Soma - LYRA-8 DIY Kit

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Addam
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Re: Soma - LYRA-8 DIY Kit

Post by Addam » Thu May 21, 2020 7:54 am

rationale_music wrote:
Thu May 21, 2020 1:33 am
I should note that I have not yet installed the PCB shield as I still want access to the back of the board if needed.
I don't believe the shield is making any electrical connections so if you've installed the shield headers and you're going in you might as well just pop that sucker on temporary-style. Slightly bend one of the header pins or put some putty to hold it (or tape or whatever) - maybe worth a shot?

I'm also curious, are you getting noise of your headphone jack? on my lyra 4 diy I get noise out of the headphone jack no matter what grounding scheme I try. Regular output has no issues :hmm:

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Re: Soma - LYRA-8 DIY Kit

Post by rationale_music » Fri May 22, 2020 12:28 am

gluepet wrote:
Thu May 21, 2020 7:25 am
rationale_music wrote:
Thu May 21, 2020 1:33 am
1. The LFO signal is bleeding into the audio path, creating this low but constant rhythmic popping sound whenever the synth is on.
I had a similar issue and the following was the recommended procedure from SOMA:
First remove the LED and see if noise is alleviated. If so, you can increase the value of current limiting resistor going from led to ground, start with double the value and work from there, you can find the balance between noise and led brightness experimentally, also throw a wire from that resistor's ground leg directly to the ground of the power supply jack.
Interesting. I wouldn't have thought to check the LED of all places. I was poking around the socketed 4093s and was hesitant to contact SOMA directly since (according to the build doc, at least) they don't give assistance on debugging. Thanks, I'll give it a shot!

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Re: Soma - LYRA-8 DIY Kit

Post by rationale_music » Fri May 22, 2020 1:04 am

Addam wrote:
Thu May 21, 2020 7:54 am
rationale_music wrote:
Thu May 21, 2020 1:33 am
I should note that I have not yet installed the PCB shield as I still want access to the back of the board if needed.
I don't believe the shield is making any electrical connections so if you've installed the shield headers and you're going in you might as well just pop that sucker on temporary-style. Slightly bend one of the header pins or put some putty to hold it (or tape or whatever) - maybe worth a shot?

I'm also curious, are you getting noise of your headphone jack? on my lyra 4 diy I get noise out of the headphone jack no matter what grounding scheme I try. Regular output has no issues :hmm:
At least on my Lyra PCB the shield is grounded, just buzzed it out. The headphone output on mine is super noisy, but I never thought to check the main output (because I've only been testing this thing with headphones so far), and it turns out that not only is it a lot quieter, but the LFO noise completely gone! There must be an amplifier for it on the board picking up the LFO and amplifying it along with raising the noise floor. There's still a little bit of bleed between the voices, but that might be the result of some errant flux I need to clean.

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Re: Soma - LYRA-8 DIY Kit

Post by Addam » Fri May 22, 2020 7:42 am

rationale_music wrote:
Fri May 22, 2020 1:04 am

At least on my Lyra PCB the shield is grounded, just buzzed it out.
Ah, of course. Makes sense.
rationale_music wrote:
Fri May 22, 2020 1:04 am
The headphone output on mine is super noisy, but I never thought to check the main output (because I've only been testing this thing with headphones so far), and it turns out that not only is it a lot quieter, but the LFO noise completely gone! There must be an amplifier for it on the board picking up the LFO and amplifying it along with raising the noise floor. There's still a little bit of bleed between the voices, but that might be the result of some errant flux I need to clean.
So.. it's working? Haha. The headphone noise is not a huge deal for me but a little frustrating. I'm not sure if I was getting the lfo signal, too, as I haven't monitored on headphones much.

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Re: Soma - LYRA-8 DIY Kit

Post by woodster » Fri May 22, 2020 8:14 pm

I was about to chime in regarding headphone noise, saying I'd not experienced any. However, a friend just did a socially distant recording session, and she had issues with her headphones, which were not apparent with any of mine. This leads me think it might be an impedance issue ?

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Re: Soma - LYRA-8 DIY Kit

Post by red-tin-dave » Sat May 23, 2020 7:12 am

Well I've finished building mine and it seems to work OK apart from the Hold knobs not having any effect. Has anyone else experienced this, or have an idea where I should start looking to fix it?
I've buzzed out all the ribbon cable connectors and they are all ok, and the test voltage points are ok too.

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Re: Soma - LYRA-8 DIY Kit

Post by Addam » Sat May 23, 2020 8:15 pm

woodster wrote:
Fri May 22, 2020 8:14 pm
I was about to chime in regarding headphone noise, saying I'd not experienced any. However, a friend just did a socially distant recording session, and she had issues with her headphones, which were not apparent with any of mine. This leads me think it might be an impedance issue ?
A-ha! I think that might be it. I just tried with my ancient koss headphones and had to crank the volume up to get any noise, at which point I got some lfo artifacts bleeding into the delay circuit but this was at a level well beyond where I would listen and even then didn't get much of that typical noisy input, amplified noise floor type garbage.

