Search found 365 matches

by JimY
Mon Jan 18, 2021 5:36 am
Forum: Music Tech DIY
Topic: Copper tape - sanity check
Replies: 4
Views: 325

Re: Copper tape - sanity check

For screening only I prefer to spray some conductive graphite paint from a rattle can on the inside. Use copper tape to make contact with the panel under a screwdown point. The graphite has some resistance, but not zero ohm - depends on how many coats you give it, but for rfi & antistatic it's adequ...
by JimY
Sat Jan 16, 2021 5:34 pm
Forum: Guitars, Basses, Amps & FX
Topic: center negative vs center positive
Replies: 26
Views: 382

Re: center negative vs center positive

Boss had a good reason to go that way. The switch contact in the 2.1mm socket isn't isolated from contact with the outer contact of the plug. To my knowledge, there isn't an isolated switch version of those sockets which would require an extra solder tag and some insulation on the sprung side of the...
by JimY
Sat Jan 16, 2021 6:05 am
Forum: Music Tech DIY
Topic: LM339 Pullup resistor value
Replies: 15
Views: 209

Re: LM339 Pullup resistor value

Fortunately, the 4017 clock input has a Schmitt trigger so can tolerate slow rising edges. Other CMOS logic clock inputs aren't so lucky, it can jitter from slow rising edges. A 4013 D-type can double clock off a slow edge. It's a pity the outputs of the comparators are that way around, but I think ...
by JimY
Fri Jan 08, 2021 5:17 pm
Forum: Music Tech DIY
Topic: Building a Voltage Controlled Flanger (question answered)
Replies: 12
Views: 561

Re: Building a Voltage Controlled Flanger (question answered)

I forgot another polarity choice. Inverted wet to output mix. Another flavour but again more interesting if the delay can sweep toward zero. Can be combined with inverted feedback.
by JimY
Fri Jan 08, 2021 10:03 am
Forum: Music Tech DIY
Topic: Building a Voltage Controlled Flanger (question answered)
Replies: 12
Views: 561

Re: Building a Voltage Controlled Flanger (question answered)

Somewhere around 20 to 30 ms delay comes a point where feedback polarity doesn't seem to matter. After a long enough delay, the 180deg difference has no effect. At short delay times, getting close to zero delay, the polarity of feedback is the difference between straight addition and complete cancel...
by JimY
Fri Jan 08, 2021 9:39 am
Forum: Music Tech DIY
Topic: How I wasted my school summer holiday in 1981
Replies: 22
Views: 592

Re: How I wasted my school summer holiday in 1981

I think errors were a fact of life in those publications. I can remember errata sheets being included with some of the books and the only sane thing to do was go through your shiny new book and scribble notes on the pages - you didn't get per-page self-adhesive corrections. As time went on, I bet lo...
by JimY
Sat Jan 02, 2021 6:04 am
Forum: Music Tech DIY
Topic: arduino top octave generator
Replies: 52
Views: 4903

Re: arduino top octave generator

Here's some of my thoughts. I'm not sure that pitch jitter is as big a problem as anticipated. The beating that results here and there between certain intervals is be interesting in my opinion (once the harsh upper harmonics of the square waves are filtered out). A bigger problem common to all divid...
by JimY
Fri Jan 01, 2021 9:49 am
Forum: Music Tech DIY
Topic: arduino top octave generator
Replies: 52
Views: 4903

Re: arduino top octave generator

As a very late update, my String Synth using the TOG developed here is mostly complete & working. In practice, after the necessary filtering (stringers cut over 5hHz), I have no concerns about the relative tuning. A CD74HC4046 proved perfectly adequate as the CPU clock which is also the master tunin...
by JimY
Tue Dec 22, 2020 5:22 am
Forum: Music Tech DIY
Topic: Anyone with a Ace Tone Rhythm Ace FR-6?
Replies: 53
Views: 815

Re: Anyone with a Ace Tone Rhythm Ace FR-6?

