18-channel DIY Stereo Analog Vocoder

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glubsch
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Post by glubsch » Sat Aug 11, 2018 1:45 am

truman_k wrote:I always dreamed of getting a fully blown analogue vocoder. Here is the one that is do-able. Not spending a huge amt of money in getting the expensive THAT chips.
Yes, these are the only ICs that are a bit more expensive than the others but there are only two of them and they are easy to find. In fact, as I generally was looking for a design based on easily procurable parts, I even sent an email to THAT Corp and asked about whether I need to worry about the THAT320 (not used in the vocoder) going end-of-life at some point. The email reply was prompt and I felt assured there are no plans to take the transistor arrays off the market.

Having made the statement about easy procurement though, I've been caught by surprise that the LM3916 is no more available. My intention though is to sell the first PCBs based on my design using the LM3916 and replace it with a different design later.

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Post by glubsch » Sat Aug 11, 2018 2:20 am

guest wrote:
glubsch wrote:The 18x CD4053 on the list of ICs should have given it away
yeah, that and the large "PWM" on the silkscreen!! ive been looking into PWM multipliers for a while now, and am suprised i dont see more of them in synth projects. what was the noise floor on the PWM version versus the LM13700? and did you consider the SSM2164 at all?

im glad you read the paper. a fair bit of work went into that, and its always nice to hear that others have gotten some use out of it.
I used a fairly non-scientific way to judge the noise: I simply listened to the results and thought I can do better :hihi:. I am quite pleased with the PWM-based solution. However, I don't want to leave a false impression and make it very clear to the community: this design is analog and therefore there's still noise. The VU's are there to help set the input signals (Voice and Carrier) high enough for the output signal to be as far away from the noise floor as possible. I've been quite content with the noise levels and therefore decided not to include a compandor. 8-)

I dismissed using the SSM2164 in general for a number of simple reasons: they are hard to come by and expensive, and if you can get them, they are only available as SMD (the only SMD parts used in this vocoder are the decoupling capacitors and those for the 8-pole filters). Besides, they'd be an overkill for this design.

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Post by glubsch » Wed Aug 15, 2018 3:06 pm

**********************
*** BOM now available ***
**********************


Alright, there are now two documents available:
  • 1) A PDF that contains the complete assembly tables and the BOM.
    2) An Excel spreadsheet that I've built up over the last couple of years and that I've just updated with the latest component cost.
I believe for many of you the spreadsheet is of strong interest as it essentially gives you and indication about the total cost for the BOM. But it is also harder to read as I have not really spent the time yet to provide a lot of information.

Note that the PDF is compiled directly from the Excel spreadsheet.

Over the next days I want to see what questions you have related to these two new documents. After that I want to shift focus to giving you more information about the schematics.
Last edited by glubsch on Sun Aug 19, 2018 3:24 pm, edited 1 time in total.

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Revok
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Post by Revok » Wed Aug 15, 2018 7:10 pm

This is some top notch documentation :tu:

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Post by Thalassa » Thu Aug 16, 2018 5:00 am

glubsch wrote: As you can see, this helps placing the Davies knobs very close to the surface of the front panel, making it look much more professional.

Image
What tool are you using for tightening those nuts ? In the picture looks like there is no enough space to use a socket wrench :hmm:

Do you have an estimated date when the project will be available ?

and BTW amazing work !

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Post by glubsch » Thu Aug 16, 2018 11:24 am

Revok wrote:This is some top notch documentation :tu:
Thanks for the nice feedback.
Thalassa wrote:What tool are you using for tightening those nuts? In the picture looks like there is no enough space to use a socket wrench :hmm:

Do you have an estimated date when the project will be available?

and BTW amazing work!
Check out post #11 on the second page. I'll provide a 3D printed socket.

I am thinking about publishing modalities and the cost for the PCBs + front panel in the next two to three weeks.

Also thanks to you for your nice comment.

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Post by Thalassa » Fri Aug 17, 2018 2:19 am

glubsch wrote:Check out post #11 on the second page. I'll provide a 3D printed socket
upps , I didn't see it :doh: Don't get me wrong but I don't think that this is good idea for several reasons. Indeed it looks nice but if you are going to sell kits the use of custom made tools can give you a lot of troubles. Imagine what will happen if one person break the socket, if the plastic wear out or in a couple of years you need to dissemble a pcb for repair and you lost the socket... The result is that you will have people complaining about it. Also think that for every kit that you sell you need to print one socket and it will be time consuming.

