John Hollis - Flatline Compressor (Layout + Transfer)

briggs · Post by **briggs** » 07 Nov 2007, 15:34

Ah yes, reactance. Thanks AG - I've learnt something new today

Cheers for that....

Page bookmarked

Hmmm, strange I prefered the extra bass roll off of a 470n?

analogguru · Post by **analogguru** » 07 Nov 2007, 15:41

The lowest frequency produced by a guitar is........: 82,4 Hz

Bass is one octave lower..... so 41,2 Hz.

analogguru

briggs · Post by **briggs** » 07 Nov 2007, 16:07

Yeah, I always try to make a point of not letting any frequencies below 70Hz run loose in my designs, I find they are the "mud" culprits, it seems to get rid of the subliminal "rumble". I don't think human ears really like frequencies below 70-100 Hz, well mine don't anyways!

analogguru · Post by **analogguru** » 07 Nov 2007, 16:33

I don't think human ears really like frequencies below 70-100 Hz .....

But the stomach does....

analogguru

msnl · Post by **msnl** » 06 Jun 2008, 12:26

Hi

I built the Flatline Compressor.
It's working 100% and I like the transparent sound it.
I use a VTL5c2 optocoupler and 1n4148 diode's instead of Ge's

I'd like to have a led indicating the level of compression.
Does anybody know how i can do this.
Just placing a led parallel to the VTL doesn't work

Thanks

MSNL

seniorLoco · Post by **seniorLoco** » 10 Jun 2008, 00:55

msnl wrote:Hi

I built the Flatline Compressor.
It's working 100% and I like the transparent sound it.
I use a VTL5c2 optocoupler and 1n4148 diode's instead of Ge's

I'd like to have a led indicating the level of compression.
Does anybody know how i can do this.
Just placing a led parallel to the VTL doesn't work

Thanks

MSNL

Do not bother unless you whant the pedal to play you ....

selectortone · Post by **selectortone** » 10 Jun 2008, 09:54

I'm about to build one of these (using Torchy's vero layout - thanks again!)

Are germanium diodes necessary in this design? - They're just forming a bridge rectifier right?

msnl · Post by **msnl** » 10 Jun 2008, 10:40

Hi,

I use 1n4148 diode. I tried Germanium diodes, but i liked the compressor with 1n4148 better.

grtz

MSNL

floris · Post by **floris** » 10 Jun 2008, 18:14

I've also build the Flatline compressor designed by John Hollis. I used germanium diodes with it because of the low threshold voltage that they have.
Imo, it' a nice simple clean opto-compressor that is a bit slow but has a nice transparent compressed sound without distortion. It retains good "playability" and has great sustain. I use it after a SHO cloned booster, that drives the compressor because it has a not enough gain to get into good compression with my Tele, and before a Blues Breaker OD clone from General Guitar Gadget. The sustained sound with compressed peak works great on the OD giving a nice consistent overdrive in the peak as well as in the release phase (sustain part) of a note. Driving a simple modified SE Valve Junior tube amp with that sounds good to me!

Build report:
http://home.orange.nl/fvrijswijk/guitar ... hollis.htm

Compact (but needs some wiring) vero layout that I made and used in two builds (guess it's verified by myself then...):
http://home.orange.nl/fvrijswijk/guitar ... o_perf.gif
http://home.orange.nl/fvrijswijk/guitar ... vealed.gif

Using the VTL5C2 optocoupler worked great! Thanks John Hollis, for a very nice transparent and simple to build opto-compressor design.

selectortone · Post by **selectortone** » 10 Jun 2008, 18:30

It's interesting to hear that people can hear a difference between si and ge diodes in this application.

Looking at the circuit it appears to me that the diodes simply form a bridge rectifier that rectifies the ac input signal to produce a dc control voltage to drive the LED.

