500 series Sontec / GML type eq

[Harpo]

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.....?

He's not. Some quick&dirty banana bread for frequency ...

 

[kante1603]

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.....?

He's not. Some quick&dirty banana bread for frequency ...

Wow!!!
Thank you very much indeed,it is good to have you here!
This teases me to do a stepped version for me too (although I already have the 500 version).
Let´s see if I can open the charts somehow (I´m on a mac).If not I have some other Windows based computers at work.
And eat some banana bread of course ;D


Great stuff Harpo!


Best regards,


Udo.

 

[bruno2000]

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.....?

He's not. Some quick&dirty banana bread for frequency ...

Thank you!

 

[kante1603]

Question for Harpo:


I have now installed Open Office on my mac,your Calc opens up nicely.
Opted for 23 positions.
So I went through it and found the frequency choice quite nice for the first four bands.
On the high(shelf) the end at roughly 60kHz was a bit high for me. ;D
Although I´m totally unexperienced with excel and the likes (I was born in the chalkboard times….) I gave it a try and altered the end frequency to 26,5kHz to make it more useful and to follow the original onlymee-design.
Gave me a ratio of 13,15.
All good so far,but at the end position (switch fully cw) the chart "adding series resistor values" gives me a value of 4,530(E96) and 4,640(E48)kilo-Ohms .
Since all other bands end at zero ohms,am I right to add this value as a series resistor at the cw end (23rd position)?


Thank you in advance,


Udo.

 

[Harpo]

Udo, if you substitute the high band formerly 3K3s R73 and R74 in cell E9 with parts value 7K867 resistors as the closest match for your new target frequency (3300+4530=7830) with keeping caps values, the CW end of the chart will return to zeroes (ignoring, the pots/rheostats resistance might not be 0 ... 100K but maybe 17ohms ...98K3, so you could measure their real world value and update the cells in chart rows 11...14 for more realistic filter response numbers). You could play with cap values as well ... just sayin'
Harpo

 

[kante1603]

Thank you very much Harpo!
This is going to be a real fun,so many variables,hahaha…….
Changing R73 and R74 is a great hint indeed.
I think I will get the kits,the parts and then with the real caps in hands put their values into your Calc,then start from there to have a good "fundament" to start with.I might order multiples of C27 & C28 to match them for stereo operation in pairs.


Thanks again and have a nice weekend,


Udo.

 

[Zander]

Hi Udo,


What brand of switches will you be using?


Zander

 

[kante1603]

Hi Udo,


What brand of switches will you be using?


Zander

Hi Zander,


not sure yet,ELMA is out of my range.
I asked URALTONE for 24 pos. switches,but the downside is that they're BMM types.
So I'm hunting for parts atm.


Best,


Udo.

 

[Harpo]

not sure yet,ELMA is out of my range.
I asked URALTONE for 24 pos. switches,but the downside is that they're BMM types.

When you join the switches CCW end (1st.pos) in the adding series resistors config with the BBM type switch pole, you prevent an open connection while switching, otherwise (single switched resistors) put a high value resistor in parallel to the switched rheostat ends ...

 

[kante1603]

Hello Harpo,


thank you,
although I´m a bit confused now.


Let me see if I got this right.
I want to go for adding series resistors.
So if I get it right the circuit "sees" the full resistor chain when in open condition using a BBM type switch,correct?
Looking at the schematic there already is a connection between the wiper (which will be the pole) and one end.
Isn´t that a rheostat configuration already?
If so I only have to run two wires per wafer,one will be the joined ccw end/pole directly at the rotary switch and the other is the cw end,right?


Here´s the schematic for your reference (although I´m sure you have it):
http://www.thedonclassics.com/schematics/250EQ_schematic.pdf


Please excuse my noob questions,


Udo.

 

[Harpo]

So if I get it right the circuit "sees" the full resistor chain when in open condition using a BBM type switch,correct?

yupp, about 100K per deck, a lot less than infinity and known working.

Looking at the schematic there already is a connection between the wiper (which will be the pole) and one end.
Isn´t that a rheostat configuration already?
If so I only have to run two wires per wafer,one will be the joined ccw end/pole directly at the rotary switch and the other is the cw end,right?

correct, a rheostat is a two legged device.

 

[kante1603]

Excellent Harpo,you made my day!
This way I can go for 24positions plus save some money,great!


Thanks a lot,


best,


Udo.

 

[SOLO]

Hey i was contacting you to ask how much would you charge to make another pair of your 500 series Sontec / GML type eq
Im looking to spotlight a lot of boutique 500 series modules and designers and my upcoming YouTube show
Thanks again

 

[kante1603]

Hey i was contacting you to ask how much would you charge to make another pair of your 500 series Sontec / GML type eq
Im looking to spotlight a lot of boutique 500 series modules and designers and my upcoming YouTube show
Thanks again

Don't get it,who do you refer to?


Best regards,


Udo.

 

[kante1603]

Another pair up and running.


Best regards,


Udo.

 

[mysticmerlin]

Just finished 4 using opa134 and 24v. All worked first time, easy build.
The sound is wonderful, very clear and surgical yet smooth.

These kits are a steal.
I have a couple of GML channel strips and these sound just as good .

Thanks David

 

[john12ax7]

Just finished 4 using opa134 and 24v. All worked first time, easy build.
The sound is wonderful, very clear and surgical yet smooth.

These kits are a steal.
I have a couple of GML channel strips and these sound just as good .

Thanks David

Isn't 24v a bit much for opa134? Might work for a bit but long term probably burn up.

 

[mysticmerlin]

Isn't 24v a bit much for opa134? Might work for a bit but long term probably burn up.

With the Zeners I have 18v .  I have a mix of 16v / 24v modules in my racks and using the 24v  rails balances out with  the rest.

 

[evilcat]

Hi there,
Small problem here! I have a pair of these EQ, working great for a year now. Recently a problem appears: my 2 channels are saturated and one of them is something like 12dB hotter than the other.
I've opened the case (BTW I've racked them with JLM PSU on +/-16V) checked voltages and continuity and there's something weird: voltages are ok BUT there's continuity between +V and 0V!!!
I've disconnected the PSU and the modules, checked the PSU alone and find the same problem. There's continuity between +V and 0V BUT only when the unit is turned ON. When I turn it OFF there's no continuity anymore.
When I say "continuity" it's my DMM ringing. As for the impedance between ground and 0V with the chassis it's 13 ohms and between +V and chassis it's 68 ohms.
Any ideas?
Thanks

Ben

 

[thomasdf]

Hi guys
This project looks amazing, how can I get my hands on a pair of kits?
Thanks