electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links
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 
 Forum index » DIY Hardware and Software » PAIA Equipment
PAIA2720-3B VC Bandpass Filter_Augmentations
Post new topic   Reply to topic
Page 1 of 2 [31 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Goto page: 1, 2 Next
Author Message
gasboss775



Joined: Jan 02, 2016
Posts: 217
Location: Scotland

PostPosted: Tue May 16, 2017 6:40 am    Post subject: PAIA2720-3B VC Bandpass Filter_Augmentations Reply with quote  Mark this post and the followings unread

I tried out the PAIA 2720-3B VC Bandpass Filter on the breadboard. I wasn't initially that impressed with its range. However I swapped the diode for a red led and drove it from an exponential current source, the result was a great increase in the range of the filter. I also changed the way in which the Q control was implemented, resulting in, in my opinion a more natural control contour.

I also made a second version with a simpler current source using just one NPN transistor. The results were still very impressive.

The most interesting characteristic of these filters is the way they behave when overdriven. With high Q settings, the LED becomes modulated by the very signal that it is controlling and things freak out somewhat, the LED flickers too in response to the large signal swing!

The original is included for comparison.


PAIA 2720-3B_LED_ExpoCurrentSource_Version.jpg
 Description:
 Filesize:  288.89 KB
 Viewed:  1158 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

PAIA 2720-3B_LED_ExpoCurrentSource_Version.jpg



PAIA2720_3B_LED_Simple_CurrentSource_Version.jpg
 Description:
 Filesize:  212.14 KB
 Viewed:  1133 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

PAIA2720_3B_LED_Simple_CurrentSource_Version.jpg



paia_2720_3b_vc_bpf_Disrete_Design.gif
 Description:
 Filesize:  11.33 KB
 Viewed:  1062 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

paia_2720_3b_vc_bpf_Disrete_Design.gif


Back to top
View user's profile Send private message
gasboss775



Joined: Jan 02, 2016
Posts: 217
Location: Scotland

PostPosted: Wed May 17, 2017 5:38 am    Post subject: Reply with quote  Mark this post and the followings unread

I tried out the PAiA 2720-3L Lowpass filter. Again it worked better with LEDs instead of diodes and a current source to drive the LEDs. I chained two Lowpass filter sections together to make a 4 pole filter. It was quite good but would really benefit from having a Q / resonance control. I'm going to have to figure out if this can be done.
Back to top
View user's profile Send private message
gasboss775



Joined: Jan 02, 2016
Posts: 217
Location: Scotland

PostPosted: Sat May 20, 2017 5:20 am    Post subject: Better Current Source Version Reply with quote  Mark this post and the followings unread

This version of the 2720-3B bandpass filter has a linear current source that doesn't have any tempco problems.


1495219802500.jpg
 Description:
 Filesize:  93.87 KB
 Viewed:  1067 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

1495219802500.jpg


Back to top
View user's profile Send private message
gasboss775



Joined: Jan 02, 2016
Posts: 217
Location: Scotland

PostPosted: Sun May 21, 2017 3:39 am    Post subject: Reply with quote  Mark this post and the followings unread

I was just trying out the circuit from my last post again and it would seem that 68K is a better choice for R12 as it allows the filter to be completely closed.
I suspect that there might need to be a bit of experimentation with some of the resistor values to accommodate different LED's. Specifically, R9 & R12.

Last edited by gasboss775 on Sun May 21, 2017 7:15 am; edited 1 time in total
Back to top
View user's profile Send private message
gasboss775



Joined: Jan 02, 2016
Posts: 217
Location: Scotland

PostPosted: Sun May 21, 2017 7:14 am    Post subject: Reply with quote  Mark this post and the followings unread

I built 2 of the PAiA 2720-3B bandpass VCFs and designed a little two transistor mixer and output stage with 10 V peak to peak maximum output.

The sinewave generators represent the 2 filters, the 10K resistor on the right represents the output load.


