Would you buy a Jh Trapezoid VCA PCB? |
no - only interested in the original EMS circuit (this is not goint to happen - sorry) |
|
2% |
[ 1 ] |
yes - if it emulates the behaviour of the EMS circuit, and doesn't need component selecting |
|
97% |
[ 40 ] |
|
Total Votes : 41 |
|
Author |
Message |
janvanvolt
Joined: Nov 24, 2005 Posts: 285 Location: Mainz, Germany
|
|
Back to top
|
|
|
MR-808
Joined: Sep 30, 2010 Posts: 28 Location: Portland, OR
|
Posted: Tue Nov 02, 2010 9:22 pm Post subject:
|
|
|
janvanvolt wrote: | Anybody got an idea for the frontpanel (5U?) |
My partner in synth-building is working on one. I hope to have something worth showing soon! |
|
Back to top
|
|
|
numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
|
Posted: Wed Nov 03, 2010 9:17 am Post subject:
|
|
|
Hoping someone doesn't mind clearing a few things up for me.
1) What exactly is the "switch trigger" input? Is it there in addition to the push-button input to give you an extra spot for easily connecting with the "audio trig" connection"? Would you want to put a jack here? If so, what input would you expect here that's different from what you'd feed into the "gate" input?
2) EDIT - I believe I understand the audio trigger - the summed input audio is converted into a trigger which you can feed into switch trigger input (or I'm guessing anywhere else in your modular you can use a trigger).
3) Just to make sure, the push button input expects a normally-open momentary switch, with the 2 lugs connected to the 2 pads, right?
Thanks! |
|
Back to top
|
|
|
jhaible
Joined: May 25, 2007 Posts: 2014 Location: Germany
Audio files: 24
|
Posted: Wed Nov 03, 2010 1:24 pm Post subject:
|
|
|
numbertalk wrote: | Hoping someone doesn't mind clearing a few things up for me.
1) What exactly is the "switch trigger" input? Is it there in addition to the push-button input to give you an extra spot for easily connecting with the "audio trig" connection"? Would you want to put a jack here? If so, what input would you expect here that's different from what you'd feed into the "gate" input?
2) EDIT - I believe I understand the audio trigger - the summed input audio is converted into a trigger which you can feed into switch trigger input (or I'm guessing anywhere else in your modular you can use a trigger).
3) Just to make sure, the push button input expects a normally-open momentary switch, with the 2 lugs connected to the 2 pads, right?
Thanks! |
Yes.
Switch trigger is used by old Korg and Moog synthesizers. Not a gate voltage, but a switch closing a contact to GND.
Pushbutton and S-Trigger have the same function. And you can use on to connect with the Audio trigger output, to get some weird self-trigger function. (Emphasis on weird).
Gate is an ordinary 5V positive-going Voltage Trigger ("Gate") input.
JH. _________________ "I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f) |
|
Back to top
|
|
|
numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
|
Posted: Wed Nov 03, 2010 4:26 pm Post subject:
|
|
|
Excellent thanks
jhaible wrote: | numbertalk wrote: | Hoping someone doesn't mind clearing a few things up for me.
1) What exactly is the "switch trigger" input? Is it there in addition to the push-button input to give you an extra spot for easily connecting with the "audio trig" connection"? Would you want to put a jack here? If so, what input would you expect here that's different from what you'd feed into the "gate" input?
2) EDIT - I believe I understand the audio trigger - the summed input audio is converted into a trigger which you can feed into switch trigger input (or I'm guessing anywhere else in your modular you can use a trigger).
3) Just to make sure, the push button input expects a normally-open momentary switch, with the 2 lugs connected to the 2 pads, right?
Thanks! |
Yes.
Switch trigger is used by old Korg and Moog synthesizers. Not a gate voltage, but a switch closing a contact to GND.
Pushbutton and S-Trigger have the same function. And you can use on to connect with the Audio trigger output, to get some weird self-trigger function. (Emphasis on weird).
Gate is an ordinary 5V positive-going Voltage Trigger ("Gate") input.
JH. |
|
|
Back to top
|
|
|
emdot_ambient
Joined: Nov 22, 2009 Posts: 667 Location: Frederick, MD
|
Posted: Wed Nov 03, 2010 6:40 pm Post subject:
|
|
|
jhaible wrote: | Switch trigger is used by old Korg and Moog synthesizers. Not a gate voltage, but a switch closing a contact to GND. |
Like a footswitch to trigger without using yer hands....
