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 Forum index » DIY Hardware and Software » fonik's place
Gate Control Expansion Board for LPG 292 (Thomas White PCB)
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The Bad Producer



Joined: Mar 08, 2009
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PostPosted: Mon Feb 22, 2010 10:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, as Tommi says, to have the option to change R18 with a switch so that you can add distortion. I mean the gate expansion board works, but it is obvious that with a lot or resonance the signal may get too close to the rails, hence the need to change R18 on the LPG (at 12V)

I looked at the signal on the scope, and as far as I could see (I didn't check every point in the circuit) the signal does not exceed 5v p-p apart from when resonance is turned up, then there is a spike or glitch on the waveform, which just nudges it up - if you look at my scope shots above, you can see the third pic - with resonance turned up - has a glitch which pushes the signal above 5V p-p, it seems to me to depend on the input waveform as well as level...

In my opinion we are talking only now about 12V versions, as it seems that the 15V has more headroom and needs a less drastic change to R18 to remove distortion...

I want to do some more research into this, but won't be able to until later in the week...

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slacker



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PostPosted: Mon Feb 22, 2010 12:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's something else to try on 12 volt versions. On the Expansion board the +-7.5 volts are generated using voltage dividers that are then buffered.
So if you changed the resistor values in the dividers you could get it running of +-7.5volts instead of +-6 volts.
12k for R1 and R4 and 20k for R2 and R3 should do it, I think.
These would need changing back to the standard values if you ever switched to +-15 volts or you'd damage the CD4053.

For what it's worth my LPG without the expansion boards distorts if you crank up the resonance so some of it is just down to the resonance mod and nothing to do with the expansion board.
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fonik



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PostPosted: Mon Feb 22, 2010 12:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

slacker wrote:
Here's something else to try on 12 volt versions. On the Expansion board the +-7.5 volts are generated using voltage dividers that are then buffered.
So if you changed the resistor values in the dividers you could get it running of +-7.5volts instead of +-6 volts.
12k for R1 and R4 and 20k for R2 and R3 should do it, I think.

Laughing sometimes it is easier that you would think...

thanks for taking care.

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The Bad Producer



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PostPosted: Mon Feb 22, 2010 3:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

wicked, I'll check this out! It seems so easy!

I've only ever wanted the LPG with Foniks expansion board, and I thought I could adapt the LPG to fit (at 12V) now it seems I can do it without going too nuts about something I know nothing about! I think I got too hung up on the issue without actually thinking about it logically...

I'll change the resistors in the divider and see what happens... thanks! Very Happy

Charlie

PS: like this?

Posted Image, might have been reduced in size. Click Image to view fullscreen.

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The Bad Producer



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PostPosted: Mon Feb 22, 2010 6:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

okey-dokey, I swapped out R1, 2, 3, 4 with those values for +/-7.5V for 12V module...this gave me -7.5V and +7.12V.

Result is a lot better, there is still a tiny bit of clipping, but with a 100K resistor in place of R18 on the LPG this is manageable by attenuating the input signals more and use of the offset and offset trim on the LPG (I would probably recommend putting the offset trim on the panel for extra tweakability). An interesting thing I noticed as an aside is that clippping was more likely to occur when the VCO was being FM'ed for some reason...

Fonik, your electronic mode control board works wonders, thanks for all your help!

Posted Image, might have been reduced in size. Click Image to view fullscreen.

PS it will clip in both mode if R18 less than 100K

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fonik



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PostPosted: Tue Feb 23, 2010 2:24 am    Post subject: Reply with quote  Mark this post and the followings unread

i thank YOU for YOUR help. and your module loos gorgeous!

BTW what's the offset effect control again?

i amended the docs:
Building Documentation:
LPG292c Expansion

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The Bad Producer



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PostPosted: Tue Feb 23, 2010 3:05 am    Post subject: Reply with quote  Mark this post and the followings unread

The 'offset' knob is the offset pot, 'offset offset' is the offset trimmer mounted on the front panel, this is it for this version, I'm only going to make 2 of these for 12V operation...

As I am now pretty happy with the metal panels and lazertran I could take this opportunity to add some kind of 'distortion' switch to the 15V version as I re-panel them...

One thing I do wonder, does it matter that the expansion board is giving slightly unequal power to the 4053 (-7.5V and +7.12V)? I may have another look at this, could be a poor solder joint or or something, I did bodge it together a bit!

Also thanks to slacker for the suggestion about the divider!

Charlie

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fonik



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PostPosted: Tue Feb 23, 2010 3:25 am    Post subject: Reply with quote  Mark this post and the followings unread

The Bad Producer wrote:
One thing I do wonder, does it matter that the expansion board is giving slightly unequal power to the 4053 (-7.5V and +7.12V)? I may have another look at this, could be a poor solder joint or or something, I did bodge it together a bit!

it should not! i am using 1% resistors, which is suffiecient. if the power is not balanced it would 'bias' the 4053.

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slacker



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PostPosted: Tue Feb 23, 2010 11:37 am    Post subject: Reply with quote  Mark this post and the followings unread

The Bad Producer wrote:

Also thanks to slacker for the suggestion about the divider!


