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Ampeg PF-20T Jam Review

#21
Bedrossian said:
Thank you Wasnex,
I have no pedals and the basse is connected directly to the amp it's a fender Precision bass passive, I think the amp have a problem, I tested different cabs, and all have the same problem, and I also tried with different basses : same problem: yesterday I tried another amp on my pf 115he cab to be 100% sure . And no problem with another amplifier on the cab, so I think my pf 20t don't work well, if anyone had the same issue?
Thanks for helping me
Have a nice day
Click to expand...
I don't have that amp, but it's something I'm thinking of buying at some point, so your problem caught my attention.

If you get an unpleasant saturated tone when dialing up the gain, my guess would be that a preamp tube might have gone bad. Have you tried different preamp tubes? 12ax7 tubes are easy to find and they are not too expensive…
 
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#22
Yes I swapped the 2 12ax7 and the problem is the same, I made many tests even the direct out from the préamp isn't clean, and the transformer output is completely saturated, on the output of the préamp we can choose pre or post EQ, on both positions I have the EQ !
My amp have a real problem, probably capacitors.that don't filtrate properly, I go to a technician that repair amps, and I will see ...
:-(
Have a nice day
 
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#23
Bedrossian said:
Yes I swapped the 2 12ax7 and the problem is the same, I made many tests even the direct out from the préamp isn't clean, and the transformer output is completely saturated, on the output of the préamp we can choose pre or post EQ, on both positions I have the EQ !
My amp have a real problem, probably capacitors.that don't filtrate properly, I go to a technician that repair amps, and I will see ...
:-(
Have a nice day
Click to expand...
Hi
Have you checked the biasing led on the back of the amp.
If it's distorting at low gain it's quite likely you haven't biased the amp circuit correctly.
 
#24
Also make sure, that the impedance switch at the back is set to correctly match your cab.
I had once mistakenly set it wrong and the amp distorted way to early. Made think I might need new power tubes, but when checking the bias setting I noted my mishap. Can't say if this is your issue, but IME is worth making sure...
 
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#25
Bedrossian said:
Yes I swapped the 2 12ax7 and the problem is the same, I made many tests even the direct out from the préamp isn't clean, and the transformer output is completely saturated, on the output of the préamp we can choose pre or post EQ, on both positions I have the EQ !
My amp have a real problem, probably capacitors.that don't filtrate properly, I go to a technician that repair amps, and I will see ...
:-(
Have a nice day
Click to expand...


Did you figure out the issue? I've got the same problem:(
 

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