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 Forum index » DIY Hardware and Software
Putting Together The Dim-C Clone - AKA LUSH Deluxe
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no-fi



Joined: Oct 19, 2008
Posts: 6
Location: the centre of the universe

PostPosted: Thu Oct 23, 2008 1:20 am    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:

I can't be the first one to have finished one of these, can I?


mine's "finished" - as in fully built and tested as working with basic toggle switches, and passing audio, but not in a case yet - just a big spaghetti monster.... it was that way about 2 weeks ago.

I've decided on what I want to do with various switches now, and got everything I need here, so with any luck I'll get around to doing metalwork this weekend.
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numbertalk



Joined: May 05, 2008
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PostPosted: Thu Oct 23, 2008 7:21 am    Post subject: Reply with quote  Mark this post and the followings unread

no-fi wrote:
not in a case yet - just a big spaghetti monster.... it was that way about 2 weeks ago.


D'oh! You're right, I see your posting earlier in the thread now. Mine (as you can tell from the photo) is in the same state. I have a case but was waiting to finish and order a panel until I made a few decisions as well. Hope to do that soon.

no-fi wrote:
I had a bit of a slow down for a while when I decided I really wanted a 4 gang interlocking switch assembly for the preset selection rather than 3 toggle switches, but I sorted that out (damn - I had no idea how much of a hassle getting one of these things would be!) and am finally ready to continue.


What did you decide on with this? Did you find a 4 gang interlocking push-buttons switch? If so could you provide a link? This might be ridiculous but given chorus is one my favorite effects I'm actually planning to build JH's Dim-D project as well and might want one of these switches for that in addition to possibly wanting one for this.
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numbertalk



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PostPosted: Thu Oct 23, 2008 11:38 am    Post subject: Reply with quote  Mark this post and the followings unread

no-fi or John (or Scott or anyone Smile) - I think I calibrated the BBD lines well, but it didn't behave exactly as I expected. The sine waves never "clipped" and actually seemed most stable when trimmed to their peak amplitude - meaning it would get really "blurry"/distorted at either side of this setting on the trimmer - it seemed to have trouble both turned up too much as well as turned down too much. Even when it seemed at a stable setting, though, the waveform would periodically get a little shaky, but I'm guessing that was from the LFO. Eventually as I incremented the amplitude of the signal at the signal generator the waveform would get warped/misshapen at certain trimmer settings but the thing I didn't expect was the waveform was smaller in amplitude when this would happen - about 1/2 way down from its highest peaks. At the highest peaks it looked like a normal/non-clipped sine wave. I guess what I'm getting at is the higher I got the sine wave with the trimmer the more stable it seemed, until I went past this point and then it would get smaller and blurry again and behave much like it did with the trimmer started out at fully CCW. I guess I was expecting it to reach a certain point where the peaks and lows of the wave form would start to clip/square off but I never really saw this happen.

Anyway, I figure I'd hear distortion if I'd pushed beyond the allowable headroom, right? On the other hand I also want to make sure I'm getting the most out of the BBD chips. I'm just wondering how subtle its too subtle. The effect does sound great, I do like my chorus pretty subtle, and with the extended LFO I can definitely get more of a less-subtle effect sound out of it, so seems good, but just wanted to compare notes/see if what I saw on my scope sounds right.
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jfromel



Joined: May 27, 2008
Posts: 79
Location: Seattle, WA

PostPosted: Thu Oct 23, 2008 12:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

I have a couple of pedals that I will be tuning up later and will take screen shots off my scope to show you. I actually tune mine with a 9k sine wave above line level.
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numbertalk



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PostPosted: Thu Oct 23, 2008 12:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

jfromel wrote:
I have a couple of pedals that I will be tuning up later and will take screen shots off my scope to show you.


That would be great, thanks!

jfromel wrote:
I actually tune mine with a 9k sine wave above line level.


What do you use for a signal generator?