2Ch Discrete transistor mixer for dual VCF.png
 Description:
 Filesize:  48.18 KB
 Viewed:  969 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

2Ch Discrete transistor mixer for dual VCF.png


Back to top
View user's profile Send private message
n.d



Joined: Dec 15, 2011
Posts: 52
Location: Talos IV

PostPosted: Fri Feb 16, 2018 6:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Nice work!
Back to top
View user's profile Send private message
gasboss775



Joined: Jan 02, 2016
Posts: 217
Location: Scotland

PostPosted: Fri Mar 09, 2018 12:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

n.d wrote:
Nice work!


Thanks dude.

I have experienced some problems with instability ( it bursts into oscillation ) that seem to be somewhat related to circuit layout ( I've only ever built it on a breadboard )
I did find that putting a 100n ( 0.1uF ) capacitor between the collector or Q2 and ground helped a bit. Does anyone else have any suggestions about making this behave. I was thinking of using either an FET optocoupler or a vactrol instead of the diode to tune the filter in order to avoid the circuit using the same ground as the control signal.
Back to top
View user's profile Send private message
Fernando



Joined: Dec 30, 2006
Posts: 286
Location: Barcelona & Emporda, Spain

PostPosted: Mon Aug 27, 2018 11:26 am    Post subject: Reply with quote  Mark this post and the followings unread

very nice gasboss!

I always think about trying the most simple PAiA circuits.

Well for the twin T filter (2720-3b) I'd try with a photocell instead of the diode and a circuit to control the LED. Or a real vactrol instead of a DIY one. But DIY you can use a more adequate range for the photocell and have less work fine-tuning it's right resistance range.

There are many schematics for vactrol CV around from other circuits (Buchla LPG, etc.) but I'd try something much simpler first, the simplest possible.
Try this: http://thesquarewaveparade.com/images/VtoR.jpg (second option, with offset)
And read here: http://www.electro-music.com/forum/topic-37628.html

_________________
Fer

.
Back to top
View user's profile Send private message
gasboss775



Joined: Jan 02, 2016
Posts: 217
Location: Scotland

PostPosted: Mon Sep 17, 2018 9:26 am    Post subject: Reply with quote  Mark this post and the followings unread

Fernando wrote:
very nice gasboss!


Thanks for the complement Fernando!

Quote:
I always think about trying the most simple PAiA circuits.

Well for the twin T filter (2720-3b) I'd try with a photocell instead of the diode and a circuit to control the LED. Or a real vactrol instead of a DIY one. But DIY you can use a more adequate range for the photocell and have less work fine-tuning it's right resistance range.

There are many schematics for vactrol CV around from other circuits (Buchla LPG, etc.) but I'd try something much simpler first, the simplest possible.
Try this: http://thesquarewaveparade.com/images/VtoR.jpg (second option, with offset)
And read here: http://www.electro-music.com/forum/topic-37628.html


I have several vactrols and have been meaning to try them out in this circuit. Using a diode or LED have their own charms due to the distortion generated when the filter is driven with a strong signal. I do like vactrol based filters though, they have a dynamic character of their own.

Last edited by gasboss775 on Mon Sep 17, 2018 3:15 pm; edited 1 time in total
Back to top
View user's profile Send private message
Fernando



Joined: Dec 30, 2006
Posts: 286
Location: Barcelona & Emporda, Spain

PostPosted: Mon Sep 17, 2018 10:04 am    Post subject: Reply with quote  Mark this post and the followings unread

gasboss775 wrote:
Using a diode or LED have their own charms due to the distortion generated when the filter is driven with a strong signal..


that's interesting

I would try with a chain of Ge diodes then

_________________
Fer

.
Back to top
View user's profile Send private message
gasboss775



Joined: Jan 02, 2016
Posts: 217
Location: Scotland

PostPosted: Tue Sep 18, 2018 1:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, Ge diodes sound like a good idea, never tried them at the time.
Back to top
View user's profile Send private message
AlanP



