[IN STOCK] Eurorack 4hp THAT2180-based Audio VCA

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pulsepsycle
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Post by pulsepsycle » Thu Jun 09, 2016 9:05 pm

I already ordered directly. Two. All went well. I did have to pay duties though although not that much. Approx €20 for two VCA and one SVVCF to the Netherlands.

BTW, I can't imagine why you want to be in Europe nowadays Jason.

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Post by negativspace » Fri Jun 10, 2016 2:13 am

... have you been to America lately? :hihi:

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Re: [IN STOCK] Eurorack 4hp THAT2180-based Audio VCA

Post by DJMaytag » Tue Jul 05, 2016 12:06 am

negativspace wrote:[1] TL074B
Would a TL074C or something different than a TL074B be suitable? I have a bunch of the linked TL074C's on the way from Tayda, and am about to order up a ton of parts from Mouser & Smallbear. I'm just curious if I should go ahead and get some of the TL074B's from Mouser, just in case, or are there other good/better options?

Am I seeing this right, but is the LM49710 back? If so, I'm glad I waited a bit longer to be able to order parts for this!
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Re: [IN STOCK] Eurorack 4hp THAT2180-based Audio VCA

Post by mskala » Tue Jul 05, 2016 7:59 am

DJMaytag wrote:
negativspace wrote:[1] TL074B
Would a TL074C or something different than a TL074B be suitable? I have a bunch of the linked TL074C's on the way from Tayda, and am about to order up a ton of parts from Mouser & Smallbear. I'm just curious if I should go ahead and get some of the TL074B's from Mouser, just in case, or are there other good/better options?
The "C" specifies standard commercial temperature range, as opposed to "I" for wider temperature range. The "B" specifies that it's selected for smaller DC offset. A chip called TL074B will probably really be TL074BC, and maybe another one or two letters after that to designate the package style. If you substitute a TL074C (no B in the part number) then it should still work, but it will have a larger DC offset. That may be no big deal in an audio VCA, but might be more of an issue in a VCA you plan to use for control voltages.
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Post by DJMaytag » Tue Jul 05, 2016 8:36 am

Hmm... looks like spending some extra $$$ for the 074B might be in order here? I can somewhat follow a circuit diagram, though I may not be able to use the right terminology to describe whats going on, but it looks like the TL074 is handling the mixing (or processing) of the two CV inputs, and the THAT & LME chips are handling the audio.

I don't know how much of a big deal the operating temps are, but is an offset of 10mV vs 3mV that huge of a deal for proper operation?
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Post by veets » Sat Nov 19, 2016 7:24 pm

:vcas:

Or perhaps you can.

I've successfully built three of these. Number 4... not so much. I can't get the voltage at TP to drop below 3.6v when performing calibration. And the fuse nearest the edge of the board gets mighty hot. Like burn your finger hot. Perhaps this is normal, but I've never experienced this before. (The other fuse might be hot, too, but I haven't checked.)

Perhaps a short? If so, and given the symptoms, any suggestions about where to look? I wonder if it's the 1K TC. That was rough to solder.

Thanks!

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Post by MPRT » Thu Jun 08, 2017 9:04 am

Hello! I just build my VCA with pcb 1.3 but when I go to calibration also if I turn the trim I measure always 2.5 V. Any idea where the problem could be?

Thanks in advance!

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Post by ndf » Thu Jun 15, 2017 1:46 am

Does your Manhattan Analog VCA output have a nasty high frequency oscillation?

All the ones I built did... The fix was pretty simple:

- replace the 330 ohm resistor near U3 (LME49710) with a jumper
- place a 330 ohm resistor between the output jack and the PCB

This takes the 330 ohm resistor out of the feedback loop around U3 and stops the oscillation on the output.

I'm not sure why the 330 was in the feedback loop - if anyone can shed some light on that I'd love to know in case my 'fix' has introduced a new problem.

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Post by neil.johnson » Thu Jun 15, 2017 6:47 pm

ndf wrote:Does your Manhattan Analog VCA output have a nasty high frequency oscillation?

All the ones I built did... The fix was pretty simple:

- replace the 330 ohm resistor near U3 (LME49710) with a jumper
- place a 330 ohm resistor between the output jack and the PCB

This takes the 330 ohm resistor out of the feedback loop around U3 and stops the oscillation on the output.

I'm not sure why the 330 was in the feedback loop - if anyone can shed some light on that I'd love to know in case my 'fix' has introduced a new problem.
The problem is that this is a poorly designed circuit. That 330 ohm resistor is supposed to protect the opamp output from capacitive loads, and putting it inside the feedback loop is the correct arrangement to ensure DC accuracy. HOWEVER the small 22p compensating capacitor is supposed to connect to the other side of the 330 ohm resistor. There are various posts on here about this.

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Post by ndf » Fri Jun 16, 2017 12:58 am

There are various posts on here about this.
Thanks Neil, could you please suggest a link to one of the posts?

You say this is a poorly designed circuit... Could you please elaborate?

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Post by paperCUT » Fri Jun 16, 2017 1:45 am

Looks like the easiest fix would be to remove the 330ohm resistor and replace it with a jumper. Then add the resistor between the output PCB hole and the output jack.

It's already AC coupled so doesn't need any accuracy, just some slight protection against shorts.

