Posted: Audix 35302 Quad Line Amp Schematics & More

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Tillmann

Well-known member
GDIY Supporter
Joined
Aug 3, 2004
Messages
378
Location
Phoenix, USA
Good Evening Lady & Gentlemen,

Here's an extensive bit of of documentation for the Audix 35302 quad line drivers for the Audix consoles of yore. Sorry for the grainy PCB scans, but that's the best me ole scanner would do. I tried to pet her a little bit, coax her to perform by whispering sweet nothings in her power jack, but alas, she refused to cooperate. Me thinks they'll do the job adequately enough anyways. Also, the front face pic is shit, but trust me, there's not a whole lot to see there. What you see is what you get. The file?s large, but if you need it, it will be much worth the wait. Me hopes this helps some of y?all out there in DIY-land.

And if some chaps here cooperate this month, hopefully we?ll finally have some scans of the 35102 Version 3 schematics of which no one seems to have a decent copy.


To the point of the post:

http://www.vintageaudiogearbox.com/Audix35302QuadLineAmp_Ver2_Schemo.zip


Yours In Solder Fumed Confusion,

T

(edited due to misinformation)
 
Wow, cool, I think.... I'm interested but not quite sure what to do with this. I guess the plan qould be to figure out how to integrate it into a 35102 by finding where the 35102 ends and the 35302 begins. Just use line driver section? would this be better than a couple of opamps?

- you posted this just as I was very close to racking my 35102s with UTC on the output. it could be a good thing or it may delay racking these since I always want to complicate things and do things right.


Thanks T
 
Well now comes the part where I fess up to the dangers of presumption. I saw the circuit and glanced at the schematic and believed what I was told it's function was. I posted the schematics at about 3AM last night and went to bed. The whole time I scanned them, I never really studied them too hard as I was doing other things while I was scanning. Well, upon further examination this morning, I realize that the T1442 is actually acting as an input transformer (VERY obviously) and is not wired in reverse as an output. So this changes all my ideas on how to use this circuit. I was under the presumption that this acted as a dual channel line driver with a XFMR balanced output. That is NOT the case, so I would just go about what you're doing until I have the time to experiment with the circuit to see what it could be used for. My apologies for the confusion. :oops: :oops: :oops:


T
 
Hey Guys,

I have an overall layout of the 35102 and 35101. I think the 35102 is slightly more readable and they are nearly identical. I have a pair of 35012's and while they are sort of interesting, they don't clip nicely at all and the "feel" of the EQ adjustments is one of the weirdest ever. They seem to be quite clean. Someone PM me with an email address and I will send you what I have.

I tacked on a BA283 output stage (and tranny) one day and it sure made the bottom end "nicer"...


Tim
 
[quote author="q2audio"]Hey Guys,

I have an overall layout of the 35102 and 35101. I think the 35102 is slightly more readable and they are nearly identical.
[/quote]

Sweeeeeeet! PM Sent. How would you compare the 35101 and the 35102 as far as sound?


[quote author="q2audio"]
I have a pair of 35012's and while they are sort of interesting, they don't clip nicely at all and the "feel" of the EQ adjustments is one of the weirdest ever. They seem to be quite clean. [/quote]

That's the first time I've ever heard anyone say that. What other gear do you have/use?


[quote author="q2audio"]
I tacked on a BA283 output stage (and tranny) one day and it sure made the bottom end "nicer"...[/quote]

Well, that's what started this whole post. Often these need a lot of work on the output stage to get them up to snuff. Sometimes, depending what is suspected to be the transistors on the output stage, they won't drive a 600ohm load without overheating. It seems that some modules used higher output transistors than others, so it depends on what modules you have. That's the rumour anyway. So it makes a lot of sense that if you put a BA283 output stage them that it sort of fixed things. What transformers did you use? What versions of the 35102 do you have (ver 1, 2, or 3)? Did you do any other mods to them?


Cheers,

T
 
Hmmm. I can't remember which version I have they are racked in a box, mounted in rack and I'm too lazy to take it all apart!

I've listened to both the 35101 and 35102 and the 35101 sounded warmer to me. I know that it does not use the 5534 in the mic front end like the 35102 does and it has about 1/2 the number of electrolytics as well. I'd trade my 102's for 101's if given the chance.

