Sony MXP3000 Mic Pre

[Siegfried Meier]

hey guys,

I'm wondering which of these transformers from Digikey would be better for 8 of the Sony MXP pres. The P/S I'm using is the one from the SSL9k pre, which is looking for 18v in. However, the amps aren't as high. Should I be worried about this? Or should I focus more on the proper voltage. Thanks.

TE62083-ND TRANSFRMR 15V 3.332A WITH WIRES
TE62074-ND TRANSFRMR 18V 1.944A WITH WIRES

Siegfried

 

[gltech]

Siegfried, I recommend the 15V (that's the RMS rating) version. This is my post from before:

Siegfried,

I just racked 8 of these along with 8 of the MXP EQs. I used this power supply:

http://www.beatbazar.com/guests/ssltech/kps-1/index.htm

I built four - each supply powers 4 pres or EQs. Works great. Here's a tip: When I tried to use a 20-0-20 (RMS) secondary trafo as specified, my rectified DC before regulation was at about +-27VDC. This caused the 7818 and 7918 to get HOT. I finally ended up using 15-0-15 (RMS) secondary trafos, which rectified out to about +-21VDC and let the regulators run nice and cool. Maybe the 20-0-20 input on the schemo means peak AC, not RMS. Also, I did have to adjust R1 to get the 48V correct. The units are sealed now, and I can't remember what I used for R1, but I'm pretty sure it was a value quite a bit higher (maybe 20K or so?). With a little experimentation, you wont have any problem with that - check the LM317 data.

The trafos I used are Digikey part # TE62083-ND. I used 2 for this project and ran 2 PS boards off of each.

My main point is that I tried a 20V trafo originally, but I later learned that the "20" was the AC RMS rating. That means the AC peaks are around 29V, and you pretty much get all that when it's rectified to DC and the caps are loaded. That meant +-29VDC running into my regulators, and they got HOT. I switched to the TE62083-ND, and I get about 20 rectified DC volts. This means that to get the desired + and - 18 outputs, the regualtors are only "limiting off" about 2V as opposed to 11V with the original trafo. I think Keith's schematic is meant for a 20-0-20 peak rated trafo.

Edit: Oh well, I just looked back at Keith's page and he does specify a 20V RMS transformer. Maybe he can shed some light. I just know what works best for me.

Glenn

 

[Siegfried Meier]

well that's what I was wondering too, and then the other 18V one came up from someone else I spoke with. Can anyone clarify which is best for these Sony pres?

Thanks,
Siegfried

 

[Siegfried Meier]

Sorry to keep rehashing this, but I'm still not entirely sure where specific connections go here. I'm using the SSL 9k P/S, and it has +18V/0V out, -18V/0V out and +48/0V out. Based on this:

2 "low" input
3 ground
4 "high" input
11 ground
12 +18V
13 -18V
14 output
15 +48V

I understand that pin 2, 3 and 4 are for the XLR input. +18V from the P/S goes to pin 12, -18V from the P/S goes to pin 13, +48V from the P/S goes to pin 15. What do I do with the three 0V from the P/S?? And it appears that I only have a single pin for output?? If it's unbalanced, I need a ground and a hot. I'm assuming that pin 14 is the hot, and pin 11 doubles up as a ground for both the in and out? Or...??

Thanks for any help anyone can give. Still a little confused here.
Siegfried

 

[cuelist]

[quote author="gltech"]I switched to the TE62083-ND, and I get about 20 rectified DC volts. This means that to get the desired + and - 18 outputs, the regualtors are only "limiting off" about 2V as opposed to 11V with the original trafo. [/quote]

A mere 2V is really cutting it too thin. You have just about no margin for line voltage fluctuations.

The "rule of thumb" is that for 18V DC, you use 18V AC secondary. Of course, the transformer should be the right size. If the load requires 30VA transformer and you put a transformer 100VA in there, you will get more than the nominal AC rating from the winding.

 

[Siegfried Meier]

Bump. Sorry, I was hoping to get an answer to get these things wired up correctly and I didn't want it getting lost.

