Amplifier Question

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Pick an amplifier. I'm trying to figure out what the circuit that "surrounds" the reverb circuit is doing. This is usually the tube section V2 with the reverb tubes being V4 and phase V5. The input and drive are V1 with the FX loop V23.

Actually I have a mesa amplifier and I am wanting to have a hard bypass for the reverb and fx loop. There reason is because they are not needed and I want to compare the tube sound without these sections. The fx loop does have a hard bypass but the reverb does not.


V1 and V5 are absolutely necessary. V3 and V4 are not. I do not know if V2 is some type of extra drive/buffer for the reverb or if it is the final preamp stage.

If V2 is necessary then I should easily be able to take out V3 similar to how the fx loop is hard bypassed(DPDT switch) else I can include V2 in the hard bypass and remove it too.

I am also curious if it would be possible to replace the tube sections in the reverb and FX bus with transistors? This would save tubes and increase the fidelity. That is, instead of bypassing the tubes I would just exchange them with a transistor based circuit.

I was also thinking about adding a jfet input stage. Would this be a good idea? Also instead of bypassing the channel 1 tone when moving from the clean to the distortion channel why couldn't I mix them? This would simply require adding a pot instead of the switches and would offer more potential. Although here relays are used for the switching so it would be more of a chore.

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As to the bypass, in the "good ole days" we used to drive the reverb from the speaker output via a selected light bulb (switched in or out), perhaps you could go that way and develop the re-injection to your taste ??

Rheilly P

Reply to
Rheilly Phoull

I've picked three at random and the valve/tube references in all of them differ, which makes nonsense of the rest of your description ...

'Bypassing' the reverb, as you put it, is not an option - all you need to do is turn it off! In all 3 circuits I've looked at, the 'Reverb' control at the output of the reverb section disconnects it entirely when set to minimum, so even noise generated in the reverb section is turned off too.

If you want the facility to switch reverb on and off, put a SPST switch in series with the line marked 'reverb out'

I would respectfully suggest that your difficuly understanding the simplicity involved in achieving your original objective suggests that anything further would be well beyond you capabilities ...


Reply to
Terry Casey

Disconnects it entirely? You arrogance and ignorance is ungodly. Maybe you do not realize that the tubes are still in the circuit and still "hot"? Sure turning the reverb "down" would work but there is something called "true-bypass" and there is the other questions I have asked along with what V2 is doing. Since you do not understand this at least you could mention it instead of personal attacks to defend your ignorance of the subject.

It's quite amusing to see people making complete fools out of themselves because of there ignorance. It's actually quite sad also. I imagine your trying to make yourself feel more important by claiming others are more ignorant than you. If it adds an ounce of happiness to your pathetic existence then so be it.

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It is amusing, and so far the only one creating any laughs is you.



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Ian Bell


Reply to
Rich Grise

You've violated the first law of intelligence and a main rule of logic. Straw man is not an argument. Get over it dumbass.

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Reply to
Rich Grise

Amazing! The guy asks a simple question and you guys jump all over him. I always new engineers were not civilized but the ignorant ones are worse than liberals. When did not understanding the question or knowing the solution allow one to substitute personal attacks. Not only personal attacks but childish ones at that.

Reply to
Bobby Joe


Turning the Reverb control to zero DOES disconnect the reverb circuit=20 FROM A SIGNAL POINT OF VIEW, which is what I understood you to require.

The reverb input has no effect on the signal whatsoever (although you=20 could physically disconnect it if you don't believe me) and the output=20 control completely isolates the rest of the circuitry from any noise,=20 etc., coming from the reverb amp.=20

Of course I 'realize that the tubes are still in the circuit and still=20 "hot"' but that makes no difference to the performance of the amplifier!

As I said before, 'I've picked three (schematics)at random and the=20 valve/tube references in all of them differ, which makes nonsense of the=20 rest of your description ...' and you still can't be bothered to clarify=20 the situation.

In the Mesa Boogie MkI Reissue, V4 =3D Reverb Driver; V3b =3D Reverb Output= . In the Lonestar, V4b =3D Reverb Driver; V4a =3D Reverb Output. In the Mesa Boogie DC-5, V5a =3D Reverb Driver; V5b =3D Reverb Output.

For good measure, I took yet another random sample ...

In the Mesa Boogie Blue Angel, v3 =3D Reverb Driver; V4a =3D Reverb Output.

So, four samples and no two alike!

So, as you seem determined to 'completely disconnect' the reverb=20 circuit, proceed as follows:

Lonestar: remove V4 DC-5: remove V5 Boogie MkI: remove V4, physically remove all components connected to V3b Blue Angel: remove V3, physically remove all components connected to V4a

(Modify above as necessary to suit you particular model.)

You will now have successfully completely disconnected the reverb=20 circuit AND IT STILL WON'T MAKE THE SLIGHTEST DIFFERENCE!

As for V2, its function is basically similar in all four models quoted=20 above, varying slightly between preamp mid-stage to preamp mid- stage/output but the difference will be minimal from your perspective.=20 Note also that in the Mesa Boogie DC-5, V2 is functional in the=20 Lead Channel only.

You never wrote a truer word!



Reply to
Terry Casey

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