Blimey, that took me a while to piece together! |
|
Back to top
|
|
|
numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
|
Posted: Thu Nov 04, 2010 6:30 pm Post subject:
|
|
|
Hi JH,
Looks like the value and taper of pot for InitGain is missing from the schematic - what should it be?
Thanks! |
|
Back to top
|
|
|
jhaible
Joined: May 25, 2007 Posts: 2014 Location: Germany
Audio files: 24
|
Posted: Fri Nov 05, 2010 5:24 am Post subject:
|
|
|
numbertalk wrote: | Hi JH,
Looks like the value and taper of pot for InitGain is missing from the schematic - what should it be?
Thanks! |
linear
JH. _________________ "I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f) |
|
Back to top
|
|
|
numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
|
Posted: Fri Nov 05, 2010 5:54 am Post subject:
|
|
|
And what value? 100K?
Thanks!
jhaible wrote: | numbertalk wrote: | Hi JH,
Looks like the value and taper of pot for InitGain is missing from the schematic - what should it be?
Thanks! |
linear
JH. |
|
|
Back to top
|
|
|
jhaible
Joined: May 25, 2007 Posts: 2014 Location: Germany
Audio files: 24
|
Posted: Fri Nov 05, 2010 6:22 am Post subject:
|
|
|
numbertalk wrote: | And what value? 100K?
Thanks!
jhaible wrote: | numbertalk wrote: | Hi JH,
Looks like the value and taper of pot for InitGain is missing from the schematic - what should it be?
Thanks! |
linear
JH. |
|
Anything between 10k and 100k will do.
Recommended: 10k
JH. _________________ "I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f) |
|
Back to top
|
|
|
numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
|
Posted: Fri Nov 05, 2010 6:40 am Post subject:
|
|
|
Thank you very kindly for the timely response.
One last thing I'm hoping you wouldn't mind saying a little about when you get a chance is the buffered versus unbuffered inputs and outputs. I'm starting to design a panel and am trying to figure out which type to include or if it would make sense to include a couple of both types together.
I understand the active summing of the input, the buffering, the signal inversion and the ability to boost the output signal by adjusting R70, but what I'm not clear about, when you say the buffered input circuit can be used to "bring the input levels down", are the implications there. Such as, what is the "ideal" signal level for this circuit? What happens to the summed signal when input through the unbuffered "core inputs" - is it being attenuated by the circuit? I know you mentioned earlier in the thread that if the input signal is high enough then the FET VCA will color the sound, but that's all the info I could find on signal levels.
Finally, what is the signal level at the unbuffered VCA output? I'd like to work out the right value of R70 to bring that signal level up to 10Vp-p at the buffered output.
Thanks! |
|
Back to top
|
|
|
jhaible
Joined: May 25, 2007 Posts: 2014 Location: Germany
Audio files: 24
|
Posted: Fri Nov 05, 2010 8:16 am Post subject:
|
|
|
numbertalk wrote: | Thank you very kindly for the timely response.
One last thing I'm hoping you wouldn't mind saying a little about when you get a chance is the buffered versus unbuffered inputs and outputs. I'm starting to design a panel and am trying to figure out which type to include or if it would make sense to include a couple of both types together.
I understand the active summing of the input, the buffering, the signal inversion and the ability to boost the output signal by adjusting R70, but what I'm not clear about, when you say the buffered input circuit can be used to "bring the input levels down", are the implications there. Such as, what is the "ideal" signal level for this circuit? What happens to the summed signal when input through the unbuffered "core inputs" - is it being attenuated by the circuit? I know you mentioned earlier in the thread that if the input signal is high enough then the FET VCA will color the sound, but that's all the info I could find on signal levels.
Finally, what is the signal level at the unbuffered VCA output? I'd like to work out the right value of R70 to bring that signal level up to 10Vp-p at the buffered output.
Thanks! |
The VCA core is using the very same signal levels as the EMS VCS3.
JH. _________________ "I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f) |
|
Back to top
|
|
|
numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
|
Posted: Fri Nov 05, 2010 8:57 am Post subject:
|
|
|
Thanks, but I'm still not clear on what effect the input signal level has when using the buffered inputs versus the core inputs.
