UCD180 questions

[stef1777]

Don't do 1.

UcD feedback is optimal when the - terminals of the speaker outputs are not connected to a common ground. Using common ground will affect quality!

This has come up at the UcD400 thread also, but for another reason - a DC protection that took all speaker grounds together.

Don't go cheap on a few inches of speaker cable when running these wonderful modules!

You're right and in fact my problem is here. What should I do when using a CC protection circuit (with common ground for the five channels)?

Stephane

In my drawing, speaker ground are not connected yet.

 

[wildbox]

Hi guys, nice to present worlds first automotive UcD.

An externally hosted image should be here but it was not working when we last tested it.

Powersupply by IVX ( http://amploid.narod.ru )

Caps: nippon chemi_con 17000uFx90V (4pcs)
(OEM for ML)

Currently running with ScanSpeak 8545K00 (10 ltrs sealed) +
Eton ER-4 (ribbon) (first order both so far).

Regards from Moscow. 😉

 

[SEIJI]

/ON ????????

Hi All,

May I know what's the (/ON) on the UCD180 input pin for? should I connect this /ON pin to power supply ground to un-mute the amplifier or should I leave it open for proper amplifier operation?

Any kind advise would be great............

Thanks............

 

[lucpes]

Re: /ON ????????

Hi All,

May I know what's the (/ON) on the UCD180 input pin for? should I connect this /ON pin to power supply ground to un-mute the amplifier or should I leave it open for proper amplifier operation?

Any kind advise would be great............

Thanks............

Yes, connect to supply ground for normal operation. Eg - you may use a switch on the case to mute the amp.

 

[patriz]

silent-off problem

I'm having problem with the small circuit for silent turn off.
I'm using the below circuit with few changes 1N4148 diode and 2N2222 bjt . In a board ,it is travelling to Hypex, I had intermitting signal output , then once turned off and then on it went completly silent with 9,7Vdc at the output and no signal . I completly semiconductors in the silent circuit seem to be ok and circuit cecked several times.
What could be the problem?
Giorgio

 

[patriz]

The JP's mute circuit.

And the PCB is here: http://audio.cyberkata.org/UcD180/UCD_PSU.pdf

T1 = 2N2222A
R1 = 100K
C1 = 220 nF

Ok this is the circuit
Giorgio

 

[stef1777]

The circuit should work. I'm using it.

Check your ground connection.

 

[patriz]

the circuit is in the same board with the diode rectifier, ground circuit is connected to central transformer wire and than to chassis.
Giorgio

 

[stef1777]

First to do.

Bypass the circuit and check the module with a direct mute's ground connexion.

 

[patriz]

Done it, 8R power resistor as load and no signal at the output except 9,7Vdc regardless of the 33k resistor betwen -V and output I added to avoid the Vdc at the output with no load.

 

[Pasi P]

About transformer size.
I have dual mono UCD180 with 180VA/30VAC transformer/channel.
If i make 4ch amp, are these transformers enough?

 

[ackcheng]

Dear Stef1777,

Using the circuit from Jan-Peter but using 2N222A instead of BC846, I got 7mV with AC and 65mV with no AC input. Is these value good enough?

 

[Pasi P]

About "hotrodding" UCD180.
I think to remove 680nF MKT output capacitor and replace it "better" quality polypropylene cap in amplifier speaker terminals (large cap does not fit to UCD PCB). Do you think it is OK?
Maybe M-Cap Supreme or something..
Any suggestions?

Can this cap be smaller value in active speaker system tweeter amplifier (Linkwitz Orion 1440Hz up)?

 

[lucpes]

@Pasi P:

Transformers: I'd get at least 300VA per UcD channel for the best sound. Bigger transformers have better regulation and you'll find that the rails don't 'sag' as much as using a smaller transformer.

Output capacitor: The cap is parallel to the signal out and it's purpose is just to filter switching noise-related byproducts. If you move it to the speaker posts you'll run into nasty emission problems and maybe some noise coupling between the amps.

Tweeter amp output capacitor: No, as the cap is parallel to the output and it serves filtering purposes, it will do no good -surely worse- to use a smaller value capacitor.

 

[Pasi P]

Thank you for information lucpes.

General about capacitor hotrodding UCD.
Seems that it is very difficult to fit bigger caps (quality caps tend to be bigger than originals) in UCD180 because there is almost any free space around caps near heatsink and 0.68uF cap space is very limited also.

Maybe Bruno should made "hotrodders" life easier in next version 😉


About transformers.
Yes, i know that 2x180VA is not very much but i will drive active Linkwitz Orions mid and tweeter, so need of power should not be very demanding.
If i remember correct, Jan Peter says that one can get 160VA transformer from Hypex to drive stereo UCD180.

 

[Pasi P]

Anybody know where can be found suitable size (LS5mm) polyprop. capacitor to mod. 0,68uF/63V output cap?

I have tried but not found

 

[Bruno Putzeys]

Anybody know where can be found suitable size (LS5mm) polyprop. capacitor to mod. 0,68uF/63V output cap?

I have tried but not found

Neither have I. I'd have put it in as standard... OTOH, the sonic differences among makes of MKT are already large enough to warrant trying out a number of them. The current one is bright and airy sounding, but lacks some body. I've heard others (e.g. AVX) that have body but no air. Etc, etc.

FYI the smallest polyprop that I found was 0.68/160V BC components MKP379. It sounds absolutely wonderful, but the size produces EMI problems (e.g. whistles). Try at your own peril.

 

[ghemink]

Neither have I. I'd have put it in as standard... OTOH, the sonic differences among makes of MKT are already large enough to warrant trying out a number of them. The current one is bright and airy sounding, but lacks some body. I've heard others (e.g. AVX) that have body but no air. Etc, etc.

FYI the smallest polyprop that I found was 0.68/160V BC components MKP379. It sounds absolutely wonderful, but the size produces EMI problems (e.g. whistles). Try at your own peril.

Would it be possible to use a smaller MKT, say 220nF to filter out the worst HF components on board and use a higher quality cap of 470nF (0.47uF) at the speaker terminals or mounted at the PCB bottom side???

Best regards

Gertjan

 

[Bruno Putzeys]

Would it be possible to use a smaller MKT, say 220nF to filter out the worst HF components on board and use a higher quality cap of 470nF (0.47uF) at the speaker terminals or mounted at the PCB bottom side???

Parallel caps will resonate among eachother (courtesy of wiring and trace inductances). If they are very close together, the resonance frequency will be too high to be of any consequence (in this application!). If they are very far apart, the Q of the resonance will be low. For realistic distances (like one cap on the PCB and the other across the speaker terminals), the resonance will be quite pronounced and cause very ugly distortion (modulator DC transfer function becomes wobbly).

 

[ghemink]

Parallel caps will resonate among eachother (courtesy of wiring and trace inductances). If they are very close together, the resonance frequency will be too high to be of any consequence (in this application!). If they are very far apart, the Q of the resonance will be low. For realistic distances (like one cap on the PCB and the other across the speaker terminals), the resonance will be quite pronounced and cause very ugly distortion (modulator DC transfer function becomes wobbly).

OK, convinced, not a good idea:-(