UCD180 questions

Gotez · 2012-03-15 9:05 am

Hi,

Thanks, I will try as you suggested, although this might be difficult due to the small chassis. Do you not think it might be a ground loop somewhere?

avr300 · 2012-03-15 6:00 pm

troystg said:
Try twisting the pwr leads and removing them from under the SMPS pcb.

Not only the 240v wires but also the DC lines from the PSU to the 180.

Keep everything as far away from the SMPS as possible.

Twist the speaker wires.

You could try running it open as shown in picture 2.

Gotez · 2012-03-17 9:20 am

Running it open the amp is dead quiet. However, as soon as I move the lid closer to the bottom the hiss/screech/noise starts. So I suspect it is due to the amp being to close to the SMPS. Strange, as there is no contact or anything.

avr300 · 2012-03-17 5:58 pm

No, that's not strange. That SMPS apparently emits a lot of EMI. You could try shielding the SMPS, but I don't think it will help you.

You could try turning the SMPS 180 degrees, so that the switching transistors are as far away from the amp as possible.

Or, try asking Cristy - I see it's a connexelectronic.

glt · 2012-03-17 7:35 pm

Gotez said:
Running it open the amp is dead quiet. However, as soon as I move the lid closer to the bottom the hiss/screech/noise starts. So I suspect it is due to the amp being to close to the SMPS. Strange, as there is no contact or anything.

Seem you have enough space to put a metal plate to separate the smps from the amp. BTW, very nice and simple case work. I have ordered the same smps and waiting for them to arrive

Jan-Peter · 2012-03-18 8:22 am

Gotez said:
Running it open the amp is dead quiet. However, as soon as I move the lid closer to the bottom the hiss/screech/noise starts. So I suspect it is due to the amp being to close to the SMPS. Strange, as there is no contact or anything.

Gotez,

Did you checked using the SMSP400A180 already? The EMI of the SMPS400A180 is very low and don't need any extra shielding or filtering....

Jan-Peter

Gotez · 2012-03-18 9:23 am

Hi,

Thanks for all the reply's!!

@avr300: Unfortunatly it is not possible to turn it 180 degrees. The ucd module hangs slightly over the SMPS and this is the only configuration that will fit.

@glt: Do youmean placing a metal sheet between the UCD and the SMPS? Or covering the entire SMPS? I will try this, thank you.

@Jan-Peter: No,I have not tried the SMPS400A180. I am afraid that it is too high. The SMPS300R has a low spot just over the aux power supply that I use to hang the UCD over. Is it possible to borrow a SMPS to try?

Again thanks for all the help, I will try you'r suggestions and report back to you.

Gotez · 2012-03-18 11:32 am

Would it help if I connected the SMPS ground to the chassis? Nothing is connected tot the chassis now.

Jan-Peter · 2012-03-18 12:11 pm

Gotez said:
Hi,

Thanks for all the reply's!!

@avr300: Unfortunatly it is not possible to turn it 180 degrees. The ucd module hangs slightly over the SMPS and this is the only configuration that will fit.

@glt: Do youmean placing a metal sheet between the UCD and the SMPS? Or covering the entire SMPS? I will try this, thank you.

@Jan-Peter: No,I have not tried the SMPS400A180. I am afraid that it is too high. The SMPS300R has a low spot just over the aux power supply that I use to hang the UCD over. Is it possible to borrow a SMPS to try?

Again thanks for all the help, I will try you'r suggestions and report back to you.

Please contact sales(at)hypex(dot)nl for the SMPS400A180.

glt · 2012-03-18 3:39 pm

Gotez said:
Hi,

Thanks for all the reply's!!

@glt: Do youmean placing a metal sheet between the UCD and the SMPS? Or covering the entire SMPS? I will try this, thank you.

Again thanks for all the help, I will try you'r suggestions and report back to you.

I think just separating the two would be enough. Also I noticed you used plastic standoffs for the smps. You could try using metal standoffs. I don't think it would cure your hiss problem but any short to the case will protect you from shock.

Gotez · 2012-03-19 6:29 pm

I'm afraid I'm going to have to give up on this case. It is clearly to small. Whatever I tried the hiss will still be there when closing the case. I even made it worse bij lengthening the connection between the XLR and the amp. I am now getting a hum even with the case open. I will try to make new longer metal shafts so I can still use the wood ends.

Thanks for all the help!

mr_push_pull · 2012-03-19 7:04 pm

pin 1 problem?
Grounding and Shielding Audio Devices

Gotez · 2012-03-19 7:09 pm

Wow, that is an interesting read. Thank you.

I tried tying pin 1 to the chassis. It made no difference. Should I leave this connection or can I remove it?

mr_push_pull · 2012-03-19 7:14 pm

it definitely needs to be there but you're not doing it right by the looks of it, the details are in the link.
anyway it's obvious that the UCD is picking up noise from the SMPS and this (solving pin 1 problem) may not cure the issue. how was your previous case different?

Gotez · 2012-03-19 7:45 pm

Indeed the connection was not there in the pictures. I added it in the afterwards.

Previously I had a liniar PSU, the PSU and the UCD's were in different cases.

Yves Smolders · 2012-03-19 7:56 pm

Could it be that you have a short between the speaker plus & case?

mr_push_pull · 2012-03-19 8:09 pm

I see.
I'm using a SMPS too with my UCDs. not Hypex and not Connexelectronic but one bought used, seller said it was removed from a Denon receiver.
I'm not taking special precautions, the modules are close to the PS and wiring is not twisted and pretty loose. it's not that I don't care but I was too lazy to fix it. please don't tell anyone

but the single thing that I'm doing right is a *very* short connection from input to chassis.
I'd investigate along these lines.

audionootje · 2012-03-20 10:58 pm

Have you checked Connexelectronic - diyAudio forum?

markusA · 2012-10-18 9:49 am

Instead of creating a new thread and I know the answer is somewhere in this behemoth of a thread I ask it here anyway.

Is there anything in particular you should think about if you decide to remove the OP-amp at the input of a UCD180ST (most recent incarnation)? New input impedance, balance between +/- inputs or anything?

My memory is shot but I seem to recall something like 1k8 as the new input impedance and loosing 13dB (4,5x amplification)?
I'm just toying with an idea while I wait for some packages to arrive.

NicMac · 2012-10-18 10:19 am

From doing it some time ago I recall exactly what you listed. As you will also be bypassing the decoupling caps on the UCD modules beware that the device will become sensitive to DC offset on the input.
Works a charm DC-coupled with low output impedance I/V stages like the IVY III from TPA. This is the way I will be going for my future 8-channel amp as soon as I get my hands on 4 more 2nd-hand UCD180 modules sold of cheap by Ncore converts

UCD180 questions

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