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Re: Soma - LYRA-8 DIY Kit

Post by Flounderguts » Sat May 23, 2020 11:30 pm

Sounds like that's it. Low impedance headphones require more current, and tend to be prone to noise artifacts with equipment like the Lyra. Your "ancient " Koss cans are probably up over 100 ohms.
I'm sure a hi/lo mod would be easy, with a 1 or 2 watt resistor on a switch, so that headphones geared toward mobie listening could play nicer with Lyra.
----------------------

Flounderguts

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Re: Soma - LYRA-8 DIY Kit

Post by rationale_music » Sun May 24, 2020 2:01 am

red-tin-dave wrote:
Sat May 23, 2020 7:12 am
Well I've finished building mine and it seems to work OK apart from the Hold knobs not having any effect. Has anyone else experienced this, or have an idea where I should start looking to fix it?
I've buzzed out all the ribbon cable connectors and they are all ok, and the test voltage points are ok too.
I had this issue with mine, and it turned out that when I had initially soldered the potentiometer I hadn't quite bridged the gap between the solder pad and the middle leg of the pot. I ended up going through both the control board and main board and re-flowing every solder joint and double-checking it.

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Re: Soma - LYRA-8 DIY Kit

Post by rationale_music » Sun May 24, 2020 2:04 am

Flounderguts wrote:
Sat May 23, 2020 11:30 pm
Sounds like that's it. Low impedance headphones require more current, and tend to be prone to noise artifacts with equipment like the Lyra. Your "ancient " Koss cans are probably up over 100 ohms.
I'm sure a hi/lo mod would be easy, with a 1 or 2 watt resistor on a switch, so that headphones geared toward mobie listening could play nicer with Lyra.
Looks like my cans are 32 ohms, so that could be the case. I might consider adding that to the mod list as I don't really have another pair of good quality headphones to use with mine, just a shitty pair of earbuds.

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Re: Soma - LYRA-8 DIY Kit

Post by red-tin-dave » Sun May 24, 2020 3:52 am

rationale_music wrote:
Sun May 24, 2020 2:01 am
red-tin-dave wrote:
Sat May 23, 2020 7:12 am
Well I've finished building mine and it seems to work OK apart from the Hold knobs not having any effect. Has anyone else experienced this, or have an idea where I should start looking to fix it?
I've buzzed out all the ribbon cable connectors and they are all ok, and the test voltage points are ok too.
I had this issue with mine, and it turned out that when I had initially soldered the potentiometer I hadn't quite bridged the gap between the solder pad and the middle leg of the pot. I ended up going through both the control board and main board and re-flowing every solder joint and double-checking it.
Thanks - I have re-soldered both the pots and it hasn't fixed it. The fact that neither of the Hold pots work makes me think it's something in the circuit that would affect both - one of the ICs for example, but I don't know which one controls the Hold function

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Re: Soma - LYRA-8 DIY Kit

Post by red-tin-dave » Sun May 24, 2020 3:54 am


For anyone who might be interested the first part of my blog post about building the Lyra-8 is on the RS Designspark web site . Including a stop frame animation of the main board being put together:
https://www.rs-online.com/designspark/b ... g-assembly

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Re: Soma - LYRA-8 DIY Kit

Post by red-tin-dave » Thu May 28, 2020 1:47 am

IMG_20200527_183353.jpg
Case finished now. Bent acrylic with wax infill lettering.
I have Inkscape and dxf files I can share if anyone would like them
You do not have the required permissions to view the files attached to this post.

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Re: Soma - LYRA-8 DIY Kit

Post by D.Tilbury » Thu May 28, 2020 4:44 pm

That looks excellent
-blippen
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Re: Soma - LYRA-8 DIY Kit

Post by Addam » Thu May 28, 2020 5:59 pm

Yeah, looks like a slick machine. Did you ever get that hold knob issue sorted?

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Re: Soma - LYRA-8 DIY Kit

Post by nourson » Fri May 29, 2020 2:42 am

Hello ! Here's a simple, but expensive mod for improvong fine tunning of the Lyra

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Re: Soma - LYRA-8 DIY Kit

Post by red-tin-dave » Fri May 29, 2020 8:17 am

Addam wrote:
Thu May 28, 2020 5:59 pm
Yeah, looks like a slick machine. Did you ever get that hold knob issue sorted?
Thanks! Just sorted the Hold problem now. I had used switched jack sockets - the ones that disconnect the tip connectors when there isn't a jack plugged in (they were some I had lying around and it never occurred they would cause a problem). :doh:
I discovered the Hold worked when I plugged a jack in the Hold Gate socket, even when it wasn't connected to anything and had a light bulb moment and realised what I'd done wrong. Quickly rectified by soldering a bit of wire across the two tip connections on the PCB.

It's droning away like massive swarm of wasps as I type! :)

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Re: Soma - LYRA-8 DIY Kit

Post by Addam » Fri May 29, 2020 8:52 am

Nice troubleshooting. I love (and hate, mostly hate) when thinking about the problem doesn't present a solution haha. Glad it's sorted and that issue is good to keep in mind.

nourson, excellent work and very nice panel.

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