How to: Build your own Hypex UcD amps

JoshK · « **Reply #20 on:** 8 Mar 2005, 03:11 am »

Like Angelo & Gosker said, the secondaries of that trannie is too high, however I think I may have an ingenius work around. Won't be compact though but would be killer!

Those caps are huge! They are better off in the Class A amp they came from, IMHO. There is a lot of talk about not overdoing the size of the caps on the diyaudio UcD threads. The idea is that you will zap all the romance out of the modules if you overdue the caps in leyman's terms. They will have tremendous bass though.

You'd be better off keeping the Threshold's as thresholds and building a PSU for the UcD specific to the purpose and it wouldn't need to be so expensive and overbuilt.

General note:
It has been said that the PSU for the switching amps are even more critical than for a classic analog SS amp because the PS rejection ratio is basically nill, meaning any modulation outside of DC will modulate the output signal (not good!). Therefore, I think it is prudent to think through and read up on PSU construction prior to building.

amandarae · « **Reply #21 on:** 8 Mar 2005, 03:12 am »

I thought the Hypex site says maximum of +- 65Vac and protection kicks in at -+ 68Vac.

The spec of the torroid says 57.5 Vac with load. Would you mind sharing why I made a mistake?

thanks

JoshK · « **Reply #22 on:** 8 Mar 2005, 03:16 am »

That is trip voltage....operating voltage is lower. Edit (doh!): Pre-rectified voltage * 1.414 = post-rectified voltage (sinusoid curve to flat voltage). So after the bridge is higher than before, so the voltage on the secondary should be lower.

Then you need to provide some headroom as well, as there can be nasty surges on turn on of the amp.

angelo · « **Reply #23 on:** 8 Mar 2005, 03:24 am »

the DC output after rectification will be 57.5VAC * 1.414 = 81.305VDC - RB voltage drop (~1.4V) = 79.905VDC (too high for the 68V protection)

and your AC main may go up once in a while so it might go higher than that... there will still be some voltage loss somewhere along the line but still... TOO HIGH

angelo

JoshK · « **Reply #24 on:** 8 Mar 2005, 04:29 am »

yeah sorry..... AC * 1.4 = DC.....can't do math today it seems.....

amandarae · « **Reply #25 on:** 8 Mar 2005, 04:57 am »

Ah yes,yes! That voltage (torroid spec) is rms. What was I thinking

So, I will buy a different transformer. As for the caps I think, I can use it as per the the site, which I will post a link later. it is a "how to.." build a pSu for amps. I remember seeing a 4 stage type in there.

Thanks for the clarification.

goskers · « **Reply #26 on:** 8 Mar 2005, 01:13 pm »

A good rule of thumb seems to be a 10% undervoltage for peace of mind in transformer selection. A 42.5VAC would seem to be ideal as this would give 60V after rectification. With the absolute high side being 68 this should work quite well.

angelo · « **Reply #27 on:** 20 Mar 2005, 01:56 am »

update on my UcD project!

here are some parts that i already have, i got 6 small chassis at work for FREE so i might as well use them, it's small so i have to separate each mono amp into two parts:

chassis 1. transformer and rectifiers
chassis 2. caps bank and UcD module

chassis 2 will make sure that the filter caps output will be as close as possible to the UcD module power INputs

i still have to find a good and safe connectors to link the two chassis together, any recommendations?

the UcD400 modules are in transit right now, should arrive this week

angelo

JoshK · « **Reply #28 on:** 20 Mar 2005, 05:44 am »

Angelo,

Like the Chassis, what caps are those? I think that Neutrik Powercon connectors might serve you well for your purpose.

angelo · « **Reply #29 on:** 20 Mar 2005, 01:45 pm »

the small blue capacitor is a Vishay 100nF MKP X2 275VAC for EMI suppression across each diode of the bridge rectifier

part#: 2222 338 24104

the filter caps are United Chemi-Con SMH Series 6800uF 80V

part#: SMH80VN682M30X50T2

angelo

angelo · « **Reply #30 on:** 25 Mar 2005, 03:58 am »

visio drawing of possible backplate setup

comments and suggestions please

i didn't put a removable power connector 'cause it's hard to drill a rectangular shape in the chassis to fit an IEC connector, round is much easier, possible additions are XLR input connectors and LEDs

angelo

JoshK · « **Reply #31 on:** 25 Mar 2005, 06:40 am »

If you want to make a removeable PC but don't want to cut a squarish hole, I recommend Powercon connectors.

