Replacement EF86 - quiet / low microphonic

[DesignTaylor]

Hey gang, just snagged a used Eros to add to my rapidly growing (doubled!) Bottlehead collection. It has a wonderful tonality, super sweet, but I'm also getting a ton of background noise. I'm thinking these are primarily microphonics and environmental interference being picked up by the tubes. They all get louder as I crank up the volume.

From my research to date it sounds like reducing vibration is key so I will be adding more dampening to my equipment stand and maybe try some silicone o-rings on the tubes.

I'm also wondering if there are some better EF86s I should try. I've read all I can find on the forum but not nothing conclusive regarding low noise performance. The Telefunken EF86 and Genalex Z729 seem to be very well regarded but have gotten crazy expensive. The E80F Valvos seem promising but I'm not sure how well they control noise.

Let me know if you've found a tube you really like that's more reasonably priced.

Thanks!

[Doc B.]

What cartridge are you using?

[Paul Birkeland]

Also which tubes are in the Eros currently?

[DesignTaylor]

Currently, my cartridge is a Shure M97xE, although I have a few others on hand if needed for testing (Nagaoka MP-110, Audio Technica AT 13 Ea).

I believe that all the tubes are the original stock ones (EF86, 6DJ8, 12BH7).

[DesignTaylor]

I should also note that what I'm mostly hearing is hiss. Sometimes it kind of pulses or sounds a bit percussive (with no input). Worse if the TT is not connected I think. I'm guessing I'm off base with the microphonics (just such a fun word).

[Doc B.]

That's a 4mV nominal cartridge, which is plenty good output-wise. That rules out too low a cart output for the preamp being an issue. Hiss is generally a tube thing, and generally you just have to find a quiet tube by trial and error.

[DesignTaylor]

Roger that.

What say your Eros people? Any luck with nice quiet EF86s?

[Paul Birkeland]

If the Eros was used a lot, the EF86s may be worn out and noisy.  I have only ever seen this in one or two of the oldest Tape Repro amps that I have serviced that were used a ton. 

[Doc B.]

Even the primo tubes can be noisy. You just have to try them. You may pay more but be able to return a noisy tube if you buy from a specialist tube dealer. Or you can buy a few Soviet tubes (6n23p, 6j32p) from ebay sellers and pick the best of the batch. They sound quite good.

[DesignTaylor]

Got it, thanks for the advice. It seems that leaving the Eros on longer seems to quiet it down a bit... does that sound right or I'm I just telling myself what I want to hear? I also noticed that right after I lift the needle off the record the Eros is very quiet but as I let it sit without playing it starts to get louder and I head the little pitter patter super soft popping start to get louder again.

[Paul Birkeland]

Leaving it on may indeed keep it quieter.

Pitter patter reminds me of the noise that can be picked up from certain cell phones and wifi routers. 

[DesignTaylor]

ah ha! it is pretty close to a wifi router... I was wondering if it didn't need more shielding.

Is it better to shield close to the tube (like putting a copper pipe around it as a rudimentary idea), or try and put a divider, or cage of some kind? I know the best move would be to move the router but I have limited layout options. Unfortunately, I've got a bunch of electronics all sharing the same corner.

[DesignTaylor]

Or is it really the cartridge that's picking up the signal?

[Paul Birkeland]

Or is it really the cartridge that's picking up the signal?

You can unplug the tonearm wires from the Eros, then cap each RCA jack with a little piece of aluminum foil, then evaluate the noise. 

The best option is increasing distance between the router and Eros, if that's the cause.  It is certainly worth your time to power down the router and reevaluate the noise again.

[DesignTaylor]

Sounds like a plan, thanks for the testing program.