82E10 Dynamics card Rev9 vs Rev12

[gertius]

Hi guys,
I have a racked SSL channel here, with a spare dynamics card, so I have 2 dynamics cards in total.
One is Rev9 and the other Rev12. They have the same VCA already, but sound remarkably different, especially the gate, which seems to be punchier and tighter in the Rev9.
I really found out today, when I compared them to the new Waves EV2, and I was a bit surprised how different they were.
See also here for some samples: https://gearspace.com/board/showpost.php?p=15742805&postcount=354

Is this because of ageing components (I cannot really imagine that, because of how big the difference is), or is the schematic different?

I only have the schematics for the Rev12 and also a very early Rev4 (which still has the old VCA). The Rev4 shows differences in 3-4 places of the gate section.

My question is, can anybody comment about these differences (is there a "definitive" revision, or one that was used more widespread, or more sought after? Are people in general aware of these differences?), and also does anybody have schematics from the Rev9?

[amillar]

Hi,

I'm guessing rev 9 may be before the "over  easy" diodes D14 and D19 were added to the compressor? There were also several other changes around the timing capacitors over the early years, and other diodes were added in. But I wouldn't like to guess what was added in when...sadly all the early history of the changes was lost when the new CAD circuit diagrams were drawn in the mid 80s

"Rev 12" is certainly what the vast majority of SSL channels were fitted with, I think the final circuit changes before this were maybe made around '83 ('84 at the latest)? Whether it sounds "better" or "worse" will probably always depend on the individual and what you're using it for.

And of course the state of the capacitors...for most things I'm slightly wary of recommending re-capping as a magical fix, but in this cases for the response to be as designed the timing capacitors C5, C6 and C9 do need to be in decent condition. But again a particular dried out cap might give just the sound you like!

That all said, I did fit a switch to the 9k to allow switching between the sound of an early 10 card and a later one because people were asking for the response of the earlier card (it was a right pain to design that switch not my most elegant piece of design). If you could find what position that was usually set to then that might give you a clue as to which is generally preferred!

Cheers,

Andy

[gertius]

Hi Andy,
thank you very much your reply!

I just checked the rev 9 card visually, and the over easy diodes D14 and D19 are already there.
Good to know that the rev 12 was on the vast majority of boards, that gives me sort of a reference.
I could always delve deeper into this by comparing the circuit on the board with the rev 4 schematic, maybe someday.

Was the 9k switch you talk about the compressor "peak" switch, or something else, maybe under the hood?

Cheers,
Christian

[amillar]

Yes, it was the compressor "peak" switch, I couldn't remember what we (me and Chris Jenkins who came up with the idea) called it!
Cheers,
Andy

[gertius]

In the meantime I had the opportunity to compare two other Rev 9 cards to my Rev 12 card and they all three were virtually identical.

I now think my Rev 9 card from my initial post has a problem and thus sounds different from the other three cards.