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

[TriplePower3]

Hi Thorsten thanks for sharing your build. Would you mind showing some more photos of your chassis, specifically showing how you mounted the tube section?

Looks like we have the same case; and while I was going for a two chassis build; if yours has no hum or noise issues this might be the most graceful option.


John - USA

Hi John,

What photos do you need. Actually my case is open and I could take some.
Mounting:
I simply mounted the PCBs with metal made PCB spacers drilled together until
I reached the required height for the tubes to come outside the chassis closure head.
From the bottom side they are fixed with screws.

Housing is a galaxy 230mm x 280mm x 80mm with 10mm front thickness.
(I use this type for all my builds for the same look)
http://www.audiophonics.fr/en/galaxy-galaxy-10mm/hifi-boitier-10mm-gx288-80x230x280-facade-noire-p-5384.html

I shielded the AC supply voltage cable by putting it into the side profile of the chassis
and covering it with a metal plate. That is the plate you see on picture one below)













Cheers,

Thorsten

[spaceistheplace]

Thank you! Very tidy. How is the microphonics and noise floor? Is it crowded at the rear panel?

Seems you could have fit the tubes inside the case. Was the decision to have them peek out aesthetic?

I believe my case dimensions are identical.


John - USA

[tabarddn]

Hi Guys, well been away for several month on my retirement holida, but glad to be back. While away the copper tape i ordered has arrive and i have installed in in the wooden case i am using. (see below). Yep buzz hum is greatly reduced but not entirely got. L/H channel is good but on the R/H I have a fairly frequent low level buzz, that i can hear when quiet music is played. So I have several questions I hope you guys can help me out with

Am planning to now upgrade it and have ordered a Hammond choke, whether this will help reduce the Buzz or not i don't know but the choke is quite a cheap starting place.   

a) looking again at the board I have not got a earth link between the main board & the power supply board. Should these 2 boards be earth linked.
b) I just want to check what is understood as ECC82 at V3, which valve holder is V3

Cheers & thanks for your help. 

[Jessica_K]

It is very important that the earth links are connected and connected correctly. As you don't have a metal case it will not be earthed but the amp board and power board and the copper cladding has to be joined at a star point. I.e. A single place, this being in this case the earth point on the power board.

V3 is the output valve nearest the connections to the output RCA's. This valve is a cathode follower and as such does not need to be so high gain. The ECC82 is a better sounding valve to the 83 but has too low gain to be used in the earlier stages. The cathode resistor needs to be changed to bias an 82. I have not done the math but guess to about 33k assuming you have not done any mods to the V2 and V3 interconnection.

Any hum, noise etc is not going to improve with the change to choke. The power design does not allow any hum to get through. Hum is introduced by pickup in the very high gain signal inputs and induction within components. The effect of the choke is to improve the sound quality by decoupling audio signal currents and reducing these currents by its low dc resistance.

Robert

[Jay]

Tabardde,   look to the previous page for the line drawing I did about Star earthing.
 Robert approves

Robert, you mentioned that an 82 has less gain than the 83.
I wonder if this could be a possible answer to my "too much gain" into the Leak ST 20.
Providing of course it doesn't mean messing about with the circuit to much.

[Jessica_K]

Hi James
I will do a simulation of using an ECC82 for all valves and see what the overall gain is. It may effect the RIAA will see. Otherwise is should be just a change of cathode resistor values.

Robert

[Jessica_K]

Just looked at the data sheet ECC82 has a amplification factor of 20 the ECC83 is 100. So replace 3 tubes will not work, replacing 2 out 3 will probably still be too low. Will check

Robert

[TriplePower3]

Thank you! Very tidy. How is the microphonics and noise floor? Is it crowded at the rear panel?

Seems you could have fit the tubes inside the case. Was the decision to have them peek out aesthetic?

I believe my case dimensions are identical.


John - USA

Hi John,

space is ok but not much left. Hole drilling should be very exact, otherwise  signal PCB will not match inside.

Only reason for the board lifting was that I like to see the lightning of the tubes 
Technically it would be better to have them inside.
I am lucky that I had no hum or noise when I tested it.
I am still waiting for my RIAA 750kOhm resistors and Mica caps to be replaced.
After that I will let you know if I can still confirm noise-free operation.

Thorsten

[Jay]

Perhaps swapping just one of the 83s for an 82 might do the trick ?

[tabarddn]

Hi Guys thanks for the suggestions on earthing I will try them next week. 

I have no problem with gain from my valve configuration of a) 1 x ECC82 PHILIPS and 2 x GE 5 STAR 5751, And I am running a Eroica M/C high output cartridge.

The sound is in another league to my battery feed upgraded Boozgound and my Micheal Dino, when you consider I have done the whole project for $230 so far, It is unbelievable value for money. 

[Jessica_K]

If all you want to do is cut the volume then changing the 220k output load resistor into two resistors as a potential divider and picking off the middle will do a good job and a much cheaper and simpler answer, for example putting a 51K to ground and 147k to the cap and tapping off centre would also give about 300mV output @ 1k, changing the ratio will change the output, and no pot to degrade the signal.

Robert

[Chris65]

Technically it would be better to have them inside.

Thorsten, I'd be interested to hear your 'technical' reasons for this?

[xdanx]

This is my diy version of EAR 834. The sound is very OK

[Jay]

Robert,  yes cutting the overall volume is the goal.
 

If all you want to do is cut the volume then changing the 220k output load resistor into two resistors as a potential divider and picking off the middle will do a good job and a much cheaper and simpler answer, for example putting a 51K to ground and 147k to the cap and tapping off centre would also give about 300mV output @ 1k, changing the ratio will change the output, and no pot to degrade the signal.

Robert

That could well be a viable solution & not having to change to much, could I prevail upon you to draw a quick wiring diagram of what value components & where to change things.

Dan, thats a very fine looking build. I see you are using an ECC 82 does it lower the output in your build.

[Chris65]

Jay, you could also look at mods to the Stereo 20 to reduce gain. Some good info here: http://www.keith-snook.info/leak-hifi.html