DAC AD1862: Almost THT, I2S input, NOS, R-2R

Vunce · 2022-11-09 12:31 pm

Hahaha!🤣

zoom777 · 2022-11-09 12:41 pm

crymen said:
Here is the Gerbers info.

crymen said:
I was playing with different I/V resistors, it was fun. Then, I came across @Vunce's OPA861 I/V build #1417. I want to make a set but realised the SMD soldering of the TPS7A39 is not an easy task. Taking it as an adventure and learning process, I took Vunce's schematic to draw a through hole version board using KiCAD.

thanks crymen, i will try this board on the miro tda1541

diyiggy · 2022-11-09 1:26 pm

Vunce said:
Hahaha!🤣

altor · 2022-11-10 8:38 am

SMD soldering of the TPS7A39 is not an easy task.

Having soldered dozens of TPS7A47/33/49/30/39, I can say that this is a very simple task. 1-2 min

You just need a hot air and flux. Many flux.

PCB must be with mask, of course, not "home-made with the laser printer and iron".

1) Apply some solder to the pads on the PCB.
2) Add flux.
3) Place the chip on the board next to it, upside down.
4) All flux to the chip's pads.
5) Heat the PCB with an air hot gun until the solder on the pads melts. The chip next to it will also get warm.
6) Put the chip in its place.
7) Continue heating from the top until the chip begins to "dance" a little. Add flux if necessary.
8) Remove the hot air and wait for cooling.

P.S. Good if you heat PCB from the bottom (I stole a toaster from my wife from the kitchen), but only for some kinds of the PCB.

jpk73 · 2022-11-10 10:40 am

miro1360 said:
use only 74HCTxx family

Miro, please explain why only HCT? Is AHCT and LVC etc. not working well into TDA1541A? I am especially interested in 74LVC because I used them with a supply of 2~2.2V to get the logic levels down before the TDA (not on your PCB though: for my PMD100->TDA1541A projects I wanted the higher speed of the 8x oversampling mode so I thought LVC gives both, speed and low voltage signals)...

mrjavum · 2022-11-10 11:14 am

Vunce said:
Stop-Clock MiroDac rev2.1 from post#3969 is alive. This board is set up for passive I/V (60R Rhopoint) feeding an SRPP 6n6p tube output stage.

Hi, Vunce. Can you advice me what Riv to use with MiroDac rev2.1 and https://aliexpress.ru/item/33005007435.html?sku_id=67019405225#reviews_anchor connected directly to DAC chip out pins?

Or can you give a howto, how to calculate Riv value by myself?

I'm planning to use 6N1P or 6N3P with it.

Thanks in advance!

diyiggy · 2022-11-10 2:45 pm

Alienxpress.ru ?

mrjavum · 2022-11-10 2:56 pm

diyiggy said:
Alienxpress.ru ?

Yes, it's hard to buy something living in Russia now except Alexpress. More pain is that aliexpress sold it's name to russian company and this company broken all usual features of Ali

NIXIE62 · 2022-11-10 3:15 pm

mrjavum said:
Or can you give a howto, how to calculate Riv value by myself?

Well, that's easy to calculate, but someone on that link wrote that the voltage gain is about 6x, that's a little, even for AD1865. That schematic looks very similar to the Broskie CCDA. The voltage gain with the E88CC can be achieved in the 17-33x range depending on the schematic, that would be just fine for some DAC chips.

That PCB is OK, it can easily be converted to a classic Common Cathode & Cathode Follower stage with about 20-25x gain.

mrjavum · 2022-11-10 3:25 pm

NIXIE62 said:
That PCB is OK, it can easily be converted to a classic Common Cathode & Cathode Follower stage with about 20-25x gain.

What I need to do this? And what about Riv calculating?

Thanks!

miro1360 · 2022-11-10 5:00 pm

jpk73 said:
Miro, please explain why only HCT? Is AHCT and LVC etc. not working well into TDA1541A? I am especially interested in 74LVC because I used them with a supply of 2~2.2V to get the logic levels down before the TDA (not on your PCB though: for my PMD100->TDA1541A projects I wanted the higher speed of the 8x oversampling mode so I thought LVC gives both, speed and low voltage signals)...

