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Circuit building: stop using antique parts (2014)

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Re: Circuit building: stop using antique parts (2014)

#51

Post by PeanutNore »

busterarm wrote: post #35
PeanutNore wrote: post #14

I build a lot of guitar effects, and that community is even worse when it comes to attachement to obsolete components. The discontinuation of J201 JFETs (in TO-92 through hole package at least) by Fairchild has caused a lot of upset. My perspective, not widely shared, is that JFETs in general have been made obsolete by depletion-mode MOSFETs, at least in audio circuits. Part of the reason, I think, is that a lot of "…

Separate from my other comment. I'm pretty much switched over entirely to AxeFX for my guitar & bass setup these days but I've been building circuits lately and figure instrument & vocal effects would be cool projects. Any places I should get started looking?

runoffgroove.com has a lot of interesting guitar effects circuits. There's also the DIYPedals subreddit

Re: Circuit building: stop using antique parts (2014)

#52

Post by HeyLaughingBoy »

Severian wrote: post #7

The irony is that the MOSFET he suggests to use, the NTD4906N, is listed as obsolete on Digikey. Which is why I pointed out. A lot of reasons people use antiquated components is probably because documentation and reference schematics are easy to find and have probably been refined to be very reliable.

Also what you have on hand. 20 years ago I bought about 100 LM324's for a dirt cheap price. I drag one out whenever I need a non-precision amp or comparator.

Re: Circuit building: stop using antique parts (2014)

#53

Post by tawayway »

PeanutNore wrote: post #14

I build a lot of guitar effects, and that community is even worse when it comes to attachement to obsolete components. The discontinuation of J201 JFETs (in TO-92 through hole package at least) by Fairchild has caused a lot of upset. My perspective, not widely shared, is that JFETs in general have been made obsolete by depletion-mode MOSFETs, at least in audio circuits. Part of the reason, I think, is that a lot of "…

Depletion MOSFETs seem to have availability problems. My local distributors only have a dozen or so models, mostly SOT-23. I can see why DIYers are not all over them.

Re: Circuit building: stop using antique parts (2014)

#54

Post by jacquesm »

makomk wrote: post #41
jacquesm wrote: post #21

Earlier quoted context omitted.

RF grade relays will cost you an arm and a leg though.

I think a lot of ham radio gear just uses standard relays for switching RF signals. Apparently they work well enough in many applications.

As long as you are loading with a resonant load then yes, it can work. But as soon as you are in any way reflecting power back on the line or have an impedance mismatch (which will result in reflected power) you're in big trouble.

Another problem is if you use one to switch from say an antenna to a dummy load, you might find that you are leaking quite a bit of power onto the supposedly disconnected antenna link. RF is tricky, especially at higher power levels.

One trick you can use is to use only single contact relays and to bend open the contacts as far as they will go as long as they reliably close again when the relay is energized.

That way you minimize capacitive coupling between the contacts. DC relays are your best bet for a starting point because they already have larger gaps than most AC relays (to inhibit arcing).

Re: Circuit building: stop using antique parts (2014)

#55

Post by failrate »

busterarm wrote: post #33
PeanutNore wrote: post #14

I build a lot of guitar effects, and that community is even worse when it comes to attachement to obsolete components. The discontinuation of J201 JFETs (in TO-92 through hole package at least) by Fairchild has caused a lot of upset. My perspective, not widely shared, is that JFETs in general have been made obsolete by depletion-mode MOSFETs, at least in audio circuits. Part of the reason, I think, is that a lot of "…

Guitar d00ds having obscure, nonsensical reasons for things because "mah tones!"? Say it ain't so. I mean, nearly every tube head on the market has an essentially pointless standby/bypass switch because of the mistaken belief that you need to warm up your tubes for some arbitrary amount of time in a modern amp and keep them warm. I forget which manufacturer it was that dropped the switch on one model and saw sales pl…

If I ever made analog audio equipment professionally, I would add an entire series of switches and dials that weren't wired up to anything.

Re: Circuit building: stop using antique parts (2014)

#56

Post by PeanutNore »

Animats wrote: post #23

If you want to switch power, MOSFETs are the way to go today. Voltage drop is near zero. Digi-Key has over a thousand MOSFETs in TO-220 packages. Here's one of the cheapest with a low gate threshold.[1] Probably good enough for most Arduino on/off applications. MOSFETs do have some problems. They can draw large gate currents for the first few nanoseconds of turn-on, which can overload whatever is driving them. The ga…

There are definitely still new through-hole parts, but the selection is limited. It seems like maybe 20% of new transistors get a TO-92 or TO-220 version.

Re: Circuit building: stop using antique parts (2014)

#57

Post by PeanutNore »

sounds wrote: post #29
Animats wrote: post #23

If you want to switch power, MOSFETs are the way to go today. Voltage drop is near zero. Digi-Key has over a thousand MOSFETs in TO-220 packages. Here's one of the cheapest with a low gate threshold.[1] Probably good enough for most Arduino on/off applications. MOSFETs do have some problems. They can draw large gate currents for the first few nanoseconds of turn-on, which can overload whatever is driving them. The ga…

I would love to see something on digikey or mouser that allowed me to search for MOSFETs in a way that was less painful. Let's say you wanted to do a special purpose switching power supply. Digikey doesn't have a column for gate capacitance (for the mosfet), or Q (for the inductor). All that manual work to read datasheets is terrible, especially if your design takes a little while to perfect and some of the component…

Mouser does have a column for gate charge that you can sort by.

Re: Circuit building: stop using antique parts (2014)

#60

Post by busterarm »

mdb333 wrote: post #48
busterarm wrote: post #43

Earlier quoted context omitted.

Sold all my heads, pedals, cabs. Have just the Axe and a FRFR wedge now. Best decision I ever made.

folks are digging the kemper profiler too. Can't argue with the results but i guess im still addicted to analog.

The profiler is okay and is likely preferred for people who already have a sample of the tone they want and aren't the kind that will want to fiddle.
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