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

[GrooveGrinder]

I think this thread's length is starting to look inversely proportional to the current speed of international shipping from China and Russia....

Welp... funny you should mention it..... My original board suddenly materialized from tracking limbo.. and started to "register"..
It *should* arrive tomorrow or monday at worst... (crossing fingers not wanting to jinx it)...

Speaking of the thread length.. its title is a bit odd at this point... "a short evaluation/ test with those chinese PCBs"
LOL!
I wonder if a mod could change it... to something like "the definative diy ear 834 build thread" or something to that effect... That might mess up some people's searches and the like?
On to more important matters...

If you go hifi2000 way (which i use a lot in my projects) you can use Front Panel Designer and export DXF/DWG from there, they should be able to work with those files

FPD is VERY good!!!  Might want to try that John!

Two cables are better then one. The reason is that the source and destination of the supply current are separated and any noise on one channels supply ( caused by signals) does not get on the other improving channel separation. It isn't necessary however as it's fully supplied with one cable.

Brilliant Robert!
At the beginning I had wondered about 2 cables, but only because I didn't know of connectors with that many pins!
The channel sep and noise rejection would be good by itself, but it would also ease assembly of the umbillical,
be less cumbersome, and ease strain relief concerns!
So, how exactly please, would that be implemented???

It's not very flexible

I wonder then about strain-relief??

I ran a 5th wire, under the braiding for earthing the PCB to the star point, rather than connecting it to the chassis.
Both chassis are grounded via the power cable's grounding mesh

This is exactly what I was thinking of! (I'm assuming it's a bare wire)
Particularly if the connectors in contact with the braid isn't practicable.. and depending on one's grounding scheme..
I have used this method in the past.... the device was verrry quiet..
(hard to know if that single item was responsible for that, but I'm convinced an aggregate of things are, including that)

A question that popped in my mind is, where to connect the turntable ground ? Would it be ok to connect it to the chassis ?

To my mind, THIS is the critical question... regarding grounding.... and system-wide grounding...
I think it needs to be an overall scheme..
(especially if I'm to avoid "cheater plugs" which defeat the 3rd prong on some equipment)

For example in my case. I connect it to the SUT case and core with the SUT not connected to the preamp gnd. This is because the mains cables of both the amp and the turntable gnd at the mains socket and to connect to the amp forms a loop.

In my case, the provider of the SUTs recommends no ground wire.. just think of the SUT as a "big bulge in the phono cable"..
Just put the RCAs in contact with the case... one wire (per channel) to the trafo.... who's case/core are common with the negative..
Seems kinda funky to me... (tho it does simplify the build of IT)... and it ties into an overall grounding SCHEME..
I have not yet built, nor obviously, tried it however...

I did not tie the signal ground to directly to the chassis or phono ground as I've seen done by others but will try for curiosity's sake.

This is what I've been thinking of.. and wondering about all along...
"Float" the signal grounds... IN the 834, let the signal grounding get handled by the Linestage via the RCA cable negative...

I don't know if/how this applies to anyone else's setup however...
In my case, I happen to also be building a Linestage too, a couple of months further in to it though... now at
the point of having to figure out this same issue..
Big part of the reason I've begun to see it as an overall system scheme...

I'm not sure I understand why not just float the audio circuit completely... let it ground back to the PS... which is ultimately grounded..
Not sure, for that matter, why it needs to be grounded to the case at all...
(plus a "safety ground" .....with appropriate cap/resistor between 3rd prong and case I guess)
As I learned it... even if you use a 2 prong only plug.... there IS a path to ground.... albeit back at the power station..
In fact, equipment pre 1980 or so had only 2 pronged plugs... (here in the U.S. at least)... not long before that, there was no such thing as a 3rd prong... and no provision for it in the wall socket!
I'm not advocating a return to that... and it was a positive advancement for safety for sure!
BUT... just to make electons flow.... and through your circuit.... 2 prongs will do!

If you meter out your AC wall socket... you'll find a slightly larger voltage differential between hot and 3rd (true earth) prong, than between hot and return prongs..
The 3rd prong being at a slightly lower potential...
(Forgive my inelegant discription, its very late here)

I realize this might be very different in other countries.... a Brit once explained to me that its "ring mains" there, branch here...
What other differences, and how they affect audio system grounding, I haven't a clue... but it MIGHT make a big difference...
Luminaries please chime in!!!

The preamp/control-center I used till recently, was a classic 1980s unit.... it came with a 3 prong line cord..
One particular power amp I happened to like... was from a few years earlier... it came with a 2 prong plug..
Tuner from same year as preamp... 2 prong....
When I connected a newer amp to the system............. HORRIBLE BUZZ! had to RUN to shut it all down..
Used a "cheater plug" on it ever after... (but I DON"T like to!!)
Preamp I used just before that one.... same maker, 4 years earlier model.... 3 prong BUT, it also has an actual "banana-jack" pair on the rear... with an integral jumper..
Removing the jumper "floats" the circuit..... for just such cases.....

So how do I design this SYSTEM... for avoiding cheater plugs, yet not having minor to horrible HUM/BUZZZZ???
How to approach it as a system grounding scheme??
(in the past I just let the preamp do all the grounding)

PS: My cases arrived today..
(or did I already mention that?)
Got 'em all cleaned up and assembled...
Moving right along now!!

Geeze this is gonna fill up a whole page.... SORRY!!!!