Old germanium transistors were mostly best and cheapest in PNP type so were more conveniently designed for negative supply (better known as positive ground). When Silicon took over, initially, NPN type was the better choice and the circuits became negative ground. It meant turning the polarity of ev...
by JimY
Sun Dec 20, 2020 5:55 am
Forum: Music Tech DIY
Topic: Anyone with a Ace Tone Rhythm Ace FR-6?
Replies: 53
Views: 815

Re: Anyone with a Ace Tone Rhythm Ace FR-6?

The TR-33 is definitely using a positive supply. Going by the polarity of the supply capacitors, the FR-6 is similar and you might expect the same DC voltages on the positive leads of the caps. +24v for the rhythm circuits and +20v for the voices. If it were a negative supply, the positive wires of ...
by JimY
Sat Dec 19, 2020 4:43 pm
Forum: Music Tech DIY
Topic: Anyone with a Ace Tone Rhythm Ace FR-6?
Replies: 53
Views: 815

Re: Anyone with a Ace Tone Rhythm Ace FR-6?

I wonder if that's a Selenium plate bridge rectifier? It looks like the layer sandwich construction of those. Will do no harm to replace it with a silicon one if necessary. The negative out of the rectifier (black) is the 0v ground. The positive output (orange) feeds a resistor and on to a filter ca...
by JimY
Thu Dec 17, 2020 9:30 am
Forum: Music Tech DIY
Topic: Replicating midi clock
Replies: 10
Views: 194

Re: Replicating midi clock

Yes 5V. The 6N137 datasheet is vague about the supply voltage. There is usually an "Absolue maximum ratings" giving min-max but I didn't see it. But it only mentions 5v supply in the performance tables so I'd "assume" it wants 5v. I didn't know you were doing that pass-thru thing, so you don't absol...
by JimY
Thu Dec 17, 2020 5:54 am
Forum: Music Tech DIY
Topic: Replicating midi clock
Replies: 10
Views: 194

Re: Replicating midi clock

The 5v or 3v3 depends on what it's driving. 3v3 would be for input to a 3v3 microcontroller chip. In any case, a "pull-up" resistor from the "open collector" output to the receiving devices supply voltage is necessary (called RL in the datasheet test circuit). For 5v, a 10k resistor is sufficient an...
by JimY
Thu Dec 10, 2020 5:03 pm
Forum: Music Tech DIY
Topic: Buy small numbers of 74HC DIP in UK ?
Replies: 6
Views: 238

Re: Buy small numbers of 74HC DIP in UK ?

I always look in Bitsbox first. If they don't have it, Farnell has an associate company CPC.Farnell holding a range sold in singles or 5 at most on multiples.
by JimY
Wed Dec 09, 2020 5:06 pm
Forum: Music Tech DIY
Topic: Where to find Fatar TP/9S 61?
Replies: 15
Views: 485

Re: Where to find Fatar TP/9S 61?

They are listed by Doepfer. Under spare parts.
http://www.doepfer.de/preise.htm
No AT version.
I know their complete products are sold in the USA, but I'm not sure if any bits & pieces are.
by JimY
Tue Dec 08, 2020 5:17 am
Forum: General Gear
Topic: When do you think hybrid users will have more options for stable MIDI clock?
Replies: 22
Views: 772

Re: When do you think hybrid users will have more options for stable MIDI clock?

The elephant in the room is that midi events from ports run by system drivers are time-stamped according to a PC system clock. DAW audio events work at the sample rate and consequently, the DAW timing is only dependent on the sample rate. The two things are not synchronised. Honestly, I've always ha...
by JimY
Wed Dec 02, 2020 7:44 am
Forum: Music Tech DIY
Topic: Hammond organ foot pedal controller conversion
Replies: 14
Views: 302

Re: Hammond organ foot pedal controller conversion

Do you only get single-action normally open contact, one per note on those things? If so, you might look at Moog Taurus schematics. I think they impose a high-frequency signal on the CV output that is detected to provide trigger/gate for the pitch CV S&H. The HF signal is easily filtered out of the ...
by JimY
Fri Nov 27, 2020 4:51 pm
Forum: Artist Discussion
Topic: What's Brian Eno Playing?
Replies: 15
Views: 764

Re: What's Brian Eno Playing?