Another reason is the price, I can imagine that adding the recessed hole to the front panel increase the front panel costs quite a bit. I don't mind to have the knob floating 2mm apart from the front panel. Most of the modules and synthesizers are made like these.

I think that you should ask the people what they will prefer, a cheaper and easy to mount front panel or a more expensive one that will require a custom made tool.

As I told you before don't get me wrong you have made an amazing job with the vocoder and even maybe I would had made myself the same with the front panel if it was a one off design but when you want to design something to sell you should have in consideration this kind of small things.

BTW , this is a picture of one module with the same kind of knobs. As you can see the knob doesn't look so separated from the front panel and it's a 1,5mm font panel.
Image

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Post by dingebre » Fri Aug 17, 2018 2:44 am

I like the recessed nut. The 3D file for the socket can be uploaded to any number of 3D printing services and spare sockets printed if needed. It looks like a standard “thin wall” socket might also work.

Plus, people will complain no matter what is done... :)

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Post by Thalassa » Fri Aug 17, 2018 2:47 am

dingebre wrote:Plus, people will complain no matter what is done... :)
Yes it's true , just look at me :mrgreen: :mrgreen: :mrgreen:

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Post by dingebre » Fri Aug 17, 2018 2:58 am

Thalassa wrote:
dingebre wrote:Plus, people will complain no matter what is done... :)
Yes it's true , just look at me :mrgreen: :mrgreen: :mrgreen:


:hihi:
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Post by cygmu » Fri Aug 17, 2018 3:57 am

I feel a bit impertinent to ask this, because I will almost certainly not build one of these, but what does the recessed nut secure to? Is the panel only partially drilled out (i.e. recessed, I suppose) at that point?

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Post by julian » Fri Aug 17, 2018 5:08 am

cygmu wrote:I feel a bit impertinent to ask this, because I will almost certainly not build one of these, but what does the recessed nut secure to? Is the panel only partially drilled out (i.e. recessed, I suppose) at that point?
Yes, panel is slightly, but not fully cut through.
.



_________

For stocked euro / buchla / midibox see - http://thebeast.co.uk/?post_type=product

For custom cnc engraved panels see - http://thebeast.co.uk/?page_id=21

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Post by glubsch » Fri Aug 17, 2018 7:48 am

Thalassa wrote:
dingebre wrote:Plus, people will complain no matter what is done... :)
Yes it's true , just look at me :mrgreen: :mrgreen: :mrgreen:
No worries. I don't see this as a complaint at all. If I get input on what can be improved, I'll certainly consider it. One thing I've learned though in the few weeks that I've been part of this community is that there are a lot of suggestions (many through email) that are often contradicted by other input. If you ask 10 people, you get 12 opinions. :hihi:

Specifically to your point: the socket is easy to reproduce. You can store it inside the case so you don't lose it (and wonder after a few years what's started to rattle inside the vocoder). And if you really prefer the knobs sticking out for easier access of the nuts, add a couple of extra washers. Just glue some felt on the socket to make sure you don't scratch the surface of the front panel.

I think the way it is now makes it look more professional.
cygmu wrote:I feel a bit impertinent to ask this, because I will almost certainly not build one of these, but what does the recessed nut secure to? Is the panel only partially drilled out (i.e. recessed, I suppose) at that point?
Julian has already given some explanation. Just as some additional info, the recess, or maybe better called cavity, is cut 1.7 mm into the 3 mm deep panel.

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Post by Thalassa » Fri Aug 17, 2018 8:32 am

glubsch wrote:And if you really prefer the knobs sticking out for easier access of the nuts, add a couple of extra washers.
You have a point there :tu:

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Post by paterursus » Fri Aug 17, 2018 11:17 am

I get Thalassa's point, and I'll probably lose the tool. That being said, I still prefer the recessed look.
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Post by Sandrine » Sat Aug 18, 2018 9:31 am

I have heavy thin tipped needle nose pliers that would do these in a pinch
Of course I have a 3D printer so it's a non-issue

BTW amazing project! Count me in as interested

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Post by glubsch » Sat Aug 18, 2018 1:20 pm

Sandrine wrote:I have heavy thin tipped needle nose pliers that would do these in a pinch
Of course I have a 3D printer so it's a non-issue

BTW amazing project! Count me in as interested
Thanks for your comment. I have a similar pliers though yours might be thinner at the tips than mine. I used them before I had the 3D-printed socket and had to make sure I don't slip and scratch the front panel surface. I think you just don't get the nuts tightened as much as with a proper socket.

