Boss GE-7 Mods

A forum devoted to mod, tips and suggestions for upgrading and rehousing your VERY CHEAP commercial stompbox to near boutique excellence.

Re: Boss GE-7 Mods

Postby rychus » 12 Jun 2013, 02:45

That's cool. I get it.

I will have to start looking at schematics sooner or later or I will never get used to them.
My common threads are, I'm a musician and a solderer. I can follow directions but creating them, not so much.
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Re: Boss GE-7 Mods

Postby candletears7 » 03 Nov 2013, 06:24

Well I've spent about an hour playing around with my Taiwanese GE-7.
I did the mods that Roseblood kindly posted and here's what I'm getting.

LED lights up when power is plugged in. Pressing the switch turns it off, and it won't come back upon repeated switching the footswitch.
Slight distortion
EQ sliders are largely inneffective
volume slider seems to work

Any ideas?
I'll go backwards through the mods and restore it to stock, but I'm very surprised it didnt work as luckily 99% of what I do fires up first time! :) :hmmm:

Pics

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Re: Boss GE-7 Mods

Postby candletears7 » 03 Nov 2013, 11:29

haha what a dick. Looks like a did the 3 chip mods on a 4 chip unit.!
:o :oops:
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Re: Boss GE-7 Mods

Postby candletears7 » 03 Nov 2013, 14:03

And done.
Let this be a lesson - make sure you know what version you have before you start ripping parts out willy nilly!
I haven't got 3 of the same chips available to try them so the original Sharps are in.
However the Panasonic caps have made a world of difference. The pedal is much clearer and less hollow sounding. Well worth doing.
Thanks to those who posted their contributions :)
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Re: Boss GE-7 Mods

Postby BigB23 » 03 Nov 2013, 17:59

Hi i have been trying to remove the flip flop and put a 3pdt switch
i removed the output buffer and the flip flop switch
but i dont no if there more i can remove
thanks
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Re: Boss GE-7 Mods

Postby candletears7 » 04 Nov 2013, 00:42

Id get one of the click less truebypass circuits. Non mechanical switching is much better in terms of reliability.
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Re: Boss GE-7 Mods

Postby mortad » 17 Nov 2013, 11:08

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Re: Boss GE-7 Mods

Postby JRM » 19 Feb 2015, 10:03

Hi,

I've got one of these lightly used on e-bay and also found the hiss issue... Should have searched here better before surfing evil-bay :slap:
Reading about hiss solving mods and I'm quite confused about which IC should I use. Options I've found were:
    JRC4580D (analogman)
    RC4559P (monteallums, Marty)
    TL072
    OPA2134
    NE5532
    LM383
I'll never operate this through batteries so current draw isn't an issue. Price of the OPA2134 is usually high and I think that it requires bipolar voltage supply (+/-9V). What's the most reasonable option?

Thanks.
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Re: Boss GE-7 Mods

Postby davizerrat » 22 Feb 2015, 01:39

Hi!

I read that installing a C 220pF in parallel with R26 10K can reduce background noise hiss .
but basing these calculations:

fH=1/(2*pi*C*R)

GE-7 works at most until 6,8KHz . if you consider 8 KHz . The value of this cap could be arround 2,2nF .... :scratch: ?
I'll try . already I comment ...

best regards DZ.
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Re: Boss GE-7 Mods

Postby davizerrat » 22 Feb 2015, 23:03

Hi,

I've installed on the GE -7 and have noticed decrease noise . It has completely disappeared in the first 3 bands (UP-DOWN). As for the sound of the guitar, I have not noticed any difference.
I will try to modify the 2 loops of r25 and r26 and I will design cut from 8Khz to test results .

Has anyone measured the frequency at which the pedal generates the hiss ?
A friend told me to 8kHz ground noises are located. Then the court is right in this place and perhaps not be avoided altogether.

Now I'm using 3 RC4559/TL072 , 1 OP275 and I changed the caps by ECQV . The issue is that I would like to attenuate noise more. Not to change the IC by coils ... :scratch:


regards DZ
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Re: Boss GE-7 Mods

Postby JRM » 24 Feb 2015, 02:36

It's strange that you still have noticeable hiss with the OpAmp swap.
I've analysed the datasheet of several OpAmps and I think I'll use JRC4580D for the U1-U3 positions and leave the U4-U5 untouched. NJM2068 isn't that bad regarding noise and THD. On the other hand TL022 really sucks. Almost every decent IC has 10 times less noise (TL072 has about 3 times less).
On my previous post I've written LM383 but that's a typo, I meant LM833 but I can't edit the post anymore.
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Re: Boss GE-7 Mods

Postby davizerrat » 24 Feb 2015, 13:08

Thanks JRM,

finally did not like the cut to 8khz..... :oops: The clean sound but no difference was seen with Metal Dist, removes some of the harmonics having the bands at 0db. Maybe me install the new PCB assembling of 470pF which cuts inaudible frequencies ...

