The Amp Garage

Fantastic Tony!

your amp feedbacks on himself my hypothesis goes to the trash

I'm going to rethink all over the we

thanks
teo

Tony unfortunately I didn't have under hand an amp behaving like yours in all my life :( my current hypothesis is that the preamp in a certain way changes the phase of the signal as the signal amplitude changes I have recently noticed this in the high-plates OD stages while it doesn't happen in the ...

@Gil

I don't get what's your current hypotheses, do you think that the clean preamp (v1a+v1b) is an almost "self oscillating" circuit?

so that when fed by a signal from guitar it starts oscillating by themselves?


thanks
teo

Please Tony,

did you tested playing guitar in one room with the speakers in another one?

otherwise this thread is a joke...

thanks
teo

Hemtt/Martin I thought that as well, so yesterday I put the amp in the cab and took it to VVT's Shop... Tony Tony, did you also played guitar in one room while the speaker was in another one? this is a crucial test to understand if feedback happens at the "acoustical feedback path" or not cheers Teo

Tony, have you tried with a different guitar?

What if you play in another room with respect to amp/cabinet?

@Gil +1 a wrong assumption here made by most is reasoning about sustain and other "envelope" related properties in terms of "signal" feedback (in phase or not) which affect only steady-state amplitude/frequency-response (considering an amp a non-resonant system on his own...) Just an idea: v1a grid ...

yes, it depends a lot on personal tastes and how you plan to use your PPIMV

without compensation basses get looser and flabby, and your PI gets into clipping sooner

in my plexi 50 without compensation I can't go down to bedroom volumes with an acceptable sound...

cheers
teo

a good PPIMV should also compensate the reduced signal on the feedback loop

if you are going the LARMAR way you need a three-ganged pot, not easy to find...

cheers

Very coool product! Years ago I managed to build an all analog circuit working exactly like that but it ended up to much complicated and I convinced myself that a microprocessor solution was needed. Once understood it wouldn't be cheap I abandoned the project. But 2 month ago I discovered an incredi...

Do all output transformers have the artifacts known as ringing? And if they are above human hearing range, (20KHz) how does one perceive it? Does it sound like a harshness on top of the signal? Yes! Some more some less, this relates to the perceived sound of different OTs. Ringing is just a symptom...

.. The HiFi guys knows All about how to find the correct cap value. Its done with a scope and a 10kHz square wave generator. You Can see the amount of ringing in the OT. We are talking about ringing in the Mhz range around 150-300 Mhz. Off course you cant Hear these freqs, but you Can Hear The cons...

attached you find the skyliner mid pot response both with 10n and 47n mid cap (47n lowers turnover freq)

basically mid control is a first-order low pass filter with r=150k and c=mid cap, you can easily calculate -3dB points by 1/(2pi*R*C)

cheers
teo

exocet wrote:
I wonder whether switching the LNFB on V1 would help to impart more overtones when driven from a clean boost pedal?

V1 with LNFB engaged sounds horrible to me when overdriven...

improves the mid control effectiveness while using 0,01 mid cap

you can go higher till 2-3nF before worsening treble response

cheers
teo