Maybe it makes more sense to ask this way - if I'm using this module in a modular synth with 10Vp-p signals, would it make sense to use the buffered input as shown in the schematic, with R56=10K? Would this configuration "massage" the signal to make it more appropriate for the circuit? Then I could adjust R70 on the buffered output to bring the level back up to 10Vp-p? If so, does this mean I would have a problem with using this module with a synth with outputs closer to instrument level, and for that would I then want core inputs as well? Just trying to figure out which inputs would be appropriate given my situation and if there would be any reason to have one of each. Again, I understand the other things about using buffered inputs and outputs, just trying to figure out the input signal level aspect as it regards this circuit.
Thanks again.
jhaible wrote: | numbertalk wrote: | Thank you very kindly for the timely response.
One last thing I'm hoping you wouldn't mind saying a little about when you get a chance is the buffered versus unbuffered inputs and outputs. I'm starting to design a panel and am trying to figure out which type to include or if it would make sense to include a couple of both types together.
I understand the active summing of the input, the buffering, the signal inversion and the ability to boost the output signal by adjusting R70, but what I'm not clear about, when you say the buffered input circuit can be used to "bring the input levels down", are the implications there. Such as, what is the "ideal" signal level for this circuit? What happens to the summed signal when input through the unbuffered "core inputs" - is it being attenuated by the circuit? I know you mentioned earlier in the thread that if the input signal is high enough then the FET VCA will color the sound, but that's all the info I could find on signal levels.
Finally, what is the signal level at the unbuffered VCA output? I'd like to work out the right value of R70 to bring that signal level up to 10Vp-p at the buffered output.
Thanks! |
The VCA core is using the very same signal levels as the EMS VCS3.
JH. |
|
|
Back to top
|
|
|
jhaible
Joined: May 25, 2007 Posts: 2014 Location: Germany
Audio files: 24
|
Posted: Fri Nov 05, 2010 9:40 am Post subject:
|
|
|
It's always a matter of taste how much you want to oerdrive a VCA like this. The resistor values in the schematics are a good starting point if you use input attenuators. If the output level is too small, increase R70.
JH. _________________ "I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f) |
|
Back to top
|
|
|
numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
|
Posted: Fri Nov 05, 2010 11:24 am Post subject:
|
|
|
Thanks JH. You pretty much hit the nail on the head of why I want to figure this out. I have an EMS VCF clone that, when used with my 10V VCO signals, does not sound so good - it requires proper attenuation to get that killer sound. So want to make sure I am set up for the best experience before I have a panel made.
So with either the core inputs or the buffer you would suggest input attenuators? Sorry to be a pain but one more question - what value of pot would you suggest? I'm not good at figuring that out - as a guess, 100K if using the buffered inputs? What value if using the core inputs?
Thanks again!
jhaible wrote: | It's always a matter of taste how much you want to oerdrive a VCA like this. The resistor values in the schematics are a good starting point if you use input attenuators. If the output level is too small, increase R70.
JH. |
|
|
Back to top
|
|
|
jhaible
Joined: May 25, 2007 Posts: 2014 Location: Germany
Audio files: 24
|
Posted: Fri Nov 05, 2010 3:44 pm Post subject:
|
|
|
10k log (audio taper) would be a good value for the attenuator(s).
JH.
numbertalk wrote: | Thanks JH. You pretty much hit the nail on the head of why I want to figure this out. I have an EMS VCF clone that, when used with my 10V VCO signals, does not sound so good - it requires proper attenuation to get that killer sound. So want to make sure I am set up for the best experience before I have a panel made.
So with either the core inputs or the buffer you would suggest input attenuators? Sorry to be a pain but one more question - what value of pot would you suggest? I'm not good at figuring that out - as a guess, 100K if using the buffered inputs? What value if using the core inputs?
Thanks again!
jhaible wrote: | It's always a matter of taste how much you want to oerdrive a VCA like this. The resistor values in the schematics are a good starting point if you use input attenuators. If the output level is too small, increase R70.
JH. |
|
_________________ "I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f) |
|
Back to top
|
|
|
numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
|
Posted: Fri Nov 05, 2010 4:47 pm Post subject:
|
|
|
Thanks!
Also, for anyone using the BOM that was attached earlier, it specifies a 1M trimmer but from the schematic looks like it should be 2M.
jhaible wrote: | 10k log (audio taper) would be a good value for the attenuator(s).
JH.
numbertalk wrote: | Thanks JH. You pretty much hit the nail on the head of why I want to figure this out. I have an EMS VCF clone that, when used with my 10V VCO signals, does not sound so good - it requires proper attenuation to get that killer sound. So want to make sure I am set up for the best experience before I have a panel made.