As for the EQ, you have to turn the knob more than 50% in either direction to hear anything happen and then it all happens in the last 10 degrees or so of travel. Hard to use. This may be fixable by changing(raising) the values of the resistors that are in parallel with the pots (to give them the "law"). I don't know what effect this would have on the rest of the circuit. I do see that these values have changed from revision to revision as well as the pot values themeslves.

The output stage seems a little wipmy with a TO-92 driver. Mine seems to drive 600 ohms fine. I have the original Sowter 4127 trannys terminated with 600 ohms. The 35101's I have seen have a TO-220 output stage but I dont' know if it is class A or AB. I have added an output fader, why I don't know, to the output stage. I removed R151 and use a 10K log pot in its place with the wiper feeding C151. There is no insert, so this seemed like the next best place.

Tim
 
Hi
The problem is you guys that you steal and rape old desks without understanding how they were designed.
The 35101/2 output will only drive a 10K or more load as it is part of a system where it feeds a routing module (the ones the rapists threw away).
following the router they go to mix busses where the transformers in the quad amp raise the level 10dB then through the preamp that is also in the Quad modules. This feeds the group fader which then goes into the line amp section on the quad amps. This feeds a large transformer (not in a module but in rear of chassis) which raises the level +6dB.
A Neve BA and transformer is one approach to regaining the headroom.
I tested these desks in early 1980's
Matt S
 
guavatone,

Could you possibly resize your avatar to the recommended 60x60 pixels - it takes up a lot of screen space in the threads that you participate in (because of the forum software)..

Jakob E.
 
[quote author="q2audio"]As for the EQ, you have to turn the knob more than 50% in either direction to hear anything happen and then it all happens in the last 10 degrees or so of travel. Hard to use. This may be fixable by changing(raising) the values of the resistors that are in parallel with the pots (to give them the "law"). I don't know what effect this would have on the rest of the circuit. I do see that these values have changed from revision to revision as well as the pot values themeslves.
Tim[/quote]

Yeah, mine are like that too. I was wondering if it was that the pots were old and dirty. has anyone modified this aspect of these EQs? The mechanical aspect of replacing pots sounds like a PITA.
 
Hi
I suggest that it may have been intentional that the control is fine over the central egion, given that the desk was designed for broadcasting where most inputs were supposedly decent anyway. Yes fiddling with the resistors and pot values would change the law but there is the possibility that the frequency points will go out if the overall end to end resistance is changed. Pull one out and try it with other pots. I think the pot values were changed due to unavailability of some values, the manufacturers rationalised their range.
Matt S
 
Hi
If they were small and white they are Sfernice. Black pots were Allen Bradley (mod pot). As they were specially made and you need them to be 'concentric' with the switches you are in for a bad time I suspect as the manufacturers will not want to know unless you buy 1000 or more of them (or a 1000 off price for a couple with 998 spares!).
You may strike lucky and I wish you well in a search.
I never took one of the assemblies apart but an investigation of the mechanical aspect is your first activity if you plan on changing the pot. Removing the padding resistors may help a bit with the 'law' but expect a frequency and max / min dB change. Putting resistors in series with the ends may help the dB aspect. All good fun if the nights are drawing in where you are.
Matt S
 
Dear Matt Syson,

Thank you so much for the info vv audix stuff. Fantastic to get it from the horses mouth, as it were. I am am a big fan of Audix stuff in general, and have owned quite a few different modules in the past. I currently own 6 x IB01's, which are amongst my favourite mic pre's, especially for drums. I also have a few of the output transformers you mentioned. I have cobbled them into a number of homemade pre's etc instead of the ubiquitous API/Profile 2503's. I absolutely love them( yes, i know they are 150:600 not 75:300). I was just wondering if you remember who made 'em? I would LOVE to be able to source them for a large project i have in mind.


ps 15 years ago I was offered a large 48 channel Audix(ex BBC - used for the Archers!) for a paltry 3 or 4 grand. Turned it down, 'cos I didn't have the space!@@@@@ Schmuck!@@@@


All the best,


ANdyP
 
Hi Andy
Sowter definately, possibly 4127 as a type number, Mr Sowter would know. These were on the desks with 35102 input modules. At the time Belclere, Cumbernauld and Marinair were also being bought but the range of equipment Audix was making was pretty large.
Matt S
 
Matt
Just out of interest - any idea on the windings and transformer specs for a Marinair T1501 as used by Audix in their headphone amps???
 

Latest posts

Back
Top