Ross Martin Repair & Mod Thread

I had a friend sent me his Super Beast II for listening to and tweaking. I finally listened to it today. Dang, they sound really nice Stock.

I will of course do some tweaks to it and see if it can go to another level.

I don't have the II. I have the I.

Duude! Let me know how this goes. I've got a MKII sitting here and I would be very interested to see what you could do. You switching out the op amps? You reconfiguring the power supply situation? I read the post above about the power being a weak link, and Jim Williams posted something similar about his MKII mod.

I heard Dan's mods in a BLIND mono L vs R configuration, they both sounded really great, but one was clearly better no doubt, I had been working all day building structures haha, so I gave Dan the disclaimer that "my ears were end of a long day... fried", and proceeded to check them out, here was the text I sent Dan in response to what I heard....

I picked the modded side easily again upon listening the next morning, again a no doubter, and the stock side sounds great to begin with! But the effortlessness, solidity, depth and clarity of image are just stunning on his super modded version.

guys like svart , dandeurloo , jimwilliams are far better suited to make suggestions than I, but i'd say try a few things, first switch out every external cable you have, from tos, to xlrs, to power cords, then try taking power from a known separate circuit from the one you've been using, then think about power conditioning..., just a few ideas, sorry for your frustration bud, i know that shit can drive ya nutz!!

edit; after listening to the sample, those seem to be harmonics of the lower hum that's there, my money is on a dirty power problem?

THANK YOU!!!

It looks like this is a defective design after all. Ross kept telling me "no offense but sounds like you've got a wiring problem."

I have combed through this thing and have found that the noise stops when the 24.576mhz clock signal on the dix9211 is stopped. I replaced the crystal with a dedicated CMOS clock osciallator - and it still infects the output with noise when the dix9211 is receiving the 24.576mhz signal. The noise is also slightly audible even when the oscillator is turned on but the output is not fed to the dix9211 - like the oscillator is infecting the ground or voltage rail.

Tony, I have already asked all three of those guys for help haha. No luck so far. Now posting here because I'm out of ideas.

Svart pointed out to me that the clock signal required for the dix9211 is 24.576mhz, and 48khz, 64khz, and 96khz happen to be multiples of 24.576mhz - so yes these are undoubtedly harmonics. (44.1khz and 88.2khz are not multiples of 24.576mhz - therefore no noise). Yes 60hz goes into all of these as well, but that hum was killed off with the toroidal psupply Jim recommended in the other thread.

Listening to the clip Dexter sent me, it's more square in tonality than sine, IMHO. I believe it might be a downmixed clock or something.

We need to figure out if the transceiver IC is being utilized in a hardware or software mode. Since the problems happen on multiples of 48K, my bet is that something is not being set in software that needs to be set.. Especially since disabling the XTAL seems to kill the noise (but will likely lead to a slow decay of lock on the incoming signal as the PLL/VCO starts to drift).

I'd like to up grade my 8 Channel unit with the proper power transformer, and possibly indulge in a few other tweaks. Mind if I jump onto this thread?

For the the power tranny, would this one from Hairball Audio work? www.hairballaudio.com/catalog/parts-store/power-transformers/dual-primary-toroidal-2x25v-30va-power-transformer

Thanks in advance.

dexter.  can you email me hi res photos of the inside of your box?  I just fixed a clients noisy headphone amp in his box.  I am curious if they are the same issue.

I know it is a different unit, but I almost ONLY use my DAC at 48K. I've never once had a clocking or noise issue. Of course, I'm always syncing off of AES sync, and not USB or coax.

I do seem to be having either an impedance issue or a ground issue with the DAC integrated into my patchbay. When I send a 1K tone out of my RMA Dac and record it back into Pro Tools, on certain gear I get what could be described as a "hair' of distortion, or I hear what seems like an octave above the 1K tone in slight distortion. Any piece of gear I have where the unit has a wall wart, or has a switching power supply it makes this sound. It also makes this sound when I simply pull the cables out of the gear, and loop them together when the cabling stretches between two bays. The way my two ADC TT patch bays are set up are half normal with DAC out on top, comps and EQ in on the bottom of the top patch bay, then outputs of said comps on top of the bottom bay, with Metric Halo and Manley mixer inputs on the bottom. Like I said, with 80% of my gear I have no issues, but on my Overstayer comps (which have a wall wart), or my Lindell audio 500 series enclosures (switching power supply), I do get the noise. In these same connections when using my Metric Halo boxes I do not have this issue, it is with the RMA Dac, and also with my Sound devices portable mixer (which runs off battery).

I'm stumped as to what the issue is. I am able to go out of the DAC outputs on the top patch bay and into my monitor controller on the bottom patch bay without any issue as well. Again, my monitor controller uses a power supply with a three prong plug. Seems like there is some issue that has to deal with either ground or impedance of the half normalled patch bay connections, though when I stick a cable into any leads that would break the connection the sound does not change.

Truly an enigma. If anyone has any ideas I'b be happy to hear them. I hope this does not count as a thread hijacking. I'm still hoping to mod/repair my Ross Martin DAC, which is the title of the thread.

Cool, welcome to the forum, i'm guessing you have the AES 8? I've got 4 of the 8 channel AES units, is this what you have? One of them is going to Dan Deurloo for some proto mods, there will definitely be a major PSU upgrade, these sound really good in stock form, I expect amazing things when they're dialed in.

Also, from your description, and everyone else's problems, i'm guessing most are having grounding issues, if not, i'm guessing a serious PSU upgrade would be the difference.