any one confirm my plan (preamp schematic)

  • Thread starter Thread starter Steenamaroo
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Steenamaroo

Steenamaroo

...
hi all,,,,quick question if you don't mind.

schematic is here.

http://avensonaudio.com/tech/auditronics/audiotronics_110b.pdf


one of my 110a modules has a minor fault and i think i know how to fix it,,,bu the way they're wired makes it a nightmare to get at the boards, so i wanted to be sure i'm on the right trail first!!


basically...eq section....3 pots..each has two freq selector switches.


the high eq works fine when set at 7.5k (although it sounds higher to me), but on 12k the high end eq is bypassed.(turning pot does nothing)


just to be sure, it's not my hearing :P:P i have another module for comparison...




in terms of the schematic...

with the switch out(12k) i figure c26 wouldn't be in the circuit... and my high eq doesnt do anything at all

with the switch in(7.5k), c26 is introduced into the circuit. and i get usable eq (although it sounds more like 12khz then 7.5 tbh)

looks to me like i need to replace C27?

can anyone who knows what they're talking about confirm?

thanks!!!
 
Last edited:
Looks like your logic is sound.

It make sense that it wouldn't sound like 7.5K. The switch parallels the caps in that position. If C27 is defective, then the LC circuit is tuned for a different frequency.

Slap a new .01 microfarad in that puppy and see what happens. You wouldn't even need to solder to test it. Just hold one across the leads of the existing C27 and see what happens. First, you may want to verify that you have continuity between the coil and one side of the cap and ground to the other.
 
thanks for the reply,,that makes sense....

the one thing that's confusing me though, is which cap is which.

the schematic states that the cap values may differ, depending on model..


i have a 0.01uf cap and a 0.0082uf cap

i shorted out the caps systematically to see which one did what, when, if that makes sense...

the hope was that shorting the cap out would change the sound, and i'd know which cap one was defective, but this has confused me more..



on the good preamp/
the 0.0082 cap ALWAYS bypasses eq when shorted

the 0.01uf cap only bypasses eq when the eq is set at 7.5k


this makes me think that the 0.01uf is actually c26, and the 0.0082 is c27??




the 'bad' amp reports the same changes,,,other than the eq not sounding right to start with.


in answer to your suggestion,,,,
i have continuity between the coil and the caps.
i have continuity between the the other side of the 0.0082 cap and ground all the time.
i have continuity between the the other side of the 0.01 cap and ground only when 7.5k is engaged.
sounds fine to me?
 
thanks man :) i'm really chuffed that i worked that out! lol


i know it's simple,,,but i would have seen myself replacing the other one in the past, and wandering why it didn't fix it!


caps ordered :)
 
just a quick follow up...


since my messy wiring made it soooo awkward to do this, i went ahead and replace both caps in both units. (just incase)

fired it up and hey presto :) worked first time...


i was concerned about polarity, cos the schemo shows non polarity caps?is that right?

anyway, it worked,and there are photo's here http://www.webforni.com/steen/photos2.html for those who care! lol


thanks for the confirmation LDS.
 
Wow, awesome. Where did you gain your electronics knowledge? Just tinkering on your own?
 
Not sure if the question was directed to me or the OP...

I initially learned in high school, through self study and a couple of semesters of vo-tech. After that about a year of training in the Army, learning to troubleshoot and repair mainly tube-based circuits in radars to the component level. Following release from active duty, I spent about fifteen years as an audio tech, repairing everything from turntables and amps to pro sound and recording studio equipment. Did warranty work for Studer, Teac, Tascam, Yamaha, McIntosh, Bang & Olufsen, Sony, Pioneer, pretty much any audio gear. Got out of the business about ten years ago when most stuff became either disposable or the repairs came down to replacing entire circuit boards.

I really love troubleshooting to the component level and some days really miss the work. I have a little workbench in the back of my mixing room where I occasionally repair amps and tape decks and stuff.
 
It was directed toward anyone, really.

That's awesome. I didn't know that most repairs come down to just replacing entire circuit boards now. Electronics are interesting to me and I studied a semester of it (at a tech school) before changing my mind back to music production. I came back to music because I missed it so much and now I actually miss studying electronics a bit. Guess I'll have to learn a little of both as time goes on. :P
 
rack some preamps austin! you know you want to!!

i don't really have an electronics knowledge at all....i just pick up the odd bit from helpful guys like LDS.(thanks again)

i am sorta getting to the stage though, where i can trouble shoot a fault, and be 99% sure that i'm on the right lines. but i still don't get the soldering iron out until someone else agrees! lol

first time i lifted an iron, other than for making cables, was to rack up those auditronics preamps.

the logic at the time was, they need power, audio in, and audio out. how hard could it be? and i figured if it doesn't work it would just be an expensive learning curve, but it worked.

now i have a pair of nice pres for like £250 plus i racked some ward becks as well for £45 each +psu and case :):)

*edit* if anyones thinking about this, ward beck gear is a great starting point cos they're cheap, easy to rack, sound great, AND theres a forum specifically for ward beck gear (WBPS) where they are immensely knowledgeable and helpful.
 
