DIY equalizer based on Studer 169 (standard and mastering)

[2Low]

I´m still looking for a affordable 15V PSU for this project
what do you guys this about this:

http://www.mascot.no/?CatID=1179

there is a 15V version of the 8710
Notes: linear

20€ at RS-components

thanks 2Low

 

[bdubya]

Here are some links to my attempt at pictures of the internals of mine:

http://yfrog.com/jkstuder169insidejx

Currently running off an external supply, but, as you can see, there are provisions for a dedicated internal one.  Still sounds good, even after the initial fire-up excitement has waned.  Sort of experimental, with the oddball caps and whatnot.  I still plan on doing a second one with WIMAs, like they were meant for, and look forward to choosing some slightly different frequencies to choose from, as I found that part to be kind of fun.  And there's still that extra filter connection . . .good stuff.



ben

 

[guidoz]

I have used this power supply for modular synths modules and has been really good. Maybe it would be fine for this project too?

http://www.musicfromouterspace.com/analogsynth/WALLWARTSUPPLY/WALLWARTSUPPLY.php

Hi !

About the PSU, an obvious choice is JLM as usual...

http://www.jlmaudio.com/

 

[e.oelberg]

funk-tonstudiotechnik produces very good PSUs, not really cheap but the beast you could get.
nicholas

 

[bdubya]

Grove Audio, in the WM, has +/-15V PSU that supply 200mA per rail for $10.50:

http://www.groveaudio.com/onlinestore/power_supplies.aspx

Seems like a winner, and there's a member discount/donation to the forum to spice the pot. 

 

[benlindell]

I got one of those power supplies from grove audio and they couldn't be easier to use. AC in, +/-15 out. They aren't the easiest things to solder to cause they're made to be mounted to a pcb. I put mine in a ratshack plastic box and use it for my bench supply for testing 500 series units.

 

[bdubya]

bench supply for testing 500 series units.

That's exactly what I was thinking.  And one of them could power four of these eq's . . . talk about a low-cost project.  What's the drawback, if any, with this type of supply?  Is there a "catch" to speak of? 

 

[benlindell]

Not that I found, just a little hard to solder wires to and a little hard to fasten down to the chassis (it's very flat).

 

[benlindell]

Just had a question about implementing bypass for this, anyone have a solution they've used?

 

[Davo]

Easy enough... run the inputs to one side of a dpdt (as well as to the first opamp)  Then connect your outputs to the common of the dpdt.... the outputs at R31 and R34 will go to the other half of the dpdt

For a visual, take a look at audiox's 500 series of the 169.

I'm working on an 8 channel of this guy... bypass is very necessary!

cheers,
dave

 

[benlindell]

Yes, bypass is easy enough.

Now just to be difficult I'd like to make my own gain steps. I'd like to do +/- 1.5, 3, 4.5, 6, 9. I made a spreadsheet to figure this out but I can only seem to get linear regression which doesn't fit this log pot. Anyone know a quick way to calculate it?

Also I'm assuming that since I don't want to go to +/- 15dB I'll need to cut a trace and add a resistor before the switch.

Thanks guys.


Mastering Steps

Step	Resistor	Resistor total
1	270	270
2	270	540
3	270	810
6	620	1430
15	910	2340

Standard Steps

Step	Resistor	Resistor total
3	820	820
6	620	1440
9	430	1870
12	300	2170
15	200	2370

 

[benlindell]

Heck, I guess as soon as I know the equation I'd maybe like to do a more lop-sided gain knob arrangement. Something like:
-6, -3, -1.5, 0, 1.5, 3, 4.5, 6, 7.5, 9, 12 would be cool to me as I'm normally just trying to sweeten things up.

 

[audiox]

Anyone know a quick way to calculate it?

Deduce the approximate starting values from the current circuit. Then simulate and find the exact values by trial and error. It is the fastest way if you are not familiar with the circuit.

 

[benlindell]

I'm not familiar with how to simulate things like this, could you point me in a direction to get started?

 

[audiox]

Also I'm assuming that since I don't want to go to +/- 15dB I'll need to cut a trace and add a resistor before the switch

That is the easiest way.

Heck, I guess as soon as I know the equation I'd maybe like to do a more lop-sided gain knob arrangement.

Same as above.

 

[benlindell]

Audiox, Thanks for the advice, I've been playing with spice all day today but I can't quite get it to work. Here's what I simplified the filter circuit to. I can't get the simulation to run, I think I don't know where to put a ground and that's why it won't run.

Here's my netlist:
* 2010-02-18 17:31:24 -0500
.AC dec 50 10Hz 30kHz
.print ac v(10)
Vin 1 -1 AC .774 0
R23 2 1 3k3
C3 2 3 15n
R24 3 10 3k3
C8 4 5 39n
C13 3 5 39n
R25 5 6 560
R20 1 6 500
R11 6 10 2870
R10 4 7 11.2k
R1 7 3 11.2k
C16 11 7 220u
R21 11 8 220k
R22 11 9 220k
.end

And attached is the schem drawing. I'm using MI Sugar to generate the netlist and run it.

 

[benlindell]

I think I'm getting closer to simulating this correctly. Still think I'm not doing quite right. I got it to run finally and it changes the plot when I vary the switch values but the results look somewhat meaningless. Attached is the schematic I got to run.

Here's the netlist I used:
* 2010-02-18 17:31:55 -0500
.AC dec 50 10Hz 30kHz
.print ac v(10)
Vin 1 0 AC .774 0
R23 2 1 3k3
C3 2 3 15n
R24 3 10 3k3
C8 4 5 39n
C13 3 5 39n
R25 5 6 560
R20 1 6 2370
R11 6 10 2370
R10 4 7 11.2k
R1 7 3 11.2k
C16 0 7 220u
R21 0 8 220k
R22 0 9 220k
.end

 

[benlindell]

Here's the results I'm getting, the top is HF@5k +15dB bottom is HF @5k +/-0.

 

[audiox]

Audiox, Thanks for the advice, I've been playing with spice all day today but I can't quite get it to work. Here's what I simplified the filter circuit to. I can't get the simulation to run, I think I don't know where to put a ground and that's why it won't run.

It would be a good idea to place the op-amp (U1 in the original schematic) into your circuit. Ground one side of the generator and the op-amp non-inverting input.

Switching the y-axis to show magnitude in desibels also helps.

 

[benlindell]

I tried putting a 741 opamp (there was one available for Mi-Sugar) and I'm getting it to run and am getting different results but still not correct.

Any chance you could share your net list? It'd be a huge help to see how you did the simulations.