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Post by LektroiD » Sat Aug 18, 2018 10:35 pm

I can see myself running into problems with the recessed pots, as I always use T-18 pots and knobs, I don't like the offcentre turning circle of the set screw type, plus they cost more for the knobs due to having brass inserts, so I bought a few thousand T-18 knobs and pots of every value and size a few years ago. The knobs would undoubtedly leave a circular rash on the panel, as they always push on so far, no amount of washers would cure that.

I wonder if there's another way of having the pots bolted to the panel, rather than recessed. It's surely cheaper to manufacture without recessing them?

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Post by tobb » Sun Aug 19, 2018 8:03 am

The recessed nuts is indeed a very bad idea + you still can see them,so totally useless,the better solution is a double front panel but the shaft length may be to short,or you have to use collet knobs.

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Post by paterursus » Sun Aug 19, 2018 8:05 am

From the pictures I've seen, you can see them only when the knobs are removed.
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Post by glubsch » Sun Aug 19, 2018 9:53 am

LektroiD wrote:I can see myself running into problems with the recessed pots, as I always use T-18 pots and knobs, I don't like the offcentre turning circle of the set screw type, plus they cost more for the knobs due to having brass inserts, so I bought a few thousand T-18 knobs and pots of every value and size a few years ago. The knobs would undoubtedly leave a circular rash on the panel, as they always push on so far, no amount of washers would cure that.

I wonder if there's another way of having the pots bolted to the panel, rather than recessed. It's surely cheaper to manufacture without recessing them?
So you are a perfectionist :hihi: I noticed the off-center rotation too and was looking into D-type and T18's because of the same reasons you've mentioned. But I wanted to make sure to use as widely available material as possible. Keep in mind that a couple of stereo pots are needed and that the pots need to line up with the plugs. So what you see in the BOM is what I ended up with.

However, if you do have T18's that are available in stereo, that can be soldered directly into the PCBs, and that line up well with the 6.35 mm and 3.5 mm plugs, please tell me about them and I'll seriously consider them.

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Post by glubsch » Sun Aug 19, 2018 10:09 am

paterursus wrote:From the pictures I've seen, you can see them only when the knobs are removed.
paterursus, thanks for pointing this out.

Tobb, just look at my web page where I've posted two pictures at a fairly steep angle and rejudge.

With the cavities shown, there's about one millimeter space between the knob and the surface of the panel. If the Davies knobs had a larger inset and the screws moved farther from the base, you could get the Davies knobs even closer. If there were collared knobs with a max diameter of 13 mm at the base of the knob, I'd switch to those. The panel is populated quite tightly, so larger knobs won't do.

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Post by LektroiD » Sun Aug 19, 2018 11:25 am

glubsch wrote:
LektroiD wrote:I can see myself running into problems with the recessed pots, as I always use T-18 pots and knobs, I don't like the offcentre turning circle of the set screw type, plus they cost more for the knobs due to having brass inserts, so I bought a few thousand T-18 knobs and pots of every value and size a few years ago. The knobs would undoubtedly leave a circular rash on the panel, as they always push on so far, no amount of washers would cure that.

I wonder if there's another way of having the pots bolted to the panel, rather than recessed. It's surely cheaper to manufacture without recessing them?
So you are a perfectionist :hihi: I noticed the off-center rotation too and was looking into D-type and T18's because of the same reasons you've mentioned. But I wanted to make sure to use as widely available material as possible. Keep in mind that a couple of stereo pots are needed and that the pots need to line up with the plugs. So what you see in the BOM is what I ended up with.

However, if you do have T18's that are available in stereo, that can be soldered directly into the PCBs, and that line up well with the 6.35 mm and 3.5 mm plugs, please tell me about them and I'll seriously consider them.
The only stereo kinds I have are these (in various values). I know One is a D shaft, but better than set screw for the above reasons.
Image

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Post by Revok » Sun Aug 19, 2018 11:51 am

I am a huge fan of the recessed nut and with the size of this project I don't think that added cost on the panel is a price concern. It's whether or not I can afford the rest of the stuff :deadbanana:
Last edited by Revok on Sun Aug 19, 2018 11:52 am, edited 1 time in total.

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Post by glubsch » Sun Aug 19, 2018 11:52 am

LedtroiD, I have a series of the T18 shown in your picture on the right in mono. For the reasons mentioned in my previous post, they won‘t work for the bundle I am planning to sell (PCBs + front panel).

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