All things Green Pre

[3nity]

Peter no sound on my 2nd board would meant what??
Bad BC550???everytime i do a switch on the rotary i can hear it. but still no sounds...like no mic at all...

 

[peterc]

Check all the dc voltages to start with. Otherwise it could be a number of things, check the non-working channel carefully against the working channel.

Peter

 

[3nity]

Alright Peter i did some voltage tests....

First: both channels are a little differents, differents caps mainly.....

seconde my psu is: +18, -18.

On the first IC:
the sounding channel:
1. -4.18
2. 15.10
3. 15.08
4. -18.18
5. 15.03
6. 15.04
7. -4.17
8. 18.36

Now the non sounding channel:
1. 14.84
2. 14.84
3. 14.82
4.-18.16
5. 14.78
6. 15.60
7. -16.45
8. 18.37

My first conclusion is that it might be something non working..

 

[3nity]

Peter some measures at the BC's seems like there is one not workin properly in the non functionnal board...

the bad board:

E. 14.80v
B. 6.66v
C. 14.29v

the good:

E. 15.06v
B. .225v
C. .865v

what should i conclude??

 

[peterc]

I've had the transistors blow up on me before. Replace them, might also have to replace the first IC if it is noisy.

Peter

 

[3nity]

Actually the first IC get quite warmth in less than a minute......

Gonna buy this tomorrow 2.50 $ each. :?

thank you

 

[peterc]

You can use cheap opamps for testing (as long as they can handle your supply voltage), TL 072 etc., then replace with the better opamp for best performance.

But I have had problems with running the Greens at +-18v. Had 4 5532's blow up & split the cases. As SSLKeith said once, is it worth stressing the IC for an extra 1 or 2 dB of dynamic range?

Peter

 

[3nity]

By the way gonna change the trimmer resistor on the PSU 2k8 down to 2k2.
Peter is alright if i use OPA2604 as the first IC and 5532 at 2nd and 3rd IC?

 

[peterc]

2604's also sound VERY nice in this preamp....

Peter

 

[3nity]

Peter i got 2 channels of the Green preamp working nicefully....
I did changed the BC's but not the IC and the sound was low....then i changed the IC and what a sound i got.....

It sounds alright...
thank you.!!!!

Gonna post samples of both channels cuz they are different.....

 

[dissonantstring]

hi peter,
would you recommend changing all three 5532s for OPA2604s or are certain positions better off leaving the 5532 (i.e. are certain ICs more influencial on the sound of the circuit than others)?
thanks.
-grant

 

[peterc]

would you recommend changing all three 5532s for OPA2604s

I used the 2604 in an early version & changed both of them. Didnt try any other config's.

Try some different combos & let us know!

Regards
Peter

 

[dissonantstring]

thanks for the reply peter!
i'll have to get some OPA2604s first, but when i do test i'll report back.
cheers,
grant

 

[3nity]

There is a hiss in one my greens is there anything i should check?? the othe one was a little distorded but i don't know why the Output trimm was bad....

BTW Still great sounding preamp!!

 

[3nity]

There is another issu on the 2 preamps, i have to go unto the 5-6 position in the rotary to have a sound is this normal??

 

[peterc]

Remember the output trim is strictly an attenuator, so winding the trim fully clockwise is the straight clean signal. The trim is just to have some level control into the next stage, usually a compressor.

If you pull out the rotary switch, the gain should be 3 dB if I remember correctly.... Either 0dB or 3 dB, so if you get that result, then check the wiring of the rotary switch.

Peter

 

[3nity]

Peter the way i solder the rotary to the board was the contrary as here, i don't know if there's really an issue there.

'bout the BC560 the ones i got are NTE replacements 2n2003. when i look at them i think that they go the other way around!! i mean the round face goes where the normal BC has his flat face? the center pin is already bended.

 

[3nity]

Still can get rid of the hiss on the second channel....suddenly i sounds like white noise....made a seach and found a thread about someone having trouble with this and opinions were to replace zener diodes???

 

[peterc]

opinions were to replace zener diodes???

You can measure them in circuit using the diode test function on your multimeter.

Peter

 

[3nity]

they seem to be fine...