Thanks,
Siegfried

 

[pucho812]

siegfried,
here is a pinout and yes they do share a ground as the pre would fit into a console. that also explains the unbalanced output.

http://www.johnhardyco.com/pdf/MPC3000.pdf

 

[Siegfried Meier]

Ok I think I'm understanding now. So the three 0V from the P/S board output, as well as the output ground of each Pre card get wired together. The input has its own ground, because it's electronically balanced in. Makes sense.

Thanks!
Siegfried

 

[Siegfried Meier]

Glenn,

I picked up that transformer you recommended but it didn't come with a wiring diagram. Do you know which leads come from the mains, and which ones will go into the SSL power supply?

Thanks,
Siegfried

 

[Siegfried Meier]

Never mind. Found it on their site:

http://www.amveco.com/Miniature_Low_Profile_Transformers_2.htm

Thanks,
Siegfried

 

[Siegfried Meier]

Hey guys,

So I've finally got around to wiring these up using Glenns great little PCB's - thanks for that BTW. However, all 8 of these pres exhibits some strange distortion, with dynamics or condensors, so I'm not sure what I've done wrong with my wiring. It's all very simple. Before the pre is connected, I get +-18 on the outs of the P/S, so I know that should be good. It can't be the pres, because they all do it. I have to crank the gain, and I can hear signal, but it's grossly distorted. Some impedance issue perhaps?

Please see the pics for the wiring. I've joined all the grounds from the P/S together in one. I trust that that is ok because all ground is shared.

I should also mention that I've Y'ed off the +18 to connect to the LED bulb, which is still seeing +18 after the fact, so voltages appear to be good.

Thanks,
Siegfried

 

[Siegfried Meier]

Ok, I don't understand what's happening, but when I connect the pre, the power bulb goes out. Something isn't getting enough voltage or current. Anyone?

Thanks,
Siegfried

 

[gltech]

Siegfried,

Let me make sure I'm clear. It looks like yellow is +18, brown is -18, red is +48, and whites are grounds.

Can you post a pic of the other side of the little PCB you're using for the pres, and a better one of the output connections on the supply? Also, I can't clearly see your input and output audio connections, both at the PCB and the jacks.

If the light goes out when you connect a pre, that would indicate a short somewhere between +18 and ground IMO.

Glenn

 

[Siegfried Meier]

Yes Glen, that colour coding is correct.

A short between ground and +18? I don't see how. The input is wired up with a tiny mogami mic cable, and the output is just from the PCB hot to Pin 2 out, and the ground and cold is wired together.

Thanks for your help.

 

[gltech]

That all looks just fine Sig. I don't know. Still thinking....

Have you tried disconnecting the LED?

Here's another thought. For some strange reason, when I did mine, if I tried to power it up without the pre connected, and then plug the PCB onto the pre while powered on, it wouldn't work right. I had to power off, then attach the PCB to the pre, then power on. :?: :?: :?:

 

[Siegfried Meier]

So it turns out that I had a faulty +18 voltage regulator. Swapped in a new one and all is good. Kind of.

1 of the pres doesn't give phantom power and the 2nd one is all distorted. The other 6 work perfectly. Any ideas where to look next?

Thanks,
Siegfried

 

[Siegfried Meier]

So I think the Phantom issue is easy enough to sort out. I think it's probably just the 22uF cap. However, the distortion issue is not so easy to sort out. I have a feeling the problem may be the large green IC. I saw the post from before about taking those apart. I'll check that out again, but first I need to determine whether that is indeed the problem. Any ideas?

Thanks,
Siegfried

 

[3nity]

Hi Siegfried.
As i see the outs are balanced? are you using xfrmrs??
Listen i'm in the process of racking two of these beauties and did power them and already did tried them but i did have to problems....

 

[Siegfried Meier]

No the outs are not balanced, I'm just using XLR's. What problems are you having?

Also, I've noticed that all these are working now that the big green IC's get a little warm. Is this normal??

Thanks,
Sig

 

[3nity]

sorry in my last post i was meant to say "i have no problems"
they're good.
i'm only waitinhg for the power supply to arrive.