Advice/experience with low noise 12AX7?!?

Discussion in 'Shock Brother's DIY Amps' started by NSB_Chris, Oct 24, 2021.

  1. NSB_Chris

    NSB_Chris Tele-Holic

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    The amps I have built so far that did not use NOS tubes, I sourced basic JJ ECC83s/12AX7 tubes. I have been really happy with them, but when chasing that last little bit of hum, I wonder if I should have paid a little extra to get a low noise version. I see that JJ has the ECC803s which they say is lower noise and just a few $ more. There are others but you can get lost in the descriptions and the hype.

    Interested what advice others have for selection of preamp 12AX7s. If you go with low noise versions, what do you purchase and do you place them only on the input tube or do you also see an advantage using them deeper into the circuit?
     
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  2. Mike_LA

    Mike_LA Tele-Afflicted

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    Don't really know but a good chop stick session in the dark can be very helpful . . .
     
  3. guitar_paul1

    guitar_paul1 Tele-Holic

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    Metal film resistors help with noise, too.
     
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  4. bumnote

    bumnote Tele-Holic Ad Free Member

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    Try looking for 12ax7 variations. I've had some good results with 7025's and Sylvania's 12AD7's. It"s been a few years since I've bought them, but NOS Sylvania's used be pretty affordable
    I generally get them off eBay....just look for sellers who sell mostly tubes and have excellent reviews. Some days you may find some good deals...other days it's slim pickings.

    http://www.vacuumtubes.com/12ax7.html

    It's also helpful to know how to look for relabeled brands. Some store brands were made by RCA, GE, Sylvania, etc. I like this page, the pictures of the boxes are interesting & there's usually some info on the make.
    http://pax-comm.com/pa01000.htm
    http://tubesound.com/category/tubes/page/4/
     
    Last edited: Oct 24, 2021
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  5. Zoso420

    Zoso420 Tele-Meister

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    Mesa Boogie "makes" an Spax7. It's a 12ax7 that's been tested to be extra quiet. They're to go in V1 of the preamp because most their models are high gain and the V1 is pushed to its limit.
     
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  6. owlexifry

    owlexifry TDPRI Member

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    i tried out the 'low noise version' of the JJ ECC83S, called the 'ECC83'.
    only tried it in the V1 position (input stage) in my SLO 40w build.

    it was worth the extra $5 over the regular ECC83S. Smoothed out and reduced harshness in the high gain tone without harming any desirable aspect of the high end.
     
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  7. NSB_Chris

    NSB_Chris Tele-Holic

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    Is this the one:
    https://tubedepot.com/products/jj-ecc83-12ax7-gold-pin-preamp-vacuum-tube
    This is the only one JJ has listed as ECC83. Or did you source another brand?
     
  8. NSB_Chris

    NSB_Chris Tele-Holic

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    I use 1W metal file throughout signal path unless unless higher wattage is called for.
     
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  9. jrblue

    jrblue Friend of Leo's

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    I find that the NOS low-noise variants (I forget the tube codes, sorry, but you can easily look them up) live up to their ratings as current production do not. I hate blowing money on tubes, and the supply is disappearing and prices are going way up, so I'm glad I secured my stash a few years back when you could lurk on EBay and get the varinats, unknown to most buyers, for little. Now they're all pricey. Current production 12AX7s are getting better, I think, but the basic, standard tubes from the familiar makers are not very good, really, and in little amps like the ones I run, it's worth getting NOS or even used/tested both to eliminate noise and to get a somewhat better sound. People swear by TAD and other tested and screened tubes, because while the build is nothing special, at least you're going to get a tube that tests well, is within spec, and probably not adding noise. Depending on the amp itself, it is sometimes wise to use a lower-gain replacement for a 12AX7, as I find the new amps are sometimes built to be too high-gain and fizzy for me, and they tend to be noisy. I can usually get a lower-gain tube of low-noise build and high quality affordably, and this tames the noise considerably.
     
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  10. owlexifry

    owlexifry TDPRI Member

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  11. Rick330man

    Rick330man Tele-Afflicted

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    I'm a big fan of the 1980s production JAN GE 5751s and JAN Philips 5751s for this very purpose. They are also great sounding tubes.
     
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  12. DavidP

    DavidP Friend of Leo's

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    If you can find them, NOS 7025s are spec'd as lower noise 12AX7s.
     
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  13. DavidP

    DavidP Friend of Leo's

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    Yep, another option!
     
  14. Mowgli

    Mowgli Tele-Meister

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    Keep in mind that noise is additive at every stage.

    As far as noise reduction steps are undertaken I suspect that low noise tubes (e.g. 7025), metal film resistors and a DC power supply for the filaments to rid the small amount of AC heater hum would go a long way to lower the noise.

    And avoid compressor pedals since they will raise the noise floor.

    Those are my 2 cents.... but I defer to those with greater experience and learning as always.
     
  15. kbold

    kbold Friend of Leo's

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    12AD7's are the quietest of the quiet 12AX7 variants you will find. (Well, the quietest I have come across.)
    The ones I have are NEC (Japan).
    Alas, also some of the hardest 12AX7 variants to find.

    Sonically, the 12AD7's are: neutral/ transparent when clean ..... thick/furry on soft distortion .... thick/lots of treble without glassiness on hard distortion.
    That's my experience, on my amp ... overall, a pleasant preamp. Individual results/opinions will vary.
    Well, that's enough cork sniffing for now.
     
  16. Fluddman

    Fluddman Tele-Holic

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    Have you tried using DC for the heaters?
     
  17. Tom Kamphuys

    Tom Kamphuys Tele-Holic

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    Are you chasing (low) hum or noise?

    The biggest noise source is (normally) the input grid stopper according to Blencowe.
     
  18. dougsta

    dougsta Tele-Meister

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    I'll be very interested to hear of any measurements around the noise floor of a pre-amp, filament hum and hiss.

    I started a '63 Fender Reverb Unit 6G15 recently and I'm very keen to eliminate all the background noise I possibly can, the signal chain is Strat -> 6G15 -> Focusrite Saffire firewire audio interface (known for good low noise preamps) -> Mac Logic Pro.

    My initial build used a 470Ω resistor instead of a choke after the 1st filter cap in the PSU, I wound a choke the other day and added it in (I have a Hammond 4H choke that I 'copied' and compare to).

    I'll do some recordings to compare.

    I have some nice 1950s Mullard and Telefunken long plate ECC83 and a bunch of chinese/russian 12ax7 to compare with each other.

    Doug
     
  19. Wound_Up

    Wound_Up Tele-Meister

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    I thought the 803's were a long plate 12ax7 or something? Not that they can't be that AND low noise lol. I just thought I remembered reading that not long ago.

    That's good to know. All of the ones I bought so far to build pedals are 1% metal film resistors. I only bought them for the 1% tolerance but it's good to know they have other benefits.
     
  20. NSB_Chris

    NSB_Chris Tele-Holic

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    Hum mostly
     
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