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 Forum index » DIY Hardware and Software » Les Hall's Projects including eChucK
The Karplus Strong eChucK DIY Project
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jeff-o



Joined: Jul 19, 2009
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Location: Ontario, Canada

PostPosted: Thu Sep 30, 2010 11:09 pm    Post subject: Re: A breakthrough! Reply with quote  Mark this post and the followings unread

kkissinger wrote:
It turns out that Q2 is reversed on the schematic -- the collector should connect to GND and he emitter should connect to R27.


Whoa, nice find! And yet, it still works (barely?) So that means Q4 is also reversed, right?
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frijitz



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PostPosted: Fri Oct 01, 2010 1:25 am    Post subject: Re: A breakthrough! Reply with quote  Mark this post and the followings unread

jeff-o wrote:
So that means Q4 is also reversed, right?

Yes.
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kkissinger



Joined: Mar 28, 2006
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PostPosted: Fri Oct 01, 2010 9:39 am    Post subject: Re: A breakthrough! Reply with quote  Mark this post and the followings unread

frijitz wrote:
jeff-o wrote:
So that means Q4 is also reversed, right?

Yes.


btw -- thanks to frijitz for identifying the reversed transistors. Smile

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Stream Operator


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PostPosted: Sat Oct 02, 2010 2:24 am    Post subject: Re: Ks and BS
Subject description: what is this?
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GodSaveMetal wrote:
Dear inventor I'm the new in this adventure; plese can you explain what is the KS and BS modules?; how I get a sound with it?? I have a electric guitar, can I conect to the Synth? where??? please be patient with me; I want to do this it´s great; in PERÚ I found all the components, I have a skill in electronics, I´ve made guitar effects like pedals and mod´s for this effects!!! and I love the fantastic sound of synth!!!! please help me!!!!!!


Hi, there is no brief summary of what a BS and a KS is, you just have to read the threads. I have thought of sending an electric guitar signal into the stim input of a KS and have tested it in software with goof results. I suggest reading this thread from the beginning to get up to speed.

Les

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PostPosted: Sat Oct 02, 2010 2:26 am    Post subject: Reply with quote  Mark this post and the followings unread

Reversed transistors!? I never would have found that. I guess it takes a fresh pair of eyes with experience sometimes. I guess it takes a community, not an induhvidual. Rock on folks!

Les

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jeff-o



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PostPosted: Mon Oct 04, 2010 6:50 am    Post subject: Run from +/-5V supplies? Reply with quote  Mark this post and the followings unread

Hey everyone,

Quick question: How well does the KS11 run on +/-5V supplies? In checking the datasheets, I can see that all the devices involved will run happily at that level. However, the only snag I can see is that the TL074 op-amps will only be able to produce an output voltage of about 7.5Vp-p. Perhaps the feedback potentiometer won't need to be turned up quite so high. And obviously, any supply-dependent resistors will need to be changed also.

So, has anyone tried this? I'll do it myself in the next week I guess, but I thought I'd ask beforehand in case anyone has tried it.
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rosch



Joined: Oct 03, 2009
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PostPosted: Sat Oct 30, 2010 9:33 am    Post subject: Reply with quote  Mark this post and the followings unread

seems like i was quite lucky being so slow Smile as i would never have found any of these issues by myself.
now i'm populating 2 KS boards. i've turned around the 3906s (the 3906/3904 pairs look like DD seen from above) and took the 27K value for R27 and R32 (i will use a +/-15V supply)

are other 'weird' values very critical or can i also take closeby values, for example:
2K (not the tempco) could i use 2K2 instead?
40.2k -> 39k ?
49.9k -> 47k ?
i guess i could use 4x 500R trimpots for the 100R guys, just because i have them here. or could i damage something here?

also i have already used a 20p cap for the specified 18p.... (hope thats ok)
i also have a bunch carbon 100k's lying around but no more 1% metal type... would they work instead or should i wait until i can order new stuff?

(i have to wait for BBD chips and some caps anyways)
thanks!!
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kkissinger



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PostPosted: Sun Oct 31, 2010 6:37 am    Post subject: Heads up! Reply with quote  Mark this post and the followings unread

From what I can see, the filter's 3906 is legended properly on the PCB. Only the VCO's 3906 is legended backwards.
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kkissinger



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PostPosted: Thu Nov 04, 2010 9:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well, I've got my K/S module working pretty good on +15/-15v.

Here are some of the tweeks that I made:

1) Changed R27 and R32 to 3.9K ohms.
2) Changed R26 and R31 to 10K ohms.

The low-end volts/8ve tracking is ok (not perfect yet) but the top two octaves don't track so well.

However, if I can find a 256 step BBD to raise the range by two octaves, I think this may work better for me -- right now the bass runs clear into the contra-contra bass range! Smile

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kkissinger



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PostPosted: Fri Nov 05, 2010 9:24 am    Post subject: Reply with quote  Mark this post and the followings unread

kkissinger wrote:
if I can find a 256 step BBD to raise the range by two octaves, I think this may work better for me -- right now the bass runs clear into the contra-contra bass range!


