Bugera v55 feedback circuit/ donated its OP to fix kustom 15 now has jtm-45

[Sowndman]

Hello,
I have a bugera v55 that i have been moding to more of a fender hot rod style.

The bugera does have a precence knob but is doe not get its signal from the usual speaker side of the OP. Would there be an advantage to wiring up the presence knob to the speaker side of the OP ?

The bugera v55 is loosly based on a peavey classic 30 so I have heard. The tone stack is last in the preamp right before the pre amp out jack. The plan was to move it back to after the fist stage of V1 to keep the clean/drive channel switching intact. I have already upgrade the coupling caps between the inverter and the 6L6's from the original 22n to
.1 uf like the hotrod deluxe.

This maybe be a beeter choice to covert into a marshall style clone than fussing too much with the kustom defender from a preavious post.

http://el34world.com/Forum/index.php?action=dlattach;topic=17366.0;attach=44483

[sluckey]

Would there be an advantage to wiring up the presence knob to the speaker side of the OP ?

That's not a well published amp. Got a schematic?

[Sowndman]

http://el34world.com/Forum/index.php?action=dlattach;topic=17366.0;attach=44483

[HotBluePlates]

The schematic you linked doesn't show any feedback connection for the output stage; the Presence control is across R39 (4.7kΩ) as it would be in a standard feedback loop/presence circuit, except there's no line showing the feedback loop itself.

Check your actual amp: see if there is a wire/trace from the impedance select switch to the junction of R78, R39, C50, C21. Typically, there would be a connection from the OT secondary, through a resistor, to this point (forming the feedback loop).

Would there be an advantage to wiring up the presence knob to the speaker side of the OP ?

Assuming this is not a schematic error, and the existing Presence control functions acceptably to you, then no. Probably no benefit to adding a feedback loop not already present.

[Sowndman]

I will install attach a wire with alligators to see if it does make a difference. Thanks for the exact location.

[jazbo8]

You will need more than just a wire for feedback from the speaker tap. Look at the V22 schematic or something similar, you will need to add at least a resistor in series with the feedback signal.

[Sowndman]

I will look at the v22 schematic

[Sowndman]

Resistors came in and the jtm45 OP. I did install a feedback wire with a 40k resistor. It doesn't seem to change the overall sound much than the original circuit. I did have the primary backwards so I heard a loud hum when I first tested. I changed all the 150k resistors on the plates to 100 k as I slowly convert this amp to a marshall. The biggest change will be the EL34's.

Is there an advantage sonically to doing the actual rewire instead of just using the 6L6/EL84 adapter plug gadgets ?

I thought about installing a switch to mis the dirty an clean channels If my guitar pkayer chooses not to used the foot switch. I don't know if I want to go to the extreme of setting up both the inputs to go thru the first tube separately then volume ,etc like a true jtm45.