500 series Sontec / GML type eq

[rob61]

I'm getting ready to start my build of these. It would probably be easier to hacksaw these shorter before soldering. Can anyone who has done this comment on the length that needs to be cut off?

 

[Unit7]

I'm getting ready to start my build of these. It would probably be easier to hacksaw these shorter before soldering. Can anyone who has done this comment on the length that needs to be cut off?

I cut mine (only the plastic shafts) just inside the groove, like 2-2.5mm. Accidentally cut one shaft a bit deeper so had to attend a little extra to get knob at same distance from faceplate as the others, but it still worked out fine.

BTW I cut mine assembled, holding unit laying on bubble wrap on edge of desk. Got a lot of plastic dust on faceplate and I was very careful to not scratch it and not use too much force to break anything, but doing it with unit assembled made it easier for me as I don't have a proper vise to hold those tiny things. But if I'd do it again I guess I'd do it without the faceplate on, assembled on the L-plate.

 

[kante1603]

The red switches.

Same here,it's allright for my taste.
For the shafts,yes,cut them down if you want them shorter.
Haven't done this on mine,but if I want it some day I'd simply dremel them assembeled,just cover the rest to prevent it from dust.


Best regards,


Udo.

 

[rob61]

Is it the plastic or metal shafts that need to be trimmed?

 

[Monoklang]

Finished! Both units sounds amazing!

Thanks David for a great kit!

 

[evilcat]

Is it the plastic or metal shafts that need to be trimmed?

It's the plastic ones. Very easy to do with a Dremel, just be careful to not cutting to much, 3mm max is cool. I've done accidently 5mm, it's very short!!!

 

[rob61]

Starting my build. For DOA 4 and 5 I plan to use the OPA134PA and later experiment with the PPA992 OpAmps. I'm not sure if I install the 12pf Ccomp 4-5 (listed as Compensation cap for audio amps) or not. Can someone tell me would I install these for my intended OpAmp selection using 16v rails?

Also, for C18, the silkscreen shows each lead pad with a "+" sign on mine. Should I then assume the square pad is the positive?

 

[rob61]

Finished my pair. They sound fantastic. Thanks so much for making this extrordinary kit available!

 

[living sounds]

Great project, I'm really tempted!

Do the 5pf caps have to be mica? At almost 3 EUR a piece (mouser) these are rather pricy, especially for a very small feedback cap. Wouldn't a COG ceramic do the job just as well?

 

[tonedude]

Got my kits on friday and they are now finnished. But, unfortunately I seemed to have had really bad luck with the quality of the tripple deck pots I got from David...

One of the pots had two 4.7k decks instead of two 100k (it was 4.7k - 4.7k - 100k, instead of 4.7k - 100k - 100k...)

The other faulty pot had a middle deck that have a bad connection in some way, it is therefore impossible to get a stable measurment out of it (it measures an unstable 120k, moving uppwards, instead of the specd 100k.) Most of the 100k decks did measure somewhere around 90k to 95k, witch should be ok, I quess. So my stereopair now have the higest and lowest freq band tracking somewhere inbetween, bad to exceptionally bad...

The really sh*tty part is that i allready had them mounted before finding out that I got pots of bad quality.  So, one tip of advice is to meassure and test them out, before soldering them in place... Maybe also match them for stereo use. Could spare you some valuable time and eliminate frustration...

I have contacted David about it.

 

[petermontg]

Anybody put together any audio samples for this

 

[kante1603]

Got my kits on friday and they are now finnished. But, unfortunately I seemed to have had really bad luck with the quality of the tripple deck pots I got from David...

One of the pots had two 4.7k decks instead of two 100k (it was 4.7k - 4.7k - 100k, instead of 4.7k - 100k - 100k...)

The other faulty pot had a middle deck that have a bad connection in some way, it is therefore impossible to get a stable measurment out of it (it measures an unstable 120k, moving uppwards, instead of the specd 100k.) Most of the 100k decks did measure somewhere around 90k to 95k, witch should be ok, I quess. So my stereopair now have the higest and lowest freq band tracking somewhere inbetween, bad to exceptionally bad...

The really sh*tty part is that i allready had them mounted before finding out that I got pots of bad quality.  So, one tip of advice is to meassure and test them out, before soldering them in place... Maybe also match them for stereo use. Could spare you some valuable time and eliminate frustration...

I have contacted David about it.

May I ask how this issue worked out,any solutions?
Could be interesting for others around here too I think.


Thank you in advance,


Udo.

 

[Sinkia]

Awesome !

I'm really thinking about ordering a couple !

I'll keep read this post !

Great job

 

[tonedude]

May I ask how this issue worked out,any solutions?
Could be interesting for others around here too I think.


Thank you in advance,


Udo.

I recieved two new pots from David and my EQ's are now up and running, both sounds marvelous!

I did however have som problems with one of the new ones. First of it does not have the same quality feel as the other pots I got. And after contacting David about it, and also after doing my own research... we found out that the lack of "qualitiy feel" when turning the pot, is dependant on some sticky oil/grease that makes the pot smoth/hard to turn (in a god way...), and that hard/smoth feeling was lacking in one of my pots. And that "feeling" is gone because the sticky oil is absent on the outer shaft on that one. The same pot also had a contact problem on one pin (middle/wiper pin on middle deck), but I gave It a light squeeze with a plier and have had no problem with it since.

// Mattias

 

[kante1603]

Hi Matthias,


thanks for explaination,glad you got it solved now.
Happy mixing,


Udo.

 

[qmp audio]

does not have the same quality feel as the other pots I got.

One of my LF pots has this issue.  It's much 'looser' to turn than the others.

 

[jona]

i finished a pair as well and i am very happy with the sound.. so much that i think about building another pair with stepped controls..
how can i calculate the resistors for frequency, q and gain ?

 

[kante1603]

i finished a pair as well and i am very happy with the sound.. so much that i think about building another pair with stepped controls..
how can i calculate the resistors for frequency, q and gain ?

Hi,


yes,a nice idea,had this in mind too.Sad to say I don't know the how-to calculate this (except for the gain pots of course  ;D ).
One way might be to derive the values from real potentiometers in circuit prior to building a stepped version.


Did you find a solution?


Best regards,


Udo.


P.S.:In the "Igor Days" member Harpo helped us with excellent excel charts to make a sontec.
He's a math genius.Maybe he wants to chime in.....?

 

[[silent:arts]]

fc = 159000 / ((R73+R75) * C27 * (R74+R76) * C28)^0.5

I did an Excel sheet for this years ago, maybe someone has saved it?
Can't find it anymore.

 

[kante1603]

fc = 159000 / ((R73+R75) * C27 * (R74+R76) * C28)^0.5

I did an Excel sheet for this years ago, maybe someone has saved it?
Can't find it anymore.

Wow,thanks Volker!But I seriously fail when it comes to it.So I will bake some banana bread instead.Cheers,Udo.