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Thread: Tascam M512 / M520 Upgrades

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    Wink Tascam M512 / M520 Upgrades

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    Well, there are a few of us around these parts that have an M512 or M520. Many of you know I have an M520 that I'm going through and cleaning up.

    Many of you have likely read my thread in this forum asking How do you know its time to recap, of which the M520 became a subject. In it dementedchord said:

    as to what chips to use... looks like most of whats in there are 4556's tl072's and such... there are way better chips available but before i would recommend some specifics i'ld want to see an actuall schematic... board layouts and parts lists dont work for me... i need to see what that one is used for... ya dont want to just add say the fastest op-amp available if there's a chance that it's used as say a line driver where current handling is more important than speed... get my drift??? also if/when you change out these op-amps ya should consider adding extra decoupling caps at each opamp...easiest way is to jumper a cap between pins 4+8 on dual opamps...
    Many of you may have read some or all of my Tascam M520 Story over in the Analog Only Forum and I inquired therein about potential upgrades to the the M520. At that time Somnium7 said:

    Well I can attempt a recommendation or two if I had the schematics.
    Well, here are the schematics. They were scanned at 300dpi from copies. I think there is enough detail to read everything. Apologies in advance for some of the larger sheets which had to span 2 or more pages...the largest scanner bed I had available was 11" x 17". There is, however, sufficient overlap page-to-page for the multiple page diagrams.

    Again, with that M520 I have 8 spare input cards and a complete spare master and monitor section, so I've got stuff I can screw up on.

    Hoping for some solid advice on conservative upgrades that would likely improve the performance of the board...noise/distortion, etc. Not looking for a lumpy high-lift race cam here, just a good street cam...does that make sense?

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    I'm divided...

    I'm starting to delve into this a bit...gearing up to start recapping, at least some of the channel cards. The board seems noisier than I'd expect, especially if I route a channel or two to all 8 busses and then monitor those busses...its a roar. Somebody said somewhere that can be a side effect of aged caps.

    But I'm divided on where to post this stuff. I have my fairly sizeable thread "Tascam M520 Story..." over in the Analog Only forum...this is all part of that story, and yet the subject matter is very DIY forum-ish, so I dunno.

    Plus there are a number of M-520 related questions over in the aforementioned recapping thread. Just getting spread around a bit.

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    i suspect that the noise you're experiencing now is the agregate of all those decoupling caps being dried out... as to the chips maybe i'll get a chance to do a search for you later today... i ahvent done much repair work in the last few years and will need to find the current offerings...
    37.8% of all statistics are made up on the spot...

    hey give a guy some room... people are trying to evolve here... for crying out loud...

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    That would be great. I'll take whatever you have to offer suggestion-wise.

    Thanks also for the confirmation from your vanatagpoint about my suspicion reagarding the noise and the caps. Funny things, those electrolytic caps.

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    I keep hearing over the years about Burr-Brown opamps...what is the stink about them? Are they really that good/worth the price difference?

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    burr-brown chips are cool... the opa2134 would be good one for you to use... the thing is all the major manu's have cool op-amps available... when i started out doing tech work my boss for some reason got off on national chips and consequently i have had a tendency to stay with them... kinda like car brand loyalty i guess... so if i was gonna try to do this with just one type of chip i'ld probably use the LM6172 good frq response/slew rate handles enough current to be used as a line driver... if you're looking at linear technology's line the LT1358 looks like a winner as well...
    37.8% of all statistics are made up on the spot...

    hey give a guy some room... people are trying to evolve here... for crying out loud...

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    Nice thing about the 2134 is that it does not need any special bypassing to prevent oscillating like some of the faster chips might, plus it has good drive.

    In your M520 I would look at swapping out U1 if you use the onboard mic pres, U2 for line in and if you use phono U3.... U5,U6 and U7 can be swapped out. Don't worry about U4 as that it only drives the overload LED.



    --Ethan
    In Sunny Vancouver ..... (Washington)

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    dementedchord and Ethan, thanks for the replies and the suggestions. This is really exciting.

    when i started out doing tech work my boss for some reason got off on national chips and consequently i have had a tendency to stay with them... kinda like car brand loyalty i guess
    Or recording gear......I can't seem to get away from Tascam vintage gear...

    the thing is all the major manu's have cool op-amps available
    Right...okay. That's good perspective...I suppose cost may become a factor too as I start looking closer at this, and what I'm reading into your statement is that there are lots of options on the market that outperform the stock IC's spec'ed a quarter-century ago...yes?

    Nice thing about the 2134 is that it does not need any special bypassing to prevent oscillating like some of the faster chips might, plus it has good drive.
    You guys are nuts......How do you know that stuff??? I guess that's my way at the moment of paying my respects. Thanks for sharing that tidbit...that's really interesting. How does that work anyway? The answer is probably beyond me, but the fact is important, because adding bypass caps will involve time, expense and risk. If the opa2134 is in range cost-wise all things weighed that may be a very good option for me.

    In your M520 I would look at swapping out U1 if you use the onboard mic pres, U2 for line in and if you use phono U3
    So, two questions:

    • I can use the same chip for U1 ~ 7 (excluding 4) even though the stock chips vary (TL072's for U1, 5 & 6, NJM4556 for U2 & 7, and NJM2041 for U3)?
    • It looks to me like U2 is for the TAPE input/2 TRACK A/B inputs, and U3 is for the PHONO inputs on channels 3 & 4 and the LINE inputs on 5 ~ 20...Am I looking at that right?


    U5,U6 and U7 can be swapped out.
    Again, with the same chip that I select for U1 ~ 3? U5 ~ 7 is for the eq section...that's cool...this is COOL!

    So...hm...we're talking close to $200 for all the input cards...maybe I could just start with 8 or something...and then would I use the same chip for the buss amp and monitor amp PCB's

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    Quote Originally Posted by evm1024 View Post
    Nice thing about the 2134 is that it does not need any special bypassing to prevent oscillating like some of the faster chips might, plus it has good drive.--Ethan

    i personally cant verify this... if i were you i'ld probably put a .1mf cap from pin 4-8... or at the very least check it with a good oscilloscope after doing the work cause if it's oscillating you aint gonna hear it...
    37.8% of all statistics are made up on the spot...

    hey give a guy some room... people are trying to evolve here... for crying out loud...

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    Quote Originally Posted by dementedchord View Post
    i personally cant verify this... if i were you i'ld probably put a .1mf cap from pin 4-8... or at the very least check it with a good oscilloscope after doing the work cause if it's oscillating you aint gonna hear it...
    good advise in general. He does have a tek 465 he can check it out with. The opa2134 can be made to oscillate but it is not common. I was making more of a comment about how tricky keeping a 100 MHz opamp from oscillating is.

    I've never had an opa2134 oscillate in any of the Tasscam equipment that I've put them in. (Mostly 32/34/38 channel cards)

    --Ethan
    In Sunny Vancouver ..... (Washington)

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