Please see my previous "rechipping" themed threads for the pertinent history.
Part 3
I've completed the process of replacing all the Linear Technologies 1358 "high
speed" opamps installed by Audio Upgrades in my
never-gonna-call-it-a-Tascam-
M3500-again-now-I-call-it-"custom" console with
various Burr Brown chips. As stated in previous posts, after becoming
thoroughly disenchanted with the LT1358s I began experimenting with
alternatives. I've now replaced all the input strips (5 dual opamps each
including the mic pre) with Burr Brown OPA2604APs. These cost $1.80 each bought
in quantities of 100 or more (I used 160). As stated previously these chips
have a great sound and do appear to be fully compatible and functional under
the circumstances, showing none of the oscillation tendencies I was warned
about (at least as far as my ears can tell - I haven't used a 'scope). The
program busses and last-stage outs to 2 buss were fitted with OPA2132Ps ($6.91
apiece). The first-stage 2 buss and control room outs were fitted with 2604s.
Some thoughts:
Like fucking *wow*! This board is slammin'! Seriously, the console sounds just
amazing now. The 2604s give the heart of the console (the input section) a
really satisfying combination of warmth, clarity and depth that is entirely
unlike the original stock sound or the original Audio Upgrades sound. I'm able
to get the kind of kicking low end and depth that was so sorely absent with the
1358s and the clarity and imaging that was unobtainable with the stock chips.
While my impressions must be taken as preliminary (I just completed the
installation yesterday) I feel quite confident that this puppy will definitely
sit up and bark when papa says bark <g>. One thing I'm noticing to my
unexpected delight is the tendency of the 2604s to react a bit like tubes when
overdriven. In other words, when intentionally turning up gain trims or
overfeeding the inputs via an outboard limiter or whatever, the chips don't go
all "hashy" and transistory as they distort. Rather, they quite calmly begin to
"fold in" the top end and seem to compress the mids in a surprisingly smooth
way. I've found this to be a very useful crayon in my coloring box as I've
experimented with some fairly gritty electric guitar sounds. Crank it up into
overload a bit and the grit smooths right out. Really cool. I must say that in
regard to this, Tascam did a nice thing by offering a metering switch that will
show post-eq level on all channels. This enables me to view exactly how hard
I'm hitting the channel and is a feature I've always used to manage headroom
issues. I wish all consoles showed this - most just show tape in.
I arrived at the decision to use the BB2132Ps in the busses and the 2 buss outs
because it seemed that too many stages of 2604s were clouding things up a bit.
The 2132s are less tubby in the lower middle and have a more extended and
really solid low end, and although they are a bit shallower sounding than the
2604s the combination seems to work very well.
While my test mixes over the last day or so with the fully rechipped console
sounds like you're enjoying your 3500, anywayz