Simply because I have not tested it with AHCT or LVC

(AHCT can work as well, but timing problems may occur because AHCT is faster), it may or may not work in my DAC
LVC or AHCT are very good logic family chips (LVC is only in SMD?) ... you can try it in your application with PMD100

Brijac · 2022-11-10 5:17 pm

miro1360 said:
Simply because I have not tested it with AHCT or LVC (AHCT can work as well, but timing problems may occur because AHCT is faster), it may or may not work in my DAC
LVC or AHCT are very good logic family chips (LVC is only in SMD?) ... you can try it in your application with PMD100

I have put ahct on pcm63 dac 😅 We will see in a few weeks if that works. But i ordered the same ones as @mikorist and it works for him well, so should be fine

bohrok2610 · 2022-11-10 5:30 pm

LVC works as well. I have used it for similar glue logic with AD1862.

Correction: I used LV logic. Bit slower than LVC.

NIXIE62 · 2022-11-11 12:11 pm

mrjavum said:
What I need to do this? And what about Riv calculating?

Thanks!

I will look for the schematic, but on that schematic it is 265-75= 190V anode voltage on E88CC (cathode follower part) and the dissipation is 0,95W. I doubt that tube can handle190V. For E88CC some recommendation is max. anode voltage 100V, max. 1W dissipation (half tube). I worked with 100V - 10mA and 120V - 8mA with E88CC, 6N23P and there were no problems, but I would not advise more than that.

diyiggy · 2022-11-11 2:28 pm

and there is a paper that has been linked in the first page of miro1360 site for such tube and shematic with all the R i/V values ! As always RTFT or flee ! Lol !

mrjavum · 2022-11-11 4:45 pm

diyiggy said:
As always RTFT or flee !

Sorry for my dumb questions 🙈. I have reread topic (274 pages, Karl) for second time and found answer for Riv here: #2742

About this Chineese tube board a have read here:

woodturner-fran said:
Speaking of valve stages, this one from Aliexpress works very well indeed.

https://www.aliexpress.com/item/33005007435.html?spm=a2g0o.productlist.0.0.54636bb9qIgcpQ&algo_pvid=5853626e-3314-4e1b-9a51-da241b2eb83d&algo_exp_id=5853626e-3314-4e1b-9a51-da241b2eb83d-1&pdp_ext_f={"sku_id":"67019405225"}&pdp_pi=-1;14.18;-1;-1@salePrice;EUR;search-mainSearch

I ended up modifying mine and using CCS instead of plate resistors, which lead to a more resolving sound, tiny bit clearer highs. Cheap as chips though to try out the valve sound.

If you buy this board and want to mess about with it, note that each valve on the board is mirrored - so if the first triode is pins 1,2,3 on one valve, then the first triode on the other will be 7, 8, 9.

It would be great if Fran could describe his modification.

diyiggy · 2022-11-11 4:56 pm

Can't get a local 6Np23-EV ?
btw : https://electrodac.blogspot.com/p/dac-ad1862-almost-tht-i2s-input-nos-r.html : at the end of the page is the thermonic valve paper from the brillant T Loesch. also a lot of inputs around ECC88 tube in the thread.

jpk73 · 2022-11-11 9:54 pm

miro1360 said:
LVC or AHCT are very good logic family chips (LVC is only in SMD?) ... you can try it in your application with PMD100

Thanks! My PMD100 projects worked well with LVC logic at 2,2V into the TDA1541A...

Vavilen · 2022-11-11 11:18 pm

Hi guys!
I'm looking for capacitors for these positions (please, check attached screenshot) for the AD1862 DAC.
For some reason I bought these Nichicons https://nl.mouser.com/ProductDetail/647-UKW1E101MED , but less number than I needed 🤦‍♂️
Also, I can see they are not Low ESR, but it's required.

Any opinion about this capacitor for these positions?
https://nl.mouser.com/ProductDetail/Panasonic/EEU-FR1E101?qs=sGAEpiMZZMvwFf0viD3Y3chMjVlP8qMGKQRWWtuhRU4=
All params look correct, but maybe there is a better alternative?

Thanks!

diyiggy · 2022-11-11 11:38 pm

I made some tests of caps and resistor above in the thread, but do not remember where, nearer to the end than the the thread beginning.

DAC AD1862: Almost THT, I2S input, NOS, R-2R

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