Search found 639 matches

by emmaker
Mon Aug 03, 2020 10:03 pm
Forum: Music Tech DIY
Topic: Simple Schematic Question
Replies: 18
Views: 168

Re: Simple Schematic Question

So presumably, I can still do my folded over vertical feedback resistor in this case with no ill effect then? Yes but put the short end of the resistor on the input pin. That would be an optimal solution but it will work the other way too. All you're circles look good there. Typically when wires/tr...
by emmaker
Mon Aug 03, 2020 8:55 pm
Forum: Music Tech DIY
Topic: Simple Schematic Question
Replies: 18
Views: 168

Re: Simple Schematic Question

So, in this example, if it were somehow physically possible, the trace going to pin 6 could have R15, R17, and both pin 1 and the wiper ALL soldered to the same trace? As EAT said yes hook them all up together. In general you literally follow the schematics. There are things like power pins that ma...
by emmaker
Mon Aug 03, 2020 6:54 pm
Forum: Music Tech DIY
Topic: Simple Schematic Question
Replies: 18
Views: 168

Re: Simple Schematic Question

Don't know if I understand what you are saying. I think the question you are asking is "Can the components that form a node at IC1B-6 be on different traces?". For what we usually do for SDIY the answer is yes. But. You usually want to keep the traces to op-amp inputs (pins 6, 7 here) as short as po...
by emmaker
Mon Aug 03, 2020 2:00 pm
Forum: Music Tech DIY
Topic: Analog Waveform divider / multiplier
Replies: 4
Views: 112

Re: Analog Waveform divider / multiplier

100Hz sine osc carrier, 50Hz sine osc modulation, ring modulator/4 quadrant multiplier, LP filter tuned below 100Hz. This is the way down converters (frequency) worked in old radios (assume most radios now days use digital down converters). Ring modulators provide the frequencies that are the sum an...
by emmaker
Fri Jul 31, 2020 7:03 pm
Forum: Music Tech DIY
Topic: Function Generator
Replies: 5
Views: 147

Re: Function Generator

Images aren't shared for the public.
by emmaker
Thu Jul 30, 2020 1:01 pm
Forum: Oakley Sound Systems
Topic: Is it safe to clean eurorack boards with 99% IPA?
Replies: 11
Views: 350

Re: Is it safe to clean eurorack boards with 99% IPA?

For a blank board I use a cleaning powder like Ajax or Comet and water, scrub it good and rinse it good. That should remove any oxidation. When dry I give it a good wipe with IPA to remove any oils or contaminates. Some times if I just want to clean a small area I use an ink eraser with a fine grit...
by emmaker
Wed Jul 29, 2020 6:01 pm
Forum: Music Tech DIY
Topic: Lead forming
Replies: 9
Views: 264

Re: Lead forming

I've had a 1/4W red lead former for 40 years and know how to use it. While it might take more time I think my boards look a lot nicer when I use it.
by emmaker
Sun Jul 26, 2020 5:57 pm
Forum: Music Tech DIY
Topic: Magic smoke and a burned out TL072
Replies: 9
Views: 307

Re: Magic smoke and a burned out TL072

The remaning fibers in that preview photo -did not watch the vid- give me the willies. I think one of the points of the video was to show the different results with the different types of papers. I haven't had issues with Kimwipes. Sometimes I do some clean up with Q-tips and IPA which level more f...
by emmaker
Sun Jul 26, 2020 12:49 pm
Forum: Oakley Sound Systems
Topic: Is it safe to clean eurorack boards with 99% IPA?
Replies: 11
Views: 350

Re: Is it safe to clean eurorack boards with 99% IPA?

