FLATLINE COMPRESSOR Problem

[maiko]

Hi guy day to you all.

I recently built the flat line i etched my board and followed the layout on the perf and pcb effects page.

http://effectslayouts.blogspot.com/2015/02/hollis-flatline-optical-compressor.html

tested it last night and it works.     I know its compressing the signal everything seems to be working right except that
the signal is noticeably lacking in low end and generally just low output.   if i bypass it the signal is rich and full sounding.  It just
sounds like the signal is thinning out through the compressor.

I notice C1 is 1nf and follows a 10meg resistor  initially it looked like some kind of RC high-pass filter.  Is this correct?(my assumption)

What could be the culprit.

[PRR]

> C1 is 1nf and follows a 10meg

What it "follows" usually isn't important.

Here it _drives_ another 10Meg, and the 1,000Meg of the opamp pin. This is 17Hz, deep enough for any music.

You sure you put 10Meg there? (1Meg would "work" but shave the lower octave of guitar...)

You sure the cap legs are really soldered? Circuit impedance here is so high that treble will "leak through thin air" if the ends are close enough.

Obvious other place to lose bass is (my link) C2 1 uFd and VR2 100K. Are those the right values?

[maiko]

yes its 10m i did try a 2.2meg but that didnot seem to do much.   It was louder but not that much of and improvement
so i switch back.   I noticed that its was not that it was not loud enough it just lacked bass.   if i hit a high note say a e on the 12 fret of the 1st string with the compressor or bypassed it was the same level.

Yess all parts are correct and soldered properly.

What really solved the problem was swapping out the 1nf cap that is on the output to 100nf.      Im really happy with it now.  Thanks for posting. 

[samhay]

It is was lounder with a 2.2M resistor, then I doubt that you started with a 10M resistor - did you measure it?
I am further convinced this is the case if your fix was to replace the input cap with a larger value.

However, if it works, and sounds good, then good job.

[PRR]

> if your fix was to replace the input cap

He replaced the OUTput cap.

> all parts are correct and soldered properly.
> swapping out the 1nf cap that is on the output to 100nf.

1n output cap?? That can't be right.

Huh. That EffectsLayouts layout does show 1n. This is *wrong*. Another randomly Googled schematic shows 1uFd (not 1nFd!).

http://stompville.co.uk/wp-content/uploads/2012/02/104SV2.png

Just because it is correct against a published layout doesn't mean it is same-as the original design. Always good to look around at other plans for the same project.

1nFd against say 50K (100K Level pot plus 100K external load) is 3KHz, WAY up the midband. MASSIVE loss for all lower frequencies.

Your 100nFd is 0.1uFd. 100nFd.0.1uFd against 50K is 33Hz and ample for guitar. A reasonable choice. There is a very small (inaudible) loss on the lowest note of drop-tune guitar.

1uFd and 50K is 3Hz and thus dead-zero loss for the lowest notes of guitar.

[maiko]

yes i did notice that schematic with 1uf thats why i tried my .1uf instead of the .001uf    i did not have any 1uf at the time.

i did measure it was 10m color code was brown black blue gold also

Thank you for the help

[maiko]

i just revisited the site its now updated to 1uf on the output cap but hehehe    maybe you had something to to with that.   
That was quick