Manhattan Analog 'Mix' - Build Thread

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col
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Post by col » Tue Feb 06, 2018 6:44 pm

Test your input, it probably has DC on it. One problem with "DC coupled" the lack of decoupling capacitors means the DC gets amplified by the opamp and comes out of the output, very bad for audio. A more complete design would have decoupling caps and switches so you can flick between AC or DC.

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negativspace
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Post by negativspace » Wed Feb 07, 2018 7:05 pm

Curious where you'd propose locating those switches on the panel. :hihi:

If there's no mystery DC signal at your input, it's possible the electro caps are tired? There's not much going on in this thing - power entry, an opamp, the resistors necessary to operate it, and the I/O. Having already swapped the opamp...

FWIW, so far the only things I've had to fix with the (few) units that have come back to me in recent years are worn-out pots. Might not hurt to treat the output pot as suspect?

If all else fails, I'm happy to take a look at it. I don't charge. :tu:

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Post by col » Wed Feb 07, 2018 7:31 pm

negativspace wrote:Curious where you'd propose locating those switches on the panel. :hihi:
Exactly! There's the compromise! I didn't intend to criticize your design the module looks great, especially for the space it takes up. Just need to be aware that not all audio signals exiting other equipment is clean of DC. If it was there would not be the need for AC coupling in the first place.

There is a whole section on this in the Doepfer DIY page 4.1.3. Changing between AC and DC coupling:
http://www.doepfer.de/DIY/a100_diy.htm

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Post by negativspace » Wed Feb 07, 2018 7:38 pm

Oh, I didn't take it as criticism, just giving you a hard time. (Thus the :hihi: )

You're absolutely right, of course - that would be a more complete and versatile configuration. But it also wouldn't be the 4hp/sub-$100 module I set out to design.

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Post by col » Wed Feb 07, 2018 7:51 pm

negativspace wrote:Oh, I didn't take it as criticism, just giving you a hard time. (Thus the :hihi: )

You're absolutely right, of course - that would be a more complete and versatile configuration. But it also wouldn't be the 4hp/sub-$100 module I set out to design.
Maybe you could add a "AC coupled" version to the line up :hihi:

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Post by negativspace » Wed Feb 07, 2018 7:58 pm

I could at least re-work the PCB so you could build it both ways - a spot for a decoupling cap at the input that could be replaced with a jumper.

Maybe it's time for v2.0. It's been more than 6 years.

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Post by col » Wed Feb 07, 2018 8:05 pm

If that was available I would have bought one! I recently had to make one of these using stripboard....

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Post by negativspace » Wed Feb 07, 2018 8:25 pm

Well, this timing is perfect. I'm on my next-to-last pack of 25 PCBs and will need to reorder soon. That's the time to do these things. I'll work up a prototype when I get a chance.

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Post by crossinger » Thu Feb 08, 2018 11:45 am

Wohooo - lot's of good ideas here! :love:

Thanks alot for your input! Highly appreciated! Since none of you put focus on a possible OpAmp issue, I'll discard this option and start another research on the pots.

I don't think there's some DC floating around. I used the Mix over years with more or less the same inputs.

@negativspace Thanks for your generous offer.. But I think that shipping costs from Germany are simply too high.

Nevertheless: I could consider buying a blank PCB from Thonk and rebuild it. For a rev.2 count me in! :tu:

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Post by negativspace » Thu Feb 08, 2018 5:17 pm

Yeah, international shipping's gone up (again) here and returning it to Europe is $23.50. I just sent one back to Belgium - a CVP with a worn out offset pot - yesterday. Still, if you (or anyone else) pays to get it here, I pay to get it back. Seems fair.

Replacing the caps and all the pots will cost you ~$6 and about 15 minutes of your time, though. Add another $1-5 for a new opamp if it comes to that... I'd say you may as well just go that route. :hihi:

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Post by crossinger » Sun Feb 11, 2018 1:12 pm

negativspace wrote:Yeah, international shipping's gone up (again) here and returning it to Europe is $23.50. I just sent one back to Belgium - a CVP with a worn out offset pot - yesterday. Still, if you (or anyone else) pays to get it here, I pay to get it back. Seems fair.
Absolutely - couldn't agree more!

