Akai MPC 1000 - modding analog stages?

Hi All,

I have an Akai MPC 1000 that I'm considering having modded. The only problem is that I have no experience soldering surface mount components. So the purpose of this thread is two-fold. One, to discuss the mod itself, and two to hopefully find a tech in the Washington DC area to actually do the work (for pay of course).

Anyhow the 1000 has balanced inputs and unbalanced outputs, using surface mount NJM5532s, through-hole 22uf caps, and surface mount 1k, 680 and 330 ohm resistors in the signal path. Seems to be a pretty simple job conceptually (basically just drop in superior replacements), but again, my shortcoming is soldering SMT components.

Now, the board is kind of packed, so for space purposes, I'm probably going to have to stick with the same value caps. Not sure if there will be room for bypass caps, but possibly they could go on the other side of the board. Would it be a waste of my time to consider replacing the resistors? Its a line level circuit of course, and from what I gather, those are not as sensitive to cheap resistors as microphone level circuits. Is that a correct assumption?

Now, for the op amps. Given that this is a pretty standard circuit, what are the best drop-in 5532 replacements that won't give any issues? There are a total of ten of them. Will this have an impact on the power supply? Will I have to look into modding that as well? Given that I don't have much experience comparing various 'flavors' of opamp, I'm probably not going to choose one model over another for those reasons, although I've used burr browns (2134) in a couple of mod jobs and was very happy with the results. I figure just about anything upmarket of the 5532s will be an improvement...

Please forgive the stupid questions, I'm somewhere in between newbie and just barely intermediate, so bear with me. I have schematics and a pic of the board itself that I found on the net if that will help.

Discuss! And thanks in advance.

Mark

Are the converters in there really going to take advantage of better analog?

???

The converter is an AD1839. Better analog can't hurt right?

105dB DAC's may do better.

have you tried running it through a digital output into a better DAC, before you start meddling with the analog stages?

More often than not, when I mod things, hoping to make it sound better, I end up making things worse.

R

While I think it can be great to experiment and see what can make a difference in sound, I think in this case the returns would be minuscule, especially given the risks of mucking about with smd components. Replacing caps, and resistors with the same values seems unlikely to get you anywhere and, in my opinion, replacing 5532s is probably not going to result in changes you can hear. But you never know for sure until you try - it's just not something I would spend time or money to find out.

Best, Ben

Rochey said:

105dB DAC's may do better.

have you tried running it through a digital output into a better DAC, before you start meddling with the analog stages?

More often than not, when I mod things, hoping to make it sound better, I end up making things worse.

R

Click to expand...

Well the AD is pretty much god awful (and that's really the problem) so I normally run signals in digitally (either from my BLA modded 828mkII or from my SSL Alpha Channel) or load samples from the computer via USB, but most of the time I use the MPC's DA because they aren't horrible (they pale in comparison to my 828 though).

Now what I really want to do is get a few more pieces of mid/high end analog outboard gear (filters, eq's, compressors, multi fx etc.) and use them to process my MPC's 4 aux outs outs, and then run them back into the MPC analog ins for resampling. If you run a sample or signal 3-4 times through the MPC's AD and/or DA (which would be my intended workflow with the outboard) you come out with really limp sounding samples, even if you're using very high end outboard...

Its just a PITA having to incorporate other devices to avoid the MPC's converters. Also, its impractical to use both SPDIF I/Os for resampling like that because the SPDIF copies the main output signal, which obviously includes the monitored input signal. You can disable input thru monitoring to avoid that feedback loop, but then you can't hear the 'effect' of the external effect (unless you simultaneously route its output elsewhere)... Its just a royal PITA not wanting to pass signals thru the MPC converters.

plumsolly said:

While I think it can be great to experiment and see what can make a difference in sound, I think in this case the returns would be minuscule, especially given the risks of mucking about with smd components. Replacing caps, and resistors with the same values seems unlikely to get you anywhere and, in my opinion, replacing 5532s is probably not going to result in changes you can hear. But you never know for sure until you try - it's just not something I would spend time or money to find out.

Best, Ben

Click to expand...

Thanks Ben, yeah I hear you about the cost/benefit aspect, but I really feel like I've spent enough time, energy, and money avoiding the MPC's converters that even a modest improvement would be worth a couple hundred bucks to me.

I love almost everything else about the box, (except the digital filters and effects - hence my desire for more outboard), and I know it like the back of my hand, so ditching it for some other piece of gear is not really an option.

As for the sound of the box, I almost feel like I can hear the characteristic sound of cheap op amps and caps as well as a bad clock (which BTW improves when its externally clocked - which may also explain my relatively favorable impression of the DA). In fact, it sounds a lot like my 828 did before I got it modded... Interestingly, its almost as if bad op amps, caps and converters is the hip hop drum sound - and that's the one and only reason for any trepidation on my part.

And again, I'm not at all experienced in soldering SMT, so I'm gonna be outsourcing this job. I would go ahead and do the caps myself, except that they need to come out in order to get to the op amps - so if I go ahead and do them, then the tech would need to take them out again, so my preference is to have it all done at once.

jonesy said:

As for the sound of the box, I almost feel like I can hear the characteristic sound of cheap op amps and caps as well as a bad clock (which BTW improves when its externally clocked - which may also explain my relatively favorable impression of the DA). In fact, it sounds a lot like my 828 did before I got it modded... Interestingly, its almost as if bad op amps, caps and converters is the hip hop drum sound - and that's the one and only reason for any trepidation on my part.

Click to expand...

It would take a really bad design of a system to sound better with an external word clock.

I don't know the MPC directly, but I do know that virtually all digital audio products have a crystal oscillator at their heart. When you run a system from a word clock it has to PLL (phase lock loop -- which is essentially a clock multiplier) up to the same speed as the original oscillator.

Running directly from an oscillator has way less error than a PLL.


Why don't you mod it to have an S/PDIF output? That way, you could plug it directly into your soundcard, and not worry about the "audio quality".

/R

It already has spdif I/O. As described above I want to use the analog I/O with outboard analog gear for resampling.

Don't want to get into a debate about clocking but I've heard other devices improved by superior external clocks.

For sound production use, as the MPC1000 has midi outputs, maybe it would be better to trigger external sampler with better audio quality through MIDI, then for live use of the MPC1000, you just record the final sounds in the PC and transfer them to the MPC via USB ?

Thanks but I'm actually just looking to discuss the mod I'm considering. Of course I could work around the converters, but without going too deep into my reasoning, spending some time and energy and a couple hundred bucks is well worth potentially not having to work around them. 


Has anyone around here performed this type of mod to a synth or sampler? I mean conceptually how is it any different from modding the buffers on compressors, eq's, souncards, converters or any other gear with crappy components in it's input or output stages?

Good luck, if you get good results, please let us know.