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 abakuzam » 11 Mar 2012, 12:31

blackbunny wrote:The HA12017 version of the GE7 has a subtle high frequency pre-emphasis (boost) at the input stage to help reduce hiss, with de-emphasis near the output. This seems to work fairly well, as the HA12017 has pretty decent noise performance anyway, and the M5218A also has low noise specification.


thank you very much, but you mean ge7-B right? :D
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Re: Boss GE-7 Mods

Postby blackbunny » 11 Mar 2012, 15:31

Yes, they are almost identical circuits, with some capacitor values increased in the gyrators (IC1 A/B, IC2 A/B, IC3 A/B) to lower the centre frequencies of each EQ slider to cover the bass guitar better.
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Re: Boss GE-7 Mods

Postby phatt » 12 Mar 2012, 06:25

blackbunny wrote:The HA12017 version of the GE7 has a subtle high frequency pre-emphasis (boost) at the input stage to help reduce hiss, with de-emphasis near the output. This seems to work fairly well, as the HA12017 has pretty decent noise performance anyway, and the M5218A also has low noise specification.


Subtle????? Holy Mackerel mate that thing is the worst circuit you would ever want to use. [smilie=rlp_smilie_207.gif]

The De-emph on the end hardly fixes it.
Besides I believe that HA chip was designed for Hifi Phono PU where the supply would be 40 VDC.

IMO a very complicated way around a simple circuit.
Just my observation after using one years back.
Phil.
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Re: Boss GE-7 Mods

Postby blackbunny » 12 Mar 2012, 14:51

It certainly is an unusual choice of IC for a pedal powered by a 9v battery, but nevertheless has pretty good noise and distortion specs.
IMO it's mainly the pre-emphasis circuit that messes with the guitar's tonal qualities, rather than the HA12017 IC.
If I was building a GE-7 clone I would ditch the pre-emphasis / de-emphasis circuits and use a readily available low noise op amp for U5. Just a flat response, linear signal path using an OP134, NE5534AN or even TL071 would give good results.
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Re: Boss GE-7 Mods

Postby phatt » 12 Mar 2012, 14:58

blackbunny wrote:It certainly is an unusual choice of IC for a pedal powered by a 9v battery, but nevertheless has pretty good noise and distortion specs.
IMO it's mainly the pre-emphasis circuit that messes with the guitar's tonal qualities, rather than the HA12017 IC.
If I was building a GE-7 clone I would ditch the pre-emphasis / de-emphasis circuits and use a readily available low noise op amp for U5. Just a flat response, linear signal path using an OP134, NE5534AN or even TL071 would give good results.


Bingo! :thumbsup

They probably found a warehouse full of cheap unwanted chips and worked out the cost factor could save a few bucks :roll:
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Re: Boss GE-7 Mods

Postby StratWiz » 17 Apr 2012, 16:11

I have a vintage Boss GE-7 (all original), except jumpered resistor & diode to make it work with 9v PDS & brighter LED.
When bypassed the sound is a bit dull or tone sucked compared to true bypass (by completely eliminating the pedal). Is this common or a problem in my pedal? What would be a solution to that?

I noted some folks said to not replace the HA12017, but I believe Monte's mod suggests replacing it with Dual Stacked Chip Adapter with a pair of Burr Brown OPA2134PA opamps. Has anyone had such a problem and solved it?

Thanks,
SW
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Re: Boss GE-7 Mods

Postby StratWiz » 18 Apr 2012, 19:10

MonteAllum's GE7 mod includes a resistor change, I appreciate more details about it.
Thanks,
SW
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Re: Boss GE-7 Mods

Postby gigant0r » 15 May 2012, 20:54

Hi all,

I've got this half broken GE-7 (Taiwan made) which I'd like to fix. Level and 1.6k sliders doesn't work.
Anyone have an idea what to look for?

thanks!
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Re: Boss GE-7 Mods

Postby blackbunny » 22 May 2012, 02:07

StratWiz wrote:I have a vintage Boss GE-7 (all original), except jumpered resistor & diode to make it work with 9v PDS & brighter LED.
When bypassed the sound is a bit dull or tone sucked compared to true bypass (by completely eliminating the pedal). Is this common or a problem in my pedal? What would be a solution to that?

I noted some folks said to not replace the HA12017, but I believe Monte's mod suggests replacing it with Dual Stacked Chip Adapter with a pair of Burr Brown OPA2134PA opamps. Has anyone had such a problem and solved it?

