DIY EAR 834p phono stage - a short evaluation/ test with those chinese PCBs

[JacquesD]

... Blank Xuling boards are now 4x the cost ($199USD) of the Douk boards ...

Wooh, I paid 19.90 USD per piece somewhere in 2018... How is inflation in the PRC?

With that difference, I'd go for the Douk board, I would say that one can build an equivalent unit with it. Better spend $$$ on some components.

Success!

[mike]

Wooh, I paid 19.90 USD per piece somewhere in 2018... How is inflation in the PRC?

With that difference, I'd go for the Douk board, I would say that one can build an equivalent unit with it. Better spend $$$ on some components.

Success!

Thanks Jacques. It seemed like a no brainer (and yeh spend the $$$ on some nicer parts), but well it doesn't hurt to aksk. I ended up ordering a blank zero-zone board which seem to be trending at $11.00USD. Hopefully that'll work.

[JacquesD]

Thanks Jacques. It seemed like a no brainer (and yeh spend the $$$ on some nicer parts), but well it doesn't hurt to aksk. I ended up ordering a blank zero-zone board which seem to be trending at $11.00USD. Hopefully that'll work.

Hi Mike,

Yes, the ZeroZone board works reasonably well, but has less room for larger components and the tracks are not very happy with repeated de-solder/re-solder manipulations -- may depend on one's soldering skills.
I particularly liked the separate tracks for pins 4,5 and 9, allowing an easy use of 6N2P-EV tubes, ignoring the labeling, of course.

But it is a good place to start this kind of project!

Success,

[frode n]

Hello !

I have made a separate power supply to the Ear 834. On the original power supply, the negative of the heater was connected to gnd.
Should I do the same her ?

Sincerely
Frode

[Taso]

Hi! What are the best high voltage diodes?
The best..the quietest..and the fastest?
UF4007, mur4100?

Wouldn't it be better to use ultrafast + SOFT .. like BYV26C?

"SOFT" wouldn't we be better also for the noise?

THX

[Jessica_K]

I use IDH03G65C5XKSA1 these are silicon carbide shottkey, about the best diodes you can get

 Revolutionary semiconductor material - Silicon Carbide
 Benchmark switching behavior
 No reverse recovery/ No forward recovery
 Temperature independent switching behavior
 High surge current capability
 Pb-free lead plating; RoHS compliant
 Qualified according to JEDEC1) for target applications
 Breakdown voltage tested at 6.8 mA2)
 Optimized for high temperature operation

Jessica xx

[Taso]

woow! many thanks! this is actually the best solution for HT?

..and the best solution for filament? my ear filament work ar 12,6v.

I don't want to compromise. I would like the best.

thanks man :P

[Jessica_K]

Be careful for use on filament, it has a forward voltage of 2.1V so can be a bit to high for your transformer to provide a DC that is in range to drive a LDO to regulate the supply

thanks man :P

Jessica (a girl lol)

[Taso]

  hemmm..sorry Jessica! 

[Taso]

Hi guys, I'm still here...
I bought a hammond 154e..20mH.. to put in my psu.
My psu pcb is not the standard one on sale..I make it on a breadboard.
I would like to do it this way.
I ask if you see something strange..something missing ... in short, if there are corrections to be made ... I would appreciate it ..and Sorry for my poor English!

In my valve pcb board i have 6 x 150uf 400v.
In this schematic i suppose is ok ...total of 333uF before the L and 183uF..after the "L".
I am looking for the "quieter solution" and I am able to change the capacities of the entire circuit according to your advice!

More or less I quantized the values ​​of C (around "L") by reading on this forum and also looking at your psu photos.
I was also taught that the capacity before and after L no must never be identical as strange oscillation phenomena can be created!

Considering these capacities before and after "L" ... and the capacities on the valve board (6 x 150uf) .. is everything ok?

In my drawer I have 3 options for diodes. The ones you recommended MUR4100..or I have MUR460 and up I also have HFA08TB60PBF.
I would be grateful if you had a look at the respective datasheets to help me understand which ones to use. They are all already in my drawer.

Diodes Option:

MUR4100 (75ns) > http://www.liteonsemi.com/download.php?hSFile=MUR4100-0.pdf&hDFile=tecfile01493279020.pdf

MUR460 (60ns) > https://www.onsemi.cn/PowerSolutions/document/MUR420-D.PDF

HFA08TB60PBF (UltraFast and UltraSoft /// 55ns or less) > https://www.infineon.com/dgdl/hfa08tb60pbf.pdf?fileId=5546d462533600a4015355bfd7ed15d5

This is my pattern (voltage values ​​are under load):



So I was wondering:

- If the capacity before and after the "L" are fine or if I have to increase / decrease them.