OK, just ordered a couple of MN3209 (256 stage BBD chips). This will raise the (output) pitch by two octaves.

As cool as this module is, the vintage chips have a limited range and the volts/8ve tracking is not as good as my VCO's.

And well... I'm wondering... would it be possible to implement a K/S VCO on a PIC (or some kind of programmable) chip? THis would open the possibility of a much wider range and excellent volt/8ve tracking.

How would I describe the module? Well... it is powerful -- punchy. With the 256-stage chip, I look forward to playing it in the higher range -- as cool as the uber-bass is, the chip will be more useful for me pitched up a bit.

Les, thank you for creating this circuit and PCB -- a wonderful and unique addition to my synthesizer.

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Dan Lavin



Joined: Nov 09, 2006
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PostPosted: Fri Nov 05, 2010 10:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello Kevin,

Well the expo converter is probably not the best design out there. Les' criteria was a simple low part design that would cover a couple of octaves to try out the concept. There are definitely better expo converter designs out there that you could try to marry to the board.
The board is still a concept that Les is fleshing out and the the work that you and others have done have really helped in the development of this concept.
One of these days, I'm going to tackle my 2nd generation board, but like so many on this forum, I'm buried in current projects, (music-related or otherwise).
Thanks again for sharing your work!

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kkissinger



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PostPosted: Fri Nov 05, 2010 10:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Dan Lavin wrote:
...expo converter designs out there that you could try to marry to the board.


Actually, this would be easy for me to implement.

In the process of troubleshooting the expo converter, I was a little klutzy with my test probes and managed to fry a few transistors. In the process of soldering and de-soldering I managed to mangle the traces to the point where I couldn't solder to them anymore. So, I used Eagle and made me a board that contains the Q1 thru Q4, the tempco's, R27, R32, R26, and R31.

Thus, I'm already set up to put updated expo converters in place.

Actually, this has been a good project for me -- I've learned a lot about expo converters. Also discovered that the converter (the NPN and PNP pair) appears in a number of less-critical circuits (i.e., to create exponential response from VCAs).

Also, this effort has forced me to learn more about transistors. I am so used to dealing with op amps and voltage control that I still struggle with the notion of variable current. And I still get confused by the arrows on the transistor symbol -- conventional current -- ugh... my brain goes into conniptions. Smile

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PostPosted: Fri Nov 05, 2010 4:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey it's m'e again, back from the sl void. I''m so thankful to you all for carrying on the project in my absence, it would have been so easy to drop it.

I am planning a move to another state soon, so i'm understandably indisposed for the next several months. AFter that if things go well i can make a contribution again.

Les

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kkissinger



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PostPosted: Fri Nov 05, 2010 4:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
Hey it's m'e again, back from the sl void. I''m so thankful to you all for carrying on the project in my absence, it would have been so easy to drop it.

I am planning a move to another state soon, so i'm understandably indisposed for the next several months. AFter that if things go well i can make a contribution again.

Les


All the best to you, Les. Keep in touch!

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kkissinger



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PostPosted: Mon Dec 27, 2010 10:46 pm    Post subject: Ah... tracking nicely through 5 1/2 octaves now! Reply with quote  Mark this post and the followings unread

Well, I just can't put this project away for too long until I'm back with it again!

I discovered that as I rotate R39 (the filter frequency) to the left of the 12 o'clock position or to the right of the 4 o'clock position that the VCO tracking changes. However, I'm not likely to use such low filter settings -- the range from 12 o'clock to 4 o'clock happens to be the most useful.

The good news is that I've achieved excellent tracking across 5 1/2 octaves -- from 8 hz (64' C) to G above middle C (392 hz) Above 392 hz, there is an additional octave however tracks at less than a semitone per 1/12 of a volt.

I am using the vintage 256 stage BBD device.

This is a very musically useful range and the deep bass sounds rather metallic and (dare I say) digital.

In order to tweak the volt/8ve tracking, I added a multi-turn trimmer in series with R19. I used a 50K trimmer however it may be a little easier to adjust with a smaller value.

The only possible improvement will be to replace the transistor pair with a matched complimentary pair -- however this part is surface mount and I have to build an adapter board in order to implement. Who knows... I might get that top octave to track, too!

I've had some time just playing it -- very nice module for both plucked string sounds and that kind of airy Andes flute sound. And the bass sounds are really cool. I will give this module a good workout during my set on the New Year's streaming broadcast. Smile

I will post a demo track ... it is late and I have to get up early so will have to post something later.

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PostPosted: Mon Dec 27, 2010 10:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Kevin, you rock! Thanks for carrying the torch in my absence. You are a much more methodical person than I am, so it is all too appropriate for you to step in for calibration and final debugging of the design!

I've been playing with the brick KS synthesizer that I built, just finding different pot settings for making different types of sounds. Don't forget that you can "jam" on a ks board by adjusting the dials while it's being driven by something else, which makes for some interesting transitoins.

