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PostPosted: Tue Jul 02, 2013 9:27 am 
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Mark II

Joined: Tue Apr 30, 2013 8:40 am
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I wanted to convert my 3-channel DR FX loop from parallel to series but after reading through all 6 pages of this thread, I'm just going to take my amp to a tech. :mrgreen:

There are too many "versions" of this mod posted here to know which one is correct. :roll:

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PostPosted: Wed Jul 03, 2013 12:02 pm 
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Mark I

Joined: Sat Oct 24, 2009 12:54 am
Posts: 44
Location: Tucson, Arizona, USA
Dino. wrote:
I wanted to convert my 3-channel DR FX loop from parallel to series but after reading through all 6 pages of this thread, I'm just going to take my amp to a tech. :mrgreen:

There are too many "versions" of this mod posted here to know which one is correct. :roll:


Wiser words have not been spoken. I lost track of what's what a long time ago. :cry:

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PostPosted: Wed Apr 27, 2016 11:02 am 
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Bottle Rocket

Joined: Wed Apr 27, 2016 10:55 am
Posts: 5
jabelardo wrote:
vuhaer wrote:
Rickyfly wrote:
The mod that I describe below is for a truly serial fx loop without any return or ground effects.

is simple to perform.

All function working only pot mix are disconnected


I hope to be state aid

Best Regards
Ricky


Interesting, Can U show me the Schematic of this mod?

thanks for your times, Ricky


it's the same mod shown in this previous post:

mikey383 wrote:
Those 3 three-pronged thingies are transistors. I suspect they are there to recover any gain lost from the loop.

The mod is actually a little easier than that, and you don't have to remove the transistors:

Image

The 0 ohm resistors are those blue ones beside the jacks with the single black stripe.

[EDIT]I removed the footswitch mod because I don't have the complete documentation.



Does anyone actually have pictures of what this mod looks like when it's done? I have no idea what the wiring diagram even means, but with some explanation and some pics I can get this thing done easy with a soldering iron.

Also, I keep hearing conflicting information. Does sound actually bleed through with this mod? For instance, if after the mod I left fx loop un-patched will I hear anything at all coming through? Thanks.

I have a Dual Rectifier "Solo Head". 3ch.


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PostPosted: Wed Apr 27, 2016 5:25 pm 
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Mark IV

Joined: Thu Aug 15, 2013 12:20 am
Posts: 655
Location: Tucson, AZ
https://warpedmusician.wordpress.com/2015/08/27/in-action-dual-rectifier-loop-mod/

This one is easier. It took me more time to remove the chassis than to mod it. It's also reversible, in case anyone ever wanted it completely stock.

Modern bleeds through. The proximity effect of a triode or capacitance in the amp lets a small amount of sound come through. Very small. Like, my-TV-drowns-it-out small. I think the lack of NFB for Modern makes the power amp pickup just enough bleed-through to whisper it.

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PostPosted: Thu Apr 28, 2016 11:28 am 
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Bottle Rocket

Joined: Wed Apr 27, 2016 10:55 am
Posts: 5
So then nothing on the schematic from Mesa? I'd be more inclined to do the one they recommend than "the really easy one someone posted on their blog that one time." :lol:


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PostPosted: Thu Apr 28, 2016 7:43 pm 
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Mark IV

Joined: Thu Aug 15, 2013 12:20 am
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Location: Tucson, AZ
I posted it on my blog and those pictures are my amp. There's nothing wrong with the Mesa way, but it doesn't have to be that much work.

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PostPosted: Fri Apr 29, 2016 9:24 am 
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Bottle Rocket

Joined: Wed Apr 27, 2016 10:55 am
Posts: 5
@afu, First thing I should have said was thank you, I understand you're just trying to be helpful. I do really appreciate it. I would just prefer to do the mod given by Mesa is all.


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PostPosted: Fri Apr 29, 2016 9:34 am 
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Bottle Rocket

Joined: Wed Apr 27, 2016 10:55 am
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With regards to bleed. Have you ever accidentally not plugged in the amp to a cabinet and heard the tubes "sing" (don't know the right word for it) when you play? Could that be what's getting misinterpreted as bleed?


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PostPosted: Fri Apr 29, 2016 9:54 am 
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Mark IV

Joined: Thu Aug 15, 2013 12:20 am
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Location: Tucson, AZ
There's even an easier way to do the Mesa mod:

    Desolder the wires going to the Return pot from the board.
    From those holes, jumper from the second hole to the third.
    Locate and remove the send and return jfets (only 2).
    Jumper the source and drain holes (which should be the outside legs for a j175).

Now there's a straight path from send to return and loop switching is defeated.

As far as bleed: I was running the send to a processor and using headphones. There was still a whisper coming from the amp when Modern was selected.

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PostPosted: Fri Apr 29, 2016 11:05 am 
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Bottle Rocket

Joined: Wed Apr 27, 2016 10:55 am
Posts: 5
Yea I've seen that one too, afu. Thanks for the input, btw. Sucks because I use the modern mode on the amp. I know almost nothing about electrical engineering, but being that the Mesa mod includes running the signal through those resistors can that have any affect on bleed?

I found these pics. Almost what I've been looking for. The step that's missing is the connections to the 0ohm resistors. So based on the documentation I understood that the "forward end" of the resistor would be the end closest to the front of the amp. Am I correct in that assumption?

http://s269.photobucket.com/user/zoomzi ... a.jpg.html
http://s269.photobucket.com/user/zoomzi ... 5.jpg.html

Won't let me add the images. :x


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PostPosted: Sat Apr 30, 2016 9:45 am 
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Mark IV

Joined: Thu Aug 15, 2013 12:20 am
Posts: 655
Location: Tucson, AZ
I do believe the end of the resistor pointing toward the front is the end to lift. If in doubt, just double check the track when you have that board in front of you.

The bleed is inherent to 12ax7 tubes. They're two stages in one tube. If one stage has a large signal on it, it's easy for the other to pick up a little of it.

The reason Modern can be heard is probably related to the negative feedback reducing gain in the power amp of the other modes. All the dirty modes are bleeding through, but the NFB filtering scrubs it out after the fact, because it makes the amp less sensitive to noise.

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PostPosted: Tue May 10, 2016 10:14 am 
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Bottle Rocket

Joined: Fri Apr 22, 2016 12:58 am
Posts: 18
I'm thinking about doing this mod for my Tremoverb. Only thing is I'd really like to keep the effects loop switchable. Earlier in this thread, someone alluded to the idea that the mod allows effects switching to remain intact on the Tremoverb. Can anyone verify if this is true?


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PostPosted: Sun Nov 26, 2017 5:13 pm 
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Mark II
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Joined: Mon Jan 30, 2006 4:24 am
Posts: 121
A question for who made this mod:

my Triple Recto has the fx loop mod made by desoldering only one wire from the MIX pot.

Is my mod the same as the one on the last posts?

I'd like to understand someone has tried different fx loop mods and also noticed sound differences between the mods, thanks!


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