In the Buff-alo

[richidoo]

Rough draft is up and running on a test board.

Unbelievable!

Believe it!  If you come to hear this, wear your Depends. Even though my new horn speakers are not stuffed correctly I can listen right through the ringing horn, enraptured, totally swept away by music. Dense, textured, alive, natural, resolved, powerful, extended.

Very special thanks to my friend Sol for diagnosing a hum during dinner, over the phone and prescribing fix from parts I have on hand, all within 5 minutes. I wouldn't even try this without you.  A source is no good without an amp, so credit must also go to Sol's i60 for this incredible sound!

Thanks to topround for lighting my fuse on transformers. It took a while to pull the trigger but now it is ON.

Still some adjustments to do, correct parts values, connectors, box, PS etc. That and some break in time, better hookup wire, local caps, there's still more to be had.

[topround]

Thank Karl he was the one who got me hooked.

Transformers can do wonders...as well as chokes..

Get the caps out and watch what can happen

[Bill O'Connell]

Rich,

Are those separate transformer's one for the digital and one for the analog?

http://www.audionervosa.com/index.php?topic=3187.0


Please excuse the self promotion.

[richidoo]

Hi Bill! They are analog output transformers, left and right

[mgalusha]

Yeah, love transformers on the DAC. That is nearly exactly what I'm running, buffalo into Lundahl's with a little forest of PH regs hanging on the board. 

[Face]

Thank Karl he was the one who got me hooked.

Transformers can do wonders...as well as chokes..

Get the caps out and watch what can happen

The best cap is no cap.

[topround]

Agreed, even the best cap can't compete with no cap. Unfortunately the industry is cap oriented.

[allenzachary]

Um...feeling stupid here.  Can you explain in English what I'm looking at in the picture?

[richidoo]

English: It is a printed circuit board with some smaller printer circuit boards sticking up out of it, with a mess of tangled wires coming out of it and 2 shiny metal things on each side. All sitting on a raw wood surface.

Audioese: It is a DAC, based around this DIY kit:
http://www.twistedpearaudio.com/digital/buffalo.aspx
I added special ultra high speed voltage regulators, and output transformers instead of the usual powered active buffer stage that follows most DACs.

[allenzachary]

Ah.  I see.  It's a DAC.  cool.

I kinda figured out the circuit board with wires stickin' out of it on my own.

[Carlman]

I would REALLY like to hear this DAC at my house...

[richidoo]

I kinda figured out the circuit board with wires stickin' out of it on my own.

I would REALLY like to hear this DAC at my house...

I'll get it into a box soon.

[richidoo]

I put the DAC in a box tonight, so it would be safer to handle with the crowd on hand. I ran into a little problem though, maybe somebody can help...

I designed a simple power supply to feed the local regulators on the DAC. I used a Hammond 5V center tapped transformer, #166L5, using the outer taps, not using the center tap. I made a full wave bridge rectifier with fast diodes, filtered it with a 4700uF Nichicon 16V cap and a 5k bleeder resistor. Blimey to hell I am getting 7.4 volts out of it. 

My wall voltage is 123V as always. Tranny is rated 115, so there wil be a bit of a bump from that, but not 3 volts! I double checked the wiring, looks good. Duncans power supply simulator predicts 5.6VDC with 30mV ripple with this power supply, which is adequate for the regulators I am using.

I measured 6.4VAC where the secondary connects to the bridge, so might it be a mislabelled transformer, or must I measure it without the bridge connected?

The part that really has me baffled, is why am I not getting the .7 voltage drop through the rectifier? Crazy! 

I rigged up a power inlet to I can use the DAC with the 5V external regulated power supply that I have been using since I first ran the DAC, have it playing now. I can also use the external power supply to power the TT, with a different plug making 12V.  I do need to label them so the 12V doesn't go into the DAC.
Rich

[_Scotty_]

The NL transformer voltage is 5.5 volts AC. When you turn AC into DC you multiply your AC voltage by 1.414 . If your transformer sags a little bit lower towards the 5 volt full load spec you could easily get 7.4 volts DC.  If you divide 7.4 by 1.414 you get about 5.23volts AC which sounds about right. You should be able to drop 2.4 volts across the regulator just fine. In fact you have to have a minimum amount of voltage above above the 5 volts the regulator is supposed to put out so that your regulator doesn't drop out. The minimum voltage the regulator wants to see before dropout occurs should be stated in the specs on the regulator data sheet.
Scotty

[richidoo]

Thanks a lot Scotty. Someone said use 6.3VAC transformer and it will drop .7, after rect, but that was incorrect. It should have been 5V * .7 for a 3.5V transformer. In addition, the Duncan simulator was way off also, predicting 5.6V from 5V transformer. Not sure why that is, I assume I am doing something wrong with the simulation.

When I designed a PS for hypex UcD400 I used a 40-0-40 which made 56V after rectification and filtering.  I should have remembered that before.

The DAC has 3.3VDC regulators, so the 5VDC is the desired overhead, so I'll need a different transformer.
Thanks again,
Rich