Preamp Tubes? - Who, What, When, Where, Why, and How?

Discussion in 'The Workbench' started by joshuaaewallen, Jan 29, 2009.

  1. mickeydg5

    mickeydg5 Well-Known Member

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    Understand, it is more headroom at a specific power.
    Remember or understand that power is the product of current and voltage.
    Distortion sets in when limits are reached for the components in a circuit/system.
     
  2. Bownse

    Bownse Well-Known Member

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    Thanks. That's what I was thinking. Glad I remembered my lessons properly.
     
  3. StingRay85

    StingRay85 Active Member

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    Such a big thread. No action lately. Time to dig this one up. I just opened up an old Dynacord Bass King 1, and this amp was packing Telefunken ECC83(2x), ECC81, and ECC808, besides 2x Pope Xf2 B9XX tubes. I saw one example of a 2204 with a ECC808, super nicely done. Is it worth the upgrade for V1 of a 2204 style preamp?
     
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  4. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    I’ve tried to get it going a few times but nobody is doing much tube swapping and comparisons. The ECC808 you have isn’t compatible with your amp. It has a different pinout than a 12AX7/ECC83. Now those Mullard xf2 EL34’s and Telefunken ECC83’s are a great find. If they test good they should sound great in your 2204. How about a pic?
     
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  5. StingRay85

    StingRay85 Active Member

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    I have to rewire V1, but that's not a big deal. Its a 2204 preamp that I built into a Sound City amp. I need to open it up anyway to add spring holders for the 6xEL34. I also use it for bass but at moderate volume I hear rattling glass. If it's the microphonics that is sometimes describes, I need to swap tubes until it's gone.

    I went through some of my amps and stash. I have more than 20 Mullard Xf2,Xf3,Xf4 blackburn valves. Around 10 RFT EL34. Preamp a few Philips, Tronal, Brimar, RCA 7025, Mazda (including a '62 silver plate), Telefunken, 1 Mullard.
     
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  6. StingRay85

    StingRay85 Active Member

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    20200525_125806_copy_1651x1238.jpg

    1 ECC81 (for PI), 4x ECC83 smooth plates diamond bottom and then the ECC808s.
     
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  7. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    That’s a hell of a collection. I don’t think I’ve had more than a quad of xf anythings at the same time.
     
  8. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    Right now I’m trying to bring a Gibson GA-77RVT back to top condition. It uses all 6EU7’s in the preamp and I didn’t have any. It came loaded with RCA short plates; the ones with the flat sided micas. Two tested good, the other two were weak but usable.

    I bought a couple of Sylvania long plate Sylvanias and just like their 12AX7s it blew thee needle off the scale. Turns out that the amp doesn’t like the Sylvanias. The RCA’s were way more warm and round sounding.

    I’m waiting on a part to fix the tremolo on the amp and it should be sounding right. It has a 15” JBL speaker in it. Way different than anything I’m used to. It reminds me of a Fender Twin.
     
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  9. mickeydg5

    mickeydg5 Well-Known Member

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    Oh them 15" JBL are nice in their own way. :D
     
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  10. StingRay85

    StingRay85 Active Member

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    I got two E130-8s sitting in a big Acoustic cabinet.

    I'm gassing on a maximatcher maxipreamp ii, but damn those are expensive. I guess it's the only way to really find out if the preamp valves are any good or not.
     
  11. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    I’ve used several different testers. My favorite was a TV-7. I did fine with it and auditioning the tubes in my amp. I’m using a Hickok 800 now since the TV-7 took a shit on me. It was my backup tester.
     
  12. StingRay85

    StingRay85 Active Member

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    Have you ever considered ECC82 in the phase inverter? As a way to replace an attenuator without the tone suck
     
  13. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    I think we’ve experimented with just about every tube in every position. What amp are you using? I remember trying a 12AU7 as a phase inverter in my old DSL50 and it doesn’t so much attenuate as neuter. I’d try a volume control in the FX loop instead.
     
  14. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    what can you do inbetween the PI & power tubes to make it so the power tubes are cooking either before, or along w/ the PI, rather than the PI getting all distorted & compressing before the power tubes are heated up?
     
  15. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    What amp are you using? A post-PI master volume might get you what you’re looking for.
     
  16. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    I'm not looking for it, for any amp inparticular. I just notice that a lot of amp's like the DSL, etc., bottleneck everything into the PI & the breakup on that drowns out the power tubes.

    A buddy of mine has a fire breathing JMP modified. The guy who modded it, supposedly put something inbetween there to boost the power tubes. So, while his amp has more distortion than almost any other Marshall, it still has dynamics, w/o everything sounding bottlenecked/choked at the PI...

    He's very finnicky about anyone touching his amp, so, it's almost impossible to get a look at what is done...
     
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  17. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    wouldn't a post PI, MV attenuate the signal after the PI?
     
  18. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    Yeah, it would. I wasn't thinking right :facepalm:. On a DSL, you're gonna be very limited in what you can do. I'm not up on mods but a JMP would offer up a lot of opportunities for tweaking the circuit. I don't really see the PI as a bottleneck, but it is part of the overall sound of the amp. I've always gone the opposite way and picked the hottest Sylvania I have for the PI. Some of the long plate Sylvanias test as much as 125% above new. I'm doing the same in my old Gibson amp. Give it a try sometime, I think it really opens the amp up.
     
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  19. StingRay85

    StingRay85 Active Member

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    What about a Telefunken ECC801s for PI? Will it help pushing the power tubes a bit harder?
     
  20. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    Quite a bit more than a 12AU7 but still well under an ECC83. Honestly, the best advice I can give you is just try it and see if you are happy with the results. It won’t hurt anything as long as you stay in the 12A_7 family. The circuit was designed for a 12AX7 and IMHO it’s the best to use if you want to really drive the output tubes.

    If you’ve read any of this thread, you should know that experimentation was the unspoken rule. As long as you do it safely for both you and your amp, it can be a lot of fun. If you aren’t sure if a tube is compatible, ask here first.
     
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