How would you go about tightening the bass response up in an amp?

[Dr. Tweedbucket]

...different value caps in the tone stack? Different filter caps?

The amp is a Mesa Lonestar Special and it sounds pretty good as is, but the bass isn't too tight. I wonder if there are any published mods for this amp?

[FrankieSixxxgun]

Easiest way might be to swap tubes.

[57paf]

All good suggestions. Switching rectifiers might be a possibility, but you would need a knowledgeable tech to verify what's appropriate for your circuit. Also, ceramics might be better than alnicos, particularly if you push the amp hard.
Don't know what circuit the Lonestar is modeled after, but if it follows the blackface schematics, flabby bass might be hard to get rid of.
Hopefully someone more knowledgeable will be able to respond. I've gone through the same agony with my SFDR.

[tommytomcat]

1. Increase the value of the filter cap that feeds the OT. If the amp has a tube rectifier, don't go higher than 40uF.
2. If the amp has a fender type tone stack .1uF/bass, .022-.047/mid, 250-500pF treb. Go with a .022 - .022 - 500pF tone stack set up.
3. If you're using speakers with 1.5"-2.0" voice coils... go with speakers that have 1" to 1.25" inch VC's... ceramic.

The speaker change outs is about all you can do with a pcb mesa.

[TweeDLX]

Lower the value of the coupling caps, or the value of the cathode cap. I took my concert's first CK from 25uF/25v to 10uF/25v and that really helped. +1 on the speaker change.

Mike

[donnyjaguar]

Sometimes this is caused by lack of inductance in the output transformer. Hence what Tweed says should help -a lot. Some of the guitar mod books say to increase the value of the coupling caps but this just exacerbates the problem.

[hasserl]

There's reducing bass and there's tightening bass. Reducing bass (reducing coupling cap and bypas cap values) gives the perception of tighter bottom end, which serves the purpose most of the time. Tightening the bass without reducing it is tougher to do. Power supplies drop when hit with a big note, causing distortion, speaker cones distort. Increasing filter capacity helps stabilize the power supply to reduce distortion, but increase it too much and the amp feels stiff. Different speakers handle the bass frequencies with different effectiveness. But what's good for strong tight bottom end may not be what's right for mid and high frequencies. It's all very subjective.

This is one of the areas of SRV's tone that has fascinated so many people. How did he get those big, fat yet clean bass notes? Big fat strings tuned down a half step, Fender amps, yet beautiful full & tight bottom end. Solid state rectifiers and increased filter capacitance along with JBL speakers I guess helped a lot with that. The right combination, along with the right effects pedals gave him what he needed.

[AR-305]

http://forum.grailtone.com/viewtopic.php?t=27487

This guy may have your answer here!

[TweeDLX]

Increasing filter capacity helps stabilize the power supply to reduce distortion, but increase it too much and the amp feels stiff. But what's good for strong tight bottom end may not be what's right for mid and high frequencies. It's all very subjective.

What's a good safe amount to increase filter capacitance, and what formula can you use (if any) to determine it? Would you increase just the one as an earlier post suggested, or all? A learning opportunity presents itself! Thanks for any response...

Mike http://www.thegearpage.net/board/images/icons/icon10.gif

[RussB]

I would call Mesa, and speak with their techs. These guys have always been very helpful and quick to share info about their amps.

[hasserl]

What's a good safe amount to increase filter capacitance, and what formula can you use (if any) to determine it? Would you increase just the one as an earlier post suggested, or all? A learning opportunity presents itself! Thanks for any response...

Mike http://www.thegearpage.net/board/images/icons/icon10.gif

As tommytomcat posted earlier, with a tube rectifier you're limited to how much filtering you can have at the first stage, 60uf for GZ34/5AR4, 40uf for 5U4, 20uf for 5Y3. For the second stage you can increase that, and some guys do with good results. But since the power tube plates are typically off the first node I'm not so sure going big with the second / thrid caps will help tighten the bass up too much. On amps with a choke the power supply from the screens on down is already stabilized by the choke.

With solid state rectifiers there are no limits. Fender ran two 220uf caps in series for 110uf total on the 135 watt SF Twin Reverbs. Marshall ran two 375uf in series for a total of 187uf on the Major. Soldano ran about 200uf (a pair of 200uf in series with another pair of 200uf) for the SLO 100. I think that gives a pretty good example of some values to try.

I don't have a formula, but guys Old Tele Man and Wakarusa (Todd) and sometimes Randall Aiken are the formula guys around here; maybe one of them will pipe in with something additional.

[RedMan]

I'd say a speaker swap would be the best way. Putting in different filter caps in a PC board amp like that can be a nightmare.

[TimmyP]

Swapping in smaller coupling caps gets rid of "unusable" low frequencies. This allows you to kick up the bass control for an increase in "usable" low frequencies. This gives more punch with less flab/farting on the bottom.