Thanks,
SW


I installed this Allums mod kit with the Dual Stacked Adapter and BB OPA2134s in one of my MIJ GE-7's. This version also has 4559 op amps in the gyrator circuits replacing the stock IRC022s, and IC4 is a TL072 replacing the 4558.
A/B'd against a stock MIJ GE-7 the sound is a little fatter or warmer, with noticeably lower noise, and the bypass is clean with almost no tone suck IF you put the GE-7 after another buffered pedal.
The guitar signal goes through the input op amp and the pre-emphasis circuit in this version, so it will still mess with your guitar tone when bypassed. It's more noticable if you plug your axe straight into the GE-7.

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.

StratWiz wrote:MonteAllum's GE7 mod includes a resistor change, I appreciate more details about it.


The only resistor change is R1, which is changed to 100 ohms in Allums kit for less voltage drop, allowing the pedal to run off a 9vdc supply. You have already bypassed the power supply series diode and R1.

IMO, the modified GE-7's should be run from a regulated 12-18vdc supply for lowest noise and improved headroom.
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Re: Boss GE-7 Mods

Postby Sadcadaver » 07 May 2013, 19:57

Hi folks, I've just got hold of an old japanese version of this pedal, completly dead though. I've given it a quick once over, and I can't find the problem.

Do you think I should go ahead with the mods anyway, in the hope that I might fix what's wrong, or is there something that's more likely to be the problem, like, the momentary switch? Maybe I should just replace everything? What is erong with using 1/4 watt resistors?

Any advice is appreciated.
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Re: Boss GE-7 Mods

Postby tasteless » 07 May 2013, 21:34

Sadcadaver ,
I reckon You should have a go at fixing it first - You just might learn a thing or two along the way.
Print out the schematic , Look at where the power enters the cct - Check the polarity protection diode and the power supply filter caps.
Are the op-amps seeing any voltage ? - If not , Ask Yourself what is between Them and the power supply.

Replacing everything is a bit extreme But , would probably work ( You would need to take a lot of care re-soldering the whole pcb - small tracks easily damaged ).
You could try replacing components in small groups - ie - start with all the electros , then the diodes , then the fets etc.. ( Probably be fixed at this point ).
1/4 W resistors are fine for 9V ccts and about all You could get away with in something as crammed as a GE-7.
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Re: Boss GE-7 Mods

Postby Sadcadaver » 08 May 2013, 01:32

Thanks for the good advice Tasteless, seems obvious-once somebody has pointed it out to you! :slap:

I've actually managed to get it working now, think all that messing about looking for the problem must have moved a connection or something. Man, this thing is hissy! I'm certainly going to have to replace those opamps and tants... might replace the electrolytic cans too...
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Re: Boss GE-7 Mods

Postby tasteless » 08 May 2013, 05:55

:thumbsup Cool !

I can't remember exactly what I did to mine But , It was more or less what's covered in the first couple of pages of this thread.
Just new electros and socketed ICs ( pretty sure I used NE5532 ).
At the time , I borrowed another one - to do some A/B testing - And the difference was quite astounding , like night and day.
It really IS almost silent.
I dare say You will also be very satisfied once completed.
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Re: Boss GE-7 Mods

Postby roseblood11 » 08 May 2013, 08:18

Sadcadaver wrote:Thanks for the good advice Tasteless, seems obvious-once somebody has pointed it out to you! :slap:

I've actually managed to get it working now, think all that messing about looking for the problem must have moved a connection or something. Man, this thing is hissy! I'm certainly going to have to replace those opamps and tants... might replace the electrolytic cans too...


I'd recommend all mods that I described on page 1 (photo on page 2), but I'd use LM833 for all opamps today. If you replace all electrolytics anyway, make sure that they are rated for at least 25V, better 35V. You could use a 18V supply or maybe add a voltage doubler later.
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Re: Boss GE-7 Mods

Postby Sadcadaver » 08 May 2013, 13:06

Cheers for the advice guys... really appreciate it! :thumbsup

I was looking at opamps from all my usual suppliers last night... the OPA2604 is nearly five quid *shudder* but it must be good for that price... right? I was thinking of using one in place of the SIP and TL072's in the other positions (but now I'll use LM833's on your suggestion Roseblood- unless you think I should use them in all positions?)

The electrolytics I was planning on replacing them with non-polorized caps if I could find the values... or if I can't, would it be detrimental to use tants in those positions? I'll make sure they're rated 25v or over anyhow... I tend to err on the side of caution when buying capacitors anyway. I was planning on running it on 9v, so I was going to change R1 and D1. My PSU can run it at 18v, which I think might be a bit excessive (especially if I change out R1 and D1 and allow more voltage through, right?). I'll probably get round to making a 12v PSU at some point.
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Re: Boss GE-7 Mods

Postby roseblood11 » 08 May 2013, 17:23

I replace cheap electrolytics with Panasonic FC, they are small, not too expensive and the quality is good.

