Sony vFET Amplifier Part 2

Jump to Latest
#2,701
Hi all,

I've got a PSU question. Got all the parts and will be using the DIYAUDIO PSU with an Antek 400 VA trafo with dual secondaries. Is it better to set the PSU up as dual mono by not connecting the grounds of the two sides, or doesn't it make much difference.

Thanks

Paul
 
#2,702
One transformer with dual secondaries makes one bipolar (+V/GND/-V) power supply. You've got to tie the Grounds on the PSU board in order to define ground.

If you want dual mono you'll need 2 transformers, 2 PSU boards, and wire each channel to its own dedicated PSU. At that point it makes good sense to just make monoblocks. 😀
 
#2,703
6L6 said:
One transformer with dual secondaries makes one bipolar (+V/GND/-V) power supply. You've got to tie the Grounds on the PSU board in order to define ground.

If you want dual mono you'll need 2 transformers, 2 PSU boards, and wire each channel to its own dedicated PSU. At that point it makes good sense to just make monoblocks. 😀
Click to expand...

Single supply it is. Thanks for clearing this up Jim.

Paul
 
#2,710
Have you two of these?
Voltages and VAs are a little bit lower than as I would like.
You can expect secondary voltages somewhat below 24VDC.
But if you will follow the description, there can't be a big mistake:
"NOTES ON SUPPLY VOLTAGES NOT +/-28V
This amplifier is designed to operate with voltages between about +/-26V DC
and +/-30V DC.
If your supply is lower than this, you should adjust R15 and R16 down so that
the R19 and R20 have at least 2 volts across them.
For example, if the supplies are +/-24V as measured at T6 and T8 (relative to
ground) then the regulators Q13 and Q14 need to be set for 2 volts below that at
22V each.
To compute the new value of R15 and R16:
22V = 2.5V * (R15+4750 ohms)/4750 ohms
22V *4750 ohms / 2.5V = R15 +4750 ohms
41800 ohms = R15 + 4750 ohms
R15 = 37050 ohms.
You would pick the closest 1% resistor, which would be 36K or 36.5K for R15
and R16.
Other parts of the circuit are not very sensitive to supply values. Practically speaking, you should not try to make this amplifier with rail voltages below 20 volts, and above 32 volts."
 
Last edited:
#2,719
grimberg said:
If you want to build independent PSUs for each channel, use two units of model 057015201.

https://shop.plitron.com/shopexd.asp?id=121

If you plan on using a single PSU, the model is 077015201.

https://shop.plitron.com/shopexd.asp?id=164
Click to expand...

Something is really odd with the sizes specified for those 160VA transformers. I somehow doubt that it is 250mm wide in diameter, seeing that my Amplimo 18V 650VA transformer is 140mm wide.

EDIT: I checked the spec sheet PDF, and it is indeed 110mm wide, so their web page for the product is in error. Probably another cut-and-past developer error.

2nd EDIT: Just picked up my kit from the PO. Now I just need the transformers and chassis.
 
Last edited:
#2,720
You shouldn't use the outer diameter alone to compare transformers. Pay attention also to the inner diameter (the doughnut hole) and, of course, the height.
Several years ago when other members started talking about Antek transformers, I was initially skeptical. I tried one and was satisfied with the results, so it became my transformer of choice. The exception was my Aleph J build in 2013. Antek had lost most of its stock to a fire earlier that year, so I decided to source the transformers elsewhere and purchased Avel Lindberg from Parts Express.
Some may be asking: Why not Plitron? Even though it is clearly better built than the Antek, when taking into account the initial cost, shipping costs and, worst of all, brokerage fees, I can't justify paying almost three times for a transformer that IS NOT three times better. My reply to WBS was not an endorsement, as I have not purchased from Plitron in a while.
 
You must log in or register to reply here.
Top Bottom