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Post by neil.johnson » Fri Jun 16, 2017 3:14 am

ndf wrote:
There are various posts on here about this.
Thanks Neil, could you please suggest a link to one of the posts?

You say this is a poorly designed circuit... Could you please elaborate?
Well, here's an example from Dave Jones showing the correct way to do the output circuit: viewtopic.php?p=1445492&highlight=#1445492

For detailed analysis try this: viewtopic.php?p=1129644#1129644

As far as this design is concerned, the control circuit has many issues, most of which could be fixed by reading the THAT datasheet.

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Post by neil.johnson » Fri Jun 16, 2017 3:15 am

paperCUT wrote:Looks like the easiest fix would be to remove the 330ohm resistor and replace it with a jumper. Then add the resistor between the output PCB hole and the output jack.

It's already AC coupled so doesn't need any accuracy, just some slight protection against shorts.
The resistor is there not to protect against shorts but to stop the output oscillating when cables are plugged in due to the cable capacitance interacting with the op-amp's output stage and the feedback circuit.

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Post by ndf » Fri Jun 16, 2017 7:46 am

Thanks heaps for the detail!

Cheers.

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Post by Sleipnir » Fri Jun 16, 2017 1:04 pm

neil.johnson wrote:
ndf wrote:Does your Manhattan Analog VCA output have a nasty high frequency oscillation?

All the ones I built did... The fix was pretty simple:

- replace the 330 ohm resistor near U3 (LME49710) with a jumper
- place a 330 ohm resistor between the output jack and the PCB

This takes the 330 ohm resistor out of the feedback loop around U3 and stops the oscillation on the output.

I'm not sure why the 330 was in the feedback loop - if anyone can shed some light on that I'd love to know in case my 'fix' has introduced a new problem.
The problem is that this is a poorly designed circuit. That 330 ohm resistor is supposed to protect the opamp output from capacitive loads, and putting it inside the feedback loop is the correct arrangement to ensure DC accuracy. HOWEVER the small 22p compensating capacitor is supposed to connect to the other side of the 330 ohm resistor. There are various posts on here about this.

Neil
Wish this had come up with my post in January.
I spent probably 20 hours troubleshooting, then chucked it in the trash.
:bang:

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Post by ndf » Fri Jun 16, 2017 7:04 pm

Sleipnir: Dang. I've had one sitting in a box for six months waiting for some knob to finally read the manual and sort it out.

I wonder how many units there are out there in racks happily oscillating wildly.

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Post by Bartimaeus » Wed Aug 23, 2017 4:54 pm

I recently built a MA VCA. While the unit sounds good, it is SIGNIFICANTLY quieter than my other VCA's. I calibrated precisely (within <1mV) to the values listed in the manual, and while the response is good, it's really low volume.

Before I go swapping any resistors, does anyone have any advice? Should I have used a 10v Zener instead of a 5.1V?

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Post by DJMaytag » Wed Aug 23, 2017 5:27 pm

You may have installed something wrong. Mine are SUPER hot on the output side.
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Post by negativspace » Mon Sep 04, 2017 4:07 am

If it's built and calibrated correctly, it'll be at unity gain @ full CW on the offset control. You'll be able to get a little bit more out of it than that if you use external CV more than ~5.2V, depending on the exact performance of the zener you chose.

I'd doublecheck parts and calibration to be sure everything is in order.

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BOM for v1.4 of the PCB

Post by ntxr » Mon Mar 19, 2018 12:21 pm

Hi, thanks for your awesome modules.

Do you have a BOM available for the version 1.4?

Thanks & regards.

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Post by negativspace » Mon Mar 19, 2018 2:30 pm

There's no change in the BOM, the board revision was just a layout update. :tu:

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Mouser BOM?

Post by Phaedrus » Mon Jun 11, 2018 5:37 am

Ive been through the entire post, but I cant seem to see anyone shared their BOM from Mouser.. And it would save me a lot of time, sourcing.. (Im kind of a noob, at it)
So.. Can anyone be so kind to share their BOM from Mouser, please. I already ordered the 2x PCB and Panel + THAT 2180 chips and knobs, from Thonk.. So dont worry about that.. :-)

All the best
Johan

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Post by negativspace » Tue Jun 12, 2018 9:59 am

I'm not sure I've seen a Mouser BOM posted for it, but let me know which parts you're having trouble finding and I'll dig up numbers for you.

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Post by gadgadasvara » Thu Jun 14, 2018 8:38 am

hi guys,
i need some help (i'm very noob at this).
just finished building the rev1.4 board, and did managed to calibrate it like instructed on first page, but when i try it (put oscillator signal into input, lfo into cv 1 and cv2) no sound coming out. been testing and checking for hours all the component, and it seems everything right to me.

i did notice something, compare the board picture from first page and my board, the layout of the resistor in the upper board next to 5v1 zener is a bit different. i don't know if its correct or not..

on the first page
100K
100K
20K
100R
330R

and on the rev1.4 board
100K
100K
100R
20K
330R

any suggestions maybe..?

thank you.

Image

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Post by negativspace » Thu Jun 14, 2018 9:43 am

Yep, i rearranged the resistors a bit between versions. Follow the silkscreen on your board and it should work out. :tu:

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