Aengus graphic EQ (thumbwheel) information sought--any leads?

[soapfoot]

No promises, but I've kind of been messing around with trying to figure out a 500-series layout that would work here with modern, compact rotary switches.

It's a real challenge because all the resistors really want to be near the switches. I'd like to add a bypass switch to the front panel as well, but it's tricky to find the space. I've got little CMF50 resistors standing on end as is. SMT resistors would probably be better.

I haven't double-checked this layout yet but I'll get there. I feel like the main PCB should be a snap compared to this.

I've never tried to make a 500-series thing before so I may be doing dumb things. I figure the main PCB should probably mount to some kind of sled/bracket and plug into this front panel PCB with an IDC ribbon cable.

Suggestions welcome; I'm still picking at it. If I get to a place where I feel confident I might see if anyone else wants to take a look.

 

[TwentyTrees]

A bracket sounds sensible for a 500 series module. The trick there is making sure your control PCB isn't the full width of the module, so there's room for the bracket on the side.

Guess how I figured out that particular nugget...!

 

[soapfoot]

Ouch, yep I would've made that same mistake. Time to revise! Tricky, because I don't have a lot of extra space to work with How close to the edge of a PCB is it "safe" to run a trace?

 

[Bobby Baird]

Ouch, yep I would've made that same mistake. Time to revise! Tricky, because I don't have a lot of extra space to work with How close to the edge of a PCB is it "safe" to run a trace?

0.2mm

Use this as a guide for pcb board setup. PCB Manufacturing & Assembly Capabilities - JLCPCB

 

[dirty1_1garry]

Hello guys!
Will be glad to add my five cents to all previous investigations about this rare EQ.
Special rays of respect for making the schematic to dpm member.
It was written earlier that it is possible to mimic the circuit on the basis of another EQ based on the same gyrator filter principle and replace complex gain switches to the slider potentiometers. Spent some time emulating this theory in LTSpice.

 

[dirty1_1garry]

First I've emulated the original filters C/R values and the gain switch steps.
Here it can be mentioned that the real peak frequencies differ slightly from the given frequencies, this is due to the choice of capacitors from the standard values. don't think that it is much of a principle, but later I also tried to keep this "error" in the transfer of frequencies to the G.TEN filters circuit.
Real emulated freq:
50Hz = 51.7Hz
100Hz = 106.6Hz
220Hz = 234,6Hz
500Hz = 517.4Hz
1000Hz = 1066Hz
2200Hz = 2345Hz
5000Hz = 5174Hz
10000Hz = 10662Hz
Q is 1.371

 

[dirty1_1garry]

Next I tried to transfer 404 gyrator C/R values to G.TEN circuit.
But I was convinced that it's not possible to simply transfer the gyrator filter C/R values to the 560'like eq circuit with saving the freq/Q/gain factors. Values of the opamp feedback resistance and the value of the gain resistance are interrelated with the C/R gyrator filter values. So it took a little time to recalculate C/R values.

 

[dirty1_1garry]

And voila! Here is what I've got.
For the beginning I emulated the original G.TEN/560 12dB gain, but also for clarity I made a 15dB variant, I do not know whether such a gain is needed in reality, however. There is a slight Q difference on 50Hz and 10kHz, it can be cleaned up, but I think it's enough for the quick demonstration.
Also with the 15dB setting the slider potentiometer will have slightly different gain curve.

Cheers,
Igor

 

[jobot]

We made one a few years ago (managed to get hold of a real one to look at) .... works fine... it is over at a friends studio.... I'll go get it back.

It is our usual full PCB implementation... in a 1U format. We actually made 2 in a 2U box.
[If I remember correctly, we did one channel with 741's and the other channel with something modern to see if anyone could tell the difference].

The only reason it was not released as a kit was because I did it with Grayhill switches.... so I decided that it was too costly for the DIY market and intended to re-lay it out for Lorlins...

I don't have a photo on hand but it looked like this:
https://www.audiomaintenance.com/downloads/ez404.jpg
We probably have a couple of PCB's left over... but it isn't cheap to make.

If there is enough demand I could make them as DIY kits.... but to be realistic cost it does need changing to Lorlins.

Colin
www.audiomaintenance.com

Couple PCBs left over you say, would any of them be for sale

 

[pinebox]

I have a few of these on the bench before they go to their new home and just wanted to notate that out of the 6 there are 3 different op amps. Nothing really noticeable to my ears, but hopefully someone might come in and say one is designed better, or sounds preferable than another.

 

[JMan]

Did this ever materialize? It seems like it had great momentum but I can't tell if it ever came to fruition! Regardless, very cool to see the ingenuity and generous spirit of our community at work in this thread.

 

[soapfoot]

Hey! I got super distracted with a home purchase and a couple of albums and tours, so kinda dropped the ball.

I’m sure I’ll get back into it if I ever get a bit of downtime