Try and try again...or as my old officer in the army said (bad translation to english) "do it again, do it right" lol
Thanks for being patient
Edit: I have Elna Cerafine's 220uF/10V, would these be a good choise when I build this eventually?
Its certainly an improvement (the E1 VCVS inputs are wired correctly) but it now has resistors on its outputs (Rload1, Rload2) which should go between each of its inputs and AGND.
Great!
Then there's just adding another buffer in front of the Filter stage 🙂
Just finished a 5Vdc low current shunt reg, haven't tested it yet though.
2pcs BC547B a red LED and vbe as Vref. 2K resistor and a 500R trimpot to set the output. Capacitors are Wima MKP and Rubycon ZL.
First one I've built actually. Will be fed from an LM317 set to 8Vdc
One of two that I'll fit on this board. One for VDD and One for VCC, using separate GND's.
If this measures ok, I'm thinking of building more for the DIR9001 board that will feed the I2S signal to the WM8740 (maybe with an AD1896 between them).
About the buffer between the pos and neg outs from WM8740 and the filter section, I need to build 4 buffer for this?
One for each of R1-R2?
I should multiply the resistor values in the buffer by 20 (except for the 4.7R) right?
One for each of R1-R2?
I should multiply the resistor values in the buffer by 20 (except for the 4.7R) right?
A first attempt/draft of the "pre-filter" Buffer.
Not sure I was correct in the orientation of the decoupling capacitors on the negative side of the WM8740 out?
Did not include the 100K load in this schematic.
I get ~ 758uV on all outputs.
(757,92 - 757,53uV highest to lowest)
Not sure I was correct in the orientation of the decoupling capacitors on the negative side of the WM8740 out?
Did not include the 100K load in this schematic.
I get ~ 758uV on all outputs.
(757,92 - 757,53uV highest to lowest)
Well...
Tried to run the whole thing in spice.
I don't understand the values I get on the buffers feeding the 100K (R1-R4)
I've only slept 4.5 hours, so I may have made some obvious mistakes.
Tried to run the whole thing in spice.
I don't understand the values I get on the buffers feeding the 100K (R1-R4)
I've only slept 4.5 hours, so I may have made some obvious mistakes.
What's connected to nets Ldac1,2 Rdac1,2? They do look to be dangerously close to the negative supply voltage (-12V).
They are supposed to be connected to the L/R pos and neg outputs from WM8740 IC.
Since I don't have the spice model for that IC I can't include it in the schematic.
I was mainly wondering if I had made an error/errors in the "pre-filter" buffer part of the schematic?
Also, I don't need to AC decouple the outputs of that buffer, right?
The decoupling after the "post-filter" buffer is enough?
Right - given the light load the filter stage now presents, there's no need to AC couple between the DAC buffers and the filter. But nothing will work while the DC levels are so out of whack - the level on the output of the DAC buffers should be around -0.6V as the DAC's analog stages are presumably running on +/-5V so their outputs should sit around 0V.
Good 🙂
My idea is to make this project as modular (and versitile) as possible.
One board for the DIR9001 SPDIF to I2S
One board for the AD1896 SRC (since I have one of these IC's), not sure I'll use it though.
One board for the WM8740 (maybe two and run one for each channel?)
Will need a different schematic if going 2x mono WM8740.
The below is for one WM8740 and is from Pavouk.org (credit where credit is due).
One board for the original Pavouk.org filter/buffer
One board with your buffer-filter-buffer design. What VA rating would I need on the transformer driving this(will use a separate transformer for the analog stage after the WM8740)? There are a few transistors on there 🙂
One shunt reg for each 5Vdc and each 3.3Vdc supply.
Shunt regs fed with 8Vdc and 5Vdc via LM317's (on separate board).
I plan on using 2pcs 0-9VAC 1200mA transformers for all 5Vdc and 3.3Vdc supplies, feeding all regs off two capacitorbanks(one for analog and one for digital power supplies) with 5x Elna RJJ 1500uF/capacitorbank.
