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Framus Cobra -20dB mod 
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Joined: Sun Jul 22, 2018 2:20 am
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Hi guys, first post ever in any forum here. And I turned 31 today. Better late than never I guess. :)

So the problem I'm having is the Cobra's loop being 0dB, and I like the channel volume up high,
which makes my dd-500 in the loop fart out. And using preamp bass past 9 o'clock isn't really helping either.

Any advice on modding the loop instrument level?

I've already done some mods to the amp:
- Switch for parallel/off/serial fx loop
- Higher gain on crunch channel
- Notch switch functions replaced with Cobra/Dragon..ish voicing
and I'm about to put a fizz cap in it, so it's not like I'm doing something completely new to me.

Thanks in advance.


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Sun Jul 22, 2018 3:29 am
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GABmiral
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Location: Same town as Lindsay Lohan, Amy Fisher, Joey Buttafucco & Debbie Gibson
Welcome to the fold brother! This is the best guitar/amp forum on the interwebznet!!! :rawk:

Can you add a volume pot to the fx loop send?
The easiest thing to do is to plug in a Carl's Custom volume box in, between the fx send and your effect....
https://carlscustomguitars.com/The-Orig ... me-Box.htm
Image

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Walt wrote:
But when the hour is nigh, and the lights are low, and I got a little toothpick of a shwag joint in my teeth, and my friends want to hear me play "Into the Void", or "TNT", "or "Cemetery Gates"...I plug my 600 dollar guitar into my 150 dollar amp, and I am a Rawk gawd.


Last edited by ajaxlepinski on Sun Jul 22, 2018 10:57 am, edited 3 times in total.



Sun Jul 22, 2018 10:42 am
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clipless

Joined: Sat Jan 19, 2013 7:06 am
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I had post already to go - but got distracted (at work) - and must not have hit 'submit'......

anyway - there are any number of pedal makers that sell pedals just to switch from line to instrument level.

Ebtech also makes units - here is their web page.


Sun Jul 22, 2018 10:46 am
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Joined: Sun Jul 22, 2018 2:20 am
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Yeah well, the thing is.. I did consider the ebtech and the g lab equivalent, but I can't justify paying 100+€ for a line level shifter
knowing I can do a small mod in the amp for a few bucks and it does the same thing. Also I like to tinker and learn new stuff.

I'm an electrician by profession, and I've seen how we are being fooled by fancy looking pc-boards costing crazy amounts of money,
like a room temperature sensor which consisted of A SINGLE resistor and two screw terminals soldered to 9x9 cm pc-board inside a 10x10 cm
cheap plastic chassis costing around 50€. I understand they need to make a living, but some things are taken too far. :bang:

And yes, I could add a volume pot to fx loop send, but my concern is will there be enough level boost on the return?


Sun Jul 22, 2018 11:52 am
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GABmiral
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The DD-500 volume level should be able to compensate for using a volume pot to reduce the fx send signal.

The Carl's Custom Volume box is only US$17.00 + shipping. You could build one for less so, why not give it a try?
Test it externally... if it works, you can install it in the amp.

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1969 Sunn Solarus ● 2x 1980's Randall RG-80 ● 2013 Hi-Tone HT103-DG (Winner Best Rig 2014) ● 2015 Mortatone 12/15 Cab w/EV SRO's ● 2017 Jubilee ● Incoming Ceriatone Model Tee
Walt wrote:
But when the hour is nigh, and the lights are low, and I got a little toothpick of a shwag joint in my teeth, and my friends want to hear me play "Into the Void", or "TNT", "or "Cemetery Gates"...I plug my 600 dollar guitar into my 150 dollar amp, and I am a Rawk gawd.


Sun Jul 22, 2018 7:00 pm
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Okay, I'll try that.
And if I want a return level adjustment should I put something like a
100K or 250K volume pot where R46 is?


Mon Jul 23, 2018 6:53 am
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So I threw in some B500K pots I had lying around, one between C36 and fx send,
the other one replaced R46.

The return level pot doesn't do much, which makes sense to me now, being that the signal doesn't
go through the pot. It can be made more effective if need be, just needs a bit more fiddling.

The send level pot has a much greater effect, which was expected.
But somehow it also acts as a low pass filter. A really noticeable one too, which is not what I'm hoping for.
Am I missing something here?


Mon Jul 30, 2018 11:47 am
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Online
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How have you wired it up? A 500k pot is going to be too big and at lower settings will shunt a lot of treble to ground, much in the same way your gain pot does and why bright caps are used.

This is the send from ye typical engl circuit:
Image

Try that. Also check this for a good series loop on page 219:
https://books.google.co.uk/books/about/ ... &q&f=false

If you just want to read on the send thats covered on pg 215.

P.S. buy the book. It's a must have.


Wed Aug 08, 2018 3:33 am
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I thouhgt about 500k pot being too big, so I took it out and tried various resistors instead, like 47k in signal path and 4.7k to ground between C36 and fx send.
The affect is always the same, very noticeable loss of highs, bite and attack. Higher master volume doesn't help.

Maybe there is a way to make the amp sound good at lower channel volume?
Right now anything below 3 o'clock is rreeaally fizzy and dull. Dialing gain back to 10:00 does take the fizz away but it's not enough brootz for me.


Sat Aug 11, 2018 8:55 am
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Sloclone has lots of mods for the slo and this is pretty much the same thing so look there for inspiration about the fizz. They'll have some thoughts on the loop too.

First things I'd try are reduce the cold clipper from 39k to anywhere between 4k and 22k. People tend to like 10-12k here. That smooths the high end hash from the cold clipper. You can also try increasing the 4th stage grip stopper from 220k to 470k or 680k to kill some fizz.


Sun Aug 12, 2018 4:08 am
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