DIY Audio Projects Forum

EAT834p tube MM phono preamp
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Author:  mwhouston [ 07 May 2019, 18:10 ]
Post subject:  Re: EAT834p tube MM phono preamp

I have not tried any other 834 deigns or cct. brds.

By flicking the tube with the back of the finger nail you can tell if the tube is overly microphonic. After saying that I’ve never done it with small tubes but have with 6AS7s. I use these in my tube headphone amps. Out of about four different tubes I found one which was dead silent when rigorously tapped. Some rang like bells. Purely on this test I chose the tube to remain in the amp.

I’m not convince that the sound of a tube is based on its microphonics. In an above post it was stated remove the microphonics and remove the tube sound. Disagree. The tube has a sound or character and is better served if microphonics are low. .

Author:  Gab [ 07 May 2019, 18:59 ]
Post subject:  Re: EAT834p tube MM phono preamp

I don’t think he meant that microphonics in general are good sounding. Microphonics are inherent to vaccum tubes, even for the ones that aren’t prone to it. That minimal amount would be "part of" the tube sound.

Author:  Gab [ 08 May 2019, 14:21 ]
Post subject:  Re: EAT834p tube MM phono preamp

I did test the tubes I use in my preamp with a light tapping and what a difference ! The GE ECC82 is practically silent when the RCA clear top rings badly. After some use (been using this tube for less than a week) I can hear some intermittent ringing than might be caused by the tube. I’ll try different tubes tonight. I never thought the difference between two tubes of the same model could be this big ! Definitely, that level of microphonics isn’t good sounding at all. Thanks for the trick !

Author:  Psychoman67 [ 09 May 2019, 13:56 ]
Post subject:  Re: EAT834p tube MM phono preamp

Hi all,

Don't want to look like I'm hijacking your post, but, I need your expert knowledge.
It's been over 20 years since I built anything, so I fancied bringing back some memories and just bought the one made by Zhili Audio.

It's a slow process and I can only do things when i have free time and space.

I am using 2 enclosures. One for the PSU and the other for the Phono Stage and nothing will be on show apart from the mains switch.

I would like to know, what would be the best and cheapest way to connect the PSU to the Phono?

I am at a complete loss. obviously safety will play a part, don't want any exposed connector pins.

What cable and connectors would you or anyone recommend?

It's going to be a long project, but i'll be taking pictures throughout the build.

I do have most parts and also pondering on whether to buy some decent capacitors.

Any help and recommendations would be most appreciated.

Thanks all in advance


Author:  mwhouston [ 10 May 2019, 21:02 ]
Post subject:  Re: EAT834p tube MM phono preamp

Not all will agree but I use XLR plug and socket. A male XLR socket on the phono amp and a flying lead from the PS with a female XLR plug. I use a right angle plug because then it sits snug to the back of the amp. No exposed pins because there is about 250V here. In the amps I make the heater voltage a smooth DC. I use white mains 10A lead and make the earth wire ground for both the HT and the heater voltage. Then (in Ozz) the brown wire with the 250v and the blue with the 12V. Used this method dozens of times works well.

Author:  Psychoman67 [ 11 May 2019, 04:00 ]
Post subject:  Re: EAT834p tube MM phono preamp

WOW Thank you for that.

I'm probably making too much of a big deal making this. Is been well over 20 years and now not really have the confidence.

Years ago I could just walk into an electronics store, browse their catalogue, ask a few question and buy cable by the meter. Now it seem so much more difficult.

I did buy some shielded mains cable, but it is way too stiff. I do have some Raychem twisted red/black 20awg cable, but not sure if this will do, as it is quite thin. I was going to untwist and double up the red and black and twist them together and cover with heat shrink. There is an IEC socket with the PSU case and I was going to replace with a filtered one. Trying to make it as good as I can and hopefully it will sound good and not have any hum at the end. Think I'm looking into this too deep.

I am also going to purchase a pair of MC Coils and wire them up inside.

What do you think about the capacitors?

Was going to replace some, but, ended up not doing it because I can't find all the values, especially the resistors. These would be from HI-FI Collective.

Don't know how I did it all them years ago lol.

Sorry for rambling on.

May be I should create a proper thread.


Author:  mwhouston [ 11 May 2019, 08:42 ]
Post subject:  Re: EAT834p tube MM phono preamp

I stayed with the kit components because they were all high end.

Author:  Psychoman67 [ 12 May 2019, 05:55 ]
Post subject:  Re: EAT834p tube MM phono preamp

Thanks for that.

Will just build it as is.

Hopefully upload pics.


Author:  Psychoman67 [ 12 May 2019, 15:49 ]
Post subject:  Re: EAT834p tube MM phono preamp

Thanks for that.

I suppose one step at a time. Get it working first, enjoy it and then improve, if it needs it.


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