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 Forum index » DIY Hardware and Software » Jürgen Haible designs
Interpolating Scanner: ...I ike to get some ....
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neandrewthal



Joined: May 11, 2007
Posts: 672
Location: Canada

PostPosted: Tue Jan 05, 2010 3:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

No prob Smile I only wish I had a third hand so I could put the camera on the blinky lights too.

This one shows it better. Wink

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jhaible



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

PostPosted: Sat Jul 17, 2010 1:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Correction / Improovement

I noticed there is a tiny, but not unimportant design flaw - I'm surpriced no one else mentioned it so far: The output amplifier gain is too high. That means, the output will clip hard and nasty way before the scanning transistors go into soft limiting action. Ok, there is a lot of ugly/hard clipping gear out there, so probably that's the reason nobody complained, but that's not the way I normally design my audio circuits. My apologies. - Fortunately, this can easily be fixed, by just cahnging two resistors. What has formerly been 13k, should now be 4k3. I won't redraw the schematics diagram, but here is a correction of the PCB layout (applies to all versions):

http://www.jhaible.de/interpolating_scanner_and_scanvib/jh_interpolating_scanner_and_scanvib.html

(scroll down to end of page)

JH.

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"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)
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Funky40



Joined: Sep 24, 2005
Posts: 875
Location: Swiss
Audio files: 1
G2 patch files: 5

PostPosted: Sat Jul 24, 2010 4:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Jürgen !


hmm, no, i never noticed something bad,
but maybe i was just leveling the sound right.
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jhaible



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

PostPosted: Sat Jul 24, 2010 7:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Funky40 wrote:
Thanks Jürgen !


hmm, no, i never noticed something bad,
but maybe i was just leveling the sound right.


I noticed when I played my Wurlitzer 200A thru the scanner chorus.
No more nasty periodical clipping after the mod. I can drive the input really hard now, which is good for the Wurlie sound.

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)
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defex



Joined: Jun 27, 2008
Posts: 33
Location: Toronto, canada

PostPosted: Sun Sep 19, 2010 11:58 am    Post subject: Reply with quote  Mark this post and the followings unread

with Interpolating scanner,

If i wanted to give each section a separate output, I guess i would have to cut the traces from the transistor pairs to the output amplifier, and replicate the output amp section and offset trimmer for the other 8 channels, then mix those for the main out?

I want to try that so i can do VC surround pan and VC effect send.
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jhaible



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

PostPosted: Sun Sep 19, 2010 1:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

defex wrote:
with Interpolating scanner,

If i wanted to give each section a separate output, I guess i would have to cut the traces from the transistor pairs to the output amplifier, and replicate the output amp section and offset trimmer for the other 8 channels, then mix those for the main out?

I want to try that so i can do VC surround pan and VC effect send.


Yes, that's the way to do it.
Much of the elegance of the concept is lost that way (having 9 VCA functions where everything but the input transistor pair is shared), but that's the pragmatic solution.
Make sure to add the latest mod on my project page right from the start, or you'll have to change 18 resistors instead of 2. Smile

JH.

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"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)
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slaughterhousesam



Joined: Aug 27, 2010
Posts: 16
Location: london

PostPosted: Mon Sep 20, 2010 2:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

hi guys

having great fun with my pair of scanners, but there is one niggle....seems the output level is down in the line level range rather than the +/-5V modular norm. for example if i send a set 5v voltage into the input of a particular stage and then use the manual control to select that stage, im getting a little over 1.5v out. when using the ac coupling cap to get normalisation this (i think..) would half the voltage again when the scanner is "in motion".

is there a quick and easy way to bump up the output to get unity gain through the scanner?

cheers muchly Smile
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jhaible



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

PostPosted: Mon Sep 20, 2010 3:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

slaughterhousesam wrote:
hi guys

having great fun with my pair of scanners, but there is one niggle....seems the output level is down in the line level range rather than the +/-5V modular norm. for example if i send a set 5v voltage into the input of a particular stage and then use the manual control to select that stage, im getting a little over 1.5v out. when using the ac coupling cap to get normalisation this (i think..) would half the voltage again when the scanner is "in motion".

is there a quick and easy way to bump up the output to get unity gain through the scanner?

cheers muchly Smile


The gain is set by two resistors (R49 and R50) - last thing I put up there is a mod that brings the gain *down* to unity gain:
http://www.jhaible.de/interpolating_scanner_and_scanvib/jh_interpolating_scanner_and_scanvib.html (scroll down to the bottom).
So I'm surprised you have such a low level.

Please check if your R79 is really 1k.

JH.

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"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)
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slaughterhousesam



Joined: Aug 27, 2010
Posts: 16
Location: london

PostPosted: Mon Sep 20, 2010 4:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

hi jurgen

r79 measures up as a 1k, checked the other resistors and they all look right too.

one thing though, the offset trimpot, is that part of the lfo? i assumed it was and as i didnt have the panel space to implement the lfo i didnt bother adjusting it, though when i look at the schematic it seems to be on the wrong side of the circuit to be related the lfo. do you think this would be able to cause problems if it was wildly mis-set?

ta
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defex



Joined: Jun 27, 2008
Posts: 33
Location: Toronto, canada

PostPosted: Mon Sep 20, 2010 7:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks for the quick reply again! great help with mods from the designer is awesome

sorry to spoil you elegant design Smile but its only a couple of quad op amps and some minor components. i bought 2 of them, and i will try it on one of them to see how useful it is.
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jhaible



