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 Forum index » DIY Hardware and Software » Thomas Henry designs
The Thomas Henry Mega Percussive Synthesizer
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Uncle Krunkus
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PostPosted: Wed Nov 02, 2011 8:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

Mylars are arguably a better cap anyway.
When you build hand-made units like this, in small numbers, I can't see any reason to use ceramic caps and will universally substitute mylar, or MKTs if I have them, and nobody recommends otherwise.
I used them right across the prototype, and it worked perfectly first time.

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jumunius



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PostPosted: Wed Nov 02, 2011 8:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
Mylars are arguably a better cap anyway.
When you build hand-made units like this, in small numbers, I can't see any reason to use ceramic caps and will universally substitute mylar, or MKTs if I have them, and nobody recommends otherwise.


Well, there seems to be a number of people who are championing C0G/NP0 ceramics over even polystyrenes these days. But I think these are more expensive than mylar even. Smile
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Uncle Krunkus
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PostPosted: Wed Nov 02, 2011 9:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

That's good to know. Thanks for the tip.
I can't say that I've even seen a COG/NPO before, but I'd like to check them out.
I imagine that capacitor technology still has some improvements possible for a while yet. Just comes down to how cost effective each level of improvement becomes.

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jumunius



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PostPosted: Wed Nov 02, 2011 10:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
That's good to know. Thanks for the tip.
I can't say that I've even seen a COG/NPO before, but I'd like to check them out.
I imagine that capacitor technology still has some improvements possible for a while yet. Just comes down to how cost effective each level of improvement becomes.


Off topic I suppose, but C0G/NP0 is a temperature coefficient, and they are supposedly very stable. For example, this one, which is on the cheap end of the spectrum in terms of what Mouser carries for .01uf.

They tend to be smaller and cheaper than a good polystyrene, and many venerable builders and designers say they are just as good. But they aren't cheap like a standard old ceramics.
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Uncle Krunkus
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PostPosted: Wed Nov 02, 2011 11:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oh, okay, They're what I would call a monolythic cap, and yes, I've heard that they are especially good for bypass use. I also use those for all the bypass caps on a board sometimes, if I have them. You can get bags of 100 * 10nF or 100nF quite cheap.

I assume they are not so good in an audio path, where I tend to use MKT, or mica.

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moonagedaydream



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PostPosted: Thu Nov 03, 2011 3:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've got another question. You guys are gonna hate me by the time I get this finished. From what i've learned so far, using an LED that isn't red (it is red, isn't it) will consume more current. Seeing as how its just a little LED, i wouldn't assume that it takes up that much more. One of my teachers gave me a small bag of blue LEDs, and I just wanted to make sure it wouldn't noticeably affect anything if i used one instead.

And this should be my last question. At least until I power it up and nothing works Laughing
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moonagedaydream



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PostPosted: Thu Nov 03, 2011 3:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

And nevermind. looks like they are too small. Rolling Eyes
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jumunius



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PostPosted: Thu Nov 03, 2011 3:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

moonagedaydream wrote:
I've got another question. You guys are gonna hate me by the time I get this finished.


That's ok I have asked plenty of questions myself.

Quote:
One of my teachers gave me a small bag of blue LEDs


Sounds like you can't use them anyways, but some people hate blue LEDs. They are kind of piercing. So maybe it's just as well if you don't.

I used a yellow superbright and it seemed to work ok.
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MR-808



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PostPosted: Fri May 04, 2012 2:41 am    Post subject: Reply with quote  Mark this post and the followings unread

I just finished my build using the Bridechamber panel and the rev 107 pcb. The gaps in the documentation cost me many frustrating hours. :( I will try to fill in some of those gaps here.

Jason Fry's wiring diagram is invaluable, however, it has a couple of errors:

* The Noise Send jack needs to be tied to 14/8.

* The 13/1 pad that the Noise Filter CV is tied to is not connected to anything. It should be jumpered to the node common to R63, R64, & R65 through a 100k resistor. I don't believe this is on any of the schematics; I had to follow the traces on the picture of the prototype pcb layout earlier in this thread to figure this out.

I added a 10k tweak pot to the left leg of the resonance pot per jumunius' suggestion to make it easier to dial in the resonance to my tastes. :)

Power draw is ~60mA on +15, ~20mA on -15.

It's definitely a fun and useful module. Thank you Mr. Henry and everyone who helped make it real.
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Uncle Krunkus
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PostPosted: Fri May 04, 2012 3:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey Mr 808,
The CV connection is a long story, (read the whole thread) The connection is there, but using it is not advised, if you send it the wrong CV, you can easily fry your LM136/700.
If you feel confident enough to put the right protections inplace,....... then go ahead and do some experimenting, but, so far, I haven't heard any positive feedback from doing these CV additions.

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mcop



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PostPosted: Sun Jun 03, 2012 6:39 am    Post subject: 820pf capacitors Reply with quote  Mark this post and the followings unread

Hi there and hello as this is my first post here. Have been lurking a while since buying a board for the MPS.