No problem, glad it helped Smile
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tommi



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PostPosted: Wed Feb 24, 2010 1:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks guys!
I implemented the modifies you suggested and it works now! Very Happy
As Charlie said, on the sum stage on the LPG board there's the need of an attenuation, since i founded that the range of the input attenuators is useful only till 12 o' clock. Then it clips.
So i am going to modify that too. The sum stage here is configurated as an inverting amplifier, so, based on the information i founded here http://musicfromouterspace.com/analogsynth/oddsandends.html#OPAMPFUNDS, i have to increase the value of the three input resistors (R27,28,29) or lower the value of the feedback resistor (R30).
The actual sum stage have a gain of 2 (100K/100K+1).
I think that a gain of 1 would be enough.
What you say about lowering the feedback resistor to 10K? scratch

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fonik



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PostPosted: Wed Feb 24, 2010 3:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

tommi wrote:
...on the sum stage on the LPG board there's the need of an attenuation, since i founded that the range of the input attenuators is useful only till 12 o' clock. Then it clips.
So i am going to modify that too. The sum stage here is configurated as an inverting amplifier, so, based on the information i founded here http://musicfromouterspace.com/analogsynth/oddsandends.html#OPAMPFUNDS, i have to increase the value of the three input resistors (R27,28,29) or lower the value of the feedback resistor (R30).
The actual sum stage have a gain of 2 (100K/100K+1).
I think that a gain of 1 would be enough.
What you say about lowering the feedback resistor to 10K? scratch

the actual sum stage is a unity gain chain of two inverting mixers, thus gain 1.
you have attenuators on the inputs? then i would use one input only and see when it clips. change the resistor in the feedbackpath accordingly (i.e. when one input clips at 12 o'clock then 47k) . so you will have max signal when using only one input. as soon as you use more inputs you can use the attenuators...

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tommi



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PostPosted: Thu Feb 25, 2010 4:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Replaced the feedback path resistor (R30) on the LPG board. As suggested by Fonik i lowered it from 100K to 47K. The clipping is gone!
Finally i can enjoy the feature of the expantion board. Very Happy
I am glad that i 've refused your offer of a refund, Fonik! Wink

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fonik



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PostPosted: Fri Feb 26, 2010 12:47 am    Post subject: Reply with quote  Mark this post and the followings unread

tommi wrote:
I am glad that i 've refused your offer of a refund, Fonik! Wink

why? you would have got your money back + working modules now! Laughing

to be honest, i am glad charlie did solve the problem. thank you again...

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frenchyinmunich



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PostPosted: Wed Mar 17, 2010 3:41 am    Post subject:
Subject description: Looking for LPG 292 PCBs
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Hello,

I am looking for 4 boards for sale.
Please, let me know.

Regards,

F
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djthomaswhite



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PostPosted: Thu Mar 18, 2010 12:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hello,

It would appear demand has grown large enough for another small run of Resonant Lopass Gate PCBs. There are many examples of these in action on the web and more information at http://www.naturalrhythmmusic.com/lopass.html. I will be taking orders from today until March 31st. Here's how it will work with ordering.

Due to having a baby on the way I will be producing these boards to order, no extras this time around. If you want boards, PayPal me $15 per board to:

djthomaswhite@yahoo.com

Your payment subject should read "LPG Order"

Shipping to the world is included in the price of the order. I will place the board order on April 1st (no joke) and the turn around time for shipping should be 2-3 weeks, but usually closer to 2. Once I receive the boards I will pack them for shipping and notify you when they ship via USPS First Class Mail. Contact me privately with any questions. These boards work with any popular power from +/-12v to +/-15v, however, the power connector on them is for MOTM or Synthesizers.com. Other connections (like Euro) require hand wiring the power instead of using a MTA connector.

Thanks folks!,


Thomas White
Natural Rhythm
www.naturalrhythmmusic.com

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fonik



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PostPosted: Thu Mar 18, 2010 3:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

all my best wishes to you and your family, thomas! great news.

i wouldl then take orders for the gate control expansion, too... any interest?

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mattias



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PostPosted: Thu Mar 18, 2010 3:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
i would then take orders for the gate control expansion, too... any interest?

Yes. Four please.

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The Bad Producer



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PostPosted: Thu Mar 18, 2010 4:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hell... Why not! A few more never hurt!

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droffset



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PostPosted: Thu Mar 18, 2010 6:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes, two for me please.
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The Peasant



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PostPosted: Fri Mar 19, 2010 10:37 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
i wouldl then take orders for the gate control expansion, too... any interest?


I somehow got missed last time around, so yes.

Take care,
Doug

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rosch



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PostPosted: Fri Mar 19, 2010 12:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

yes yes! 4 please!
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fonik



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PostPosted: Mon Mar 29, 2010 12:52 am    Post subject: Reply with quote  Mark this post and the followings unread

not that much interest so far!
i will need the actual count of boards everyone wants. it won't make any sense for me to order less than at least 25 PCBs.

Recommendations for PCB offers on electro-music

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fonik



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PostPosted: Tue Apr 13, 2010 7:08 am    Post subject: Reply with quote  Mark this post and the followings unread

currently there is interest in about only 20 PCBs. since this is a very low number and i wanted to keep the price i assume all pre-orders as firm. if you changed your mind let me know ASAP, at least on thursday. thank you.
(so this is a last call, i won't order spare PCBs).

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The Bad Producer



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PostPosted: Tue Apr 13, 2010 8:37 am    Post subject: Reply with quote  Mark this post and the followings unread

to confirm then Fonik, I'd like 4 PCB's please!

Thanks,

Charlie

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The Peasant



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PostPosted: Tue Apr 13, 2010 10:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Please confirm me for two pcbs.

Take care,
Doug

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