The analog section after the WM8740 will have it's own dual rail supply with 1x NCC KMQ 4700uF and 1x Nichicon Muse 2200uF per rail.
That and the enclosure I'm going to use is about as far as I've gotten in planning 🙂
Sorry about the long winded and a bit of topic post...
About the output capacitors(the two 220uF on the post-filter buffer), is Nichicon Muse FG 220uF/10V a decent choise?
I'd suggest if you're going the whole hog to doing a board then double up on the analog stages (two further opamp filters, add two more output buffers) to support balanced outs. The current draw of all those transistors is still quite low (say 4 * 4mA buffers and 4*400uA buffers) - totalling under 18mA. Thus a 5VA trafo to generate both rails will still be overkill.
I'm no connoisseur of caps in the signal path so I'd guess Nichicon Muse will be fine. I tend to prefer 16V capacitors as a minimum though, except where space is really at a premium on larger values.
I'm no connoisseur of caps in the signal path so I'd guess Nichicon Muse will be fine. I tend to prefer 16V capacitors as a minimum though, except where space is really at a premium on larger values.
thanks for your advice 🙂
I'd rather not have caps in the signal path at all, and if I must I'd rather go MKP...but at 220uF that would get real expensive real fast lol
I have a 12-0-12VAC 500mA I'm not using, that should work for this then.
I won't be making PCB's for this unfortunately.
It will all be done on this type of board(5x7cm FR4):
I might make PCB's for it later though, it's too bad I sold my PCB equipment a couple of years ago...
I plan on using this DAC mainly with my headamp(I have a TDA1541A with passive I/V and tube output in my main system), besides I don't have any balanced equipment except the DCX2496 doing the low end x-over and dipole compensation for my speakers.
Or did i misunderstand your post?
Since I have a 2-3pcs genuine TDA1541A I could make a board for one of those as well. I'd need an I/V and buffer specificly for that board though.
That'll be a later project if it ever happends.
The 220uF is bigger than it needs to be because I chose a 'lytic. Depending on what load resistance you have at the receiving end you can go quite a lot smaller if you have particular caps you love.
Going balanced makes the circuit more immune to PSU issues in my experience, I often use a trafo at the output to convert back to SE.
If you're using the SOT-23 SMT transistors I'd recommend going for double-sided PTH PCBs. They're seriously cheap here - the size you've shown is around $0.25 on Taobao. Going to double-sided lets me wire on the reverse side while soldering components on the top.
Going balanced makes the circuit more immune to PSU issues in my experience, I often use a trafo at the output to convert back to SE.
If you're using the SOT-23 SMT transistors I'd recommend going for double-sided PTH PCBs. They're seriously cheap here - the size you've shown is around $0.25 on Taobao. Going to double-sided lets me wire on the reverse side while soldering components on the top.
I've ordered 20pcs SOT-23-3 adapter pcb's(double sided).
I see your point on the double sided pcb's, didn't think of that way of using them actually.
I'd go trafo on the outputs, but I can't afford to atm plus I want to try a different solution as I have trafos in one dac and tubes in another.
Well, my head is now spinning from lack of sleep and too much thinking lol
Going to go salvage upgraded parts I've put in TDA1541A based cd-players, only use PC as source these days and it would be a shame to waste those nice components...plus, that is a good job for me now as minimum thinking is involved 😉
The project is not dead 🙂
I'm just waiting for parts, lots of parts actually.
Got a few today and more are waiting at the local post office.
I've also gone through my "parts stash" and found a lot of good parts.
Still not enough parts at home to start any of the boards yet though (I want to have all parts ready when starting each board).
I'm just waiting for parts, lots of parts actually.
Got a few today and more are waiting at the local post office.
I've also gone through my "parts stash" and found a lot of good parts.
Still not enough parts at home to start any of the boards yet though (I want to have all parts ready when starting each board).
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