Les

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Skrog Productions



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PostPosted: Fri Jan 28, 2011 11:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Les Smile

nearly finished populating the boards , just been sorting out a test panel layout for the controls before i commit to lazer printing the design on white adhesive vinyl at my local sign shop, hope to get some alum panels cut to size (100mm x 250mm) in town at the engineers workshop through the week Very Happy

Thanks to everyone who has posted about the KS , a very helpful & informative thread when starting with bare pcb's & a blank look on my face , heh Smile
Time to wire .......

Dave


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rosch



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PostPosted: Fri Jan 28, 2011 1:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

looks good!
i have my 2 boards populated, except the 2K tempcos. as i still don't have them i just put in ordinary 2K metal film guys temporarily. 1st tests showed that both boards do NOT smoke and don't blow fuses, which is already a good result for me Smile

but i have to finish the last few wires of a little sequencer first before i can test them with proper trigger and cvs. i should have that done this weekend. i'm really curious how this will sound here!
so far this has really been a fun project. i hope to see more stuff from your lab in the future, Les!
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PostPosted: Fri Jan 28, 2011 1:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ah, builders building my boards! OUr boards, it was a team effort. wow! That really IS satisfying! Hey guess what Kevin Kissinger inquired about one more board and I talked him into three freebies WITH BBD chips including the new 4k buckets! lol. I'm giving these boards away to previous customers. Anyone want another?

Really they ROCK together, in groups, two side by side or one making notes and the other as a resonator. Or more multi-config setups. Just ask, I'll send you a board, pm me your address! Got like 8 or 10 boards left.

Les
making the world a better place, one KS board at a time....

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kkissinger



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PostPosted: Fri Jan 28, 2011 1:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
Kevin Kissinger inquired about one more board and I talked him into three freebies WITH BBD chips including the new 4k buckets! lol.


Very generous of you. Can't wait to build these and put them to use!

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PostPosted: Fri Jan 28, 2011 1:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just got the newly manufactured repro 4k buckets from smallbear today, can't wait to put them to good use and send a few out to unsuspecting customers like Kevin, haha. I'm serious, if these KS boards don't go out they will be just junk piling up in my closet. With the transistor mixup, whatever that is I gotta learn about it, nobody but someone already on board is gonna want to mess with these boards.

Also I am NOT JOKING about they rock in multiples. you want at least two of them. maybe four. PM me and I'll mail them to you, just gonna keep one or two for nostalgia purposes and the rest must GO!

I sound like that guy selling Televisions in the '70s lol

Les

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wmonk



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PostPosted: Fri Jan 28, 2011 1:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
Just got the newly manufactured repro 4k buckets from smallbear today, can't wait to put them to good use and send a few out to unsuspecting customers like Kevin, haha. I'm serious, if these KS boards don't go out they will be just junk piling up in my closet. With the transistor mixup, whatever that is I gotta learn about it, nobody but someone already on board is gonna want to mess with these boards.

Also I am NOT JOKING about they rock in multiples. you want at least two of them. maybe four. PM me and I'll mail them to you, just gonna keep one or two for nostalgia purposes and the rest must GO!

I sound like that guy selling Televisions in the '70s lol

Les


This is Les (Billy) Mays with a fan-tas-tic new product. You need this. This is going to change your life Laughing

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PostPosted: Fri Jan 28, 2011 1:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

KABOOM! It slices, it dices, it chops onions and you get no tears. It's the ginsu knife of music, never goes dull and always cuts the tomato after the beer can! Play PacMan with it or just use it to stir soup, it's amazing the KS board! get one now, get two, get three while they still hot off the presses!

OK wmonk?

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Skrog Productions



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PostPosted: Sun Jan 30, 2011 6:40 am    Post subject: Reply with quote  Mark this post and the followings unread

been working on 1 of 2 KS boards...

Checked pcb with a multi-meter and Q2 is correct to the schematic , but when powered up, the pitch pot exhibited a fall in pitch then a spike, then normal rise to high pitch (turning a low to high sweep).

Turning Q2 around (emitter to ground / collector to R27) fixes it and now has a nice low to high sweep.

i turned round the vcf Q4 but have now lost a bit of character with the feedback , will try something later Smile.
im using 2N3904 / 3906 with 2K tempco on vco section only.

i liked Woody's mod with a cap change for the vcf C7 , im trying out a dp/dt/center off switch for 2N2 center , +3N3 or +1N5.

going to try another cap for the vco , i only had a 22pf not an 18pf like on the schematic ,

sounding very interesting so far , good twangy bass sounds with a 3209 and triggering with a slow pulse train.

also at high frequency trigger in it produces some great metallic phasey drifts Smile

off to try a fine tune control pot for the vco , 2 of these together will be evil Very Happy Very Happy Very Happy


Dave


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PostPosted: Sun Jan 30, 2011 7:21 am    Post subject: Reply with quote  Mark this post and the followings unread

kick butt dave! I love to see the mods. Let's put all this into the design to make it extra cool.

I know I gave this design to em, but am I gonna have to do the final edits on the schematic? I'm cool with that. Just let me know what to change.

Les

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