Ashly SC-55

[Siegfried Meier]

Hey guys,

Just acquired one of these, and it's obviously one of the first models(knobs & power switch are different than the ones I've seen online, and no limit section).  I've read in the manual that these are balanced (+) on tip - is it possible that the older ones were unbalanced?  I couldn't seem to get it to work properly at all when going balanced, and it would only work properly in a Mackie type insert jack.

If it is indeed balanced, and maybe it's reversed polarity for some reason, that would explain it I guess - I'm simply going by what the manual says.

Sounds cool and dirty though, very neat comp.

Thanks!
Sig

 

[Siegfried Meier]

It appears this is an older model of the ones I see online - this one has different switches, knobs and no limiter section.  So it's clearly older, is it possible they didn't balance this one, and the newer ones were balanced?

I pulled all that gross, disintegrating foam out of there, and cleaned up all the boards.  I get why they used the foam, but what a bad idea...this thing will only see studio use now, so no need for the foam.

Thanks!
Sig

 

[Siegfried Meier]

Got an email from Ashly this morning.  Even though on their site they say the SC-55 was dated 1984, he send me a schematic dated 1979, and said:

I think this might be it ? 9/12/1979 is the oldest one I can find. The outputs on these were Z balanced. Inputs true balanced. The premise here was that the if receiving unit had a true balanced input the circuit would be balanced.

Hope this helps,
Regards,
Mike

I've never heard of a piece of gear that does this.  Anyone else know anything about Z balanced?

Thanks,
Sig

 

[abbey road d enfer]

Anyone else know anything about Z balanced?

Quite common. Used extensively on Spirit mixers and many transformerless condenser microphones. When well implemented, it gives excellent CMRR.
At line level, it has a practical advantage: since the signal is on one pin only there are less risks of out-of-phase connections.

 

[Siegfried Meier]

Ok, so can someone tell me why it sounds totally screwed after wiring it pin 2 hot/pin 3 cold to the patchbay?  Pumping in the right, heavy signal in the left.  Very crazy sounding.  (it did this before the bay too, even when I just plugged some 1/4" TRS cables into it).

When I tried running this with the insert jacks on a Mackie it worked perfectly, although it would have been running unbalanced.

Should I be cutting a pin on the output of it going to the patchbay?  Something is def not right...

Thanks for any help.
Sig

 

[Siegfried Meier]

Ok, so I've discovered that if I unbalance the inputs, then the compressor seems to work properly - outputs are wired fully balanced.  The second I connect the negative pin 3 on the input, it goes all squirrly and crazy.  However, it's noisy now when I increase the input gain...

Anything else to suggest?

Thanks,
Sig

EDIT - got confirmation from Ashly that despite what's written in the manual, up until the mid 80's they had things wired pin 3 hot.  Reversed it on the patchbay and all weirdness disappeared.  For some reason, my logic was that pin reversal would simply put it out of phase, but perhaps because of the Z balancing or something else beyond my understanding it had adverse effects...

 

[scott2000]

Digging up an old thread as I have aquired on of these and was wanting to know about the transistor matching.

I asked someone at someone about replacing the 394 cans as mine are extremely corroded along with many other parts. I also asked about a possible ssm2120 or older mat02 or 12 replacement because I heard they may be better matched.....

The reply was....
“there’s nothing else in the world like those matched transistors, and they are no longer available, so if one actually does ever go bad, the unit is junk”. They are matched and thermally linked, they share a common diode junction, (more than just identical transistors)."

If I were to replace these out of necessity, what should I be looking for in regards to matching or are there any clues that will tell me they aren't matched??

or is this unit junk if these 394 are bad???? :-[

Hope this makes sense.....

I've uploaded the schematics in the docs as well...

Thanks!

 

[rackmonkey]

The reply was....
“there’s nothing else in the world like those matched transistors, and they are no longer available, so if one actually does ever go bad, the unit is junk”. They are matched and thermally linked, they share a common diode junction, (more than just identical transistors)."

There was another thread about the LM394 here just a few months back. PRR came across a possible direct sub and some others had luck ordering them. No idea what the results were, but it’s worth checking into. Found a link to the thread:

https://groupdiy.com/index.php?topic=37866.msg857962#msg857962

BT

 

[scott2000]

Thanks! I had actually read that and

I  ordered some 394 from member Bill Wilson earlier today. I am still curious if I  should be looking for anything in regards to the matching.

This statement regarding the SC-55 transistors....

"They are matched and thermally linked, they share a common diode junction, (more than just identical transistors)."

Has me confused as to whether or not I can just replace the old 394 with new 394....

Thanks again!

 

[analogguru]

This statement regarding the SC-55 transistors....

"They are already internally matched and thermally linked, they share a common diode junction, (more than just identical transistors)."

 

[scott2000]

Good to know...
Thanks!