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

PostPosted: Mon Sep 20, 2010 11:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

slaughterhousesam wrote:
hi jurgen

r79 measures up as a 1k, checked the other resistors and they all look right too.

one thing though, the offset trimpot, is that part of the lfo? i assumed it was and as i didnt have the panel space to implement the lfo i didnt bother adjusting it, though when i look at the schematic it seems to be on the wrong side of the circuit to be related the lfo. do you think this would be able to cause problems if it was wildly mis-set?

ta


Yes, it's just an offset pot for the LFO, for the VCA that controlls the LFO depth, to be precise. And even thought it seems connected at the "wrong" end of the circuit, it's actually a trimmer for the offset voltage of the OTA U14B. I thought I'd give you guys something to think about instead of re-iterating the same old circuits, connecting the offset control to pin 13 or 14 of the LM13600. Smile (No, seriously: it was a matter of layouting, with all that cramped space. Just look at where the diode for PSU voltage reversal protection is located, and you can get the insanity of in all ...)
But no, that trimmer won't change any gain.
If your input signal is small, just reduce the value of the input resistors to the differential pairs - you want 10mVp (20mVpp) here. Maybe 20mVp.
Then get additional gain by changing the resistors in the output stage (like the mod, but increasing resistors)

JH.

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"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)
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slaughterhousesam



Joined: Aug 27, 2010
Posts: 16
Location: london

PostPosted: Tue Sep 21, 2010 1:27 am    Post subject: Reply with quote  Mark this post and the followings unread

I have set up a static test case where a constant 5v voltage is fed into the 9th stage and this stage selected with the manual control, and recorded the voltages im seeing around the tl071 and relevant SSM chip.

TL071 Pin 6 =1.63v
TL071 Pin 3 = 2.97v
TL071 Pin 2 = 2.97v
TL071 Pin 7/4 = 15v/-15v

VCA 9 entrypoint (going into the 33k resistor) = 4.96v

SSM Pin 1 = 2.97v
SSM Pin 2 = 0.01v
SSM Pin 3 = -0.55v

SSM Pin 8 = 2.97v
SSM Pin 7 = 0
SSM Pin 6 = -0.55v

Are there any issues with these numbers that jump out at anybody? I thought the SSM Pin2 voltage looked a bit strange but it fits with the voltage division of the attached resistors.

Its a very odd problem, i have built two boards about a month apart and they are both showing this low gain.
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slaughterhousesam



Joined: Aug 27, 2010
Posts: 16
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PostPosted: Tue Sep 21, 2010 11:31 am    Post subject: Reply with quote  Mark this post and the followings unread

i have set the offset trimmer to mid point so its a bit easier to see what is happening now (the tl071 has been set up as a differential amplifier, right?).

On a statically selected stage, varying the incoming input signal between +5v and 0v, i see
+5v 0v
TL071 Pin 6 1.58v -0.024v
SSM Pin1(and8) 2.96v 2.43v
SSM Pin2 0.01v 0v
SSM Pin3(and 6) -0.554v -0.556v
SSM Pin7 0v 0v

Deselecting the stage sends SSM pins 3 and 6 to 0.

So it looks like a 0-5v swing coming in to the module causes a 0.5v swing in the output of the SSM, which is amplified by around 3x for a 1.5v in the TL071 output. Are these SSM swings in the right ballpark? If so then I think I need x10 gain on the TL071 rather than x3.
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jhaible



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

PostPosted: Tue Sep 21, 2010 12:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

If your output level is too low and everything else seems right, just increase the gain of the output amp, by choosing larger resistor values.

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)
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slaughterhousesam



Joined: Aug 27, 2010
Posts: 16
Location: london

PostPosted: Tue Sep 21, 2010 12:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

cool, im going cross eyed trying to find something thats out of place Smile
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slaughterhousesam



Joined: Aug 27, 2010
Posts: 16
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PostPosted: Tue Sep 21, 2010 3:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

13k resistors get me unity gain again....rofl

thanks for your time and patience jurgen Smile
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jhaible



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

PostPosted: Wed Sep 22, 2010 1:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

slaughterhousesam wrote:
13k resistors get me unity gain again....rofl

thanks for your time and patience jurgen Smile


Then my original calculations/simulations which led to 13k resistor value weren't that bad after all. Shocked

I just found, empirically, that in the Hammond-style vibrato application, the output was too hot, and clipping, and I changed the gain accordingly, and put it on the web as mod. Hmm ...

JH.

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"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)
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neandrewthal



Joined: May 11, 2007
Posts: 672
Location: Canada

PostPosted: Tue Oct 05, 2010 12:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

I love my Scanner but I keep dreaming about how great it would be if one could adjust the width of the function generator waveform. For example, at one extreme it would be so narrow that each input would just be heard as a quick blip when it is scanned by with silence in between. At the other extreme, several stages would blend together instead of just two adjacent ones.

Would this be very hard to implement, or impossible without starting again from scratch?

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jhaible



Joined: May 25, 2007
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Audio files: 24

PostPosted: Tue Oct 05, 2010 12:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

neandrewthal wrote:
I love my Scanner but I keep dreaming about how great it would be if one could adjust the width of the function generator waveform. For example, at one extreme it would be so narrow that each input would just be heard as a quick blip when it is scanned by with silence in between.


Just increase the modulation depth:
Make R81 = 10k (was: 100k) and use an external LFO.

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)
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