Am I wrong? (I usually am

)

floris · Post by **floris** » 11 Jun 2008, 10:08

> ... hear a difference between si and ge diodes in this application.
Like you say, its just a rectifier bridge. Perhaps the difference in voltage threshold makes the compressor behave slightly different between the Si and Ge rectifier and that is what people can hear.

bajaman · Post by **bajaman** » 11 Jun 2008, 11:22

I'd like to have a led indicating the level of compression.
Does anybody know how i can do this.

answer: add another opamp - TL071 for example, and duplicate the 10k input resistor(fed from the output of the gain stage), 47k feedback resistor , diode bridge, capacitor, LED and 330 ohm resistor back to the output terminal of the gain stage. this should work fine as a visual indicator.

cheers
bajaman

intricatecode · Post by **intricatecode** » 11 Jun 2008, 20:50

first post here

anybody know if instead of the vactec you can use something like this http://www.banzaieffects.com/Audio-Opto ... 17349.html

or this
http://www.banzaieffects.com/Clairex-CL ... 18261.html

because if you can than it makes this pedal a much cheaper build

What kind of optocouplers and/or led/ldr combinations have you guys use so far with success on this circuit?

floris · Post by **floris** » 13 Jun 2008, 16:35

The optocoupler preferably needs to go from >1MOhm to <1kOhm. Also, I found that using a "slow" optocoupler with a release time (Toff) of >100ms works nicely in this compressor.
I have used a VTL5C2 optocoupler with success. It sounds great. "faster" optocouplers give a little "distortion" in the release phase especially noticable with lower frequencies. I had this with faster VTL5Cx optocouplers and a homemade LED-LDR combo.
John Hollis and others have reported succesfully to use homemade LED-LDR combo's probably using a "slow" LDR and a yellow LED (I think...). This is the cheapest solution I guess.
Check also:
http://home.orange.nl/fvrijswijk/guitar ... ements.htm

intricatecode · Post by **intricatecode** » 13 Jun 2008, 17:51

thanks

I'll try building this pedal one of these days and will try different led/ldr combinations and or optocouplers, will post the results here when done.

ManCas · Post by **ManCas** » 26 Aug 2008, 04:59

Hello guys, first post here

. I've been lurking around the forum and have succeeded in my first builds (Gus Smalley's NPN Boost, Briggs' Clock of Tone and Axis Face). I took a shot at this circuit 'cause it looked rather simple but it isn't working. Basically the LED isn't working, I think it's compressing (it sounds almost like an od when Sustain is maxed) but since the LED is not working it's useless.

I did it based on the Hollis schem and the MarkM layout posted here, they have a couple of differences, tried both ways but none is working for me. I'd appreciate any help, thanks in advance.

My V readings on the TL072 are: 1: 4.03, 2: 4.03, 3: 4.01 (coming from the 1/2V output) 4: 0.00 (To ground)
5: 1.01 (coming from Input), 6: 4.03, 7: 4,04 and 8: 8.08 (coming from V+)

I'm sorry I don't have a camera around. Cheers!

floris · Post by **floris** » 26 Aug 2008, 08:17

Which LED do you refer to:
- The LED indicating if the effect is on or off, controlled by the 3pdt footswitch?
- The LED that is part of a "home-build" LED-LDR optocoupler combo?

Silent Fly · Post by **Silent Fly** » 26 Aug 2008, 12:55

msnl wrote:(...)
I'd like to have a led indicating the level of compression.
Does anybody know how i can do this.
Just placing a led parallel to the VTL doesn't work
(...)

You can use another opamp and create a buffer with very high input impedance. Connect the buffer input to the positive of the 100uF cap and the output to a LED that shows the compression level. It should do the trick.

earthtonesaudio · Post by **earthtonesaudio** » 26 Aug 2008, 15:06

I think you could also drive an LED with an emitter follower connected to the output of the envelope section, at the junction of the existing LED and the op-amp. That could save you a few solder connections.

ManCas · Post by **ManCas** » 26 Aug 2008, 16:24

floris wrote:Which LED do you refer to:
- The LED indicating if the effect is on or off, controlled by the 3pdt footswitch?
- The LED that is part of a "home-build" LED-LDR optocoupler combo?

Sorry, I was refering to the LED in the LED/LDR combo. Thanks.