Metropoulos Forum

emartine wrote:Good evening everybody! Anyone who has built the loop for boosting or just tried it just like Larry explained us can tell me if this brings a clean boost (just increase in volume) or acts as another gain stage giving more gain to the preamp? May be both?

Just remove the 820K entirely and put the 220p across the other 220K from the Return Level, to make it to a serial loop, then jumper the Send to the Return jack by a simple guitar cord or jumper it internal - then you can dial in any color of gain boost, if the Master is after the recovery stage just in front of the PI

emartine wrote:Saludos and thanks Larry once again for the loop!

You're welcome

Larry

Hi Larry
Thanks for reply.
You said in first post this loop could be usable with ecc81 with some modifications as so: 560 ohm and 22 K for CF .
Sorry if I wrong.

Catalin

catalin gramada wrote:You said in first post this loop could be usable with ecc81 with some modifications as so: 560 ohm and 22 K for CF .

That's correct, but I must admit, that I haven't experimented much with a ECC81/12AT7 in the loop. I've swapped in one, have changed a few values and have noticed, that it works also with this tube. That's all, no voltage notifications, no gain measurements, nothing else...

... because I can't see any benefit with a 12AT7 - only confusions and trouble, when you don't have a 12AT7 on hand at the moment.

Who of the Marshall guys does have a 12AT7 in the service box

The Fender guys they have

Larry

novosibir wrote: Who of the Marshall guys does have a 12AT7 in the service box

The Fender guys they have

Larry

that is true.

Thanks

Hi Larry
If I want to put your loop in a MV circuit, can I leave MV path as it is and put the loop in parallel with MV path, without degradation the tone ?
Thanks

Catalin

Go and read the page before this one, from about halfway down. Larry describes the pros and cons of putting the loop just before or just after the master volume control. That should answer your question.

I want to say like this:

That's maybe some kind of "modern art", but nothing technically useful.

Larry

Thanks for PM Larry
Have a question , please : I dont understand from your drawing if sinal pins of jacks stay on the ground position when loop it is not in use. I have cliff jacks for this project and for me, acording to circuit, seems to be normal to put send/return jack to the ground when loop is inactive, but I want a confirmation ,please.
I put the loop in a MV circuit, after the MV pot, and at relative low volume level signal is at low limit for my processor. Can I raise the level of send stage a bit ?

Thanks

Catalin

the ecc81s are often better driver tubes than 83s since they deliever about 8-10 the current of the 83s. 81s can be absolutely great for some things. however, they will sound a little brighter and cleaner than 83s.

catalin gramada wrote:I have cliff jacks for this project and for me, acording to circuit, seems to be normal to put send/return jack to the ground when loop is inactive, but I want a confirmation ,please.

Confirmed.

catalin gramada wrote:I put the loop in a MV circuit, after the MV pot, and at relative low volume level signal is at low limit for my processor. Can I raise the level of send stage a bit ?

No! The Send driver stage doesn't amplify gain. Open the Master or move it after the loop section!

Larry

Roe wrote:the ecc81s are often better driver tubes than 83s since they deliever about 8-10 the current of the 83s. 81s can be absolutely great for some things. however, they will sound a little brighter and cleaner than 83s.

As you've said, the ECC81 is a great end driver tube! Correct, but...

... but then the other half of the ECC81 is the Return recovery stage, whats sound I don't like in a British Style circuit.

Larry

Roe wrote:the ecc81s are often better driver tubes than 83s since they deliever about 8-10 the current of the 83s. 81s can be absolutely great for some things. however, they will sound a little brighter and cleaner than 83s.

Thanks Roe
It draw much current ,indeed

Catalin

novosibir wrote: As you've said, the ECC81 is a great end driver tube! Correct, but...

... but then the other half of the ECC81 is the Return recovery stage, whats sound I don't like in a British Style circuit.

Larry

Thanks Larry

I love it as tone just you design with ecc83 after MV pot. Open sound , transparent and little more gain
Thank You

Catalin

novosibir wrote:
When you try the Master after the loop section, don't forget the additional coupling cap! one .022 from the recovery stage's plate to the Master and another .022 to the PI's input.

Larry

You then have two 22n caps in series, Larry?