You could use LM833 for all positions, I think the OPA2134 is actually a bit noisier. But that really doesn't matter...
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Re: Boss GE-7 Mods

Postby rychus » 11 Jun 2013, 21:11

roseblood11 wrote:Hi,

-replace the three JRC022D with RC4559P
(NE5532AP, OPA 2134, OPA2132 or OPA2604 should work as well and maybe even sound better, but the 4559 is a good and cheap choice here - it´s most important to replace the NJM2068 with a high quality, low noise chip, see below...)

-replace capacitors:
C18,C25, C29, C30 : 0.047 µF
C21, C22, C32 : 1 µF
C13 : 0.1 µF
(use stacked metal film caps (MKT) for all positions!!! Panasonic ECQ-V series sounds very good here)

-Replace NJM2068 at position IC3 with a OPA2134 (use a DIP-SIL-Adapter or built an adapter using perfboard). (Look at the photo below)
DIP-SIL-adapter: http://www.musikding.de/product_info.php/info/p1639_Adapter-DIP---SIL.html (you can buy them from Monte Allums, I guess)


These mods only work with the new version of the GE-7, which looks like this:




Hi guys, reading through this thread in prep to mod my vintage GE-7. Roseblood11, is this whole comment only for new GE-7's or just the part with the DIP-SIL-Adapter? I like the simplicity of this procedure but I want to make sure it's appropriate for my vintage box.



Qatbyte wrote:Here is my compiled list of changes that I've gleaned from the various postings for the VINTAGE Boss GE-7 with three TL022 opamps in a row. FWIW.

Replace the following capacitors with Panasonic ECQ-V stacked metal film poly caps unless noted.
C1 .047uF
C2 .039uF
C4 .1uF
C5 .15uF
C7 .33uF
C9 .68uF
C10 1.5uF
C11 1uF
C13 0.1uF (to give better base)
C16 10uF
C17 100uF
C18 47uF
C19 1uF
C21 47pF silver mica
C22 0.047 uF
C23 0.047 uF
C24 0.047 uF
C25 1 uF
C26 0.047 uF

Add silver mica 270 pF x R26

Replace the following resistors with 1/2 watt MF
R1 47R for greater opamp current with newer opamps or jumper instead.
R10 380R LED resistor
R14 1K
R24 3.3K
R25 3.3K
R26 10K
R27 10K
R30 10K
R33 4.7K

Diode
D1 replace with Schottky diode 1N5817 or similar. Or, jumper connection. Or, upgrade zener to 12v and change input power to 12v. I chose to keep it at 9v and thus will try 1N5817.

IC1,2,3 install DIP sockets then plug and play to your heart's content any of the following opamps: OPA2134PA, NE5532AP, RC4559, RC4558P, RC4558DD, TL072.

IC4 is JRC4558DD and is acceptable as is.
IC5 is a SIP that is not acceptable but is too much trouble to upgrade.


Two questions for Qatbyte,
What is meant by the "270pF X R26"? Does it mean to place in parallel?
For R1 and R10, What does the R after the value mean? (ie. 47R and 380R )

If your still out there I would really appreciate some clarification.

Thanks everybody for great info and fun projects.
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Re: Boss GE-7 Mods

Postby roseblood11 » 11 Jun 2013, 23:39

rychus wrote:
roseblood11 wrote:I like the simplicity of this procedure


It's simple because someone else did the thinking. Why don't you compare the schematics of both versions (both are online) to identify differences in the circuits or the parts numbering?

"47R" means 47 ohms.
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Re: Boss GE-7 Mods

Postby rychus » 12 Jun 2013, 00:03

I hope I wasn't misinterpreted, I didn't mean to imply the circuit was simple in complexity. It is just a whole lot less work than the quote that followed. I thought it was clear that I didn't design this and I assumed since you posted it in a forum it was meant to be shared.

It is OK if you don't want me to use your mod. I was just gonna change the amps and call it a day but this thread got me ambitious. I don't have the time or the experience to start analyzing schematics so op-amps it is. Thanks for the 'R' definition.
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Re: Boss GE-7 Mods

Postby roseblood11 » 12 Jun 2013, 01:07

What I wanted to say was: modding a pedal like playing "color by numbers" IS a simple procedure. Figuring out the mods isn't... - And now you have to figure out, how these mods can be transfered to the vintage version. I think both versions were a bit different and the parts numbers were definitely different.
By the way: I didn't invent these mods, I just wrote down, what I did with my pedal - I don't remember, who came up with those mods first.
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