I'm going to be using this strategy for when I'm soldering components onto the boards. But I was asking about cleaning the boards before any soldering has started. Appreciate the feeback. OK, to me cleaning the boards is an essential part of soldering a board. A lot of people don't do it and end up...
by emmaker
Sat Jul 25, 2020 5:26 pm
Forum: Music Tech DIY
Topic: OPA1654 vs OPA1679
Replies: 36
Views: 994

Re: OPA1654 vs OPA1679

To me I'm not all that worried about distortion in a synth circuit since most op-amps have ridiculously low distortion levels but more interested in keeping the noise down. Considering that a 100kohm resistor generates twice as much noise as a TL7X opamp, it will be difficult to reduce the noise le...
by emmaker
Sat Jul 25, 2020 5:10 pm
Forum: Music Tech DIY
Topic: Magic smoke and a burned out TL072
Replies: 9
Views: 307

Re: Magic smoke and a burned out TL072

Don't forget that flux IS conductive. It looks like there is quite a bit around the caps. To that end OP, a toothbrush and rubbing alcohol will clean up most flux, just be liberal with the alcohol. I'm more of a fan of using something to wick (Kimwipes) the flux immersed in the alcohol of the board...
by emmaker
Sat Jul 25, 2020 4:56 pm
Forum: Music Tech DIY
Topic: Magic smoke and a burned out TL072
Replies: 9
Views: 307

Re: Magic smoke and a burned out TL072

Don't forget that flux IS conductive. It looks like there is quite a bit around the caps. ??? Never had resistive issues with flux soldering for over 50 years. Some flux is hygroscopic and can absorb water and become conductive but I clean the water soluble flux soldering really well, don't worry a...
by emmaker
Sat Jul 25, 2020 3:08 pm
Forum: Oakley Sound Systems
Topic: Is it safe to clean eurorack boards with 99% IPA?
Replies: 11
Views: 350

Re: Is it safe to clean eurorack boards with 99% IPA?

I'm going to be building a handful of Oakley eurorack boards soon. I've got some 99% isopropyl alcohol. Is it safe for me to use this to clean the boards before I start soldering components on? Cleaning with IPA is messy, hard sometimes and it's flammable. Better solution would be solder water wash...
by emmaker
Sat Jul 25, 2020 2:48 pm
Forum: Music Tech DIY
Topic: OPA1654 vs OPA1679
Replies: 36
Views: 994

Re: OPA1654 vs OPA1679

To me I'm not all that worried about distortion in a synth circuit since most op-amps have ridiculously low distortion levels but more interested in keeping the noise down. Considering that a 100kohm resistor generates twice as much noise as a TL7X opamp, it will be difficult to reduce the noise le...
by emmaker
Fri Jul 24, 2020 5:50 pm
Forum: Music Tech DIY
Topic: OPA1654 vs OPA1679
Replies: 36
Views: 994

Re: OPA1654 vs OPA1679

Any other newer audio op-amp (later than the TL7X) info that people would like to share.

To me I'm not all that worried about distortion in a synth circuit since most op-amps have ridiculously low distortion levels but more interested in keeping the noise down.

Jay S.
by emmaker
Thu Jul 23, 2020 8:49 pm
Forum: Music Tech DIY
Topic: Four-Layer PCB Stackup
Replies: 12
Views: 314

Re: Four-Layer PCB Stackup

Unless you're doing some dense, high frequency, sensitive (uV, mV range) or analog/digital hybrid circuit in my not so humble opinion (actually I'm a f'n ass) this is overkill for SDIY and don't think this will gain you anything. I think learning good, basic PCB skills and not trying to pack a PCB a...
by emmaker
Wed Jul 22, 2020 3:29 pm
Forum: Music Tech DIY
Topic: DIY Mutable Unsuccessful Builds
Replies: 3383
Views: 193291

Re: DIY Mutable Unsuccessful Builds

Using the "beep" test? Yes, sort of, but just using an ohm meter and looking at the resistance is better. The meters I'm familiar beep with a low resistance value which is not necessarily '0' ohms. If it doesn't beep then you have an open circuit path so check for bad soldering and broken traces bu...
by emmaker
Wed Jul 22, 2020 2:49 pm
Forum: Music Tech DIY
Topic: DIY Mutable Unsuccessful Builds
Replies: 3383
Views: 193291

