Modding Echo MIA.. anyone?

[Svart]

I just received my Echo MIA in the post today and was checking out the circuitry.. of course I got the box open and immediately started looking for something to mod... :green:

Well, it has a few electrolytic coupling caps.. 47uf.. It also uses JRC NJM2068 opamp.

Comparing the 2068 to the 5532 (pin compatable), the 5532 shows better slew rate as well as better numbers at other tests like unity gain bandwidth, etc.

so my question is.. do I change the 2068 to something better and give it a try? The current consumption of the 5532 is twice that of the 2608 however I have noticed a to-220 Vreg on the pcb, as well as another smaller SMD vreg but have not traced out where the opamps source their power from yet.

should i try something from Burr-Brown? My Tascam mx-2424 uses the exact same AKM converter as the one on the MIA but uses OPA134 opamps..

so in a nutshell, I would like to change the coupling caps and the Input Op-amps. (output opamps can stay for now) any suggestions for the products to try? I would like something with a clean sound. any powering/decoupling issues I will deal with once I get an idea what i need to power!

thanks!

:guinness:

 

[Svart]

thanks Butta, I'll get some of the opa2604s and give them a try along with the 5532s to see which one i like better. Yep they are SMD but that doesn't bother me much..

as for the opa134 being "soft".. do you mean midrange is low?

thanks again!

:guinness:

 

[Svart]

thanks again butta, you just saved me days of booting, playing, shutting down, resoldering, booting, playing, shutting down, resoldering, booting..etc... :green:

I'd like to have a crystal clear and accurate soundcard and leave the tube sound to my tubes.. :thumb:

 

[Svart]

ok got some more probing done while i wait for my "samples" to show up. the coupling caps are between the input stage opamp and some kind of buffer op amp. these are 47uf16v 'lytics. would there be any benefit to changing these to something like the panasonic FC? I also thought about gain/offset problems after noticing a large network of feedback resistors/caps. I would like an opinion on just "trying" a different opamp but leaving the same gain networks.. has anyone done this and received decent results or should i just bust out the calc and textbooks for this one?

also, tracing the inputs to their opamp inputs I came across something I see as maybe strange?? lets take the second input for example. it is balanced and +4 for those interested.. the Tip traces through a 10k and goes to input B-. the Ring goes through the 10k and to input A-. i would think that one should go to lets say, A- and the other for A+ (differential inputs?) The other input jack traces the same only going to a different op amp, tip to input A- and the ring going to B-.... one of the outputs from each opamp go to the feedback network, the other goes to the 'lytic coupler and to another opamp and out to the A/D.

that was a simplified version.. maybe if i get a few hours I'll draw it up in cad.. but that's unlikely with my schedule.. maybe someone has this schematic?

I haven't traced the +- power to the opamps fully but the power is NOT derived from the pcb anywhere.. I believe it to be powered from the +-5v from the mother board..? I'll have to trace this out with more time.


:guinness:

 

[Svart]

ok, +-opamp power is from the mother board, dunno if it's 12v or 5 v though. I hope it's +-12 at least..

started on a schematic for what i have traced out too. got my samples from TI today also.

http://pg.photos.yahoo.com/ph/noireclipse/detail?.dir=/ac1a&.dnm=984f.jpg&.src=ph


i think it might be hard to see, maybe you can save the picture for the big view?

 

[Svart]

echo just dissed me and denied me schematics for my card.. :sad:

oh well back to hacking the circuit.

 

[Svart]

sorry butta, I hadn't finished the schematic when i posted that pic. the non inverting inputs on that 3rd opamp are actually hooked up to a few caps in another sort of feedback network but i ran out of time to put those in my schematic. I should be able to finish it tommorrow hopefully. I guess I just expected to see something like the Tip going to the non-inv input and the ring going to the inv input (first thing that comes to mind is the GSSL input stage..)


Not sure which mia it is.. it's the discontinued/without the midi i/o.

do you think I'll have problems with the established feedback networks using FET input opamps(opa2604) instead of BJT input opamps(njm2068)?

I'd love to just throw those in there and have it work but i feel that's just TOO easy... :?:


thanks again!

 

[Svart]

any ideas anyone?

bump..

 

[Svart]

bumpity bump bump! :guinness:

 

[Svart]

thanks Butta, I'll change them out tommorrow. I have some good panasonic caps to swap in too. I'll let you know how it works out.

:green:

PS: what card were you working on.. i think you kept it a secret didn't you? :thumb:

 

[12afael]

you are inspiring me to mod my layla echo... just I have a lot of projects on the table.

jcm800 almost finished
engl preamp almost finished
midi E-drum almost finished
mic pre on design stage
moog taurus project on mind.
and a lot of guitar pedals.

maybe some day ...

I will wait to know how your mods goes

12afael

 

[Svart]

ok got the card in over the weekend, got it running.. and amazing! it's a clear difference between the old card and the new one. now just for the fun of it, I put the old chips n' caps back on.. i do hear a difference between the original setup and the BB opamps and better caps. it's definately clearer and more rounded sound.

i would recommend this mod and sound card to anyone looking for simple in/out. total cost me around 100$usd

:guinness: thanks butta!

PS: now my soundforge program won't work with the sound card.. however all my other apps work fine.. can't find any info on echo's site nor soundforge's site, or by searching the internet..

 

[Svart]

yeah it seems to be a software issue, not a hardware one. other programs run great with no problems. I AM using echo's beta drivers.. maybe i should try the older drivers first?

:thumb: