Topic: PMD 660 DIY Modifications

[Bravin Neff]

Hello everyone.

Does anybody know of schematics for Marantz modifications (I have a PMD 660) so that you can clean up the pres and/or line signals yourself?  Unfortunately I didn't buy mine from Oade, and Oade won't do the mods on equipment they didn't sell.

Regards,
Bravin Neff

[bdasilva]

sold mine on ebay at a loss (cuz it sucked) I was rid of it and now I can buy one from Doug... Holding off to see what the Microtracker has in store. Sorry I can't answer your question. Its a bear to reverse engineer gear.

[Bravin Neff]

Yeah, I'm kinda leaning the same way now, which is a shame... because feature wise, the PMD660 is awesome.  Too bad it doesn't hold up well on the electrical and audio level.  Anybody else?  Has anyone managed to figure out how to modify their Marantz into useable form?

Regards,
Bravin Neff

[dklein]

I may be oversimplifying but generally the fixed gain levels of an opamp based pre are set with a single resistor value.  Find the opamp, lookup the datasheet on the interweb to determine which pins to trace back to the gain setting resistor.  The pin outs are mostly standardized - you really just need to know if it's a mono or dual opamp.  Crunch a few numbers and change that resistor.  That can address the gain levels.  Of course you can always start playing with different opamps.

As far as cleaning up the path, swap film caps in place of electrolytics and using tighter tolerance film resistors is the usual procedure.  It often becomes a real estate game as the film caps are bigger.  Hope that's helpful!

[Bravin Neff]

That's great info and very helpful.  Thank you very much!

Regards,
Bravin Neff

[Nick's Picks]

I know that Dougs modifications render he internal mic and line inputs usless...probably a space thing to get good parts on the board, he had to kill those.
line in would have been nice to keep...but for mic taping...fuck em'.

[cwfen]

I think, also, with Doug's modifications, the Mic In can support a line level signal without clipping.  At least that is the case for the Advanced Concert Mod, from what I remember...

[Nick's Picks]

yea...i think you might be correct.  the minijack line in is dead, that much i know

[bdasilva]

The reason it's done that way is because it was all soft switched (menu driven) selections to  route those signals into the preamps. Those "switching"  ICs are noise Doug chose to do away with.

[Nick's Picks]

sounds good to me.

you know..this thing (acm from Doug) sounds so damn good...i'm tempted to bypass 24bit recording in favor of it.  Its the best sounding thing ive heard in a long time....especialy for $749. 
do I really need to spend nearly 2x this for 24/44.1 improvements?
my stereo says yes...but now it cant make up its mind. 

if anyone is intersted, listen to that ratdog recording I just did last weekend.  check out the sound of the venue..the 3d presentation.  its quite slick.
the total lack of coloration is awesome.  its almost v3 like, only a little different.  maybe not as detailed.  but fuckin-a-good.

[krebsy]

Along the lines of a T+ UA-5?   

[Nick's Picks]

yes...along those lines for sure.

[Nick's Picks]

I think i'll be reviewing that as well.
but its 15v DC requirement....that sucks