Steenamaroo said:
rack some preamps austin! you know you want to!!

i don't really have an electronics knowledge at all....i just pick up the odd bit from helpful guys like LDS.(thanks again)

i am sorta getting to the stage though, where i can trouble shoot a fault, and be 99% sure that i'm on the right lines. but i still don't get the soldering iron out until someone else agrees! lol

first time i lifted an iron, other than for making cables, was to rack up those auditronics preamps.

the logic at the time was, they need power, audio in, and audio out. how hard could it be? and i figured if it doesn't work it would just be an expensive learning curve, but it worked.

now i have a pair of nice pres for like £250 plus i racked some ward becks as well for £45 each +psu and case :):)

*edit* if anyones thinking about this, ward beck gear is a great starting point cos they're cheap, easy to rack, sound great, AND theres a forum specifically for ward beck gear (WBPS) where they are immensely knowledgeable and helpful.
Click to expand...

So, by 'rack up' you mean you built these from scratch, correct? Or you took existing preamps and made them rackable?

I think that actually does sound really fun. I guess it would just be a matter of finding all the parts I need, really. I have a soldering iron and a bunch of tools for electronics (had to buy them for school)... I don't see a reason why I shouldn't start building things. :drunk:

So you just find out all the parts you need from the schematic and find some place to order them all online? Simple as that?
 
nah, what i did was easier than all that.
but you can buy diy kits and build them from scratch if you want.

i didn't like that idea cos it's more like 'paint by numbers'.

i didn't think i'd learn a lot just building from a schematic and instruction guide.



the idea with mine is, you're taking channel strips or input modules from old recording consoles, and giving them power supplies, in and out jacks and a nice box to live in :)
if you haven't already, check out the auditronics and ward beck pics on my site, cos there should be pics of each stage.


the modules have stips, like a computer graphics card? and i just soldered on to them, but it means i can't remove them without a whole hassle.

from that experience, i would recommend that you find the proper edge connectors and do your soldering to them, so you can slip them on and off easily in future.




http://www.webforni.com/steen/photos2.html
the second pic down shows the blue JLM transformer, then going clockwise the jlm psu, output transformers (not always needed) and input modules.


if you have a jigsaw, set of drill bits and a file, the metal work for the faceplate is dead easy :)
 
Steenamaroo said:
nah, what i did was easier than all that.
but you can buy diy kits and build them from scratch if you want.

i didn't like that idea cos it's more like 'paint by numbers'.

i didn't think i'd learn a lot just building from a schematic and instruction guide.



the idea with mine is, you're taking channel strips or input modules from old recording consoles, and giving them power supplies, in and out jacks and a nice box to live in :)
if you haven't already, check out the auditronics and ward beck pics on my site, cos there should be pics of each stage.


the modules have stips, like a computer graphics card? and i just soldered on to them, but it means i can't remove them without a whole hassle.

from that experience, i would recommend that you find the proper edge connectors and do your soldering to them, so you can slip them on and off easily in future.




http://www.webforni.com/steen/photos2.html
the second pic down shows the blue JLM transformer, then going clockwise the jlm psu, output transformers (not always needed) and input modules.


if you have a jigsaw, set of drill bits and a file, the metal work for the faceplate is dead easy :)
Click to expand...

Ah, okay. I thought this might have been what you meant.

I did check out your pics.

I guess my question now is where did you get a hold of a single channel strip like this? Did you own the console and rip it out from there or did you find someone selling just a single channel strip or two?
 
ebay is your friend:)

i suppose it makes sense in the digital age.

everyone wants a piece of 'analogue sound' or whatever, but very few people can afford, or want a console.

for this reason (i guess) people seem to be breaking consoles for sale. i suppose a broken console might not always be worth repairing too.

plus there's the consoles that are found in old radio stations or whatever, stored for 20 years,and some lucky fart inherited it.




i didn't know anything about the brands..i took a chance with a little bit of research, but check out proharmonic racking, cos rob over there has loads of pics of finished products, with the model names and numbers.

i mean, you could buy a shitty cheap yamaha one, or a nice neve one, but there are plenty in the middle to try out too.


the beauty of it is, you can do the same with ssl eq modules, dbx compressors....anything like that :)



this is a wee bit pricey for my liking, but here's an example for ya.
http://cgi.ebay.co.uk/WARD-BECK-Cha...tem&pt=LH_DefaultDomain_0&hash=item41510988a3

this guy almost always has modules on the go, but he's far too expensive IMO.


**EDIT** here's a perfect example.
http://cgi.ebay.co.uk/Wheatstone-mi...tem&pt=LH_DefaultDomain_0&hash=item415101eebc

no idea if it's any good or whatever, but it's a cheap learner project.

plus whatever you spend on a psu and transformer is kinda irrelevant, cos if you get this one right,and end up not liking the module, well you've learned a little, and you can reuse the psu etc with the next project :)
 
Steenamaroo said:
ebay is your friend:)

i suppose it makes sense in the digital age.

................
Click to expand...

Awesome, thanks for the info and advice.

I can definitely see this as something I may be doing a lot of in the future. Seems so fun.. and cheap'ish.. :P I wonder if the Wheatstone is any good. But yeah, it'd be great to do as a first one either way.
 
hmm..yeah. i really don't know.

i couldn't find much out about them, but i'm fairly sure that they own, or are the new name for auditronics now adays.

still, hard enough to find info on auditronics themselves.



it's not very likely, but if i can ever help, just drop me a line.
 
That is a really amazing looking plan. How did you know how to do all that, did you go to school for engineering?
 
who me ?

far from it! i'm a noob with a soldering iron :laughings:

very much just learn as you go.

i think i said earlier in the post, i was well prepared for it all to go badly wrong and be a waste of money, but the gamble makes it fun i guess :p
 
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