Ross Compressor hiss question

[ronh95]

I just completed my first scratch build, a Ross Compressor clone using the Tonepad layout/parts list.  I also used the Fuzz Central attack switch in it.  This is my first post (besides one response to another thread).  I'd like to thank all those on this forum and on GGG, Tonepad, Geofex and many others that have provided so much useful information. What a great community here!  I did build BYOC TS-808 and enjoyed the process enough to venture into etching/drilling my own board for this pedal.

On to my issue.  My pedal seems to work, although it has a pronounced 'hiss' which only allows me to turn up the Level control about 1/8 turn before it becomes just too intrusive.  I used 1% metal film resistors and poly caps along with the recommended electrolytics for certain positions. The tonepad parts list called for a 100K linear volume pot, whereas the Geofex site has a 50K log pot there.  I ended up soldering a 100K resistor across lugs 1 & 3 of the 100K pot which I think made it a 50K. I used the 100pf ceramic cap (tone cap) instead of the original 220pf one to lesson the loss of highs. I believe the tonepad layout contains the R.G. Keen filter cap additions reflected in the Geofex schem as well as the FuzzCentral one.

I was hoping this effect would perform more quietly, based on the great reviews the Keeley compressor gets for quietness.  I know it's no Keeley, but are there some components I could swap out, perhaps metal film caps in some locations that would help with this?  Maybe I'm expecting too much, just don't know.  Should I swap the modded 100k linear pot for a 50K log?  Any suggestions would be appreciated.  Also, if I need to post the pin readings, etc. please let me know.

Thanks all!   Ron   

[Mark Hammer]

I have to run right now, but search the previous threads about compressor noise.  There are a LOT of them because it is an issue endemic to compressors, period, not just the Ross.  You'll find all the help you need there.

[ronh95]

Thanks Mark.  I'll search again.

I did forget to add, that I used some 2SC1849 transistors for this build.  Wanted to add that in case it might have some bearing on the hiss issue.  It was my understanding that these were used in the original Ross and are used in the Keeleys.  I assume, perhaps wrongly, that the pinouts on those are oriented the same as the 5088s.  Occurs to me now that maybe they're switched around.  Maybe my pedal isn't really working at all!  I'm just starting to learn about this transistor (collector, base, emitter, ay-ay-ay) stuff and am not even sure how you go about determining the pinout orientation of these older model transistors.  Please pardon my density and thanks for your patience....

[markphaser]

compressor noise?

Compression always has the effect of increasing the noise level. This is because the peaks of the signal are brought down in level, bringing them closer to the noise floor.

It could amplify the line noise maybe try a better power supply that has "decoupling" or filtering better with the same voltage/polarity/current draw

Are your parts really close together? maybe its stray inductance or capacitance creating noise
"space your parts out more" and away from your power supply lines

Effects like compressors or fuzzes/distortion boxes its good to use a AC isolation transformer to isolate all the AC noise coming out of the wall because it just going to amplify it

I'm just taking guesses don't quote me on this stuff

[Mark Hammer]

Thanks Mark.  I'll search again.

I did forget to add, that I used some 2SC1849 transistors for this build.  Wanted to add that in case it might have some bearing on the hiss issue.  It was my understanding that these were used in the original Ross and are used in the Keeleys.  I assume, perhaps wrongly, that the pinouts on those are oriented the same as the 5088s.  Occurs to me now that maybe they're switched around.  Maybe my pedal isn't really working at all!  I'm just starting to learn about this transistor (collector, base, emitter, ay-ay-ay) stuff and am not even sure how you go about determining the pinout orientation of these older model transistors.  Please pardon my density and thanks for your patience....

Pinout differences between transistors doing the same task are the continuing bane of a many people's existence.  If you don't have one currently, I suggest getting yourself an inexpensive digital meter that does transistor hfe testing.  The nice thing about these is that you can use them to identify the pinout by flipping them until you get an hfe reading that makes sense.  It's saved my butt more than a few times.  Sadly, they don't get us over the hurdle of FETs with different pinouts. 

Also, remember that you can often get datasheets and an accompanying pinout for most devices by entering the part number and "pdf" (e.g., "2SC1849 pdf") into your favourite search engine.  Regrettably, the diagrams that show pinout are not always perfectly unambiguous, but happily most are.