Parallel effects loop for Marshall style amps

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GuitarManiac32
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Re: Parallel effects loop for Marshall style amps

Post by GuitarManiac32 » Mon Feb 22, 2010 12:39 pm

Yes, I already had removed the loop like this: http://s51.photobucket.com/albums/f358/ ... utloop.jpg" onclick="window.open(this.href);return false;

So I used the extra tube V4 for the Larry loop. I grounded everything to the same place except jacks and pots. I´ll change their grounding too and see what happens :) Thanks for the help! The interesting thing is that the hum is only on clean channel. When I´m using the overdrive channel I can´t hear the hum at all. I´d think the overdrive channel would make the hum even louder...

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Re: Parallel effects loop for Marshall style amps

Post by novosibir » Mon Feb 22, 2010 2:57 pm

GuitarManiac32 wrote:The interesting thing is that the hum is only on clean channel. When I´m using the overdrive channel I can´t hear the hum at all. I´d think the overdrive channel would make the hum even louder...
That depends on, where the hum in the circuit occurs - 1-st stage or later...

So when you play the clean sound CLEAN, then you have the Volume dimed, whereas the lead Volume maybe is set to 3...4 - hence hum in clean comes unattenuated from the previous stage.

Larry
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GuitarManiac32
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Re: Parallel effects loop for Marshall style amps

Post by GuitarManiac32 » Wed Feb 24, 2010 2:39 pm

I was wondering if someone could post for example voltages at the tube pins of their fx loops as a reference? Would be useful to see If my voltages are in the right "ballpark" :)

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Re: Parallel effects loop for Marshall style amps

Post by Just Mike » Thu Feb 25, 2010 12:28 pm

To install this in a Master volume 2204, would I still use the treble pot wiper as my in and the MV hi side as the out? I read a few pages back that I would need another coupling cap going into the MV. Is this also correct?

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Re: Parallel effects loop for Marshall style amps

Post by novosibir » Thu Feb 25, 2010 1:03 pm

Just Mike wrote:To install this in a Master volume 2204, would I still use the treble pot wiper as my in and the MV hi side as the out? I read a few pages back that I would need another coupling cap going into the MV. Is this also correct?
Correct!
Interupt between the Treble wiper and the MV input, where the loop section comes in-between.
And of corse then a coupling cap has to be between the recovery tube's plate and the MV's input.

Larry
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Re: Parallel effects loop for Marshall style amps

Post by thinlizzy » Sat Feb 27, 2010 1:53 pm

Hi,

I also put the loop in a 2204 but placed the loop between the master wiper and the PI.
It works fine there for me. What is the effect of placing the loop before or after the master volume of a 2204?
Larry?

Regards Marcel

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Re: Parallel effects loop for Marshall style amps

Post by novosibir » Sat Feb 27, 2010 2:32 pm

thinlizzy wrote:What is the effect of placing the loop before or after the master volume of a 2204?
Ok - you've adjusted your rehearsal loudness, then adjusted the effects by Send & Return Level, so that nothing is clipping.
But at the next gig you need some more loudness on stage. No prob - dial in the Master to the right loudness, but...

... oh shit, the effects are clipping now :roll:

You know, what I mean :idea:

Larry
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Re: Parallel effects loop for Marshall style amps

Post by Just Mike » Sun Feb 28, 2010 7:02 pm

Thank you Larry. I finally got it working and it sounds great. I run a Boss GT-6 in the loop and it does everything I want it to without the yucky degradation that a serial loop had.
Now I can get back to voicing my 2204!

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Re:

Post by thinlizzy » Mon Mar 01, 2010 10:58 am

Hi Larry,

Now I'm confussed in the beginning of this tread (see page 2) you say it must comes after the master in a MVamp.
Maybe I did not understand you correctly?

Regards Marcel

novosibir wrote:Correct! In a MV desingn the loop section connects right after the Master's wiper, as it does connect right after the Treble's wiper in a NMV design!

Larry

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Re: Parallel effects loop for Marshall style amps

Post by novosibir » Mon Mar 01, 2010 12:38 pm

Maybe this, what I wrote at the beginning just two posts later might answer your question?
novosibir wrote:
thinlizzy wrote:Is there a reason why I can't place it between the treble wiper and the master volume?
In principle, no!

But I'll tell you (all) now the pros and cons:

When a Mastervolume control is placed directly before the PI stage and set to a low setting, the sound becomes pretty thin - therefore it's always a good mod, to place a 100K resistor between the wiper and the 22n PI's input cap, to avoid this phenomenon as much as possible. A higher value than 100K will cost you some highs and gain, because you create a voltage divider with the input impedance of the PI stage!

When you go from the loop's Return recovery stage directly into the PI, the upper phenomenon doesn't occur.

But when you place the Master after the loop, then you can boost the Return recovery stage from the preamp, to obtain more gain, as with the upper constellation. Although this would be sound colouring - you won't have your previous MV sound any longer.

Larry
So as I've said several times in the entire tread, you can go both ways - before or after the Master. both ways do have their advantages and their downsides - but YOU must know, what you're looking for and what's more comfortable for you.

Larry
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Re: Parallel effects loop for Marshall style amps

Post by thinlizzy » Tue Mar 02, 2010 3:47 am

Oke thanks, that make things clear.
Maybe I try it before the master just to see how that is working.

Regards MArcel

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Re: Parallel effects loop for Marshall style amps

Post by catalin gramada » Sat Mar 13, 2010 5:49 pm

Hi Larry
I want to use "send" section of your loop like a buffer to feed a line for recordings .
I don't want to put a variable pot control level. I want to use just a impedance and signal level adapter for recordings line.
What is a best position for a resistive divider, please ? Before or after the tube ?
Thanks

Catalin
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Re: Parallel effects loop for Marshall style amps

Post by catalin gramada » Mon Mar 15, 2010 3:18 pm

Hi
For ECC81 with 22K CF load must keep 350-320 V over plates ?

PS: I put just one section of ECC81 at PI B+ (via 4,7K) and seems it take a lot of current .Voltage drop in B+ PI point from 352 V to 318 V.It is normal ? I don't know what is happened cause this stage take just 5 mA.

Thanks

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Re: Parallel effects loop for Marshall style amps

Post by emartine » Mon Mar 15, 2010 7:02 pm

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?

Saludos and thanks Larry once again for the loop!
Andrés Martinelli
Marshall for Tango

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Re: Parallel effects loop for Marshall style amps

Post by novosibir » Mon Mar 15, 2010 7:50 pm

catalin gramada wrote:For ECC81 with 22K CF load must keep 350-320 V over plates ?

PS: I put just one section of ECC81 at PI B+ (via 4,7K) and seems it take a lot of current .Voltage drop in B+ PI point from 352 V to 318 V.It is normal ? I don't know what is happened cause this stage take just 5 mA.
I haven't designed the loop for or around this tube!

Larry
The fault almost always is sitting in front of the amp :wink:

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