Cheap components...



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Cheap components...

Postby garyg » Wed Oct 17, 2018 6:30 am

Yeah, one of those self-answering questions really but is there any guide/advice on which components are ok to buy cheap?

As in, maybe obviously, cheap foot switches (two for £2.50 from ebay) don't feel as good and won't last as long as the decent brands but does that go for stuff like diodes too?

eg. 1N34A diodes, my regular (UK based) supplier has them for about £1 each, Tayda for $.28 or I could get twenty for 99p on ebay... (these aren't NOS I'm talking about incidentally). I'm naturally weary of the too-good-to-be-true ebay prices but would the Tayda ones be sourced from the same place, maybe even the UK ones too...?

So, TL;DR: is it ok to be a tight arse with discrete components (within reason).

Cheers.
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Re: Cheap components...

Postby Scruffie » Wed Oct 17, 2018 6:36 am

Tayda germanium diodes are horribly brittle, I've tried them before and had to throw away probably 70-90% from the glass breaking when bending the leads gently. Also be wary of places selling Schottky diodes with germanium part numbers.

Pick your battles for where you save money, 'rare' parts and hardware are not a place to try and save.
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Re: Cheap components...

Postby BetterOffShred » Wed Oct 17, 2018 9:13 am

I have only ever had one Tayda 1N34 break, but I use other germanium stuff now mostly anyway. I think the only Tayda part I have really been burned on was the 7660 chips.. they all whistle in audio applications.

Caps, resistors, pots, cases, jacks, etc.. go for it I say.

As far as eBay goes I rarely get bunk shit. Recently I got 4/6 of a 4PDT order showed up as 3PDT and were momentary.. but that was $4 and they refunded me 3$..

There's enough Russian stuff coming out of Ukraine Bulgaria and Russia itself that has nearly the same curve as 1N34A (see the recentish thread on Ge diodes at DiySBs) to get pretty close if not nearly exact. :)
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Re: Cheap components...

Postby crochambeau » Wed Oct 17, 2018 12:16 pm

It's really going to boil down to the circuits you're building and how important stable operation is. It is safe to assume you're not banging out life critical builds based on the line of inquiry..

Super cheap resistors are going to have terrible thermal drift characteristics, but you can often ignore that if your build is A) not dissipating gobs of power or B) not a tuned or alignment circuit. Generally speaking, an effects pedal is going to remain comfortably within the center area of any temperature tolerance - unless the part in question is used in power regulation. I'd keep the cheap resistors out of amplifiers (and out of tubed circuits in general, unless you go deep enough to plan for any drift).

Cheap caps are often going to have little to no SOA over designated voltages, so selecting caps rated at double or triple your operating voltages might be advisable.

I have little experience with cheap "counterfeit" parts in the actives, but steering clear of bullshit where power supplies or power amplification is concerned should have you okay in terms of magic smoke inhalation. For most analog pedals your power range is small enough that for MOST things you're still in the realm of harmless.

That said, the processes involved in component manufacture coupled with whatever circuit your working on may not sound as good as wish. This is where adjusting the values of the circuit can come into play, but unless you have a scope or a lot of patience that's a subject for another day.
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Re: Cheap components...

Postby garyg » Wed Oct 17, 2018 3:49 pm

...
Last edited by garyg on Wed Oct 17, 2018 3:50 pm, edited 1 time in total.
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Re: Cheap components...

Postby garyg » Wed Oct 17, 2018 3:50 pm

Thanks all, will take all this into consideration next time i'm ordering anything.

crochambeau wrote:It's really going to boil down to the circuits you're building and how important stable operation is. It is safe to assume you're not banging out life critical builds based on the line of inquiry..


(to paraphrase Bill Shankly) My fuzzes aren't a matter of life and death, they're much more important than that. ;) But quite right, I'm just getting back into building after a couple of decades(!) and the landscape's much changed. My stuffs hardly critical (guess I'm more of a noise head than a tone purist) but still don't want to throw money away on cheap stuff that turns out to be crap.

Super cheap resistors are going to have terrible thermal drift characteristics


Didn't know that, I have been pondering those cheap packs on ebay too (y'know, 1200 resistors for a fiver or so...)

Cheap caps are often going to have little to no SOA over designated voltages, so selecting caps rated at double or triple your operating voltages might be advisable.


And then you end up with much bigger caps I guess? Point taken.

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Re: Cheap components...

Postby eatyourguitar » Sat Oct 27, 2018 4:46 pm

1N34A are likely to break if you tug on the leads or bend them where they connect to the glass casing. I don't think it is ever possible to have a batch of 1N34A that is so robust that they can have unbreakable glass and immovable leads. buy the cheapest germanium diodes you can find on the whole internet. just make sure you check them with a curve tracer or maybe at least a signal generator and an oscilloscope. the trace of a germanium junction looks completely different on a scope compared to silicon. you can see and hear the difference. I have purchased fake 1N34A but the problem was that I got silicon instead of germanium. the junction failure rate caused by handling and installation was invariant for all germanium 1N34A. this is a trap for young players doing repairs on OEM vintage guitar pedals containing 1N34A. if the diodes must be removed for some reason, they should be tested or replaced before they are installed again.
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Re: Cheap components...

Postby garyg » Mon Oct 29, 2018 9:04 am

Thanks for the advice.

As an aside, is there a reason some diodes like 1N34As are housed in glass and not plastic like other diodes? Or is it just historic?
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Re: Cheap components...

Postby eatyourguitar » Mon Oct 29, 2018 12:47 pm

glass is an insulator used in vacuum tubes. I would speculate that the mindset of a component manufacturer was to just keep going with the same industry standard materials. a lot of the vintage soviet diodes I have that were manufactured the same year as the 1N34A were actually plastic casing with silicon junction. if I had to guess I would say it looks like polyethylene. I have noticed a lot of the push to innovate in 1967 was done through new diode designs for the soviet military. the americans were working on silicon integrated circuits. the soviets had all the high precision high frequency temperature stable diodes sorted well before we did. we had them too but I think they were probably way more expensive in the US and probably reserved for the small number of radios with very demanding requirements. it could be possible that the soviet diodes were never cheap but they are very abundant and cheap now. there are still huge stockpiles of diodes from that era with basically no documentation at all but very unusual properties on a curve tracer and also very high bandwidth. the plastic casing works great for airplanes and tanks that experience a lot of vibration and possibly shockwave. I would assume that the glass casing and the germanium junction was just the bog standard mass produced part used in many consumer electronics in america. america was pumping money into silicon transistors through bell labs. even today, we use glass in the 1N4148. also consider that the highest bandwidth germanium transistor was a soviet part. the americans would just switch to silicon if they needed something like that.
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Re: Cheap components...

Postby Bartimaeus » Fri Nov 02, 2018 11:58 pm

For pedal applications, I think Tayda or even ebay can be perfectly good for resistors, capacitors, and standard diodes. For chips and some transistors I recommend a site like mouser or digikey, although Tayda can be fine for some applications. If you're looking for NOS parts or germanium diodes, I'd go with a specialty pedal parts store like Smallbear. The difference in cost only makes much of a difference if you're building dozens of pedals, and it's worth it to ensure that you're actually getting a part with properties within the desired range.
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