Greg

[spaceistheplace]

Robert thanks that's beginning to sink in. I will address it when I get the rest of the chassis complete / build guide up.... been fiddling around with the cad drawing, and trying to sort out this umbilical saga.

Chassis should be here Monday-ish and I'll get to it.

I'll send it over your way to have a second set of eyes on it before I post.

Just as a note to myself, part #'s for your RIAA suggestions:

x4 71-RN65D-F-680K (1% 1/2W 680k)
x2 71-RN65D-F-110K (1% 1/2W 110k)
x2 598-CD15FD271FO3F  (1% 500V 270pf)
x2 598-CD15ED330GO3F (2% 500V 33pf)
x2 598-CD15FD101FO3F (1% 500v 100pf)

Would you go with a 1kV 1% cap for the 33pf? It was the only 1% available, but I imagined it would be prohibitively large. Might make more sense just to look elsewhere.

[GrooveGrinder]

so, easier on the psyche.

LOL!
That's rapidly becomming the prime consideration!!

[spaceistheplace]

Also, from my reading it seems generally recommended that a capacitor be placed between chassis and phono ground, and perhaps also one between phono ground and signal ground?

I've always just used a 0.1uf ceramic, but some say a resistor is sometimes used but did not indicate a value or rating. It's always served me well but I'm unsure if there's room to improve on this practice.

What locations and values should I be looking at? Should it be an X2 type or is this just used across the ground/line power pins?

[Jessica_K]

Hi John
Voltage is not important.
However, 2% of only 33pf  makes 0.66pf error in 303pf so maybe it is good enough. Checked with the sim and worst case stays at 0.37db

Robert

[spaceistheplace]

Did you mean 303 or 307pf?


John - USA

[spaceistheplace]

Regarding the USSR Power connectors: The seller wants me to mail it back to Russia but the shipping is probably the same as my refund. The listing was a bit deceptive, but what can you do... It's not worth having a battle over.

So, in the state that they are in, the cable is like a hotdog in a hallway.... large opening and no lock down strain relief connected. Even a ton of heat shrink won't create a firm hold.

Rather than let it completely go to waste I was thinking, as a MacGyver solution, to solder the cables as usual, test them to make sure they are conducting properly, and then reassemble the connectors and "pot" them with marine epoxy or perhaps caulking or silicone sealant? Maybe even that gap filler stuff?

Since the two sides of the casing are wedged together with screws, I was thinking just put a length of tape to prevent any of the sealant getting out.

Is this a bad idea? I believe all those materials to be non-conductive, but not exactly sure if they are mixed with other stuff.

I read this about Silicone: "Silicones are excellent electrical insulators with grades available with volume resistivities as low as 0.004 ohm.cm. Their thermal stability means that properties such as volume resistivity, dielectric strength and power factor are not affected my changes in temperature. They also display arc and corona resistances surpassed only by mica."

Pic of opening vs the cable size:

[GrooveGrinder]

Woohoo... Board FINALLY  arrived!
The built one..... 
I won't waste space or my time taking/posting pix of what everybody's seen... Unless someone wants a pic..
I could put the blue board and the douk board side by side for comparison.... IF that's useful to someone..
Just.. the blue board is bare.. the douk assembled..
Maybe we should start calling it the ZHI HiFi board as is printed on it, rather than douk...

But dangit... the RCA jacks I had on hand don't have insulators.... Grrrr..
Back to searching on that..

John..
Potting them seems a good idea... I've used Silicone sealant as an insulator..
Just make sure to get the pure kind....... not mixed with something else, marketed as a different product with a different purpose..
Tube should just say: Silicone Sealant.

Can you cut a round piece of metal to screw to that flange? Then you could just make a hole of the correct size in the center of it.
Using a small "zip tie" around the cable inside of that, would help to retain the cable from pulling out...
Just a thought...

[GrooveGrinder]

So no further thoughts on grounding?
Anyone???

[Jessica_K]

Did you mean 303 or 307pf?

Corrected post should have been 303pf. Oops

[spaceistheplace]

These were the build pics I was looking at with the caps. Xdanx did this one. Had to dig around this post is getting longgggg. Figure if it's theoretically good, can't hurt?

Also, noticed the giant 330uf caps up front. Anyone venture a guess what he was going for with that?












John - USA

[spaceistheplace]

So no further thoughts on grounding?
Anyone???

Read the Star grounding how to's littered about the web.

Like Robert said there is no global right or wrong it's highly dependent on your system configuration and build.


John - USA

[Jessica_K]

Hi John

The caps across the valve are across the heaters as I thought. The value is not that important but need to be poly films. It's low voltage so the original suggested 1uf will be quite small

The gert large cap at the front is just an extension of the PSU filtering. No harm in increasing its value. I would bypass it with a wima 10nf though specially as it's so large


Robert

[Jay]

So no further thoughts on grounding?
Anyone???

hears my interpretation on Star Earthing

& this is it in practice The Star point is just above the Tranny

Hope its of help.

I will have the box finished in a couple of weeks, I'm just about to 'turn' the knobs on my 'new' 70 year old lathe that I have just very recently acquired 

[Jay]

Was watching 'Big Little Lies' & part of the sound track was Grace Slick singing an Acapella version of 'White Rabbit" looked it up & it's on YouTube, where else. So I got my headphones (Monster beats mixr) out plunged them into my Laptop & WOW, anyway it struck me that listening via the 834 just might be a tad better.

 So can I simply add a headphone socket wired into the output ? Or would I have to do some alterations to the output.....