But I always read "DIY" as "get your homework done first" - before I request other people's time & money.

Ok, I had 30 minutes today to revive the Mix in a Doepfer Beauty Case and feed inputs 1 and 2 with two oscillators.

All input pots full CCW (unipolar) - and I got impressive loud sound as output! :zombie:

I jiggled the cables a bit - and I got crackle. I pushed the cable a bit more into the jacks and it got quiet. After releasing the cables the sound returned, then after jiggling more, I could keep it quiet. Then I was able to raise the volume by turning the input knobs.

So it looks like there's nothing wrong with the electronic part. I should first check the jacks and if there's some short circuit.

Sometimes it's good to change perspective. Wouldn't have investigated more if I have kept it in my big case (or leave it in the drawer).

Never considered the jacks as the possible culprit...

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Post by negativspace » Wed Feb 14, 2018 5:41 pm

Definitely sounds like the jacks are fertile ground for exploration!

I wouldn't have assumed that either, and for what it's worth I haven't had more than one or two bad jacks in the ~decade I've been doing this. But they are mechanical components, like pots, and they do wear.

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low volume output

Post by bump909 » Fri Mar 02, 2018 3:26 am

Hi,

Just built the Manhattan Audio Mix and tested all 3 inputs in U.P and B.P mode. In both cases the output is somewhat lower in volume. I've read here that this is not normal, so what could be the problem?
All soldering is decent.

I bought the PCB and Panel from Thonk Uk last month together with the A50k & B50K Pots. All other components where got eleswhere:

Ferite Beads:
https://www.ebay.co.uk/itm/282843004959 ... 2843004959

LME49720NA IC OPAMP AUDIO 55MHZ 8DIP

Any other components I can post if needed.

Also, plugged my cans into the output to check functionality and sound only coming out of one can. I presume this is normal though as wires were only soldered to the tip of the output.

Please help?

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Post by negativspace » Fri Mar 02, 2018 9:37 am

Yep, the jacks are mono so you'll only get a signal in one ear. No worries there.

If the signal level is below unity you almost certainly have an incorrect resistor value in there somewhere. Double check that R1-5 + R7 (the 6 parallel resistors at the top of the board) are all 47k and the other one is 470R. There's not much else that can go wrong here, really.

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Post by bump909 » Wed Mar 07, 2018 4:40 am

Hi nnegativspace, I have taken a closer look at the resistors and re-soldered several of them. After this I re-tested by comparing the raw output from my Braids Oscillator module and the same going into the Mix module. It seems that the mix loses some high frequencies as it is definitely not as raspy sounding as the direct output from Braids. I've sent you some photo's in a PM and here is a list of the components I used:

470 Ohm 0.25w Metal Film 1/4w Resistor 1% 470R
https://www.ebay.co.uk/itm/10-x-470-Ohm ... w-Resistor -1-470R/122785991491?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2 749.l2649

100nF (104) 50V Ceramic Disc Capacitor
20pF 50V Ceramic Disc Capacitor

https://www.ebay.co.uk/itm/Ceramic-Disc ... lues-10-10 00pcs/231179599601?ssPageName=STRK%3AMEBIDX%3AIT&var=530393684080&_trk sid=p2057872.m2749.l2649

LME49720NA IC OPAMP AUDIO 55MHZ 8DIP
https://www.ebay.co.uk/itm/LME49720NA-I ... DIP/192415 958142?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Radial Aluminium Electrolytic Capacitor ±20% 105°C
Voltage-35VVoltage: 35VPack Size-10Pack Size: 10Capacitance-22uFCapacitance: 22uF
http://www.ebay.co.uk/itm/Radial-Alumin ... citor-20-1 05-C/282663316578?ssPageName=STRK%3AMEBIDX%3AIT&var=581872504983&_trks id=p2057872.m2749.l2649

1A Silicon Rectifier Diode 1N4001
https://www.ebay.co.uk/itm/1A-Silicon-R ... -to-1N4007 -Pack-of-10-25-or-50/111777815515?ssPageName=STRK%3AMEBIDX%3AIT&var=41 0768753437&_trksid=p2057872.m2749.l2649

47K 1% 0.6W Royal Ohm Metal Film Resistor
http://www.ebay.co.uk/itm/47K-1-0-6W-Ro ... sistor-Pac k-of-50/122919277344?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2 749.l2649

Ferrite bead link anti-parasitic bead PCB axial mount FERROXCUBE
https://www.ebay.co.uk/itm/282843004959 ... 2843004959

Do you think the ferrite beads are on the large side?

