Author Topic: Green Bean Low(ish) Gain / Sustain ETC  (Read 1266 times)

Zerstorte Zelle

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Green Bean Low(ish) Gain / Sustain ETC
« on: October 16, 2012, 04:47:34 PM »
Hey all.

Just built a Green Bean without the "Bright" switch. 1N270 in the asymmetrical and 3mm LEDs in the Symmetrical diode spots. with an ON/OFF/ON comp switch.

The 1N270 are significantly lower output. Almost off and fairly useless. It sounds like there is a little fizz underneath some clean but pretty low.

Both LED and No Clipping options are much louder but not a wild amount of gain on tap ( or rather drive ) but plenty of volume in those two settings. Op Amp is JRC4558D. I don't have a tube screamer on hand to compare but it's not blowing me away right now. I remember the sound a bit differently. Anyone have any opinions?

Best,

ZZ

jkokura

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Re: Green Bean Low(ish) Gain / Sustain ETC
« Reply #1 on: October 16, 2012, 04:51:35 PM »
It sounds like you are having some sort of issue, that doesn't sound like it's right.

Have you taken any debugging steps thus far? Perhaps even sharing your voltage readings would tell us something.

Jacob
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GermanCdn

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Re: Green Bean Low(ish) Gain / Sustain ETC
« Reply #2 on: October 16, 2012, 04:55:44 PM »
Further to what Jacob said, the first thing I'd do is see if you didn't maybe crack the housing on the underside of the 1N270, as they are pretty fragile and if you don't bend the legs just right, you might break the housing but not notice it because you've got it soldered down against the pcb.

You will naturally get less output in the germanium stage, but not drastically less.
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oldhousescott

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Re: Green Bean Low(ish) Gain / Sustain ETC
« Reply #3 on: October 17, 2012, 07:26:01 AM »
I once had a CMATMODS Signa Drive (TS-ish) that switched between LEDs and asymmetrical small-signal diodes (914s or 4148s) and there was a big difference in volume between the two, so that part of the situation is not necessarily unusual.

You should, however, get plenty of drive in any position -- smoother with the diodes, crunchier with the LEDs or no diodes/op-amp only clipping (with the drive cranked up, obviously). Check your R6 value is indeed 4.7k and not 47k or 470k. Perhaps it was swapped with R7 by accident.

Zerstorte Zelle

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Re: Green Bean Low(ish) Gain / Sustain ETC
« Reply #4 on: October 17, 2012, 09:08:43 PM »
thanks for the input all. it will be some days before i get back home to the bench i'll check it all out for sure and get back.

also im seeing that the bright option may be subtractive so i suppose if Im not using it i should jump those pads as well.

ZZ

oldhousescott

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Re: Green Bean Low(ish) Gain / Sustain ETC
« Reply #5 on: October 18, 2012, 07:50:56 AM »
Yes, if you don't use the bright switch, jumper the pads.

Zerstorte Zelle

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Re: Green Bean Low(ish) Gain / Sustain ETC
« Reply #6 on: October 23, 2012, 11:54:57 PM »
so looking at the voltages now. from the solder side of the board starting with the square pad and moving clockwise i have...

4.61
4.64
4.61
0
4.61
4.62
4.62
9.24

As far as the germ diodes no open leads there according to my meter. I'm at a loss currently.

ZZ

slimtriggers

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Re: Green Bean Low(ish) Gain / Sustain ETC
« Reply #7 on: October 24, 2012, 07:18:32 PM »
Check the pot value, too.  I once used a 500r pot instead of a 500k for the drive and it gave similar results.