I wasn't really interested in music at all until I saw that Ladytron performance. Soon bought the first Roxy LP I found, which was For Your Pleasure. Ladytron wasn't on that of course so I had to wait until I found the first album (not much stock by non-pop acts in my hick town). Was gutted when Eno...
by JimY
Tue Nov 10, 2020 8:04 am
Forum: Music Tech DIY
Topic: Small Digital Synths, Jan Ostman and Me
Replies: 30
Views: 1075

Re: Small Digital Synths, Jan Ostman and Me

I'm no great fan of inscrutable PCB's either. I have something that suffers LFO ticking noise and the design has no chip power filtering/decoupling. The only sane way I can see to fix it is to pull the chip power pins up and directly fit an RC filter to it. Lovely looking pcb though, but I won't see...
by JimY
Mon Nov 09, 2020 4:41 am
Forum: Eurorack Modules
Topic: Cheapest damn way to play a sample?
Replies: 75
Views: 2342

Re: Cheapest damn way to play a sample?

Greeting card chips are cheaply available as a proper module (about 3quid on e-bay). Their problems are many - Mono. Short duration. Sound quality is poor. Can't make them loop without a big glitchy gap in between. Input has an auto gain control that doesn't help. Fun can be had with them, but they ...
by JimY
Thu Nov 05, 2020 5:30 am
Forum: Guitars, Basses, Amps & FX
Topic: Classic filters as pedal / Overview
Replies: 10
Views: 374

Re: Classic filters as pedal / Overview

MS20 and EDP Wasp filters get built as guitar FX pedals - sometimes by boutique brands or DIY pcb only or stripboard projects. https://reverb.com/item/32983766-mode-machines-wasp-filter-mw-01-edp-wasp-filter-unit-2016-black https://www.matrixsynth.com/2013/06/korg-ms-20-filter-pedal.html I've DIY'd ...
by JimY
Tue Oct 13, 2020 8:29 am
Forum: Artist Discussion
Topic: Best/Favorite Bassists
Replies: 58
Views: 1327

Re: Best/Favorite Bassists

Nothing from the ladies? Carol Kaye - countless memorable bass line hooks. Tina Weymouth - funky & melodic. Kim Deal - may sound basic punk, but Pixies song structures are not as simple as they seem. Some boys... Andy Fraser (Free) J. J. Burnell (The Stranglers) Mike Howlett (classic period Gong) Ra...
by JimY
Mon Oct 05, 2020 4:14 pm
Forum: Music Tech DIY
Topic: Any of these ICs worth keeping?
Replies: 19
Views: 874

Re: Any of these ICs worth keeping?

If it had a 74c04, then they have linear use just like the CD4069UB and 4049UB inverters do in amplifiers/distortions/oscillators and there's plenty of examples around. The basic gates though (74c00 and CD4011A) have the tantalizing possibility of more complex uses, but the only ones available now a...
by JimY
Sun Oct 04, 2020 5:16 am
Forum: Music Tech DIY
Topic: Any of these ICs worth keeping?
Replies: 19
Views: 874

Re: Any of these ICs worth keeping?

I saw a 74C00 in there. Long obsolete unbuffered CMOS NAND gate. There were some experimental linear things you could do with those. Similar to the original CMOS 4000A logic but with pinout same as 74xx TTL parts.
by JimY
Fri Oct 02, 2020 4:11 pm
Forum: Music Tech DIY
Topic: DC coupled digital delay
Replies: 29
Views: 880

Re: DC coupled digital delay

BBD is DC , its a chain of sample & hold circuits - but they only have a small linear headroom range and the more stages, the more error drift. You could also go digital without coding old school with parallel bus chips. 8bit ADC & matching DAC, 8bit static ram and counters for the addressing. You w...

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