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eeone
Bronze Member
Yugoslavia
121 Posts |
 Posted - 01/27/2007 : 00:52:00
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Some time ago I started a topic about how noisy GE-7 is. Especially the MIJ ones. Well, I addressed that problem tonight. Basically, I replaced stock TL022 chips (dual opamps) with TL072, added a 200ohm resistor in parallel with R1, and a 270pF capacitor in parallel with R26. I got this idea from a schematic on free info society. And after that, clean as a whistle.  To tell you the truth I jumped for joy.
Anyways, here're some pics.
Unmodded :
Sockets installed :
With new chips :
Close up :
Old chips are now ready for retirement :
I was so anxious to try it out that I forgot to take a picture of the other side of the board.  It's no fun anyway, just a resistor and a capacitor added, so it doesn't matter.
So, there you go. An hour long mod can really improve the performance of your GE-7.
Cheers!  |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 01/27/2007 : 07:31:17
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Hi eeone
Great work & nice detail in the pics, you should also upload the track side mods, for those members that aren't all that technical, but can use a soldering iron & desolder wick.
Or maybe they have a tech friend that will do it for them.
Can you also post the link to the schematic on the F.I.S. web site.
Well done.
It is strange, how some of us have, nothing but noise problems with the GE-7, & others like myself never have a complaint.
Perhaps we should document GE-7 serial numbers verses IC's used verses noise or no noise.
Got another column on your spread sheet Bossarea?
Regards Dr. Bob  |
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eeone
Bronze Member
Yugoslavia
121 Posts |
Posted - 01/27/2007 : 14:26:25
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Hello Dr. Bob
As I said, I forgot to take pictures of the other side of the board. I'll open the pedal and post those a bit later.
Here's the link to FIS : http://www.freeinfosociety.com/electronics/schematics/audio/bossge7.pdf
I've got to say that there is significant amount of clipping even with the mod. Of course, this only happens when more sliders are over 10db. This is a natural thing since opamps saturate when the output volatge is equal or greater than the opamp supply voltage (or even at lower voltages if the opamps used are not rail-to-rail).
quote:
Originally posted by Dr. Bob
Perhaps we should document GE-7 serial numbers verses IC's used verses noise or no noise.
This is not a bad idea. Here's mine:
S/N : B979738
stock opamp : TL022CP
replaced with : TL072
Cheers!
eeone |
Edited by - eeone on 01/27/2007 14:27:47 |
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diggum12
Silver Member
USA
282 Posts |
Posted - 01/30/2007 : 17:33:37
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| Not to argue or be condescending, but why did you choose TL072 chips for the pedal? I don't think those are any quieter than the stock chips, apart from their age maybe being different. |
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diggum12
Silver Member
USA
282 Posts |
Posted - 01/30/2007 : 17:46:25
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| Nevermind, found it. |
Edited by - diggum12 on 01/30/2007 17:47:07 |
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diggum12
Silver Member
USA
282 Posts |
Posted - 01/30/2007 : 17:53:17
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| Try 100 Ohms on R1. That may eliminate the clipping. |
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eeone
Bronze Member
Yugoslavia
121 Posts |
Posted - 01/30/2007 : 18:04:35
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Well, the TL072 were my first and obvious choice. They are working pretty well for now. I'll try different chips when time permits me. That's why installed the sockets. 
I'll definitely try 100ohm R1 ASAP.
Thanks for suggestions.
Cheers! |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 01/31/2007 : 14:13:01
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quote:
Originally posted by diggum12
Not to argue or be condescending, but why did you choose TL072 chips for the pedal? I don't think those are any quieter than the stock chips, apart from their age maybe being different.
Hi Duggum12 & Guys
What would have been your Op-Amp of choice?
Regards Dr. Bob |
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diggum12
Silver Member
USA
282 Posts |
Posted - 01/31/2007 : 18:03:16
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Hey Dr. Bob! Been VERY busy lately...
The TL072's are great IMHO, but I like them better in distortion pedals. Very smooth, but a little noisy. I put RC4559P's in my GE-7 (MIJ), because even though they produce slightly more midrange they are more Hi-Fi.
In then end, trust your ears though. |
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adamskyyy
Copper Member
Poland
9 Posts |
Posted - 02/20/2008 : 00:02:01
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Hi !
Can You show on the shemes hot to modificate g7 boss ?
Thx |
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ChristoMephisto
Platinum Member
Canada
1288 Posts |
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stinkfoot
Silver Member
Sweden
181 Posts |
Posted - 02/20/2008 : 15:16:13
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quote:
Originally posted by eeone
I'll definitely try 100ohm R1 ASAP.
Personally, I'd remove both D1 and R1, and replace them with jumpers. They are the components used to bring the 12 volts DC from the old-style ACA adapter down to about 9 volts, and if you plan on using it with a regular PSA adapter those components need to be jumpered for the pedal to receive full power. Unless of course you power the GE-7 with a daisy-chain or other common ground power supply, together with at least one regular (PSA) pedal - in that case, both D1 and R1 are bypassed, and changing the value of R1 won't make any difference at all.
Keep in mind this applies to pre-1997 pedals - pedals made after that date already have this mod done (the sticker next to the adapter jack will say "ACA" if it is the earlier version). Also, at some point after that date, Boss did a complete redesign of the circuit board layout.
/Andreas |
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ChristoMephisto
Platinum Member
Canada
1288 Posts |
Posted - 02/20/2008 : 15:36:52
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Someone suggested to leave the diode in for protection.
Any truth to this?
Anyone try playing with the values the sliders respond to?
200->250 or the 3.2 slider to 6 to give it a treble presence like on a vox or fender?
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stinkfoot
Silver Member
Sweden
181 Posts |
Posted - 02/20/2008 : 16:06:03
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D5 is the polarity protection diode, so the pedal will still be protected against polarity mishaps. D1 and R1 was removed and jumpered by Boss themselves, to make the pedal fully PSA-compatible.
I don't have the schematic/parts layout for the newer pcb layout, though, so I don't know the component number for the protection diode in that one. Likewise, I don't know what the resistor labeled "R1" in that circuit does, but as it is a PSA-compatible pedal you don't have to worry about that part anyway, if you have one of those.
/Andreas |
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adamskyyy
Copper Member
Poland
9 Posts |
Posted - 02/20/2008 : 23:33:39
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| Thx ! But what is MIJ EQ,s ? How can I check this ? (sorry I am new on this forum) |
Edited by - adamskyyy on 02/20/2008 23:35:30 |
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ChristoMephisto
Platinum Member
Canada
1288 Posts |
Posted - 02/21/2008 : 00:40:21
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MIJ is Made in Japan, like MIT is Tiawan
There should be a country of origin on the bottom label.
cheers, and welcome to the forum |
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Topic |
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GE-7 Noise. Revisited. (pics inside)
