AC 178, any use for stompboxes?

[brother numsi]

I am gutting this old ITT radio and found a few trannies in it. There's 2 AC 178's and two AF 138's. Can they be used as substitutes for anything stombox-related?
If anything else seems to be "worth it" in the pic, please let me know!
Also what are the copper thingies? Trimpots?
Thanks

[frequencycentral]

I'm pretty sure you can use AC 178's and AF 138's to make an ITT radio clone.

[brother numsi]

Yeah, yeah funny funny. I know it's a silly question, but still...funds are low, so gutting is my only way of getting parts.
I don't know much about these things (obviously), so I figured asking here was a good idea. Now I'm not so sure
Still a funny answer though


(wiseass!)

[frequencycentral]

Hehehe! Just searching the forum, I found this thread where a guy had used an AC178 as part on a Tonebender.

http://www.diystompboxes.com/smfforum/index.php?topic=69202.msg554178#msg554178

The AC178 is a  PNP germanium, so you may be able to make a positive ground Fuzz Face with two of them. Normally two AC128's are used, the specs seem similar. I would socket them instead of soldering them in though.

http://pdf1.alldatasheet.com/datasheet-pdf/view/131459/ETC/AC178.html

[brother numsi]

Ok, cool. Thanks. I did a search but didnt find anything...(ac 178 instead of ac178...doh )
I have a low-volume FF clone and will try them in there

[frequencycentral]

Good for you! Hope it works out. I felt I had to contribute something meaningful after that wisecrack!

[col]

Just looked in my Transistor Equivalents Guide and both can be subbed for a large range of other PNP Ge transistors. Be careful de-soldering them so you don't damage them with the heat and like FC says socket them and try them out. My book doesn't give the hfe so you'll have to swap them around to get the best results.
You migth want to try and get those carbon comp resistors for your FF as well and see how much mojo (hiss) you can introduce into it.

Col

[darron]

i was talking to some old electronics repair guy once and bought some ac128's off him, and he asked me if i wanted his ac127's too as they were pretty much the same, so i agree that you could try the fuzz build

[earthtonesaudio]

Wire that big air capacitor as an input cap to a fuzz for variable bass.  Might be better for a high input Z type effect to have a useful roll-off point.

[alfafalfa]

Aren't you mistaken with AC187 ??

Alf

[DougH]

Any GE PNP type that is not too leaky is a potential candidate for a fuzz face. You will get "optimal sound" if the hfe falls within the range specified in the "technology of a fuzz face" article at GEO. It could also be used for a Rangemaster.

[brother numsi]

Thanks all for your advice so far!

Wire that big air capacitor as an input cap to a fuzz for variable bass.  Might be better for a high input Z type effect to have a useful roll-off point.

what "big air cap" exactly? (I'm STILL learning the lingo... )


@alf
yup, I'm pretty sure they're 178's...unless you meant to adress darron. Then I concur with a "huh?!"

[darron]

for some reason i read ac127... disregard

IT's KURNS! .... no it's not.

[dxm1]

Wire that big air capacitor as an input cap to a fuzz for variable bass.  Might be better for a high input Z type effect to have a useful roll-off point.

Hmmm... Most AM tuning air-variables are in the 0-450pF range.  Maybe the input coupling cap is not the optimum place for it.  It _would_ be cool to
attach a BF knob and have the plates standing up outside the stompbox.  There are spots where that value cap appears in stompboxes, but is there
anywhere that it would make a major difference to the sound?

[petemoore]

  Leakage and Gain determine the applications that the transisitor is likely to sound good in.
  Also Leakage and Gain matter.
  Other than that, when going by looks, only a few this's and that's's that sort of apply....for example there are a coulpe kinds of AC128's, the re-issued ones being less favorably reviewed than the old ones..
  Don't quote me except to say that Leakage and Gain are what is said to be the determining factors by those who've tried 'em 'all'.
  And not even that is all that important if you're just having transisitors provide a service you find useful.

[earthtonesaudio]

what "big air cap" exactly? (I'm STILL learning the lingo... )

The thing with all the "fins" taking up the upper right hand portion of the first picture.  Probably has a tuning knob attached to it.

Hmmm... Most AM tuning air-variables are in the 0-450pF range.  Maybe the input coupling cap is not the optimum place for it.  It _would_ be cool to
attach a BF knob and have the plates standing up outside the stompbox.  There are spots where that value cap appears in stompboxes, but is there
anywhere that it would make a major difference to the sound?

You could modify the MiniBooster circuit to take advantage of it.  With a 10M gate resistor, a 450pF cap has a roll-off at 35Hz.  Turn the knob down halfway and the roll-off starts at 71Hz.  Turn down to about 50pF and the roll-off starts at 318Hz. 
http://www.muzique.com/amz/mini.htm
http://www.muzique.com/schem/filter.htm

[brother numsi]

Really?? Holy shizniz!!
I am definately gonna use that one way or another and try to make it prominent in the design aswell!
Thanks for all the answers! It's highly appreciated to learn new stuff about old stuff