Hi
There are 2 AC Powered DACs that I am considering to buy.
The first is PCM1793 based, and works on 15v AC:
It costs 20$ on ebay.
The second is AD1955 based, and works on 9v and 15v, both AC.
It costs 40$ on aliexpress.
Has anyone here maybe heard one of them and can say any impressions?
Thank you
There are 2 AC Powered DACs that I am considering to buy.
The first is PCM1793 based, and works on 15v AC:
It costs 20$ on ebay.
The second is AD1955 based, and works on 9v and 15v, both AC.
It costs 40$ on aliexpress.
Has anyone here maybe heard one of them and can say any impressions?
Thank you
Last edited:
The pcbs have rectifier diodes and regulator(s) on baord so do work from AC. BUT you can also supply them with DC.
A lot of Chinese boards run off AC in this way, which can be convenient as you do not need a separate psu. However, you are stuck with whatever regulator design they have used. (probably not the lowest noise type)
A lot of Chinese boards run off AC in this way, which can be convenient as you do not need a separate psu. However, you are stuck with whatever regulator design they have used. (probably not the lowest noise type)
That's nice..
So one does not need to bother and get an AC-AC Transformer?
Didn't know that..
It's much easier to provide DC..
(it won't affect the result in some way?)
BTW,
Unlike the second board which takes 2 separate power sources (15v, 9v),
the first one only takes one: 15v..
Does that mean that they implemented some isolation between the Digital part and the Analog part of the circuit?
If you didn't want to run it off the AC mains then you could use batteries. eg a 22v Lipo rechargeable RC model battery.
If dual supplies are needed, the higher one will be for the opamps so you'd need two batteries.
Batteries usually give better sound because there is no mains borne noise and ripple.
If dual supplies are needed, the higher one will be for the opamps so you'd need two batteries.
Batteries usually give better sound because there is no mains borne noise and ripple.
You may be under the impression that you can supply the DC voltage directly to the AC input (inputs) on the boards you've shown in the first post... This would be very wrong. Those boards need a bunch of DC voltages for feeding the various stages (digital and analogue) of the DAC board (5V, 3.3V,+15V, -15V) so the correct DC voltages required by the boards' particular designs will have to be produced with separate power supplies (linear power supplies i.e. LPS / switch-mode power supplies i.e. SMPS) should you choose this solution. Those DC voltages need to be 'injected' somewhere after the POWER IN stage (rectifying diodes/bridge and voltage regulator). The many AC adapters that many of us may have at home are generally not good for audio devices. Some of them can used for initial testing only. I do not know your level of d.i.y. skill in regards to electronic circuits... You may want to start building a DAC on the basis of one of those presented in the first post by simply supplying the required AC voltages. After you get an idea of the sound you may start to mod the DAC and a good place would be looking for providing better DC supplies. The better the power supply/supplies the better the sound...
I cannot see the markings on the boards, there may be more revealing pictures on the seller's site. Whatever AC voltages are marked on the board this is what needs to be supplied... The board designer has resorted to a more straightforward circuit where this DAC board needs just the addition of one mains transformer with three secondary windings supplying the required AC voltages OR two mains transformers, one with two secondary windings for providing 2x 15 VAC and another one with a single secondary winding providing 1x 9VAC (if the markings on the board show: 15V - 0V - 15 VAC and 9V - 0V). The onboard rectifying diodes and voltage regulators will 'transform' those AC voltages into the necessary DC voltages for the digital and analogue stages of the DAC board.
The markings on the first board are: AC 15v,0v,15v
The markings on the second board are: AC 9v,0v and AC 15v,0v,15v
(exactly what you said on the second part of what you wrote)
Both boards only require AC,
no DC is mentioned near any connector.
Right..
But what batteryman said is that we can also provide DC instead of AC, and it will work well,
and you say something different,
so who is right?
@batteryman assumed that you had a higher level of experience with electronics D.I.Y. and the design of power supplies in general. I do not know what will be the music source for your future DAC but I dare suggest a complete USB DAC (like SABAJ DA2 or DA3)... that is unless you want to enter the world of 'D.I.Y.-ing'
I agree with callmemike, you don't know enough to decide when & how to do it.
EG if there are 3 AC terminals labelled Ac, 0v, Ac then you need two identical Dc supplies connected + {-+} - because the board is using + & - supplies.
If it was just using +ve supplies eg +5 & +3.3 then the board would be labelled Ac, Ac with no centre tap and a single DC supply could be used. (& could be connected either way round)
What are the markings on the pcb? You still cannot use an adaptor if the pcb has 3 terminals, you'd have to use a mains transformer with dual or centre tapped secondary so there is the 3 connections you'd need.
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