The signal generator I use is software for the mac called Perfect Tone: http://los.dtcurrie.net/projects/ - it allows you an amplitude that ranges from 0-1 ( e.g. .25, .30, etc...) I'm not sure if 1 is line level or above - maybe that's part of why I never saw clipping, if it's at or below line level.
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jfromel



Joined: May 27, 2008
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PostPosted: Thu Oct 23, 2008 1:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

a crusty old Tektronics tube driven one. I would use a 1k sine but I think that tube is burnt out.
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whomper



Joined: Dec 15, 2007
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PostPosted: Fri Oct 24, 2008 7:24 am    Post subject: Reply with quote  Mark this post and the followings unread

jfromel wrote:
Superior sound is very subjective. In my pedal version I have tried using all Burr Brown OPA2134 op-amps and the sound was too soft and warm. I kept the 2134's in the input and output stage and put TL072's in the BBD's and LFO and they sounded great. I think mica's may soften things up too much, don't know.


Have you placed the OPA2134 in IC201, IC202 and IC12?

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jfromel



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PostPosted: Mon Oct 27, 2008 9:12 am    Post subject: Reply with quote  Mark this post and the followings unread

I got a PM regarding the manual controls for rate and depth not being vairable enough.... try this.....

For the depth put the coltrol around r38 and r39 so they are not in the circuit when using the pot, for the rate do the same for r36 and r37.
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numbertalk



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PostPosted: Mon Oct 27, 2008 9:18 am    Post subject: Reply with quote  Mark this post and the followings unread

jfromel wrote:
I got a PM regarding the manual controls for rate and depth not being vairable enough.... try this.....

For the depth put the coltrol around r38 and r39 so they are not in the circuit when using the pot, for the rate do the same for r36 and r37.


So where exactly on the board could we connect that lug of each of these pots to correctly accomplish this?
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whomper



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PostPosted: Fri Oct 31, 2008 2:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

well, I finished building the Dim-C and am in the testing phase.

Unfortunately, the LFO and MODE3 do not work, when trying to tweak them, nothing happens.

Observing the schematics it looks like the two are placed after IC7 whereas MODE1 and MODE2, which do work, are placed before it.

Any debugging tips that might help out here?

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jfromel



Joined: May 27, 2008
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PostPosted: Sat Nov 01, 2008 12:26 am    Post subject: Reply with quote  Mark this post and the followings unread

well you would have to do a bit of hot wiring on the board, the idea is that to have the greatest control of the rate and depth from the pots you want to have all the resistance controled from the pot and none from the resistance between P2 of IC5 and P1 of IC7, same goes for the resistance between P2 of IC7 and P7 of IC7.
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numbertalk



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PostPosted: Sat Nov 08, 2008 9:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

Whomper also mentions that Mode 3 doesn't seem to do much - would you also want to bypass these resistors in the auto modes (change the wiring permanently for the connections at S-B & S-D to always bypass those resistors) or only when you switch SW103 and/or SW104 to manual control (change SW103 & SW104 to DPDTs and have them switch past these fixed resistors when you go manual with either of these)?

jfromel wrote:
well you would have to do a bit of hot wiring on the board, the idea is that to have the greatest control of the rate and depth from the pots you want to have all the resistance controled from the pot and none from the resistance between P2 of IC5 and P1 of IC7, same goes for the resistance between P2 of IC7 and P7 of IC7.
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jfromel



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PostPosted: Sun Nov 09, 2008 12:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Lets think about how the LFO works. The resistantce between P2 of IC5 and P1 of IC7 controls the depth, The lower the resistance the greater the depth. The Capacitance between P1 of IC7 and P2 of IC7 sets the range, more capacitance = more range. The resistance between P2 of IC7 and P7 of IC7 sets the rate, the lower the resistance the faster the rate.

When you understand these concepts you can hotwire this however you want. On my next test board I am going to socket everything on the LFO and try and sweeten it up a bit.

I think I did all the reistance calcs for the presets earlier on this thread. SW101 and SW102 just increase capacitance across P1 of IC7 and P2 of IC7.
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mono-poly



Joined: Jul 07, 2004
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PostPosted: Sun Nov 09, 2008 3:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Did anyone do a MOTM format panel?
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numbertalk



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PostPosted: Sun Nov 09, 2008 8:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the info - still learning about how specific parts of circuits work exactly. Going to hotwire this up today possibly.

I made a 1U 19-inch rack panel based off of Scott's, if anyone is interested. It's got a TMZ output but otherwise should have the same panel connections as this one.

jfromel wrote:
Lets think about how the LFO works. The resistantce between P2 of IC5 and P1 of IC7 controls the depth, The lower the resistance the greater the depth. The Capacitance between P1 of IC7 and P2 of IC7 sets the range, more capacitance = more range. The resistance between P2 of IC7 and P7 of IC7 sets the rate, the lower the resistance the faster the rate.

