electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
Live streaming at radio.electro-music.com

  host / artist show at your time
  mosc Live music with Twyndyllyngs - Bill Fox and Howard Moscovitz
Please visit the chat
 Forum index » DIY Hardware and Software » Jürgen Haible designs
Trapezoid VCA anybody?
Post new topic   Reply to topic Moderators: Scott Stites
Page 5 of 7 [160 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Goto page: Previous 1, 2, 3, 4, 5, 6, 7 Next

Would you buy a Jh Trapezoid VCA PCB?
no - only interested in the original EMS circuit (this is not goint to happen - sorry)
2%
 2%  [ 1 ]
yes - if it emulates the behaviour of the EMS circuit, and doesn't need component selecting
97%
 97%  [ 40 ]
Total Votes : 41

Author Message
janvanvolt



Joined: Nov 24, 2005
Posts: 285
Location: Mainz, Germany

PostPosted: Tue Nov 02, 2010 5:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Anybody got an idea for the frontpanel (5U?)
_________________
Homepage - http://www.czmok.de
My dIY - http://diy.czmok.de
Film/Music - http://gfm.me
Back to top
View user's profile Send private message Visit poster's website AIM Address
MR-808



Joined: Sep 30, 2010
Posts: 28
Location: Portland, OR

PostPosted: Tue Nov 02, 2010 9:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message
numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Wed Nov 03, 2010 9:17 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message
jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Wed Nov 03, 2010 1:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

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. Smile

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
View user's profile Send private message Send e-mail Visit poster's website
numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Wed Nov 03, 2010 4:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Excellent thanks Very Happy

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. Smile

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
View user's profile Send private message
emdot_ambient



Joined: Nov 22, 2009
Posts: 669
Location: Frederick, MD

PostPosted: Wed Nov 03, 2010 6:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
Switch trigger is used by old Korg and Moog synthesizers. Not a gate voltage, but a switch closing a contact to GND.

Idea Like a footswitch to trigger without using yer hands....


Blimey, that took me a while to piece together!
Back to top
View user's profile Send private message Visit poster's website
numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Thu Nov 04, 2010 6:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message
jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Fri Nov 05, 2010 5:24 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message Send e-mail Visit poster's website
numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Fri Nov 05, 2010 5:54 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message
jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Fri Nov 05, 2010 6:22 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message Send e-mail Visit poster's website
numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Fri Nov 05, 2010 6:40 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message
jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Fri Nov 05, 2010 8:16 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message Send e-mail Visit poster's website
numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Fri Nov 05, 2010 8:57 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message
jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Fri Nov 05, 2010 9:40 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message Send e-mail Visit poster's website
numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Fri Nov 05, 2010 11:24 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message
jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Fri Nov 05, 2010 3:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message Send e-mail Visit poster's website
numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Fri Nov 05, 2010 4:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message
jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Fri Nov 05, 2010 4:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message Send e-mail Visit poster's website
numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Fri Nov 05, 2010 6:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message
numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Tue Nov 09, 2010 6:18 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message
jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Tue Nov 09, 2010 9:44 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message Send e-mail Visit poster's website
numbertalk



Joined: May 05, 2008
Posts: 980
Location: Austin, TX
Audio files: 5

PostPosted: Tue Nov 09, 2010 9:48 am    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message
zarko



Joined: Mar 25, 2010
Posts: 22
Location: France

PostPosted: Thu Nov 25, 2010 10:15 am    Post subject: Reply with quote  Mark this post and the followings unread

here is my small contibution its the front panel in dotcom format 2U 222x108 mm


TRAPEZOID VCA copie.jpg
 Description:
 Filesize:  552.39 KB
 Viewed:  152 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

TRAPEZOID VCA  copie.jpg


Back to top
View user's profile Send private message
jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Thu Nov 25, 2010 2:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
View user's profile Send private message Send e-mail Visit poster's website
zarko



Joined: Mar 25, 2010
Posts: 22
Location: France

PostPosted: Fri Nov 26, 2010 11:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Jurgen, i made a new front panel with the attenuator pot,would you tell
me what do you think about Wink


TRAPEZOID VCA V2 copie.jpg
 Description:
 Filesize:  505.04 KB
 Viewed:  122 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

TRAPEZOID VCA V2  copie.jpg


Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: Scott Stites
Page 5 of 7 [160 Posts]
View unread posts
View new posts in the last week
Goto page: Previous 1, 2, 3, 4, 5, 6, 7 Next
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » Jürgen Haible designs
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use