Modify B1 Buffer for DAC output stage

[Ian Greenhalgh]

Zen I/V contains first order LPF. How much filtering and type of filtering is important decision in DAC design. Use only polypropilen or polystyrene capaciors for this purpose (or same grade types). For more than first order filtering you need more active stages between i/v and output B1.

Thankyou for the explanation. I suppose I'll try it first with ZEN directly into the B1 and see how that sounds. I can always add filtering f needed.

I was thinking of going for Russian K72-10 or similar PIO caps as they are cheap, but I'll consider polypropylene if I can find some not too expensive good ones.

 

[chip_mk]

Physical dimension of capacitor is important in filter circuits. Large capacitors have higher parasitical inductance that makes them less efficient in suppression of the highest frequencies.

 

[Ian Greenhalgh]

Isn't that why a smaller bypass capacitor is used in parallel?

I need two outputs for my dual power amps so I wondered how to modify the B1 circuit for two outputs.

I wondered if I could do it like this:

Simply add another R104 and R105:

 

[Itsmee]

Move second R104 connection to the other end of the first R104.

 

[Ian Greenhalgh]

Like this?

or like this?

 

[androa76]

Move not delete. I don*t understand why B1 after already one output stage. More is better? Which dac is part of game?

 

[Soundhappy]

At the moment it is simply 1465 transformer connected directly to DAC out with 6k8 resistor on the secondary.

Thanks Qwertyl!
Kind regards 🙂

 

[Ian Greenhalgh]

Move not delete. I don*t understand why B1 after already one output stage. More is better? Which dac is part of game?

This is for a pre-amp, not a DAC. It will have four inputs and two outputs as I use two power amps and prefer to avoid y-splitters to connect them to a single output.

 

[Itsmee]

Like this.

 

[Ian Greenhalgh]

Aah, cheers.

 

[Ian Greenhalgh]

I've redrawn it, to have two outputs:

 

[Ian Greenhalgh]

Sorry, I got completely mixed up with threads and the entire last page of posts, about adding a second output shouldn't be in this thread, it should be in my other one about building a B1 based pre-amp. My apologies for the confusion.

 

[androa76]

I have one pair B1 with dual Tpsxxx low noise power supply small compat design. No big signal capacitors are needed. Ready made for easy job. Plug and play. Just connect transformer and listen. Quality parts have been used.

 

[Ian Greenhalgh]

It's interesting how many variations there are on the basic B1 design, thanks for sharing.

 

[Ian Greenhalgh]

Here is my revised schematic for the B1 buffer as intended to be the output stage of a DAC:

 

[Itsmee]

You don't need R100 & R200

 

[Ian Greenhalgh]

Well spotted, I'd already done that and posted the wrong schematic, whoops.

Much appreciate the second set of eyes though, I'd probably have carried that mistake through into the build if not spotted now.

 

[Ian Greenhalgh]

I've redrawn the schematic again, to better reflect how I intend to lay it out on the matrix board:

 

[Itsmee]

If your drawing it to lay it out, swap top and bottom circuits to put the ground in the middle, that way later, you can choose to have separate +V L/R supplies; oh, and move the bias circuit up between the channels.

 

[Ian Greenhalgh]

Cheers, is the bias circuit the part on the right of the outputs starting with R2 and R3?