ross compressor farting..

[tam]

hello all!
just finished the ross compressor (from tonepad) and im geting signal and gain,(and compresion) but the sound is distorted or gating or what ever you want to call it...ive built and debugged many fx pedals before,but this one just drives me crazy...
i checked the pcb for problems like 4 times.
i checked component placement and values.(measuring on board)
i tried messing with the trimer.
checked the battery.
i meassured the voltages from ic and transistors,and compared to the list in the fuzzcentral page-all of them correct.
im using humbacker pickups-so i tried playing trough the effect with low volume on the guitar-didnt help..
i searched to read some posts about this problem-with no luck..
does anyone have an idea of what the ##@# could be wrong?!
ill be very greatfull with any suggestion...thanks alot.

[Fret Wire]

What are you using for an IC (chip) and transistors?

[tam]

i used the ca3080e and all 2n3904.i also tried another chip(from the same type)...

[ragtime8922]

I built 3 of these (1 complete and 2 on breadboard) with top of the line components with the 2SC1849 transistors once and 5088's and 4401's the other time. The 2 breadboard units were made as both ross and dyna variations and I got the same result on all three. A WAY TOO BASSY OUTPUT. I used the CD3080E. Is this also part of your problem? Is this the nature of this pedal or are we having the same problem? On the complete model I used Military Vishay-Dale metal film RN55D and ERC resistors, panasonic polypropylene ECQ-P's for the caps with a silver mica 220pF roll off cap that was changed to every value in the world. I had dreams of Keeley comp tones but......

[ragtime8922]

BTW Tam, if you get it working and then you want to have the final touch of the exact Ross transistor hit me with an e-mail. I have a bunch as I couldn't find any other way to get the 2SC1849 without buying a bunch.
I used them in a ton of other apps and I like them. Most recently as an input transistor in a TS variant of mine. (Can't locate a damn data sheet though). A Japanese site I found just last night rates the Hfe at 250.

[tam]

i dont know if we have the same problem...
the sound is way to much distorted  for it to be the nature of the pedal.
i guess that one or two of the transistors are misbiased.
ill try to invastigate a bit more.. :shock:

[Fret Wire]

http://diystompboxes.com/sboxforum/viewtopic.php?t=24957&highlight=ross+compressor

[Fret Wire]

They are know to be somewhat bassy, but it's starting sound like an off board wiring problem or a bridged solder trace. Did you check out the board with a good magnifying glass?

[ragtime8922]

http://diystompboxes.com/sboxforum/viewtopic.php?t=24957&highlight=ross+compressor

Thanks so much Fret/Mr. Soze. Seriously! As long as I've been in to FX building I made the grave mistake of not joining the forum until yesterday offically. (I signed up a while back but never participated) That link helped a ton. The comp was on the back shelf but will come back out to the bench.

[Steve C]

i dont know if we have the same problem...
the sound is way to much distorted  for it to be the nature of the pedal.
i guess that one or two of the transistors are misbiased.
ill try to invastigate a bit more.. :shock:

I'd start with the bias and in particular the voltage reading of the 150K resistor right after pin 6.  What is your reading there? If this isn't just right you'll get the results you are describing no matter where you turn the trim pot.

Did you follow the parts list?  Especially the resistors in the power section that give you the Vb?  What is the reading of your Vb?

I just made a compressor that's a cross between a Ross, Saffron Squeeze, and Boss CS-2.  I ended up using the biasing on the CS-2 which is a little different, but worked better.

[tam]

hi,thanks for the replyes everybody.
im getting a vb of 2.4v with my power supply at 7.5v on load.(battery is 8.15v).  should it be more like 3.7v?
where should i target my search for fixing that?
thanks :roll:

[Steve C]

Well I looked at the Tonepad ross project (actually I think they all say 56K) and it says to use a 56K from V+ to the 27K to ground which you get the Vb from, but it should really be a 5K6, or 5.6K.  I'd set your trim pot to the middle and change the 56K resistor to a 5.6K and the problem should be solved.  

The Vb should be more like 3V, less than half the supply voltage.

[tam]

changed the 56K resistor to 33K for getting 3.1V at Vb ,wich gives a better resolt, but still the sound is like pumping with a bit of distortion.
steve,can u try to explain why the Vb should be at 3V?
and another thing:wich are the caps that give this very bassy sound?
thanks

(i should mess around more with the music then with this... :idea: )

[Steve C]

changed the 56K resistor to 33K for getting 3.1V at Vb ,wich gives a better resolt, but still the sound is like pumping with a bit of distortion.

I'd still change it to a 5.6K to know for sure it's not that.  

steve,can u try to explain why the Vb should be at 3V?

Read this: http://www.generalguitargadgets.com/diagrams/geo_d&r_comp.pdf


I put a new battery in my clone and with a battery measuring 9.5v, I got a reading of 3.1v at the point of the 150k and Vb (with a 7.7v battery I got 2.5v to the same point).  So therefore the problem may be somewhere else.

[Thomas P.]

Did you notice that there were minor changes to the component values over at GGG which (I think) fp didn't implement? I too had the problem of too much bass and that's exatly what the changes are about.

[Kleber AG]

Also on GGG schem C11 is 0,01 but I have a "script logo" Dyna Comp that is original and for C11 have 0,001

RGs schem also uses 0,001

I think that C11 with 0,01 would filter too much treble :shock:

I may be misunderstanding something, but...

Regards
Kleber AG

[tam]

thanks again for trying to help, but im starting to think it is the nature of the pedal....could that be? i dont know.
i have the right caps(220p-not 0.0022u,and 1n at c11) and the right voltages at the transistors and ic pins,but still the thing sounds bad...
i dont think its playble-it makes this "poof" every time i hit a note and it goes into compresion.altough u can here the compressor working just fine at max sustain, the sound is just not clean.
do you guys have it working clean?like really clean notes?
:cry:

[tam]

hi people.....
at last i found the problem....
as u all can guess- it was a solder bridge....
it conected the .05 cap at the emiter of q2 to the 10k thats going to the level control....so now its clean! :wink:
and now its tweakble for getting the sound i like....
thanks everybody,this place is great-it seems everyone is a technician
here...let us not forget the music...

regards