room, no soldering required )[/QUOTE]

Well, as for only playing it quietly ... LOL! Boy, that just ain't gonna happen.

That said, the cabinet fell apart (literally disintegrated - particle board is a sin against man and nature). And the speaker disappeared years ago. I play it through my 4x12 mostly. And I never use low wattage speakers anyway, don't like 'em ... at least as compared to my favorite speaker(s). And while I'm not going to be drilling any holes (I'm going to build a box for it and will drill into a back panel), there's not much in the way of collector value left, if there was ever any in the first place.

So this is great news, Steve. That there's hope for more bottom.

I'm about to start a recording project, that could prove to be a pretty big deal. I was hoping to be able to use the Kalamazoo for some of it. It just doesn't have enough bottom currently though.

So, details???? Inquiring minds, yadda.

Thanks for the reply.

[Boy Howdy]

Thanks, Chuck. I replied to Steve before I saw your message. I think I addressed most of what you talked about there. But just as an fyi, I generally don't turn it up over 1-2:00. It gets muddy and the distortion doesn't sound good any higher than that. And with bigger bypass caps the situation is worse yet. Which is why I went with small ones on the preamp cathodes. The amp doesn't really distort that much in any case. I actually often use it to overdrive my bigger amps. I have a master volume and a preamp out/power amp in jack installed for the purpose. Sounds amazing when used in the preamp/power amp loop I installed in my modded '68 Traynor Bassmaster. But again, it sounds too thin.

[Steve Conner]

I see... How about a bigger output transformer then? The OT has a major effect on the bass response, and small single ended practice amps often had a tiny, weedy one.

[Jazz P Bass]

How about a little research on that wannabe "tone" control?
Tone Controls
And, yeah, a bigger OPT will help.
Here is a really nice tone stack calculator from Duncan.
Link:http://www.duncanamps.com/tsc/

[Chuck H]

I generally don't turn it up over 1-2:00. It gets muddy and the distortion doesn't sound good any higher than that...

But again, it sounds too thin.

Generally muddy AND too thin aren't problems with the same amp. I don't think you like the sound of this amp. Have you heard any little amps (in person) that you do like the sound of?

To muddy on the distortion means the circuit is passing too much bass. You can trin bypass cap and coupling cap sizes for this. Too thin means your not passing enough bass or low mids. You can increase bypass cap and coupling cap sizes for this, BUT, that would mean your distortion would get muddier. As I mentioned, the only real bass improvement to be had with the little amps is a bassier speaker (and as added by Steve, a bigger OT). Then you may be able to trim some bass through the amp for an overall better tone. I also agree that a tone control may serve you with this amp.

Also, re: bypass caps, You can use smaller value caps like .1uf up to 1.5uf to get more treble and mids for your overdrive tone without adding bass that will make the amp muddier.

[Boy Howdy]

Transformer, that's the issue, I think.

When I say it sounds thin AND muddy I mean it in the sense that an amp can sound small or big depending on whether you use a 4" speaker vs. a 15" speaker. An amp can sound muddy regardless of what size speaker is used if you use big caps in the preamp and crank the volume. But in this case it sounds small even running through a 4x12. 'Small' being a relative term, of course.

I like small caps in the preamps to keep it from getting muddy (I'm using a 1mf and a 2mf at the 1st and 2nd stage cathodes - I may try something a bit smaller). And I like to get the bass as late in the chain as I can get it (from the speaker working my way back). That said, I don't care for 15" speakers (Celestion K-85s are my favorites).

I did change the tone control to the one on Miles O'Neals site. It works a lot better. Kalamazoo Amp Field Guide (frames)

I do quite like the sound of this amp for certain things, but it's not perfect. It can certainly be better than stock. I'm just trying to get as much as is practicable out of it.

So I guess I gotta get me a better transformer.

[Boy Howdy]

Ooh, juicy!

Thanks for that tone control link, JPB. Me likey.

[Jazz P Bass]

Google: Tube bass boost.

[Chuck H]

It sounds like your understanding of building gain and how to EQ through the preamp to get the most out of it is pretty solid. So yeah, bigger OT. Hell, you might even want to build a small extension cabinet with a port for big bandwidth from a small package. I actually think a little closed back cab with an 8" speaker and a port would probably sound pretty good with a little single ended amp.