Now I use 3 x 4559P and 2 x opa2134pa. The sound is very good and the hisss has greatly diminished but hey up the bands...

I guess some noise has to be right? i always when you have bands to + 15dB ..... Regards
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Re: Boss GE-7 Mods

Postby Ramsay » 24 Mar 2015, 16:08

My favourite modded MIJ GE-7 has a 5534AN input op amp on a single Stacked Chip Adapter board, pre-emphasis circuit removed, and LF353 dual op amps in the gyrators. It's clean and quiet with low hiss and noise when bypassed or engaged, and sounds...."musical", when I push the sliders up. I run all my GE-7s one from a regulated 12vDC supply.


I think that LF353N is still noisy (25nV). The stock TL022 is 50nV.
Why not use RC4559 (5nV), RC4558 (8nV) or TL072 (15 nV) in the gyrators?
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Re: Boss GE-7 Mods

Postby Ramsay » 25 Mar 2015, 22:58

Finally I made mods in my Boss GE7.
In the gyrators, I pulled out the three TL022 and put three RC4558P.
In place of the two 4558 "in line" put two Burr Brown OPA2134 through sockets installed in two mini-card.

I turned on and all that the "hiss" practically disappeared, and the sound, at least apparently, is more transparent, more hi-fi.
But this I will only know for sure when playing loud guitar at the weekend.

Below a picture of the pedal after the changes:

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Re: Boss GE-7 Mods

Postby mildew » 20 Oct 2016, 06:28

http://www.hobby-hour.com/electronics/s ... ematic.png

I would like to remove the pre and post emphasis on my ge7, cctsim said "I have removed them both from my unit by converting the first op-amp to a voltage follower and removing C27 and R33. Also, R33 needs to be replaced by a short."

I can do the component remove / short part, but how do i convert the first op-amp to a voltage follower? (circuit in link above)


thanks in advance :)
Last edited by mildew on 20 Oct 2016, 08:05, edited 1 time in total.
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Re: Boss GE-7 Mods

Postby phatt » 20 Oct 2016, 08:05

mildew wrote:http://www.hobby-hour.com/electronics/s/schematics/boss-ge7-equalizer-schematic.png

I would like to remove the pre and post emphasis on my ge7, based on the circuit diagram above can anybody tell me what to change?


thanks in advance :)


Remove C27 & R36. (the easy bit)
Then make C20 larger.
You may have to try a few values at C20 to find the balance, values between 1uF up to 10uF should deliver. If the bass is too much then just lower the value of C20
It will likely have more volume but you just find the balance with the Volume control.
HTH,, Phil.
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Re: Boss GE-7 Mods

Postby mildew » 20 Oct 2016, 08:07

thanks phatt, i edited my post for clarity just as you were answering it, thanks for the info.
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Re: Boss GE-7 Mods

Postby phatt » 20 Oct 2016, 08:55

Cool,,, Yes if you can find a way to convert first stage to a follower then That will likely make a big improvement on this noise prone circuit.
Just bridge R31 with a link and lift one end of C20 or R28 ,, either end takes them out of circuit. If it works then remove and clean up later.
The circuit will have less gain but in the case of EQ extra gain is likely causing or adding to the noise problems.
Just be aware that the PCB is the only part that is non replaceable so the less soldering the better.

A friend purchased a cheap Behringer EQ pedal last week ($20) and it does not suffer from the noise problem,,, Quite impressive considering how cheap they are. I use an old Hifi graphic EQ sometimes and it works magic but a bit bulky to carry around,,hum I might have to get a Behringer for myself.
Phil.
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Re: Boss GE-7 Mods

Postby phatt » 20 Oct 2016, 09:02

I just realized,,, if you do the follower mod and find there is too much difference between on and bypass then look at raising the value of R25 to give it a kick. That should (I'm guessing here) give you gain but with less noise.
Phil.
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Re: Boss GE-7 Mods

Postby mildew » 21 Oct 2016, 03:57

thanks for the help phatt - but i now realise my circuit diagram is for the wrong version of the pedal. duh :slap:

Based on my (wrong version) diagram it seems to me that the pre emphasis is a cathode bypass cap and the post emphasis is a passive RC network, so both should be far less nasty on my guitar tone than the eq gyrators anyway.


On the positive side, today i did the opamp swap out and now have 3x RC4559's and a OPA2134 working, and the changed caps for c13 and c23

Once my order of Panasonic caps arrives i can finish of the cap replacements and start sculpting toanz 8)
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