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Recommended 12au7/5814s for Atma-sphere MP-3

I'm told these are the tubes that make the most difference in the MP-3; I have Sylvania 6sn7GTBs for those tubes in the unit. I think that how a tube sounds has a lot to do with the circuit that it is in, so I would like to hear from those that have rolled the 12au7 tubes in this particular unit; although I also welcome general comments on the 12au7/5814 breed. I have RCA Clear Tops, Siemens 5814s, RCA Black Plate 5814s, RFT 12au7, and RT 5814s, and Tungsol 5814s - I haven't started rolling yet; I have the Siemens in the unit and it seems to be very clear and spacious, but I'd like to know what other flavors I can expect with some alternatives. Thank you.
pubul57
pubul57 OP
3,712 posts
 
So what 6sn7s have you settled on for the MP-1? I'm using the early production Sylvania GTBs - stick with this and focus on the 12au7s? - I'll be looking for some Mullards based on comments so far.
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pubul57 OP
3,712 posts
 
Thanks Tvad. I'm going to give the Mullards a try (either CV4003 or 12au7).
mboldda1's avatar
mboldda1
575 posts
 
some of the great 12au7s i've found are the cbs/hytron 5814wa, rca 5814 triple mica blackplate, rca command 5814a triple mica blackplate,raytheon 5814 blackplates triple mica,brimar 13d5, raytheon 12au7 blackplates.
dekay's avatar
dekay
5,668 posts
 
Nice (inexpensive if purchased on Ebay) Mullard Blackburn 12au7's are the late 60's/early 70's which often have Amperex Orange Globe labels.

Can't access my tube cabinet right now, but the pair I'm currently running have GF2/B1K1 etched codes (early 70's).

They sound more like an Amperex Holland 12au7 than a typical/earlier Blackburn 12au7.

5-6 years ago you could buy NOS 5 counts on Ebay for $20, or so, as most thought them to be Richardson relabel's and/or fakes (the auctions did not mention the etched codes)

I thought they were of either RFT or Japanese manufacture, due to the sloped getter and dark flashing, only to find them to have Blackburn codes.

The Holland Orange Globe 12au7's of the same time period would be another good/inexpensive bet.

Look for TV-7 readings of over 100, per section, for an as new tube (my sealed units were typically between 105 & 110).
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