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HighFidelityGuy
12-01-2010, 16:47
Hi,

As some of you know I've decided to build a WDPhono3 (http://wduk.worldomain.net/acatalog/info_WDPHONO3S.html) phono stage and matching WDPSU3 (http://wduk.worldomain.net/acatalog/info_WDPSU3.html) power supply. I'm not buying the whole kit though, I'm sourcing all the components and casing myself to save money. I've so far ordered the PCB's and acquired the schematics and parts lists. I'm now trying to source all the components. This is going fairly well but I've got a quick question about resistors:

The parts list has some resistors that are specifically stated as carbon film, while other are metal film. I know metal film generally have better tolerances and lower noise, so I was wondering why carbons are being used?
Is this purely a cost thing and would I be better off using metal films all round?

Cheers. :)

Ali Tait
12-01-2010, 17:08
I think they would recommend that for sound purposes.If you fitted all metal-film it would probably sound to toppy and edgy.Generally better to mix a few different resistors to balance the sound if you see what I mean.

Mike
12-01-2010, 18:41
Hi Dave,

Can you send me the parts list?... I may be able to help out with some components from stuff I ordered when I built mine, I should be able to save you a few quid. Many items came in bags of five or ten hence I have 'leftovers'!

I can give you a few tips which might save you some hassle too... :)

Cheers...

HighFidelityGuy
12-01-2010, 19:57
Awesome, thanks Mike! PM me your email address and I'll send you them.

Cheers.

HighFidelityGuy
13-01-2010, 12:42
As WD can't supply the correct transformer or choke at the moment I decided to try and get a price for some equivalent models from another supply. I emailed "Living in the Past (http://livinginthepast-audioweb.co.uk/transformers.php)" to see if they had anything suitable and I quickly got an email with some recommendations.

I was recommended THIS (http://livinginthepast-audioweb.co.uk/xfrmrvt426.php) transformer and THIS (http://livinginthepast-audioweb.co.uk/xfrmrvt1314.php) choke.
The transformer has all the wrong voltages compared to what the schematic asks for but apparently this can be worked around. The schematic asks for 270V and 9V supplies but the transformer above has 250V, 15V and 6.3V.
According to Mike at the above store the HT winding will be fine at 250V and won't require any modification. Also I'll need to use the 15V winding for the heater supply which will mean I need to change C6 to 25V or above and R9 to 1.2K.

Here are the schematics for reference: (click to make bigger)

PSU:
http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Valve%20Gear/WDPhono3/th_WDPSU3.jpg (http://s2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Valve%20Gear/WDPhono3/?action=view&current=WDPSU3.jpg)

Phono stage:
http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Valve%20Gear/WDPhono3/th_WDPhono3S.jpg (http://s2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Valve%20Gear/WDPhono3/?action=view&current=WDPhono3S.jpg)

I hope WD don't mind me posting these. :uhho:

I know next to nothing about electronics design, so does anyone know if this transformer and choke will be suitable providing I make the above modifications?

Cheers. :)

Primalsea
13-01-2010, 13:06
The changes are possible but not really trivial if you have no experience of electronics. You could try asking the transformer supplier if it is possible to add windings to the 250V tap and increase it to 270 and remove some from the 15V tap to change it to 9V.

It can be a tricky thing to do and depends on the particular transformer but it is possible sometimes.

Dave Cawley
13-01-2010, 13:57
Dave

I hope you don't mind me saying this? but you are way out of your depth here. In particular R9 does not need modifying. I respectfully suggest you get all the parts for the kit from the supplier, and build it like they suggest. Otherwise don't attempt it.

Regards

Dave

Mike
13-01-2010, 14:37
I need to change C6 to 25V or above and R9 to 1.2K.

No don't do that!

Well, you could change C6 to 25V without causing any harm, but R9 (and R8) are there to hold 'Vout' to the correct voltage. It would be better to drop 6V or so, before C6.

Or find a different transformer!

HighFidelityGuy
13-01-2010, 15:22
Hi Dave, I don't mind at all and frankly I partly agree with you. I feel comfortable sourcing all the resistors, caps and diodes etc myself as the parts list I have is very detailed but as the transformer and choke are quite specific I'm hoping to get these from WD. I just wanted to get a 2nd quote to compare against WD's price (once they send me one). I really don't want to modify the design if I don't have to as that's the point where I'm outside of my area of expertise. I can read component values, buy them and solder them but that's my limit.
It was the guy from Living in the Past that said I would need to change R9. I'm glad I double checked now.

Ok, so I'll avoid using a transformer or choke from another supplier at all costs so that I don't have to worry about changing the design. I just hope WD manage to sort out their supply problem.

Cheers. :)

Primalsea
15-01-2010, 19:06
Hi Dave, I had a thought on the transformer but I suggest you PM Anthony TD and ask him to confirm as I'm not 100% sure about it. If you get you transformer and connect in series the 6.3, 15 and 250V sections you will end up with 271.3 volts which in transformer terms is as good as 270V as the voltages spec'ed are fairly nominal. You then just need to get a separate 9V transformer for the heater supply.

Mike
15-01-2010, 23:40
Hi Dave, I had a thought on the transformer but I suggest you PM Anthony TD and ask him to confirm as I'm not 100% sure about it. If you get you transformer and connect in series the 6.3, 15 and 250V sections you will end up with 271.3 volts which in transformer terms is as good as 270V as the voltages spec'ed are fairly nominal. You then just need to get a separate 9V transformer for the heater supply.

Sounds like a bit of lateral thinking there. I like it! :clap: