any subjective comments regarding the new opamps?
thanks for your reply!
I managed to glean this from Jim Williams (audio upgrades) on the gearslutz forum -this was from a rambling and frequently unbelievable 35 page "discussion" on a forthcoming MalcomToft/PMI 'Trident' desk- its build quality, VFM etc- worth a look if you have several million hours to kill
"First thing you need to know is this: If you're recording quality acoustic instruments, you won't be happy with a TL07X, period. You are considering purchasing a console, to be honest, that is designed for rock music. As with most of the English stuff, the dual package TLO72 and maybe a few 5532 opamps will be found, just like back in 1976, thirty years ago. Nothing new under the hood except maybe a BB1N217 mic pre chip (commonly selected rather than design a real mic pre circuit in low cost consoles).
So, no single package opamps, these are all duals, to save pcb space and money. Next, you need to determine whether there are components needed to stabilize a wideband opamp are already mounted. These include local .1 uf psu bypass caps located next to each opamp. I doubt there are more than a couple for the entire input card as the TLO7X are forgiving to pcb parasitics. Next you need to determine whether there are feedback phase lead compensation caps on each stage. Earlier Toft/Oram designs left many of these out forcing the tech to install a zillion of them. Once these requirements are met, then the game of stabilizing opamps begins.
For stereo single opamp design summing amps, the LT1358 is the best contender as it's the only 25 mhz bandwidth opamp with 90 db of loop gain in the audio band that still remains stable after hanging 40 or so buss resistors on it. This chip is 30 db cleaner than the 5532 opamp. Take 30 db of dirt off an acoustic mix and you will hear it. It also is fast, a 600 v/us slew rate
vs 6 v/us slew for the 5532. That's 100 times faster and you can hear it. TL07X opamps are limited to 40 db open loop gain at 10k hz, so they are dirty. Put them in an EQ and boost 15 db and then you have only 25 db of loop gain left to correct distortion, not too good.
Then again, some folks like a certain amount and flavor of dirt with their music.
For EQ, line amps, etc. many devices could be auditioned. Try these:
LT1358
OPA2604
OPA2134
OPA2132
OP275
TLE2072
AD823
LM6172 etc.
With S08 to dip adapters you can play with either single opamps or surface mount only opamps. You can then try a
OPA627, OP42,
AD825, etc.
You will need a scope to check each stage as a flat line in the absense of signal is the goal. Precision devices like the LT1358 can usually have the electrolytic coupling caps removed as they have no offsets. That allows low end below 5 hz without phase shift."
I was wondering whether the LT1358 might be worth a look for the summing amps, as i might not need to replace the mic pre's (unless they're faulty) because i really only need line level mixing at the moment- I have a Trident 4t Celebration Channel Strip which is waaay more than i need (but superb!), and
a MOTU traveler with 4 decent Pre's already. Also, i think i've heard enough "dirty flavour" having previously owned
a Soundcraft 400b from the early 80's- time for a bit of soap methinks.
Referring to the above lengthy quote it seems he likes the LT1358, but there may be a P/S penalty i suspect. anyways, thanks for your reply and maybe this thread may be useful to other Tascam heads!
)!
but know there are better options out there!
