SMPro TB202 mods?

Here is the interior of my TB-202. I'm wanting to mod it in a couple ways, but want to know how easy it would be, or even worth it (it's a $250 unit).

First thing I noticed is that, though it's a two channel unit, there's only one tube, but a place on the board for a second. I've not yet graduated to building my own tube gear yet, so I don't know if adding that second tube would help much or be difficult to do.

Secondly, the eq is a 3-band fixed freq. (+/- 16dB @ 80Hz, 1.8kHz, 8kHz). How difficult would it be to make the mid freq. knob a sweep and the high freq. the gain for that sweep? I'd like to keep the low and select the other to be between like 120Hz-10kHz. Actually, any sweep range would be better, but whatever's reasonable.

...and now the money shots :grin: :

Anyone? Yes? No? Maybe?

A couple of comments...

We need a schematic for this. You can probably get one by emailing the co. It might match your unit but you'd better be prepared to check it against your unit.

I am guessing this is a "toob" ckt. ie, starved plate. Might be a better idea to bypass the toob anyway?

I see they are using the same arrangement for the LED and LDR as in the OC8. It can get knocked around in shipping. I like the simplicity and the sound of the OC8.

Lots of TL072 and TL074. Not bad chips but not so many options to replace the quads.

Peace!
Charlie

digging up an oldie... I have been considering upgrading the op amps in my TB202... unfortunatley SM Pro Audio has not been so quick to provide me a schematic... and by the looks of the pics previously posted mine appears to be a bit different.  Anyone with a suguestion for where I can get my hands on a schematic?

My Plan was to replace the tube with a telefunken NOS smooth plate 12AX7 as well as swittch out the TL084s.  I picked up a direct replacement TLE2074 as well as 2 other possabilities LME49740 and AD713.  However, I am abit hesitent to try out the LME49740 & AD713 until I can grab a schematic to help with input.

Is anyone framiliar with the SM Pro TB202, or the Op amps referenced who might have some input and guidance for a guy just begining to learn?

Thanks

Second "zombification" of this topic, i'm afraid :-\

For what it's worth, i got my hands on one of these units for real cheap the other week, and i reverse-engineered a large part of it (minus the EQ, 'cause i couldn't be bothered tracing out what's essentially a Baxandall tone control plus the 1.8k bell filter).

https://khronscave.blogspot.fi/search/label/TB202

PS: For whomever may be interested, i've just completed part four of the mods / upgrades on this thing - pretty much all i can (or at least all i'm willing) to do to it. Or with it, whatever ;D

The best mod one can do is:

1.) remove the tube from its socket
2.) place a jumper between each gate and cathode of the previously installed tube (the pcb is already prepared for it).

Explanation:
The whole "Tube"-sh*t is only dupery in this design.  The tube is used only as a cathode follower, therefore it can not contribute to the sound in any (positive) way - it does nothing, it does not amplify or anything else, it is simply an unnecessary buffer to give the unit some "warmth" - but only temperature-wise.

What if, say, one wanted to use it as a bass preamp? That's a big reason why i bothered with the whole channel-daisy-chain part of the mods