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Should I remove the effects loop circuitry from my BDRI?
Yes. It will greatly improve the tone of the amp. 100%  100%  [ 1 ]
Are you nuts? That's a stupid thing to do. 0%  0%  [ 0 ]
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Post subject: Removal Of BDRI Effects Loop Circuitry
Posted: Wed Oct 17, 2012 10:09 pm
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Ok. I admit that being unemployed for the last two months has left me bored and a little depressed. I would like to build a another amp, but there is no money for it. So, I have been looking at modding my existing amps.

I have already modified the power output stage of my BDRI to more closely reflect my 5F6A Bassman clone, as well as modified the bias circuit to allow me to run the output tubes a bit hotter.

My next thought is to remove the circuitry used for the effects loop (basically the preamp output/power amp input buffers). My gut feeling is that even though they are not in the signal path when not used, the active and passive components are having some sort of effect on the signal paths they are attached to.

Why do I want to do this? Because I can. :lol: :lol: :lol: I'm long past worrying about the warranty, nor do I care about resale value.

So what do you think? Should I or shouldn't I?

PS: I've also figured out a way to allow the master volume to be allowed to be used with the clean channel. Not sure of the value of that mod.

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Post subject: Re: Removal Of BDRI Effects Loop Circuitry
Posted: Wed Oct 17, 2012 10:27 pm
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bluesky636 wrote:
PS: I've also figured out a way to allow the master volume to be allowed to be used with the clean channel. Not sure of the value of that mod.


You might find that this mod is significantly more useful than diddling around with the op-amps in the effects loops......

Arjay

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Post subject: Re: Removal Of BDRI Effects Loop Circuitry
Posted: Thu Oct 18, 2012 12:40 am
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Retroverbial wrote:
bluesky636 wrote:
PS: I've also figured out a way to allow the master volume to be allowed to be used with the clean channel. Not sure of the value of that mod.


You might find that this mod is significantly more useful than diddling around with the op-amps in the effects loops......

Arjay


Who's diddling? I would rip them out completely! :lol: :lol: :lol:

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Post subject: Re: Removal Of BDRI Effects Loop Circuitry
Posted: Thu Oct 18, 2012 3:39 pm
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That the spirt Bill dig in and post pic,s


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Post subject: Re: Removal Of BDRI Effects Loop Circuitry
Posted: Thu Oct 18, 2012 4:06 pm
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tbazzone wrote:
That the spirt Bill dig in and post pic,s


Planning on taking a closer look at things this weekend. :wink:

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Post subject: Re: Removal Of BDRI Effects Loop Circuitry
Posted: Thu Oct 18, 2012 7:23 pm
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Sounds interesting at least. As you mentioned, the OA for the loop is virtually completely out of the circuit when not in use, so I would say that it wouldn't matter if it was removed or not, as far as affect on the tone. The Power Amp In half of the OA output is disconnected and input is grounded so that half is completely out of the circuit, while the Preamp Out half of the OA input is still connected, although through a 1 meg resistor, I would think that it wouldn't have much, if any, affect at all. I use the preamp out for a tuner, and haven't noticed any difference with tuner and without.

While we're on the subject, as an alternate suggestion to removing the loop circuit, I've thought about putting in sockets for the reverb and loop OAs to be able to try different ones. I've read about claims of different types/brands of OAs having an affect on the tone of those two circuits. The OAs for the switching circuits wouldn't really matter for tone, but maybe for reliability. If you did install sockets, you could pull the op amp for the loop, and easily reinstall, for easy comparison as well as the ability to easily try other types/brands.

I agree with Retroverbial, using the master for the clean channel sounds like it has some potential sonic benefit.

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Post subject: Re: Removal Of BDRI Effects Loop Circuitry
Posted: Thu Oct 18, 2012 9:25 pm
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shimmilou wrote:
Sounds interesting at least. As you mentioned, the OA for the loop is virtually completely out of the circuit when not in use, so I would say that it wouldn't matter if it was removed or not, as far as affect on the tone. The Power Amp In half of the OA output is disconnected and input is grounded so that half is completely out of the circuit, while the Preamp Out half of the OA input is still connected, although through a 1 meg resistor, I would think that it wouldn't have much, if any, affect at all. I use the preamp out for a tuner, and haven't noticed any difference with tuner and without.

While we're on the subject, as an alternate suggestion to removing the loop circuit, I've thought about putting in sockets for the reverb and loop OAs to be able to try different ones. I've read about claims of different types/brands of OAs having an affect on the tone of those two circuits. The OAs for the switching circuits wouldn't really matter for tone, but maybe for reliability. If you did install sockets, you could pull the op amp for the loop, and easily reinstall, for easy comparison as well as the ability to easily try other types/brands.

I agree with Retroverbial, using the master for the clean channel sounds like it has some potential sonic benefit.


A simple test I will try is to just pull the 1M ohm resistor that feeds the buffer for the preamp out. You are correct that the power amp in buffer is completely disconnected from the circuit via the input jack switching.

The reason I am not sure about the value of a master for the clean channel in my case is that with a 12AY7 in V1, even the drive channel is quite clean. With the master up all the way, there is no real difference between the clean and drive channels unless the drive gain is also up all the way AND has an extra push from a clean boost. It might be a different story with a 12AX7 in V1.

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