- Would it be better to put on capacitors..of low capacity bypasses? If yes, how much? One per capacitor or one per group of capacitors?

- If on the capacitors I have to put R's in parallel .. to discharge them and to make the transformer see more a "resistive" rather than capacitive load.
I read something about it but I didn't understand much (I would prefer for the capacitors to discharge quickly on shutdown).

- Which diodes are the most suitable for my situation and my availability? I already have the three options.

-....and finally ... the snubber talk about diodes. Should I put them yes or no? I suppose YES...but....but I would like confirmations .. especially based on the diodes that are used. Does it depend on the diodes?
I did some reading and there are also options to put only one snubber at the exit of the bridge..and therefore not a snubber for each diode.
Someone says that if you put subber on fast diodes ... it doesn't make sense because the snubber slows them down !! I have no idea ... I would only like the quieter solution!


I really hope that you will clarify these doubts because I would like to get down to work immediately to make this pcb ... definitive again.

Thank you so much.

[Jessica_K]

Hi Taso,

I have looked at your schematic and it has a fundamental error, the DC side of the diodes are not connected, this could just be a typo but below is the corrected diagram

As for capacitors, the quality is more important than quantity. In my PSU's I only use 10uF caps and there is no hum, but I use polypropylene, these caps have very low series resistance and can deliver huge amount of current when required. However the amount of electrolytic capacitance needs to be higher and made of caps in parallel to get the same effect.
You are correct to have more capacitance before the inductor than after, as this is the bulk storage of capacity, the cap after is the filter with the inductor. The values are good.
As for diodes I always recommend SiC (silicon Carbide) rather than just silicon, but if I was to choose from your options then use the MUR4100.
Snubbers, are to remove the switching recovery charge that occurs in silicon diodes and the reason why I use SiC is that they do not have this switching noise.

Hope this helps

Jessica xxx

[Taso]

1000 thanks Jessica, yes the bridge of diodes I had drawn it wrong ... but I will mount it correct.
Well, they used these values ​​of capacitors and the mur4100.
They also put the snubber .. hoping that their value is correct.
To finish the doubts and questions .. do you think resistances are suitable to discharge the capacitors?... or the 120k in the scheme is already sufficient?
It is also appropriate to bypass electrolytics (or groups of electrolyte) .. with lower value capacitors, perhaps MKP?
In my drawer I have 10 x 0,68uF 400V MKP and some MKP4 1uF 400V.
Could I put 3x0.68uF before and 3x0.68uF after the "L"? It would be a good idea?

Thanks

[Jessica_K]

Hi Taso,

The problem of using a simple resistor to act as a discharge without a switch of some sort is that the value required to discharge the 600uF or so total supply of capacitance in a reasonable time say 10 secs is quite low and that means a large amount of lost power heating the resistor up under normal use.

There are a few options
1 using an active switch that detects the loss of AC and switches in a low value discharge resistor
2 use a 4 pol mains switch, 2 to switch the power and the other to switch in the discharge resistor when power is off (one spare) .
3 continue using the 120K, it will drag 2-3mA from the circuit during normal use, but will bleed the caps over a min or so when turned off

using bypass caps across the electrolytics is a good idea as they have a lower ESR and hence provide current for edge speed demand that can depending on the amp design give a more dynamic sound. Any value of 100nF or over will do.

Snubber values are a bit of a black art, as it is hard to measure the effect, best to use what you have selected to start and later try different resistor values to see if there is any improvement

Jessica xx

[mamakasou]

Dear friends,

I have recieved the EAR PCB from Douk and I am looking at populating it.
The information gathered around this specific design is of great help.

Thanks to all you guys out there that have contributed your knowledge.
For a lot of us, it can be quite easy to lose track of everything that has to be done, so all the help is appreciated.
 
I have been reading through the many pages and if I understand correctly, there are two main paths to be followed regarding values for those RIAA capacitors in the feedback loop.

One i've seen in various schematics (in Douk as well) using a 330pF followed by a 110pF capacitor.
And another proposal (i might be wrong but I think originally by Robert), that replaces the 330pF with a 300pF and the 110pF with a 100pF.
Please correct me on the above if I am wrong.

Now if anyone has used both, can they describe what's the difference in sound?
I was ready to try both sets of values, but those silver MICA are not exactly cheap, so I thought I ask you guys.

Thanks in advance!

[Taso]

..someone also says that an R would be missing in parallel to a C .... on the original scheme from where the china copied .... The riaa equalization group is lacking in a component, which has given the apparently high value some esoteric carazy thought it was useless.
It is a resistance to be placed in parallel with the cell's 330pF capacitor.