ECC85 vs. PCC88

Discussion in 'Tube Audio' started by nevermind, Apr 10, 2005.

  1. nevermind

    nevermind Active Member

    Messages:
    264
    Location:
    Lisbon -Portugal -Europe
    Hi
    Someone told me that i should tried PCC88 in the M.F. X10-D instead ECC85.
    I'd like to know some opinions before i try this.
    The first tubes that came with this device were ECC88,but when i changed to ECC85 from Siemens the sound become much better with more detail and the bass more tight and firm.
    Do you think that i give a try with the PCC's88 ?.. :scratch2:

    Have fun .
     

     

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  2. LPD

    LPD Super Member

    Messages:
    2,085
    Location:
    Greater Vancouver, BC
    The PCC88 tube has a 7 volt heater which is different than the 6DJ8 tube family (7308/ECC88). I would check with the manufacturer of your gear to make sure it would be ok as you would be operating the tube cold on the heater thus causing problems.
     
  3. DanTana

    DanTana Super Member

    Messages:
    2,514
    Location:
    Illinois
    I tried some 6DJ8's in my amp, same as the ecc88, and I wasn't very impressed either. The ECC85 is a higher MU and lower plate resistance than the ECC88, that could account for the better sound your hearing? My amp originally had 6N1's in that spot, they are a very good tube if your setup can handle the higher filament voltage. I am now using a ECC99 that is a 12v heater filament and same amperage as the 6N1's but has lower plate resistance and higher transconductance, and I think it sounds better than the 6N1. I have no experience with PCC88's except it uses a 7.6v heater filament, you may be on shaky ground using that tube in that spot.
     
  4. Thatch_Ear

    Thatch_Ear Addicted Member

    Messages:
    7,735
    I get that the filament volts is 1.4 volts higher but would that really make a difference? ECC83 is a 12AX7 and is made for a 12.6 volt filament but works fine on 6.3. The 7.6V might not work correctly on 6.3V but if the transformer is only giving up 6.3 it shouldn't damage the amp, should it?
    What I want to know is if using a 7.6V tube in place of a 6.3V would damage anything? I don't know but feel the worst that could happen is that the tube doesn't sound good.

    PCC88s made for use in TV? Lots of filament voltages in those things.
     
  5. LPD

    LPD Super Member

    Messages:
    2,085
    Location:
    Greater Vancouver, BC
    Not sure about damage, I guess if a person had a wack of em' in an amp it might put stress on the tranny, but you are going to run em' cold and if its a pair or three at 6.3 volts your going to sag the filament vltage and be lucky to see 6 volts on a tube for 7+ Stip em' cold!!! I think it would sound horrible, but if you want to try I have a pair...I won em' on E-Bay but they were advertised as 6DJ8's... :D
     
  6. nevermind

    nevermind Active Member

    Messages:
    264
    Location:
    Lisbon -Portugal -Europe
    Let me say this:
    I'm really new in Tubes.I was til now a solid state guy in terms of hi-fi ( i was for many years a bass player and i still have an Ampeg preamplifier with 12AX7) and than i bought this used Musical fidelity can X10-D with two ECC88 Philips and when i upgrade it to ECC85 NOS Siemens,the sound became stunning in therms of detail and depth.
    This small device was the sparkle for my new recent interest in Tubes.
    "Tubes make the difference"
    Anyway,thanks for all your advises.
    I am learning a lot in this fantastic forum.
    Have fun.
     

     

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  7. Thatch_Ear

    Thatch_Ear Addicted Member

    Messages:
    7,735
    The ECC85 is in the US a 6AQ8 and I have run across this tube a few times in FM tuners. I wan't even aware that it had the same pin out as a 6DJ8, but can easily understand why it sounds better. 6DJ8s were used in industrial occiliscopes and tend to be noisy and harmonic. Finding ones that sound good isn't always easy and from what I understand it is used a lot only because it is easy to design around, not because of sonic qualities. I have only heard this, so it might not be true. On the other hand I have only seen 6AQ8s in good FM recievers so it should be a quieter tube.

    If the 6AQ8 is working good for you I would stick with it. They are fairly easy to find and you can get Telefunkens, Mullards, Amperex and others. If I had a choice between using 6DJ8 types or 6AQ8 I wouldn't hesitate on using the 6AQ8s.
     
