UCD180 questions

[gunwoo]

Hi Guys

I have a 6 channel UCD180HG power by 3 SMP180 built by my friend. I have been using it trouble free for some time, until recently I purchase a Behringer DCX2496 to do crossover work for my 3 way speaker.
As soon as plug it in, i got a really loud hum from my speaker, and I do mean really loud, I have to disconnect my mid and tweeter to prevent damage. I have talk to the Behringer support, and they replace with another unit, same problem...
My friend told me that the amp is floating ground, and I know that DCX2496 is grounded, is it the reason that it hum? Below is my connection diagram

USB Soundcard -> TRS/XLR (balance) -> DCX2496 -> XLR -> amp.

I have try disconnect everything leaving only DCX2496 -> XLR -> amp, the DCX is power off and disconnect from wall socket, but it still hum. I have try to find way to fix this problem no solution yet.

Any help is much appreciated, thanks in advance.

[Koifarm]

hey, i had a sort like setup.6 x UCD180st and 2 x conventienal powersupply and behringer DCX2496 for 3 years. No humm at all.

I think you need to starground the SMPS powersupply's.

And i did not used the opampstage of the hypexmodules, just bypass it.

Ronny

[rtd]

Originally Posted by maxlorenz

To whom it may be of interest:

UCD amps also benefit from the "charge transfer" power supply develloped by -ECdesigns- on his thread about Ultimate NOS DAC. Just adapt to needed voltages and current capability of active units.

Picasa Web Albums - mauricio

I did not implement the "capacitance multiplier" part of the circuit yet, because of space constraints.

This mod cleans up the sound quite a bit.
I used IRF5210 for the Pchannel Mosfet, IRF930 for the N channel (if I remember correctly) and a high current high V for the power Schottkies. C1 is a 10000uF Panasonic TSHA and C2 is a 10000 BHC big can capacitor, per side.

I hope you like it,
M

Hi maxlorenz,

I would be greatful if you can answer...

Did you use for one way a transformer with 4 secondary or only 2 ?
Did you join (-) for the positive side and (+) for negative to form GND before connecting to UCD GND
And may be stupid question, but is the rectifier & charge transfer to be directly connected to secondary or can the transformer be first tight to some bride rectifier and then to the charge transfer PSU ?

[maxlorenz]

Hi Rtd,

My Tx has dual secondaries and center tap is formed the usual way, as you commented (your Tx or the seller-s website surely shows a connection diagram). Only one ground is formed> the two CT circuits must combine as this is the non floating version. ECdesigns has shown on his ultimate DAC thread a floating charge transfer PS that could be also adapted for this amp, but that needs 4 secondaries...

The Tx can be connected directly to the CT circuit as the diagram shows, but I guess you can interpose some passive like rectifier diode or power resistor, should you want to reduce V or limit charging current...

Regards,
M

[rtd]

Hi Maxlorenz,

thx for answer. No doubt anymore on how to use the first version. the second floating version with four secondaries should be interesting but a little bit expensive.

Is The gap between classical ( Bridge + 10000uF per line) and that charge transfer PSU significant ?

[maxlorenz]

I think so.

[soundcheck]

Hi folks.

I'd like to try a 180 to drive my 98db/SPL speakers. Currently it is driven with a Tripath 2021B (12V battery supply).

I am planning for a gain setting of 9db (instead of 26db).
This way I could drive my DAC without severe digital volume control on the PC side.

As far as I've seen I need to change RG (=R10 on UCD180 according to application note) to accomplish this.

Can I go that low with the gain? Any problems I'd run into? What's the lowest possible gain - since I could also use a 2V differential output of the Zapfilter instead of my SE 1.6V passive output of my DAC?
What type of resistor should i use? Any advise how to handle the tricky SMD-R swap?


THX for your advise

Cheers

[Koifarm]

Do it like this:

Link: Hybrid Hypex UCD



Bypassing the pre/opamp leave's 4,5 x gain and you got less noise and better sound.

First i used to resitor change, then i tryed the opamp bypass. For me the last was the best and the easiest to perform.

Ronny

[soundcheck]

Hi Ronny.

That looks interesting. Though I have a UCD180HG V2 board which looks different.

Gain (Voltage?) of 4.5 might do at 0db=1.6V =7.2V ends up at 3.2W at my 16R/98db/W speakers.
Better choice would be to use my Zapfilter in differential mode. I'll see later how it works.

Anyhow - I need to figure out how to do the tweak on my modules.

Step one: I would like to leave the coupling caps in and just bypass the LM4562.


BTW: I have the funny feeling that it can't be RG=R10 on my module. R10 is sitting on the Regs. R11/R12 (should be R12/R13 I guess ) seems also to be wrong There must be an error in the Hypex application note.

[glt]

Remember reading in one of the Hypex technical papers that the PSRR or the amp (which is kind of "low" at 60 db) depends on the gain of the input stage.