MixBuzz500 build/support tHread

man, this bloody beast turns into a real challenge!  ;D
i just burned my fingers on a f***ing hot 2181. need some cold beers first before i start crying for help.  :
cheers, alex

I was wondering if any of you folks could point me in the right direction.  After solving the problem with the 2nd channel line driver, everything now works except for the makeup gain.  I turn the knob and there is no change in level after compression.  I've tested the pot and it works.  Not sure where I should be poking around. Any ideas?

check your tl074 ic7

Thanks Stereokillah.  I think I will order another one.  Is there a way to test it?  I know pins 5,6,7 are the op amp for the makeup, I just don't know what to look for.  Thanks again.

Check the voltage on wiper of makeup pot changes from 0 to about 8V; check R53, R59;
of course, at pin 6 IC7 there's 0V, it is inverting ground-referenced amp;
if compressor works, i.e. you get compression when changing threshold, the problem is not IC7B.

It was indeed the TL074.  I replaced it and the compressor works beautifully.  TL and TM are still doing funny things, but I'll do some investigation when I have more time.  Thanks guys!

If the compressor was working with bad TL074, but has no makeup....
Gain reduction signal, or control voltage, comes to IC7B, thru R54.
Makeup voltage comes to IC7B thru R59. Op-amp which passing gain reduction signal
but not passing makeup voltage... Same electrons Strange selectivity!
:  :  ???  ???
Anyway, I am happy it works, check the ratios etc, if you already did it,
let us know about sound!

I thought it was wierd myself.  The ratios are correct. I did a drum bus test last night and this thing is fantastic.  It's really handy to have both 4k and GSSL in the same unit.  I'm finding the GSSL to be more aggressive, and it worked well for the raunchy style of beat I laid down.  I could see myself using it in 4k mode most of the time though.  It seems I forgot to put the stop on the release switch and if I go beyond auto, it distorts...but actually sounded really cool with the dirty beat.  I will post some clips when I get the time. 

Great news! Regarding the release switch, you easy can have 6th position, just install
R||C, between A6 or C6 point of release switch to gnd...Try 220K and 0.1uf,
for very fast aggressive setting, or you can mix two RC for another auto mode.
Yes, 4k is my default mode too
Clips-welcome!

Just to be clear, as I have found some conflicting or confusing wording in this thread:

JP1 on the audio board DOES NOT need to be jumped?

and

The three pads on the back of the control board by the bypass switch DO need to be jumped?

Thank you in advance for clarifying.

Merry Christmas!

Received some of the last parts for this project today and finished it nearly (only meter is missing). 1 channel worked from the beginning, the other had a very distorted signal. Could trace it to the output of the Audio VCA. At the end it was a defective 5532 (IC11B). Now everything works. Just need to put it together (install boards in the metalwork, put knobs on), then ordering a meter and of course finishing my GDIY 511 Rack PSU.

Igor, nice project as always and a breeze to put together.

Flo

Brolik said:

Just to be clear, as I have found some conflicting or confusing wording in this thread:

JP1 on the audio board DOES NOT need to be jumped?

and

The three pads on the back of the control board by the bypass switch DO need to be jumped?

Thank you in advance for clarifying.

Merry Christmas!

Click to expand...

Brolik, it really should be clear when looking at the schematics.
JP1 only needs to be jumpered if you don't populate the sidechain filter.
Yes all the three pads on the back of the control board need to get joint together, so you can switch between GSSL and Turbo mode and the relays still get switched.

Thanks for the help! I'm almost done as well. I have to admit that schematics of this complexity still fluster me a bit. I'm getting there, but still working on small psu's and gain stages and such. Great build though! Can't wait to get my 51x up and running so I can try it out!

I know its lazy, but does anyone have a farnel or mouser cart made u for this? I am about 40% putting one together but thought I would ask

Cool. Seems this built goes OK.
Curoius: how many people have tested and working MixBuzz500?

Igor said:

Cool. Seems this built goes OK.
Curoius: how many people have tested and working MixBuzz500?

Click to expand...

Me, for 1...

The Gimmer

14 MixBuzz500 are working for sure, as I know, including 6 I built myself... Not bad!
If you have working MixBuzz500, why not write here?

I have two that`s working great!!

One "Hifi" with four VCA on the VCA board and the other with only one VCA.

Thanks alot for this mixglueing project!!

Mattias

14 working units this is good to hear.  This project is rising to the top of my pile and I hoped the reason for no posts was that no one had any problems. 

I am testing the unit outside the rack.
Audio passes through in standby.
Audio passes in 4000 and gssl mode.
I can use make up to increase level but no compression. I hear the relays when switching from bypass to 4k and gssl.
Meter is not moving.
Can someone give me a starting point for troubleshooting?