JM · « **Reply #32 on:** 29 Mar 2005, 04:54 am »

I'll be building a UcD400 based amp soon.
I thought I'd share my power supply design. I designed it after Dejan V. Veselinovic's article.
I'll be building two mono amps that would only be sharing the IEC inlet, main fuse, switch and chassis.

speedcenter · « **Reply #33 on:** 31 Mar 2005, 04:57 pm »

Quote from: angelo

i still have to find a good and safe connectors to link the two chassis together, any recommendations?

Neutrik Powercon - absolutely the best for safe high voltage connections. These aren't cheap, though - male and female combined for a single +/- link will be about $1.

I used them in the past for my DAC to connect to external battery and am currently building a preamp with remote Power supply where I'll be using them again. They lock securly in place so there's no risk that the wire will get pulled out by accident while the music is playing

Peter

speedcenter · « **Reply #34 on:** 31 Mar 2005, 04:59 pm »

Quote from: angelo

i still have to find a good and safe connectors to link the two chassis together, any recommendations?

Neutrik Powercon - absolutely the best for safe high voltage connections. These aren't cheap, though - male and female combined for a single +/- link will be about $1.

I used them in the past for my DAC to connect to external battery and am currently building a preamp with remote Power supply where I'll be using them again. They lock securly in place so there's no risk that the wire will get pulled out by accident while the music is playing

Peter

Occam · « **Reply #35 on:** 1 Apr 2005, 02:37 am »

Julien,

I like your inclusion of the 'ground loop buster', D3.D4,R3 & C23 very much!
A couple of very minor points -
Assuming the purpose of C25 it to arc quench the hot side of the switch, you should add an equal cap accross the neutral side of the switch. The neutral side is subject to equivalent arcing during turnon/turnoff.
If you would ever even consider using a non X2 rated cap, such as the pervasive 'Auricap Tweeeeeek', across the line, put cap C24 across Live and Neutral after the fuse, F1.
Assuming you are switching both live and neutral for the possibility that live and neutral are reversed, you should add a fuse F2 in series with the neutral line (same as F1 on the Live line), to complete precautions against reversed lines.

Dejan (DVV) frequents these boards and hopefully he will comment, and possibly opine on snubbering the PS of a switching amp. Dejan commented on snubbering with his original articles in TNT, and then his own website, but it seems to have taken a few years for it to become all the rage....

JM · « **Reply #36 on:** 1 Apr 2005, 04:18 pm »

Thanks for the comments Occam.
I was actually thinking about building the amp with an integrated switch, fuse holder, and IEC inlet. So I'll probably not be using the double switch.
But your point is valid. I'll be changing the schematic accordingly.
Yes that C24 is based on the "'Auricap Tweeeeeek". I've used it in many pieces of equipment with good to neutral results. It doesn't have to be an Auricap though. It could be an X2 rated cap, or another good quality film cap with a high DC rating.
Lately I've been working on my CD-PRO2 kit and one filtering that really made a positive difference was placing small value caps across the transformers secondaries. 0.1uF seems to work well, but I used different values I had at home (there are 5 secondaries to filter) from 0,022 to 0,1uF, either Solen or Panasonic.
So far, the caps paralleled to the diodes in the rectifier bridge always worked for me. Again either in a good or neutral way, never in a negative way. I guess it all depends on how sensitive the rest of the circuit is to PS noise.
I was reading the UcD400 thread at DIY audio and someone had tried a different filtering scheme that apparently was more effective. That involved connecting 4 small value caps between the AC input to the DC output in the bridge. The caps were connected between ~ (+40V) and DC+, ~ (+40V) and DC-, ~ (0V) and DC+, ~ (0V) and DC-. I'll have to try that when I build my UcD400 amp...

rha61 · « **Reply #37 on:** 1 Apr 2005, 06:00 pm »

Hi Julien
you forget an important thing : the snubber
I've heard a noticeable improvement on my ucd180 with it

alain

angelo · « **Reply #38 on:** 1 Apr 2005, 09:32 pm »

Quote from: speedcenter

Neutrik Powercon - absolutely the best for safe high voltage connections. These aren't cheap, though - male and female combined for a single +/- link will be about $1.

I used them in the past for my DAC to connect to external battery and am currently building a preamp with remote Power supply where I'll be using them again. They lock securly in place so there's no risk that the wire will get pulled out by accident while the music is playing

Peter

where can i get them for $1, last time i checked they were ~$7 each connector... i think that price was from newark.

angelo

JM · « **Reply #39 on:** 1 Apr 2005, 11:37 pm »

Quote from: rha61

Hi Julien
you forget an important thing : the snubber
I've heard a noticeable improvement on my ucd180 with it

alain

Hi Alain.

How did you build your PS?
What value resistor and cap did you use in your snubber.
I left it out of the schematic because I wasn't sure about the cap value yet.
How do you like your UcD180 amp?