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Modding the RME PAD

post #1 of 243
Thread Starter 
Just for the heck of it, I gave my RME PAD a look over to see what the parts in the analog ouput section are and if they could be replaced for better sound. I would appreciate the knowledge of anyone familiar with DIY electronics or modding sound equipment in general as to what the replaceability of the folling parts would be.

Right behind the output jack is a chip labelled IC24, the chip reads:


I have no idea what this chip does, any ideas?

Behind that is an opamp, which reads:


I presume this is the opanp that drives the output, if so what (better) opamps could be used to replace it? It appears to be surface-mounted, is that a problem?

Above that and to the right is the AD1852 DAC chip. Directly below it are two electrolyic caps, which are rather small, that ream: SMG, 5.0V, 2.2 μF. If these are the output caps, what could they be replaced with for a better sound? It seems they would be rather easy to take off and replace.
post #2 of 243
The AD1852 has balanced voltage outputs and can work with a transformer output stage. When I was experimenting with it, I liked this best. It's also a fairly easy mod to do, and it would bypass the RME's entire analog output stage. You would remove the coupling caps on the AD1852's balanced outputs (all four are very close to the AD1852 -- two electrolytics towards the top of the board, and two towards the bottom) and connect up two transformer where the coupling caps used to be (one per channel). Obviously you could reverse this if you didn't like it.

There are instructions for adding a transformer output stage to a DAC here (using Lundahl transformers):
There are similar instructions here, as a mod to the ART DI/O:
post #3 of 243
Thread Starter 
That sounds like a very interesting idea Wodgy, however, I don't know how practical that would be iniside a PC, since those trnasformers look pretty large. What differences in the sound did you find the transformer output stage to make in your experiments with this DAC chip?

Also, since, as you state, all 4 of the caps are output caps, would they all need to be replace for improved SQ (even though the PAD only has unbalanced outputs)?
post #4 of 243
The Lundahl and Jensen transformers are fairly small, but you pay more for that (much more in the case of the Jensens). I'd just go with the Edcors in a box mounted outside your computer. You'd have to use shielded wires from the board to the external box.

The transformers smooth out the high end, making it less gritty, but without taking away the essential sound of the AD1852. Also, the speed and dynamics are awesome -- Andreas Ciuffoli claims this is because there's no feedback; I'm not sure that's the reason but I do agree with him about the results.

If you just replace the output caps, you do need to replace all four. They're located on each of the op-amp's balanced outputs, before the op-amp on the RME that sums the balanced outputs to create one single-ended output.

If you're looking to make the RME sound warmer, I'd replace the caps with Elna Silmics. If you're looking to preserve a more neutral sound, the standard mod is Black Gate N/NX series caps.
post #5 of 243
Thread Starter 
If I were to try the black gates, would I want to use the 6.3V, with as much uF as possible, or am I wrong about this?

BTW The transformer trick would require an external PSU, no? One of those links you provided had them doing it with a 9V battery, if I understood correctly. If I wanted to do an in-computer setup, could I use the PC's power supply (12V) with some caps to help eliminate the noise?
post #6 of 243
You could use 6.3V or higher. I'd stick with the same capacitance (uF) as is already there, or maybe one value higher. Otherwise the caps will get too large physically for the board. I suspect that the RME folks use an appropriate amount of capacitance in the stock caps, and there's no reason to second-gues them (these are coupling caps, not power supply caps, so larger isn't necessarily better beyond a point).

The transformer mod doesn't require a power supply -- transformers are passive devices. The ART DI/O mod page I linked to might be a little confusing, because they do need a power supply for that project, and so they talk about two different types of transformers: the power supply transformer and the coupling transformers. You just need the latter. The Ciuffoli page I linked to might be easier to understand.
post #7 of 243
Thread Starter 
I see. After looking it over more, most of that seems a bit over my head, I would almost be better off just forgetting that and going with an external DAC.

I will try pursuing the blackgates mod, though, just since it seems quite doable, and could provide tangible results. What about replacing the opamp(s), would there be any merit to that? I know people like to replace the 5532 that comes on many soundcards, but I haven't read anything about the 4580 on this one.
post #8 of 243
Yeah, replacing the caps with Black Gates would probably be the best thing to do a first modding project, since it's relatively easy and the improvement will almost certainly be noticeable.

That op-amp is SMD (small), so it's not as easy to replace as a larger op-amp. If you decide to do it, you should look for someone handy with SMD rework (it's not a good beginners mod).
post #9 of 243
Thread Starter 
Speaking of which, do you know any good places to order Black Gates? I found "Handmade Electronics" though google.
post #10 of 243
Percy Audio and ReferenceAudioMods also sell them.
post #11 of 243
post #12 of 243
Thread Starter 
post #13 of 243
I've got some fine Cardas solder to donate if you are going to be brave. Any tools you'll need as well. Solder sucker, etc.

post #14 of 243
Thread Starter 
Well, I'll see about ordering those caps tomorrow, maybe we could make a day out of it, you bring your computer, and we can compare head-to-head to see just how much (if any) difference it makes. I should have my Zu Mobius AKG cable by this weekend as well
post #15 of 243
You'll need to give the Black Gates quite a lot of burn in before you do the comparison. When they're directly in the signal path, burn in makes a huge difference, and Black Gates take forever. But they're worth the wait.
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