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

[spaceistheplace]

Yes John, I completely agree with what you said about how we perceive the change in the sound coupled with our mood and about jumping to conclusions.

I tried different recordings and gave it a few hours before reverting back the changes. I faced the issue only with 120K resistor with ECC83 at v3, ECC82 sounded right.

I have not given up yet and will try the better quality 120K resistor as suggested by you (3watts 1%).

I believe there's a little over 1 watt on that resistor, so derating is important in that location. What wattage resistor did you use? I don't think a 5% resistor would make the kind of obvious difference for the worst you heard.

Just to be clear: you swapped the correct resistor yes? the 68k resistor? Just making sure... we all make silly mistakes.

But, I would suspect the tube before the resistor.

I was talking in a PM I think with Robert and it seemed an AY7 might be the ultimate compromise between the AU and AX in V3. Lower output, more linear response.

I don't recall it we (he) determined what the proper resistance change would be for that tube. I will check, or he might chime in with more info.

[Jay]

John, as my build is effectively starting from Scratch, use whatever you need from it if it's appropriate for the build guide.

[spaceistheplace]

Thanks Jay. I will keep that in mind. Mostly it's the copy, and it will be nice as I'm using the same chassis as recommended in the build guide, but I will definitely cherry pick some useful pieces. I will also put a link to your diy tube dampers.

[Jay]

Hold off on the link John as I'm going to do some better ones

[Scott Moore]

What is a tube damper and what does it do?

[Jessica_K]

I think I calculated that ideally the 12ax7 needed 1mA (120k) the 12at7 and 12au7 was 5mA (22k) and 12ay7 required 3mA (36k)  the 68k for the au is only 2mA so a bit light

Robert

[Jessica_K]

Tube damper is something you put around the vavle(tube) such as a silicon band that reduces microphony. All sorts of methods are used to do this but the result is to stop vibrations on the tube surface from getting to the electrodes, that if they do vibrate cause electrical noise

Robert

[Jay]

Well thats 100 pages & still going strong

[spaceistheplace]

What is a tube damper and what does it do?

Further reading: http://forums.stevehoffman.tv/threads/tube-damping-rings-do-they-make-a-difference.21597/

Also do a search within the forums for Jay's DIY dampers.

[spaceistheplace]

Well thats 100 pages & still going strong

Do we get a free t-shirt or something? 

[Jay]

  I wish  

Just had a look at the Stereo-Mono Mute switch $12.00 not bad at all   Till I tried to buy one & shipping cost was $32.00 = $44.00  

so no switch on my 834
 
Their appears to be no other source of these simple but useful switches

[spaceistheplace]

I used one briefly and took it out as I just wound up using the volume knob on line preamp to turn down the volume, and well I guess I am just too lazy to flick the switch when playing a mono album... Seems useful from a distance, but you will not be losing out...

This last build for me has been an exercise in part removal not addition. I found I added some functions just because I could, rather than because I'd use it.

Shipping from US is tough.

I really had to do some "Tetris" maneuvers to get all the kit parts to fit in the small flat rate boxes... $35 is the cheapest noncommercial rate for priority international.

However, here's a consolation prize! Something of more clear and present interest to you:



Antek transformer in 100% silicone, and I cut out a circular piece of thick sorbothane which I will sandwich on there as well to dampen any mechanical vibrations in my final single chassis build.  

Looks messy but it's still drying... and obviously you won't be looking at the underside.

You could also try epoxy.

[Jay]

I'm sometimes even to lazy to turn the volume down..... still Ill persevere with just the volume 

Potting the tranny in silicon or resin is likely to be a one way ticket !
If one used some kind of release agent then it might be possible to remove the cover at a later stage, I say might as they are quite tight around the core of the can.

The silicon may take up to a week to Cure properly.
The Extra Sorbothane is also a good idea.

I was thinking about lining the inside of the can with a single layer of Copper foil.
 would their be any milage in doing that as a bit of extra screening of the coils...

Am off shortly to see some LH members who are having a bit Soirée, I'm taking 834 & SoB.

[spaceistheplace]

Nice! Let me know how it fares with them and enjoy.

Yes there's a special type called mu metal for wrapping transformers.

The sorbothane will likely make the biggest difference, use a nice big slab.

I used the silicone mostly to adhere everything together for tight bonding to the chassis.

I have no conceivable reason to remove the toroid from the cover again.

[spaceistheplace]

https://www.lessemf.com/mag-shld.html

Also U.K. Retailers are available so no exorbitant shipping.