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Post by negativspace » Thu Mar 08, 2018 12:17 pm

Interesting... audible high-frequency rolloff isn't one I've come across yet. Maybe pull C5 and try without it? If you had too large a value in that position it would roll off the highs in an audible way, but that really shouldn't be a thing with 20pF.

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Post by bump909 » Thu Mar 08, 2018 4:47 pm

Ok, so I removed the 20pF and hey presto no more HF loss. There is still a slight drop in volume when comparing the direct output of the oscillator to the mix output. However this is now quite slight. Because I was only getting output in one ear testing this way, I routed the output into a Motu Traveler audio Interface and tested from it's phones output. Result - I can no longer hear any level change when swapping between direct and mix outputs and no rolloff in the HF & LF range.

Could the 20pF cap be damaged and is it ok to leave it removed?

Thanks for the valuable help negativespace 8-)

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Post by negativspace » Thu Mar 08, 2018 4:58 pm

Awesome, glad that was it. :party:

The 20pF cap (I use 22pF) is there to keep the chip from oscillating under certain conditions, but in testing that was only a problem when I tried it with 10' output cables. You're probably ok without it, but it wouldn't hurt to add a
~22pF cap to your next parts order.

On the slight volume difference, yeah, even with 1% resistors there's a little margin for error. If you really need precision, you'll want to match the resistors manually or buy 0.1% parts.

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Post by negativspace » Thu May 17, 2018 3:46 pm

Heya builders, this is just a heads-up... mix v2.0 is out now and will be exclusively available once existing stock is sold. (I'm out of older boards, some of my vendors may not be.)

Don't panic, the mixer itself has not changed nor has the physical size of the PCBs. All I've done is update the power section to use resettable fuses and a 10P header like my other 4hp modules.

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Post by pppier » Sat Aug 25, 2018 8:30 am

hi there,
I've just received v2 mix pcb.
what about ptc fuse? some parameter to match?
(ferrite beads too, is there something to prefere?)

and about the 2 upper holes, it looks a cascade bus to me, to link various modules, isn't it? how can we use it easily?

:love:

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v2.0 bom

Post by ilovesoldering » Fri Aug 31, 2018 10:17 am

Hi negativspace,

I just received the ver 2.0 from thonk. Can you please update the BOM and build guide?

same questions as pppier about the 2 ptc and the 2 upper holes.

thank you so much!

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Post by negativspace » Tue Sep 04, 2018 8:12 am

The 2 upper holes are just a convenience for builders who aren't using my Euro panel. They're a spare ground pad and a tap into the input summing node if you want to add extra channels.

The beads I use are Mouser #623-2743001112LF. The fuses you want are #652-MF-R005-0.

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Post by pppier » Tue Sep 04, 2018 5:23 pm

really thank you 8-)

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Post by Rafi » Mon Oct 28, 2019 12:40 pm

Got a kit from synthcube. Aside from the different jacks, (see previous posts) the Thonk At-At-At build shows which is tip and ground, build was straight forward otherwise. The bi-polar shunt threw me off, then dug around the webs and placed it as uni-polar for the main out. Utilities, gotta have ‘em! :goo:

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Re: Manhattan Analog 'Mix' - Build Thread

Post by dkmb » Tue Sep 15, 2020 1:05 am

built one of these today from synthcube :)

in bipolar mode, there is full volume output when the mixer out is set to 0. is this intended? sadly could not find a manual to query myself. once you start turning the pot, it immediately attenuates and then works as expected.

the synthcube kit comes with 2 resettable fuses (pptc 0.5A 60V, bourns 652-MFR050-LF) not mentioned in the thonk document. I soldered these to the PTC spaces on the board, hopefully the right choice. it also came with a 5 pin friction lock header (0.1 mta, te connectivity 571-6404565) which I wasn't sure what to do with and didn't use.

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