I have a few 820pf Silver Mica capacitors to hand and was wondering if they could be used in place of the polystyrene specified for the build?
Having had a look around on line the only effect I can foresee is that they may sound a little harsher than Polystyrene. As they are in the filters of the noise section would this really be an issue?

Admittedly the Silver Mica caps are a bit big and will take a bit of modifying to mount but thought I'd ask before buying any other capacitors.
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Uncle Krunkus
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PostPosted: Sun Jun 03, 2012 6:53 am    Post subject: Reply with quote  Mark this post and the followings unread

As long as the actual value is in the same ballpark, (sorry, I can't remember where that was?) I'd always recommend trying a different type of cap. You never know, it might sound bad, but it may just make it sound great!
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mcop



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PostPosted: Sun Jun 03, 2012 7:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for a very speedy reply Smile

The value is correct for the filters, it's just a different dielectric. Will report back as to whether it works when I've finished my build.
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jumunius



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PostPosted: Sun Jun 03, 2012 8:16 am    Post subject: Re: 820pf capacitors Reply with quote  Mark this post and the followings unread

mcop wrote:
I have a few 820pf Silver Mica capacitors to hand and was wondering if they could be used in place of the polystyrene specified for the build?
Having had a look around on line the only effect I can foresee is that they may sound a little harsher than Polystyrene. As they are in the filters of the noise section would this really be an issue?

Admittedly the Silver Mica caps are a bit big and will take a bit of modifying to mount but thought I'd ask before buying any other capacitors.


FWIW I used them in my build, and the result sounds, um, filtery to me. Wink

I've actually read a lot of positive things about the sound of silver micas, but then I've also read people say that all caps sound the same. In this case I even wondered how obvious the differences would sound given that the source is noise.

But yeah, they are big and the leads were larger than the pcb holes. I don't like having to enlarge the holes particularly for fear of destroying pads but it worked out ok.

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netpusher



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PostPosted: Tue Jun 19, 2012 12:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

I posted this on the bridechamber wiring diagram topic too, but figured I would try here too. My 4046 chip on my mps is getting really hot, would anyone know off hand what might cause this? Wondering if the resistor in r88 might be bad. Everything is working except for the Impact section, and recently the led stopped working as well. When I check the voltage from pin 3 to pin 4 for the led there is no voltage going through.

Anyhow, thought I would ask in case anyone has any ideas that I could try. Thanks!
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russma



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PostPosted: Tue Jun 19, 2012 3:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

This may be no help at all, but fwiw, I offer this excerpt from Ken Stone's FAQ page:

Q. Why does my 4015 get stinking hot? (4015 is just a randomly chosen 4000 series number - this applies to all 4000 series chips such as 4017, 4024, 4066 etc.)
A. It is probably a 74HCT4015, or some other 74xxx variant designed to run on 5 volts. It is possible that these chips may not have the "74" in their part number, so avoid any that start with "HC". You want CD4015, HEF4015 or MC14015. Note that Motorola includes "1" at the beginning of their part numbers. A MC4015 is a different device altogether and will also get stinking hot. If the salesman behind the counter tells you the 74xxx will work just as well, IGNORE HIM - he's a salesman, not a technician or engineer. There will be letters after the device number. "B" is the most common. these extra letters indicate whether the chip is buffered, and what package type it is. Make sure you get a DIP package and not an SMD package.
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netpusher



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PostPosted: Tue Jun 19, 2012 4:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

russma wrote:
This may be no help at all, but fwiw, I offer this excerpt from Ken Stone's FAQ page:

Q. Why does my 4015 get stinking hot? (4015 is just a randomly chosen 4000 series number - this applies to all 4000 series chips such as 4017, 4024, 4066 etc.)
A. It is probably a 74HCT4015, or some other 74xxx variant designed to run on 5 volts. It is possible that these chips may not have the "74" in their part number, so avoid any that start with "HC". You want CD4015, HEF4015 or MC14015. Note that Motorola includes "1" at the beginning of their part numbers. A MC4015 is a different device altogether and will also get stinking hot. If the salesman behind the counter tells you the 74xxx will work just as well, IGNORE HIM - he's a salesman, not a technician or engineer. There will be letters after the device number. "B" is the most common. these extra letters indicate whether the chip is buffered, and what package type it is. Make sure you get a DIP package and not an SMD package.

Oh wow, thanks! The chip that's in there is a CD74HCT4046AE, which according to the data sheet is 5v. If that's the issue you just saved me a ton of time troubleshooting this. Many thanks my friend. Once I get a 15v replacement in I will let you know if that fixes it!
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ghostarcade



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PostPosted: Mon Jul 30, 2012 11:16 am    Post subject: Reply with quote  Mark this post and the followings unread

hello I just finished stuffing and wiring the MPS based on the bugbrand wiring diagram and its not quite at 100%. I'm hoping for some troubleshooting guidance -

the noise part works, the shell part works for the most part (i think) although the decay seems very short, and the impact decay is barely a click. also the led never fires. any advice is appreciated!