When you understand these concepts you can hotwire this however you want. On my next test board I am going to socket everything on the LFO and try and sweeten it up a bit.

I think I did all the reistance calcs for the presets earlier on this thread. SW101 and SW102 just increase capacitance across P1 of IC7 and P2 of IC7.
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numbertalk



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PostPosted: Sun Nov 09, 2008 4:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Today I switched out SW103 & SW104 with DPDTs and now my board bypasses the resistors to each of those opamps when the manual switch is set for each. You definitely get response from the pots this way, but there are 2 weird things I notice. For rate, close to fully CW it gets very fast but then at fully CW there is no rate modulation - it's as though it's turned all the way down. For depth, around a setting of 9 you start to get LFO type ticking in the audio. So long as you stay below about 9 on each of these pots it sounds okay and does what it should.
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jfromel



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PostPosted: Sun Nov 09, 2008 4:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

measure the resistance across the pots at the point just before it stops operating within acceptable parameters then add that much resistance in series with the pot. Also try a TL062 or an overrstable rail to rail op-amp in the LFO.
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numbertalk



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PostPosted: Sun Nov 09, 2008 4:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

I will try this, thanks!

jfromel wrote:
measure the resistance across the pots at the point just before it stops operating within acceptable parameters then add that much resistance in series with the pot. Also try a TL062 or an overrstable rail to rail op-amp in the LFO.
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numbertalk



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PostPosted: Sun Nov 09, 2008 8:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

Fixed the rate pot with an added series resistor. Got the depth one really close. After trying a couple different values of resistors it still clicks right at 10. If it really bothers me enough will try switching op amp IC like you suggested.

Now just need to get my panel in the mail and I'm set. Will try to get a clip up at some point. My work bench is in a different area than my studio and without a panel and all the switches and wires on this board I haven't really taken it into the studio yet and really gotten to dig into it beyond testing as I build.
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jfromel



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PostPosted: Mon Nov 10, 2008 9:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Good op-amps to try are TL062 or TLC2272
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numbertalk



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PostPosted: Mon Nov 10, 2008 5:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Tried a TL062 for IC5 and the depth pot with extra resistance in series still ticks at full 10 setting.
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jfromel



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PostPosted: Mon Nov 10, 2008 7:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

the key is to find out the min - max range you can get out of it, set the min with resistance in series before the pot, set the max with the value of the pot and resistance in parallel with the pot. Measure the resistance just before it starts clicking and make sure you always have at least that much if less makes it unstable or never more than that if the inverse is true. It may be the case that too much resistance causes the click in which case you may need to cap the total resistance, try some resistance in parallel across the pot to lower the effective value of the pot.

http://www.1728.com/resistrs.htm

is a great on line parallel resistance calculator.

If you are using a 500K pot and it starts freaking out above 350K put a 1m resistor in parallel across the pot and you have a 333K pot.
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numbertalk



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PostPosted: Mon Nov 10, 2008 9:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the tips and the link to the very useful calculator. Finally got it. Unfortunately now there's so much resistance back that the depth pot is pretty subtle again, though somewhat more responsive than before, but the rate pot definitely has more of an effect and has a nice safe range to it now as well.
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numbertalk



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PostPosted: Tue Nov 25, 2008 9:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Finally got my panel and got it housed in an enclosure. Of course the day after I submitted my order to FPE I realized I'd left off holes for the manual LFO freq & depth switches. Could drill them myself and probably will at some point, but to be honest it's such a tight fit on the panel as it is that I'm not sure where they'd go. I'm posting a few photos. Based on Scott's panel with few changes.

The board sounds fantastic, by the way! Soooo good. The CV seems to work really well too - played it with the LFO on my Moogerfooger CP-251 for a bit. If I weren't pressed for time with leaving town tomorrow I'd get some audio up. I'll try next week. Thanks for such a great project.

I am having 1 problem though. I'm getting a loud pop when turning it on & off. Could it be the power indicator lamp I have wired up? It's a lamp, not an led, but still wondering if that could be the culprit. For now I'm working around it by just powering it on & off while my amp is off. Any thoughts?


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Scott Stites
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PostPosted: Tue Nov 25, 2008 10:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sweet!!!!
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