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    Passive Preamp vs. Tube Preamp

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    Sprags

    Posts : 123
    Join date : 2013-02-27

    Passive Preamp vs. Tube Preamp

    Post by Sprags on Sun Mar 24, 2013 8:49 pm

    Quite simply...what are the differences? What makes a tube preamp worth more and worth having more than a passive preamp?

    hawaii.ken

    Posts : 157
    Join date : 2012-01-31

    Re: Passive Preamp vs. Tube Preamp

    Post by hawaii.ken on Sun Mar 24, 2013 9:32 pm

    Sprags wrote:Quite simply...what are the differences? What makes a tube preamp worth more and worth having more than a passive preamp?


    If you don't play vinyl and your power amp has enough sensitivity you probably don't need an active preamp.

    corndog71

    Posts : 444
    Join date : 2013-03-19
    Location : It can get windy here

    Re: Passive Preamp vs. Tube Preamp

    Post by corndog71 on Sun Mar 24, 2013 10:46 pm

    I've played with passives vs. active and while there may be a touch more clarity in the passive it usually lacks the dynamics and drive of an active line stage.

    sailor

    Posts : 269
    Join date : 2011-04-04

    Re: Passive Preamp vs. Tube Preamp

    Post by sailor on Mon Mar 25, 2013 3:03 pm

    I have an OPPO 105 Blueray player. It has a built in volume which actually lowers the output in the digital stage. That's really cool because it causes no distortion I hooked it direct to my best amp and had plenty of volume but as corndog71 stated it lacked dynamics. Don't know why but with my preamp installed the dynamics were restored.
    It does work well however on the Dynaco SCA35 which has a volume but no line stage. When I tried to hook a preamp to it for unknown reasons it sounded worse. My guess is because the input impedance resistor for the amp. is 4.7 meg. but the 250k pot is in parallel with it which brings the actual input impedance to about 237K. This is opposite of today's thinking on passive which says to go as low a resistance as possible like 5K or 10k.

    Bob Latino
    Admin

    Posts : 2374
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Passive Preamp vs. Tube Preamp

    Post by Bob Latino on Mon Mar 25, 2013 5:24 pm

    A passive preamp works well if you only have high level signal sources like a CD player, Mp3 player, FM tuner, output from a computer etc. and you don't need balance, bass/treble or loudness controls. If you need these controls or you need a phono or tape head inputs then get an active preamp.

    Passive preamps also work well with power amps that don't require much gain. All the VTA amp kits only require about 1 to 1.1 volts for full output. Most high level OUTPUTS like a CD payer are about 2 volts out so with a passive preamp all you are doing is padding down the full output of the CD player with resistors in the passive preamp. Some passive preamps use transformers (TVC passive preamps) instead of resistors to alter the output voltage.

    Bob

    Zimmer64

    Posts : 112
    Join date : 2013-01-29
    Age : 52
    Location : Switzerland

    Re: Passive Preamp vs. Tube Preamp

    Post by Zimmer64 on Fri Mar 29, 2013 3:14 am

    Hi there,

    Nelson Pass wrote a great article about the subject, which made a lot of sense to me.

    Best

    Michael

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