So with either the core inputs or the buffer you would suggest input attenuators? Sorry to be a pain but one more question - what value of pot would you suggest? I'm not good at figuring that out - as a guess, 100K if using the buffered inputs? What value if using the core inputs?
Thanks again!
jhaible wrote: | It's always a matter of taste how much you want to oerdrive a VCA like this. The resistor values in the schematics are a good starting point if you use input attenuators. If the output level is too small, increase R70.
JH. |
|
|
|
|
Back to top
|
|
|
jhaible
Joined: May 25, 2007 Posts: 2014 Location: Germany
Audio files: 24
|
Posted: Fri Nov 05, 2010 4:49 pm Post subject:
|
|
|
Right. (2M, 2M2, or 2M5 will work)
JH.
numbertalk wrote: | Thanks!
Also, for anyone using the BOM that was attached earlier, it specifies a 1M trimmer but from the schematic looks like it should be 2M.
jhaible wrote: | 10k log (audio taper) would be a good value for the attenuator(s).
JH.
numbertalk wrote: | Thanks JH. You pretty much hit the nail on the head of why I want to figure this out. I have an EMS VCF clone that, when used with my 10V VCO signals, does not sound so good - it requires proper attenuation to get that killer sound. So want to make sure I am set up for the best experience before I have a panel made.
So with either the core inputs or the buffer you would suggest input attenuators? Sorry to be a pain but one more question - what value of pot would you suggest? I'm not good at figuring that out - as a guess, 100K if using the buffered inputs? What value if using the core inputs?
Thanks again!
jhaible wrote: | It's always a matter of taste how much you want to oerdrive a VCA like this. The resistor values in the schematics are a good starting point if you use input attenuators. If the output level is too small, increase R70.
JH. |
|
|
|
_________________ "I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f) |
|
Back to top
|
|
|
numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
|
Posted: Fri Nov 05, 2010 6:04 pm Post subject:
|
|
|
Also, not to be nitpicky, but for anyone going strictly by the BOM posted on this thread, the 100K trimmer is a single-turn, not a multi-turn. |
|
Back to top
|
|
|
numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
|
Posted: Tue Nov 09, 2010 6:18 am Post subject:
|
|
|
One more question, since like I proved earlier, I'm not good at figuring out the best values/tapers for these things - if I want to add an attenuator for the Decay CV in, what value/taper pot would be good for that? |
|
Back to top
|
|
|
jhaible
Joined: May 25, 2007 Posts: 2014 Location: Germany
Audio files: 24
|
Posted: Tue Nov 09, 2010 9:44 am Post subject:
|
|
|
numbertalk wrote: | One more question, since like I proved earlier, I'm not good at figuring out the best values/tapers for these things - if I want to add an attenuator for the Decay CV in, what value/taper pot would be good for that? |
This depends on the knob response you prefer.
My preference is to use no attenator pot at the oinput for the Decay CV at all. but use a 10k linear pot at the DeacyCVPol connector instead: Then you have a (linear) reversible attenuator.
JH. _________________ "I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f) |
|
Back to top
|
|
|
numbertalk
Joined: May 05, 2008 Posts: 992 Location: Austin, TX
Audio files: 5
|
Posted: Tue Nov 09, 2010 9:48 am Post subject:
|
|
|
This sounds much better - thanks!
jhaible wrote: | numbertalk wrote: | One more question, since like I proved earlier, I'm not good at figuring out the best values/tapers for these things - if I want to add an attenuator for the Decay CV in, what value/taper pot would be good for that? |
This depends on the knob response you prefer.
My preference is to use no attenator pot at the oinput for the Decay CV at all. but use a 10k linear pot at the DeacyCVPol connector instead: Then you have a (linear) reversible attenuator.
JH. |
|
|
Back to top
|
|
|
zarko
Joined: Mar 25, 2010 Posts: 22 Location: France
|
|
Back to top
|
|
|
jhaible
Joined: May 25, 2007 Posts: 2014 Location: Germany
Audio files: 24
|
Posted: Thu Nov 25, 2010 2:38 pm Post subject:
|
|
|
Just a hint:
In a system with input attenuators (most modular concepts) you should add an input attenuator potentiometer, or better a reversible attenuator, for the Decay Time CV.
In an EMS-like system, where there are no input attenuators, you should have an *output* attenuator for each output, typically a 5k log potentiometer.
JH. _________________ "I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f) |
|
Back to top
|
|
|
zarko
Joined: Mar 25, 2010 Posts: 22 Location: France
|
|
Back to top
|
|
|
|