OK, I've got a couple of old Acoustic 60 watt guitar tube amps. Actually I find the tone very unique and warm, that's why I bought a backup.
But here's the deal, I'm always playing through pedals that boost the signal in a clean fashion. The tone is decent when I do this, but less "tubey" and more solid-state sounding. But the pedals (specifically my "treble booster" pedal) clean up the tone tremendously and get rid of a major problem: the bass while boomy is very very muddy and indistinct, not punchy at all...sloppy would be a good term.
When I go direct from guitar into amp this sloppy muddy bass is intolerable, even when I increase treble with my tone knobs. I've tried everything on amp and guitar but this never goes away.
I have replaced the tubes in the past but no dice, its still there.
I guess my big question is this: what do you think is the culprit here? Could it be that my transformers are low grade, too weak or something. Guess I just need to know some likely suspects in the circuit of the amp.
Tubes havent been changed in a few years, I ordered some new ones that should be an upgrade, but I'm skeptical they will remove the problem.
Thanks for any help I really want to "fix" this amp.
But here's the deal, I'm always playing through pedals that boost the signal in a clean fashion. The tone is decent when I do this, but less "tubey" and more solid-state sounding. But the pedals (specifically my "treble booster" pedal) clean up the tone tremendously and get rid of a major problem: the bass while boomy is very very muddy and indistinct, not punchy at all...sloppy would be a good term.
When I go direct from guitar into amp this sloppy muddy bass is intolerable, even when I increase treble with my tone knobs. I've tried everything on amp and guitar but this never goes away.
I have replaced the tubes in the past but no dice, its still there.
I guess my big question is this: what do you think is the culprit here? Could it be that my transformers are low grade, too weak or something. Guess I just need to know some likely suspects in the circuit of the amp.
Tubes havent been changed in a few years, I ordered some new ones that should be an upgrade, but I'm skeptical they will remove the problem.
Thanks for any help I really want to "fix" this amp.
Per FORUM policy since this post relates to an acoustic instrument amplifier it belongs in I&A.
Additional information such as who made your amps, the specific model and an out of copyright (or hand redrawn) schematic would really help a lot.
Have the power supply capacitors or any other components in these presumably old amps been replaced?
The fact that your pedals make it sound better point to a possible interaction between the guitar and the input electronics in these amps, again having a schematic or something more to go on would help..
Have the power supply capacitors or any other components in these presumably old amps been replaced?
The fact that your pedals make it sound better point to a possible interaction between the guitar and the input electronics in these amps, again having a schematic or something more to go on would help..
Kevin is your tube amp master
I won't mess with him
but that your pedals change the 'issue', and sounds better
it could indicate impedance problems
I wonder if some owner before you lowered input impedance
that you got a couple, maybe tells that they might have been used fore hifi/stereo
sounds like a power supply problem, is it valve or diopde rectified? switching to diode rectification might help and as kevin said, the caps probably could do with replacement. as for impedance problems, i doubt this is the case, although it can contribute, i cant see it making a significant difference. also, if any bypass caps are electrolytic then it probably wouldnt be a bad idea replacing them either, and if theyre relatively big, making them slightly smaller wont hurt.
if any of these amps worked well before hand then i cant see there being any big problems with the design so a schematic wouldnt help, also showing impedance isnt the issue (ive used impedances of 2.2K with decent highs, just saying, although i wont deny a high impedance will add a bit more sparkle)
after a bit of googling i found a 60 watt acoustic amp schematic here,
not good quality but a start http://www.cornelvis.com/Schematics/newamps/acoustic_g60t.pdf
not good quality but a start http://www.cornelvis.com/Schematics/newamps/acoustic_g60t.pdf
He said that it sounded ok with a pedal to boost the treble, not that the amp sounded good beforehand and now it does not.
2.2k input impedance to the guitar? I would be surprised if any sparkle was left.
ok did a little analysis of whats there, i think there should be another stage of power supply filtering, this should help alot, feeding 4 valves with one supply could pose a problem, change the 1st valve bypass cap from 22u to 1u/2.2u change coupling caps to 22nf instead of 47nf. all should lead to less bass and more highs
but yes 2.2k, hehe your right there wasnt alot of sparkle, but the highs were enough.
but yes 2.2k, hehe your right there wasnt alot of sparkle, but the highs were enough.
Good enough. I would narrow it down to preamp or amp first. Feed the guitar in the amp power amp input with a pedal and see how it sounds. If it does not sound muddy it may be the preamp. Mind you as said it might just be the speakers. I have been working on an amp today and there is night and day between the 12" I'm using and the 10".
The 0.1uF coupling caps after the PI are also large.
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Well those are some really good replies, thanks.
I suspected the caps, nice to hear someone else might agree. It is over 30 yrs old so maybe time. They are big blue ones, got a nice vintage look to them.
Speaker I am using is brand new, bought an Electrovoice 12 inch classic, this heavy bad boy will take 200 watts, the stock speaker was indeed a poor one, relabeled "acoustic" with a smallish magnet, I was hoping this was the main problem since my other one (the backup) seems a bit less muddy but still pretty bad, it's internal speaker was replaced with a "vintage 30", those are well thought of.
update: After long hard searching I can't find the schematic so I had to buy it again online. Waiting for the return email and dload link, then I will post it.
One thing I was told by someone along the way was that the OT is largely responsible for how "strong" the bass is, not sure if that is true, interesting that my "treble boost" loosely based on the old rangemaster circuit, makes the bass much cleaner, but like I said, it also seems to remove some tube "goodness".
I suspected the caps, nice to hear someone else might agree. It is over 30 yrs old so maybe time. They are big blue ones, got a nice vintage look to them.
Speaker I am using is brand new, bought an Electrovoice 12 inch classic, this heavy bad boy will take 200 watts, the stock speaker was indeed a poor one, relabeled "acoustic" with a smallish magnet, I was hoping this was the main problem since my other one (the backup) seems a bit less muddy but still pretty bad, it's internal speaker was replaced with a "vintage 30", those are well thought of.
update: After long hard searching I can't find the schematic so I had to buy it again online. Waiting for the return email and dload link, then I will post it.
One thing I was told by someone along the way was that the OT is largely responsible for how "strong" the bass is, not sure if that is true, interesting that my "treble boost" loosely based on the old rangemaster circuit, makes the bass much cleaner, but like I said, it also seems to remove some tube "goodness".
schematic
OK here's the schematic. I also considered that the amp needs a cap replacement job.
Would bad caps cause this problem? I'm assuming it is the large blue caps (about 2 inches long) that need to be replaced.
Any help is much appreciated, as well as any comments about this schematic.
I had a real hard time trying to extract the schematic from a pdf in a small enough format to upload here, so I just took a couple screenshots. thanks!
OK here's the schematic. I also considered that the amp needs a cap replacement job.
Would bad caps cause this problem? I'm assuming it is the large blue caps (about 2 inches long) that need to be replaced.
Any help is much appreciated, as well as any comments about this schematic.
I had a real hard time trying to extract the schematic from a pdf in a small enough format to upload here, so I just took a couple screenshots. thanks!
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