Circuit Salad's *Optical* Orange Squeezer -- layout and discussion

[Kipper4]

I've just started populating the board and i already cant wait for the opto's to arrive even though it's going to be a couple of weeks comng from china.
Hurry up already

[alparent]

I think the H11F1M is FET based. None of the one at Tayda or FET based.

When I got my multiplex board, Josh was nice enough to sell me a couple extra H11F1M.......so I have all I need to try this one. 

[Kipper4]

heres the bare bones board

https://www.dropbox.com/sh/7ma9n53c5jqdgsr/d-0TvwYXDL#f:opto%20fet%20comp.jpg

[Kipper4]

i had my transistor the wrong way round
It's a great little compressor with lots of squish.
it looses some high freqauncys when the compression is flat out but i expected that.

[midwayfair]

Please note for future builders if you use the MPSA14 transistor the oreintation is incorrect in the above layout.
As jon Pointed out when i debugged mine.
It's a great little compressor with lots of squish.
it looses some high freqauncys when the compression is flat out but i expected that.

I've fixed the layout. It's correct now.

[Kipper4]

Great stuff. I love it when i build something i cant stop playing with and i was wrong theres no real drop off in the highs to my ears.
i'm going to put it through its paces infront of and behind some other pedals just to see how it behaves.
Which pin do i connect the the anode of the led to on the op amp was it pin 7?
How do I make the attack adjustable please?
BTW thanks to R Ring at Circuit salad too

[midwayfair]

Which pin do i connect the the anode of the led to on the op amp was it pin 7?

Yes, it's pin 7 in the schematic.

How do I make the attack adjustable please?

What are you trying to accomplish by adjusting the attack? You're limited by how fast the LED turns on and how fast the opto-FET can respond. You can put a 1nF cap across the comp pot to maybe slow it down a little, but you can't make it faster. Also, that's technically just raising the threshold, which is exactly the same thing as turning down the compression pot. You could change the LED limiting resistor (R5) to make it easier or harder for the LED to light up, which could give the impression of a different attack but is really affecting the threshold. This is a limitation of most compressors - it's very rare for the attack to actually be adjustable. The DECAY, on the other hand, is adjustable. You could pull R8 and stick a 1M pot in there (probably with some minimum resistance, like 100K) and see where that gets you.

[Kipper4]

It's very well behaved.
I tried it in front of and behind my boss SD1 and i liked it best after the SD1.
Depending on the pick up used (strat) the compression needs a little differant setting or it can sound a bit poppy. if you know what i mean.

[Kipper4]

I'm loving the LED compression idicator mod. It'd look good driving a pair of led's as eyes with the right graphics on the box.

[PRR]

> How do I make the attack adjustable please?

Snip diode. Insert resistor.



1K is probably inaudible. 100K is very slow; also upsets levels.

Try several fixed resistors before you pick a pot.

[midwayfair]

> How do I make the attack adjustable please?

Snip diode. Insert resistor.



1K is probably inaudible. 100K is very slow; also upsets levels.

Try several fixed resistors before you pick a pot.

Hah! Right. This is a resistor that's usually there in envelope circuits, and it didn't even occur to me that it wasn't in this one.

I'm loving the LED compression idicator mod. It'd look good driving a pair of led's as eyes with the right graphics on the box.

If you use a red and a green, they'll light up at slightly different compression levels (though those will be fairly low levels to be fair). Not sure it can drive more than two.

[Kipper4]

That would be D3 in your layout then Jon?
and thanks for the responses. Once i get home from the grandkids later i'll give it a whirl.

[midwayfair]

That would be D3 in your layout then Jon?

It's the diode attached to Pin1 and pin 6, the one to the right-hand side of the chip.

[Kipper4]

Thats the one D3 i see from the schematic people are using 1n4148s.
I used a 1N4002 for all the diodes.
thats probably why i'm getting a lot of compression.
I'll try this mod with a 50k pot first and see how i like it.
I guess lug 1 and 2 are bound together and lug 3 goes to other end of where D3 was.

[PRR]

'4148 versus '4007 won't be a big difference.

[Kipper4]

thanks ppr
i couldnt make the attack knob mod work.
i tried it with 5k , 20k 100k pot wired to lug 2 and 1 and all it did was start farting when it got to the end of the pots range. no discernable differance in attack