SWR ST220 clipping

[myrios]

My ST 220 clips really really easily with pretty low volumes, like bedroom volumes almost, even with the aural enhancer at 10 o'clock, flat slider eq and treble at noon. Pulling the treble knob for transparency really limits my volume… And much treble above noon or adjustments to the EQ sliders above flat also makes it clip pretty quickly. I have a 2x10 and 1x15 and have experimented using each of those solo and also combined with the 220.

The only way I can get much punch/low end for example is to turn off the enhancer completely, treble at 10 or so, increase the lowest frequency slider a bit above flat, and increase the bass knob to 3pm or so. At that point adding higher frequencies using an EQ slider or treble knob will quickly cause clipping.

I've heard a lot about these being under powered but because it overloads so quickly I'm wondering if there is something wrong with it… my Fender M80 chorus head quickly and easily gets louder and punchier with walls vibrating than the 220 and it's only 100 watts.

One thing I noticed that seems odd, is that - following the guidelines from the information I have - I leave the master off or very low and set the gain to where it is just below clipping when I play hard. It's my understanding that at that point it should not clip anymore, but as I turn up the master volume past a certain (not high) point it does start to clip. My understanding is that clipping only happens in the preamp gain stage… But maybe I'm confused on how it works…

 

[agedhorse]

Turn the master up and turn the input gain down a little more.

 

[myrios]

Thanks, I did try that... just does not respond as an amp should...

 

[agedhorse]

They you may not have enough rig for your needs or expectations…

 

[myrios]

Well... I don't know, I've got a GK 1x15 and Eden David 2x10 with the PB200 works great, plenty of volume, with my Fender M80 head (100 watt) those cabs are plenty lud. But the ST220 is just acting weird...
It just feels off. I've had plenty of amp over yeras.

I am suspecting a problem in the power amp section and wonder if there are some things I can try to replace rectifiers? diodes? or if there's some tracing I might find faulty... before spending money on a tech...

The preamp section works fine when using direct out.

 

[ardgedee]

I am suspecting a problem in the power amp section and wonder if there are some things I can try to replace rectifiers? diodes? or if there's some tracing I might find faulty... before spending money on a tech...

If you don't know how to diagnose the problem, you won't know how to fix it.

If you're convinced the amp has a problem, take it to a tech or plan on a replacement. Those are your two cheapest options. Randomly swapping parts will cost much more, and risks damaging the amp or you.

 

[ddnidd1]

OP, unfortunately, guessing what the problem is is not troubleshooting. You've mentioned all you have tried and you followed some of the advice above.

With the info you have provided its impossible to tell you what the problem is or if there even is a problem.

If you can locate an ST 220 to compare it to or take it to a knowledgeable tech to evaluate the amp - those are pretty much your choices at this point.

 

[Passinwind]

I am suspecting a problem in the power amp section and wonder if there are some things I can try to replace rectifiers? diodes? or if there's some tracing I might find faulty... before spending money on a tech.

If you want to end up spending more money on a tech, doing unqualified repair attempts is a pretty sure bet!

 

[beans-on-toast]

I am suspecting a problem in the power amp section and wonder if there are some things I can try to replace rectifiers? diodes? or if there's some tracing I might find faulty... before spending money on a tech...

The preamp section works fine when using direct out.

You tested the pre-amp by decoupling the pre and power amp. Now test just the power amp. Plug your bass into the power amp input. Be careful if it is an active bass, enough voltage and you can drive the power amp to full power. Now repeat the same into the effect return. See if they are the same level. See how the power amp sounds.

It never hurts to clean the effect and preout and power in jacks with deoxit as a standard maintenance task.

 

[agedhorse]

It never hurts to clean the effect and preout and power in jacks with deoxit as a standard maintenance task.

Sure it hurts, when it makes a mess without solving a completely undefined and undiagnosed problem.

It's also a way to make an amps repair a more expensive repair for the tech that actually works on it.

I see these messes all the time, always costs more to clean up and repair properly down the road.

 

[myrios]

You tested the pre-amp by decoupling the pre and power amp. Now test just the power amp. Plug your bass into the power amp input. Be careful if it is an active bass, enough voltage and you can drive the power amp to full power. Now repeat the same into the effect return. See if they are the same level. See how the power amp sounds.

It never hurts to clean the effect and preout and power in jacks with deoxit as a standard maintenance task.

Thanks I'll give that a try

 

[myrios]

Sure it hurts, when it makes a mess without solving a completely undefined and undiagnosed problem.

It's also a way to make an amps repair a more expensive repair for the tech that actually works on it.

I see these messes all the time, always costs more to clean up and repair properly down the road.

Thanks for the input. Are you saying that things like Deoxit and CRC Quick Dry are bad for cleaning things like this (input jacks)? I understood that those were the go-to clean and lube sprays for electronics parts. yikes.

 

[agedhorse]

Thanks for the input. Are you saying that things like Deoxit and CRC Quick Dry are bad for cleaning things like this (input jacks)? I understood that those were the go-to clean and lube sprays for electronics parts. yikes.

They are bad when incorrectly used. Spraying ANYTHING into an amp has the potential for causing additional problems. I know that there are all kinds of stupid videos about how miracle cure-all sprays can fix anything and everything (they can't and don't), but I also see the results of such DIY (and hack tech) repairs gone wrong. It's messy and more expensive.

 

[ajkula66]

My understanding is that clipping only happens in the preamp gain stage… But maybe I'm confused on how it works…

Well, there are two LEDs on ST220...one for preamp clip, and the other one for power amp clip so...

I always felt that ST220 seemed pretty darn quiet for its supposed wattage but can't say that I've experienced clipping at low volume.

If you *really* like the "baked-in" sound that these have - at least IMO - then it's worth taking it to a qualified tech.

If not...just move on.

My $0.02 only...

 

[agedhorse]

Clipping can occur anywhere in the signal path, from the input gain stage all the way to the power amp.

 

[beans-on-toast]

You have to know how to properly apply deoxit. Spraying onto areas where you don't want it can cause harm. Many techs even do this and they should know better.

Only apply deoxit where it is needed. It's better to apply deoxit onto an interdental brush and use that to clean the metal-on-metal contacts on the jacks.