R/E/P > Dan Lavry
Motu 24I/O Upgrade?
Magnet:
Hi,
I have a Motu 24I/O and i am thinking of have Matt at Black Lion Audio do his opamp mod on my unit. http://www.blacklionaudio.com/828.htm here is a quote from Matt on what he does with this box.
"It's a complete upgrade of the analog stages--I upgrade all the inputs
and outputs from the stock JRC4580 opamps to Analog Devices AD8066 FET
opamps. It's quite nice sounding--THD and noise are dropped, and transient response improved. The mids are smoother, and the high and
low end become much clearer, less muddled. There's also a slight
increase in headroom, about 6dB."
The price is approx $500 for the entire job. Since 24 great channels of conversion in and out would cost at least $10k i thought about having this mod done as well as adding an external clock like a big ben, mytek or Isochrone and if i choose a Mytek should i get one of there 2 channel converters and use that as my master clock for the motu box. Now if i do use a AtoD or DtoA as my master clock i will also have to add a motu 2408mk3 just for the digital in and out which i really need now anyway but i have been hesitating to buy a 2408mk3 just for spdif in and out.
So if i get this done and add a clock i'm talking about a $1500 investment instead of $10k or more.
What do you think, I can't afford 24 channels in and out of apogee etc and my clients won't pay a dollar more per hour even if i spend another 20 grand on converters anyway.
This seems like it may make the most sense if this mod and the clock can really step up the quality. Please help.
best
magnet
compasspnt:
Can you go anywhere and listen to the difference between the original and modded versions?
That would tell you a lot.
The analogue side of many converters is indeed a weak link in the chain.
The price seems fair.
The BL site looks pretty straightforward.
zmix:
I would like to play "devil's advocate" and ask:
What do you hope to improve with this upgrade?
Comparing the data sheets of the NJM4580 and the AD8066 is not particularly convincing to me. When dealing with A/D and D/A conversion, there are really important 'bread and butter' concerns like input offset voltage, input bias current, unity gain stability, CMMR and output current capability.
GBP is another concern, but since there is a really finite frequency range, less so in digital audio.
Here are some important differences which can drastically affect the sound of the conversion process:
The output of the AD8066 can only swing 9V p-p.
The NJM4580 can swing 27V p-p
Many D/A converters use a differential output circuit, so common mode performance can affect the result.
The maximum common mode input signal of the AD8066 is stated as -5v to +2.4v (7.4v asymmetrically).
The NJM4580 can accept -13.5 to +13.5 (27v symmetrically)
The maximum output current of the AD8066 is only 35ma.
The NJM4580 is 100ma.
Another design consideration is that the AD8066 is intended as a video amplifier. It operates from a single supply with a maximum voltage of 24 volts. The NJM4580 is designed for high performance audio and can operate on =/- 18V rails.
Back to my original question, will these other factors negatively affect the performance improvements you are imagining?
For the additional money, you could upgrade to the MOTU HD192 or the discontinued but superior sounding 1296, both of which use state of the art converters in them. The 24 i/o uses a lesser converter, and well, you cannot make a silk purse from a sow's ear.
-CZ
Magnet:
Hi Terry,
Thanks for your reply. I wish there was someone who could give me a good A/B Comparison or someone who can say anything about the results of this mod on their Motu unit. Matt at Black Lion seems busy doing these but i cannot find any posts anywhere from anyone who has had the mod done.
To Answer Zmix question; My goal would be to get a significant upgrade in all my ins and outs with the opamps mod and the addition of an external clock. If i can step up the quality for Approx $1500 and not have to spend $10k for 24 channels of I/O that would be great as that is about the most i can invest into my studio at this time. Over the past year i have added a perfectly restored Yamaha PM2000 console and a Studer A810 as well as a bunch of outboard. I really do need 24 in and out and this seemed like a way to step up the overall quality for a price i can afford. Can anyone suggest another way to step up without breaking the bank?
zmix:
Mr. Magnet,
Take a look over this forum and read Mr. Lavry's comments about external clocking. In addition, speak to the designers at MOTU about these mods, they are accessible people. They also know more about the layout and the internal environment in which the chips live and work.
The few details I posted about the 'upgraded' opamps are enough to convince me to keep the unit stock. And in addition to the above, do you want 180mHz capable amplifiers in a hostile RF infested box?
To put this into simple dollars and sense, you can spend around $3500 on a 24 i/o, mods, cabling and external clocking or spend $2400 on a pair of HD192 and have 24 channels of conversion of much higher quality than the 24 i/o is capable of even with the mods. In addition, the HD 192 has real metering with 1dB steps, AES I/O with SRC and are fitted with XLRs. These things are really much more important once you stop worrying and start working.
-CZ
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