My pcb is a rev 107.
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jumunius



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PostPosted: Tue Jul 31, 2012 4:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

ghostarcade wrote:
the noise part works, the shell part works for the most part (i think) although the decay seems very short, and the impact decay is barely a click. also the led never fires. any advice is appreciated!


It is interesting that 2 of the 3 decays seem short to you -- that might imply a more general problem with your triggers but then you'd expect trouble with all 3 decays. Would you say the noise decay is similar to that of the shell, or is the noise significantly longer than the shell? How about the sweeps (if you can tell given the short decays)? Do they offer dramatic pitch variation at max settings?

One possibility is maybe that your trigger sensitivity is too low. Assuming you've turned your trigger input pot up sufficiently, you might check that part of the build (both the wiring of the trigger pot and the corresponding components in the upper left-hand corner of Schematic P1). The common bugaboo of bad solders aside, could you have used a 100k in place of the 100ohm R1 by mistake?

If the problem is really unique to shell and impact decays, the relevant components appear in the upper left of P2 and lower left of P3. Check diode and electrolytic cap orientation for one thing.

I'd check the solders and wiring corresponding to these parts of the circuit first.

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ghostarcade



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PostPosted: Thu Aug 02, 2012 8:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the reply, the noise decay is significantly longer than the shell decay. I am using the trigger out from a 909, so it is a very short pulse, but yeah the noise aspect working as expected is what is throwing me off. To answer your other question, the shell sweep set high does indeed produce a dramatic pitch variation.

I will try to post a demo soon to youtube for further assistance after attempting the led switcheroo probably this weekend. Thanks again!!
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ghostarcade



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PostPosted: Fri Aug 03, 2012 7:21 am    Post subject: Reply with quote  Mark this post and the followings unread

I flipped the LED and now its just permanently on, so I'm guessing it was right the other way and there is some other issue. I have a feeling I have to just go over all the wiring again, but wonder if I'm missing something because of the rev107 pcb and not having any kind of 'official' wiring diagram. I will get a youtube demo up this weekend regardless.
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jumunius



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PostPosted: Fri Aug 03, 2012 11:22 am    Post subject: Reply with quote  Mark this post and the followings unread

ghostarcade wrote:
I flipped the LED and now its just permanently on, so I'm guessing it was right the other way and there is some other issue. I have a feeling I have to just go over all the wiring again, but wonder if I'm missing something because of the rev107 pcb and not having any kind of 'official' wiring diagram. I will get a youtube demo up this weekend regardless.


I don't think you should be having the issues you are having simply based on the Bugbrand diagram / rev107 mismatch. If you haven't already you should read this thread from about page 24 on for details about what has changed since Bugbrand's diagram, and I think a more complete wiring diagram (Bridechamber one?) I believe was also posted to this thread. I know I wrote some extensive details about the mismatches between Bugbrand's diagram and the current design a few pages back.

It does sound like something is funny in your trigger settings but it's weird that it is only effecting a few things. Good luck and keep us posted!

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jumunius



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PostPosted: Fri Aug 03, 2012 11:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Oh wait, that new diagram is here:

http://electro-music.com/forum/topic-49897.html

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NoizeToyz



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PostPosted: Sun Aug 12, 2012 11:34 am    Post subject: Shell Generator not sounding quite right Reply with quote  Mark this post and the followings unread

I've just finished building my first MPS and it all seems to be working as it should, however the shell generator doesn't sound quite right;

It's creating a sort of pitched/filtered noise rather than the 'boom' tone that I think it's supposed to make.

I double-checked my panel wiring, as I thought I may have accidentally wired the audio out from the noise generator, but can confirm that this is the sound coming directly from the shell generator circuit.

I've uploaded an audio file attachment as an example - anyone else getting this sound?

I wonder if there is a component problem? I switched IC3 for a new LM13700, but no joy there. The Exar chip is XR-2206CP - is this 'CP' on the end perhaps the issue? The ring mod seems to work correctly (although there is a dip in level almost to silence when the 'balance' control is around 12 o'clock).


MPS Test.mp3
 Description:
Audio test of just the shell generator. The pitch/frequency control is being swept through its full range.

Download
 Filename:  MPS Test.mp3
 Filesize:  846.35 KB
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jumunius



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PostPosted: Tue Aug 14, 2012 11:40 pm    Post subject: Re: Shell Generator not sounding quite right Reply with quote  Mark this post and the followings unread

chivaros wrote:
I've just finished building my first MPS and it all seems to be working as it should, however the shell generator doesn't sound quite right;

It's creating a sort of pitched/filtered noise rather than the 'boom' tone that I think it's supposed to make.


There's a switch that allows you to route noise or impact to the Shell CV. Perhaps you have it set on noise, with the Shell CV at max? Without verifying how mine sounds, that's the most obvious explanation. Try playing with Shell CV level and see if that makes a difference.

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