Re: DIY Mutable Unsuccessful Builds

I’ve been trying to troubleshoot a Rings I’ve built from a synthcube kit. I’ve reflowed the STM and codec and finally got the LEDs to act right but I’m not getting anything to happen on the strum or v/oct. nothing comes out of odd or even. I’ve been through every single page of this thread and have...
by emmaker
Tue Jul 21, 2020 12:58 pm
Forum: Modular Synth General Discussion
Topic: Two Tektronix 545As: Can oscilloscopes drone?
Replies: 13
Views: 220

Re: Two Tektronix 545As: Can oscilloscopes drone?

One thing to think about with these scopes is they were made when quality counted. These are probably about 50-60 years old and still working. What electronics made today will last that long.
by emmaker
Mon Jul 20, 2020 10:42 pm
Forum: Modular Synth General Discussion
Topic: Two Tektronix 545As: Can oscilloscopes drone?
Replies: 13
Views: 220

Re: Two Tektronix 545As: Can oscilloscopes drone?

Do you attach the ends of the probes direct to the tip of a 1/8" ts patching wire? Unless you're using something really old the jacks are 3.5mm these days. Euro is 3.5mm. Possibly, depends on the probe. You can use a BNC to 3.5mm cable they are out there already. But if you use those you are limite...
by emmaker
Mon Jul 20, 2020 8:12 pm
Forum: Modular Synth General Discussion
Topic: Two Tektronix 545As: Can oscilloscopes drone?
Replies: 13
Views: 220

Re: Two Tektronix 545As: Can oscilloscopes drone?

No, a green line is all you're going to get out of them. I would get some real oscilloscope probes, low end ones don't cost that much. These are test equipment that shows you voltage over time. They are used for trouble shooting and calibrating circuits and systems. While this covers newer oscillosc...
by emmaker
Sat Jul 18, 2020 7:42 pm
Forum: Music Tech DIY
Topic: uO_c 8hp ornament and crime.
Replies: 317
Views: 41991

Re: uO_c 8hp ornament and crime.

I hope it's OK that I ask a question about the full-size O_C here, but this is the thread I could find in the DIY forum and this piece seems to be the same between the two. I'll make references to the uO_C schematic to try to keep this as on topic as possible. My questions are: According to the O_C...
by emmaker
Wed Jul 15, 2020 11:56 pm
Forum: Music Tech DIY
Topic: OPA1654 vs OPA1679
Replies: 36
Views: 994

Re: OPA1654 vs OPA1679

Synthiq wrote:
Wed Jul 15, 2020 9:52 pm
When reading the TL074 datasheet, I read the input resistance to be 1 tera-ohm (10^12) which would be 6 times lower than the OPAs, which kind of makes sense since the input bias current is about 6 times higher.
Yes you're correct, thanks.

Jay S.
by emmaker
Wed Jul 15, 2020 7:59 pm
Forum: Music Tech DIY
Topic: OPA1654 vs OPA1679
Replies: 36
Views: 994

Re: OPA1654 vs OPA1679

The opa1652/54 has a lower input impedance, and is not really suited for high impedance synth circuits, unless you buffer the inputs (using a tl072 or something). Don't know if you are comparing OPA165X to OPA167X or TL07X here. Looking at the TI datasheets I have the OPA165X and OPA167X have input...
by emmaker
Wed Jul 15, 2020 12:03 pm
Forum: Music Tech DIY
Topic: DIY Mutable Unsuccessful Builds
Replies: 3383
Views: 193291

Re: DIY Mutable Unsuccessful Builds

mrtweed wrote:
Wed Jul 15, 2020 9:03 am
emmaker wrote:
Wed Jul 08, 2020 12:38 pm
Validate that the attenuation pots are working. If not then check the 4051 power (~3.3V), INH being at ground and MUX_ADDR_x pins (A, B, C) from the processor. If all those look good then the 4051 might be bad.
thank you sir! it was a dodgy 4051, working perfectly now.
Excellent!

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