  8. nevermind

    nevermind Active Member

    Messages:
    264
    Location:
    Lisbon -Portugal -Europe
    Once again,many thanks thatch.

    Ciao.
     
  9. ModernClassic

    ModernClassic Well-Known Member

    Messages:
    500
    Location:
    United Kingdom
    ECC85 used in audio frequencies behaves like 12AT7 but with only 6.3 v filament option.
    Mc
     
  10. wa2ise

    wa2ise Super Member

    Messages:
    4,303
    Location:
    USA
    Running a signal level tube at reduced heater voltage won't hurt it or the amp. See http://www2.famille.ne.jp/~teddy/datalib/heater.htm (in Japanese though). The curves move to the right some (plate current drops some for the same grid voltage and plate voltage). The curves actually get a bit more linear. Running the 7V heater tube on 6.3v may actually get it closer the linear sweet spot. I've done this with 12AV6 triode double diode tubes (triode = 1/2 12AX7) and it works fine. Main reason I did this was to get better AM diode detector performance (lower contact potential and more linear) and the triode didn't suffer any. I ran the 12AV6 on 10V, normally 12.6V. Your 7V tube on 6.3V is a similar reduction.
     
    Last edited: Apr 11, 2005
  11. Thatch_Ear

    Thatch_Ear Addicted Member

    Messages:
    7,735
    So a PCC88 could sound better than a good 6DJ8? Very interesting!
     

     

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  12. DanTana

    DanTana Super Member

    Messages:
    2,514
    Location:
    Illinois
    PCC88 has a low plate resistance and high transconductance, two good features.
     
  13. nevermind

    nevermind Active Member

    Messages:
    264
    Location:
    Lisbon -Portugal -Europe
    Hi guys

    I'm listening now to my X10-D with used Philips PCC88,and my opinion is :
    The highs and mid frequencies are far better than the ECC85.The highs are also very smooth and with lots of detail the same with the mids.The low,for my taste,are a little
    (how i say this?) far back.
    Sorry about my english.
    Now i'm gonna try to find some PCC's88 from Mullard or Telefunken,because the PCC'88
    have a stounding detail.Why...? i do not know. But that's a fact.

    Have fun.
     
  14. Thatch_Ear

    Thatch_Ear Addicted Member

    Messages:
    7,735
    Thanks for the info. There is a lot of gear out there that uses 6DJ8s some of which is owned by members. This gives them another option for tube rolling and tailoring the sound to the system and the owner's taste.

    If you try other brands of the ECC85s give us a report on that too, if you would. Seimans tubes are good, but not the best.
     
  15. DanTana

    DanTana Super Member

    Messages:
    2,514
    Location:
    Illinois
    Like running a 110v house light bulb at 90v you will shorten it's lifespan. I hope this isn't the case here?
     
  16. andy

    andy Super Member

    Messages:
    4,780
    Location:
    Austin, TX
    A 12AX7 actually has two 6.3v heaters wired in series with the middle connection on one of the pins. When it's run on 6.3v, both sections are connected in parallel, so it's not operating at half voltage.
     

     

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  17. nevermind

    nevermind Active Member

    Messages:
    264
    Location:
    Lisbon -Portugal -Europe
    Sorry Dan,

    but a 110v light bulb at 90v lasts longer.

    Ciao.
     
  18. DanTana

    DanTana Super Member

    Messages:
    2,514
    Location:
    Illinois
    Certain filaments require them to get hot to replenish themselves, others don't. If this is one of those cases then your looking at a shorter lifespan, if not then your probably safe.
     
  19. Thatch_Ear

    Thatch_Ear Addicted Member

    Messages:
    7,735
    Odd voltages are often cheaper to buy.......could be a bargain for 6DJ8 users.

    Is there any kind of a price difference nevermind?
     
  20. wa2ise

    wa2ise Super Member

    Messages:
    4,303
    Location:
    USA
    The tubes in question are indirectly heated cathode types, and low (80%) heater voltage on a signal level tube where the cathode current being drawn is less than half the max spec should be safe. No loss of life.
     

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