Joined: Mar 11, 2014
Posts: 746
Location: New Zealand
Audio files: 41

PostPosted: Tue Sep 18, 2018 10:21 am    Post subject: Reply with quote  Mark this post and the followings unread

My experience of clipping diodes in pedals is that Ge diodes have a "softer" sound than Si diodes. You need a couple in series to match the Fv of silicon, though.
Back to top
View user's profile Send private message
gasboss775



Joined: Jan 02, 2016
Posts: 217
Location: Scotland

PostPosted: Thu Sep 27, 2018 8:56 am    Post subject: Reply with quote  Mark this post and the followings unread

AlanP wrote:
My experience of clipping diodes in pedals is that Ge diodes have a "softer" sound than Si diodes. You need a couple in series to match the Fv of silicon, though.


Today I tried Ge diodes with a similar filter circuit and it did sound more agreeable ( less harsh than the Si diode ), I also tried an led but I think it sounded worse than the silicon diode !
Back to top
View user's profile Send private message
Fernando



Joined: Dec 30, 2006
Posts: 286
Location: Barcelona & Emporda, Spain

PostPosted: Mon Oct 01, 2018 10:38 am    Post subject: Reply with quote  Mark this post and the followings unread

but in the same position as in the PAiA band pass?
I mean, as the variable resistance to ground at the bottom of the twin T?

gasboss775 wrote:

Today I tried Ge diodes with a similar filter circuit and it did sound more agreeable ( less harsh than the Si diode ), I also tried an led but I think it sounded worse than the silicon diode !

_________________
Fer

.
Back to top
View user's profile Send private message
gasboss775



Joined: Jan 02, 2016
Posts: 217
Location: Scotland

PostPosted: Wed Oct 03, 2018 3:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes the diode was in the same position as with the PAiA circuit.
Back to top
View user's profile Send private message
AlanP



Joined: Mar 11, 2014
Posts: 746
Location: New Zealand
Audio files: 41

PostPosted: Wed Oct 03, 2018 8:40 am    Post subject: Reply with quote  Mark this post and the followings unread

LEDs have a fairly high Fv compared to silicon or Ge, they're pretty harsh in pedals, too Smile translates to high levels before clipping.
Back to top
View user's profile Send private message
cslammy



Joined: Apr 27, 2018
Posts: 206
Location: USA
Audio files: 1

PostPosted: Fri Nov 30, 2018 9:12 am    Post subject: Re: PAIA2720-3B VC Bandpass Filter_Augmentations Reply with quote  Mark this post and the followings unread

gasboss775 wrote:


The most interesting characteristic of these filters is the way they behave when overdriven. With high Q settings, the LED becomes modulated by the very signal that it is controlling and things freak out somewhat, the LED flickers too in response to the large signal swing!

The original is included for comparison.


Gasboss, what power are you using for V++ and V--? +/- 15V?

_________________
Visit my AUDIODIWHY blog and website
Back to top
View user's profile Send private message Visit poster's website
gasboss775



Joined: Jan 02, 2016
Posts: 217
Location: Scotland

PostPosted: Sun Dec 02, 2018 2:26 pm    Post subject: Re: PAIA2720-3B VC Bandpass Filter_Augmentations Reply with quote  Mark this post and the followings unread

cslammy wrote:
gasboss775 wrote:


The most interesting characteristic of these filters is the way they behave when overdriven. With high Q settings, the LED becomes modulated by the very signal that it is controlling and things freak out somewhat, the LED flickers too in response to the large signal swing!

The original is included for comparison.


Gasboss,j what power are you using for V++ and V--? +/- 15V?


The circuit works from a single +Ve supply rail +12 to + 15 V, 15 would provide more dynamic range for the signal.
Back to top
View user's profile Send private message
vladosh



Joined: Aug 02, 2010
Posts: 659
Location: macedonia
Audio files: 46

PostPosted: Fri Dec 07, 2018 11:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Here's some PCB layout for this ,if that's ok . I didn't made the add-on mixer ,just the last linear response version ,wanna try this version , have built this filter once earlier as the original on 18V ,PCB is 70x100mm


Paia BPF Adaptation - Parts View.jpg
 Description:
 Filesize:  496.74 KB
 Viewed:  426 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

Paia BPF Adaptation - Parts View.jpg



Untitled.png
 Description:
 Filesize:  19.19 KB
 Viewed:  425 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

Untitled.png



_________________
http://synthacks.blogspot.com/ шематикс
Back to top
View user's profile Send private message
danielfiction



Joined: Jul 15, 2009
Posts: 9
Location: nyc

PostPosted: Wed Jan 09, 2019 12:53 pm    Post subject: notch? Reply with quote  Mark this post and the followings unread

i'm really interested in this filter. i'm going to build it.

but what about modifying it for "notch", aka, band stop output? how would you go about that?

daniel
Back to top
View user's profile Send private message
vladosh



Joined: Aug 02, 2010
Posts: 659
Location: macedonia
Audio files: 46

PostPosted: Wed Dec 25, 2019 2:13 am    Post subject: Reply with quote  Mark this post and the followings unread

really like how this filter sounds ,however i replaced that 47K resistor with 62K and it wouldn't close all the way , it's powered with 15V so thinking to try 82K and see how that goes i even wonder if connecting the freq pot to -V via 47K resistor is better ,nice resonance
_________________
http://synthacks.blogspot.com/ шематикс
Back to top
View user's profile Send private message
vladosh



Joined: Aug 02, 2010
Posts: 659
Location: macedonia
Audio files: 46

PostPosted: Wed Dec 25, 2019 5:12 am    Post subject: Reply with quote  Mark this post and the followings unread

i that's how i messed it up ..
_________________
http://synthacks.blogspot.com/ шематикс
Back to top
View user's profile Send private message
MapacheRaper



Joined: Feb 15, 2018
Posts: 166
Location: Spain

PostPosted: Fri Jan 31, 2020 5:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

So a lot of chat on how good it sounds but not a miserable audio demo? C.mon guys...

I would love to build one of these but Im a disaster breadboarding
Back to top
View user's profile Send private message
cslammy



Joined: Apr 27, 2018
Posts: 206
Location: USA
Audio files: 1

PostPosted: Mon Feb 03, 2020 5:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

I am terrible at breadboarding/stripboarding as well.

I have created BRD and SCM in eagle, posting it here in zip along w/ gerber
I'll send it off on my next fab and let you know what happens.
Relatively Big board, not a lot of vias, room for jumpers, kludge wires etc.
No ground pour, no fancy stuff.

Warning: doing this while at work--checked it once, think i got it right, but may be mistakes. Passes DRC and ERD checks.


PAIA4720BOARD.PNG
 Description:
 Filesize:  48.53 KB
 Viewed:  161 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

PAIA4720BOARD.PNG



4720FILTER-EAGLE.zip
 Description:

Download
 Filename:  4720FILTER-EAGLE.zip
 Filesize:  170.43 KB
 Downloaded:  201 Time(s)


_________________
Visit my AUDIODIWHY blog and website
Back to top
View user's profile Send private message Visit poster's website
MapacheRaper



Joined: Feb 15, 2018
Posts: 166
Location: Spain

PostPosted: Mon Feb 03, 2020 6:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

Great!! That´s exactly the kind of project for your blog. Waiting to read the post Smile

It´s a pity that China is halted, tho. Who knows when they will produce it. I have some PCBs paid, and in the schedule to fab in JLCPCB. Not looking good at the moment...

Whatever, cool project
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic
Page 1 of 2 [31 Posts]
View unread posts
View new posts in the last week
Goto page: 1, 2 Next
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » PAIA Equipment
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


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