First tube amp?

halo71
halo71 Posts: 4,603
edited December 2013 in Electronics
I have never had an audio tube amp before. I have had many tubed guitar amps over the years. But audio tubes....is new to me. Can someone tell me about a 6ca4 single end magnavox tube amp? Is this a pretty decent amp?

Pic of it here....

http://www.flickr.com/photos/71542092@N00/11472733005/

Inside looks sorta rough though. Sloppy solder joints!

http://www.flickr.com/photos/71542092@N00/11472828216/in/photostream/
--Gary--
Onkyo Integra M504, Bottlehead Foreplay III, Denon SACD, Thiel CS2.3, NHT VT-2, VT-3 and Evolution T6, Infinity RSIIIa, SDA1C and a few dozen other speakers around the house I change in and out.
Post edited by halo71 on
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  • mhardy6647
    mhardy6647 Posts: 33,806
    edited December 2013
    amplifier.jpg


    That amp's been profoundly modified from its Maggotbox origins - most likely started life as single-ended EL84 stereo amp in a phono or low(er) end console.

    They look like this "as found" :-) (borrowed photo, not mine!)

    maggotbox 86-01.jpg


    Umm... a 6CA4 is a rectifier :-) the outputs are probably (still) EL84 (6BQ5) although those look like modern Russian or Chinese ones rather than the original US or European tubes that Magnavox'd put in there.

    Solder work looks OK to me at a quick glance; good quality parts.
    It's cute that someone put a stepped attenuator volume control on it.

    If it's a good circuit design and well implemented, it'll probably slaughter anything storebought under a kilobuck or so... with suitable loudspeakers. Should be about 4 watts per channel if in its normal (pentode) mode; if it's been modified to run the outputs in triode mode, you're looking at 1 to 2 watts per channel. Fine with, for example, Klipschorns, Altec Voice of the Theatres, Altec Duplexes, or Lowthers. You'll want loudspeakers with sensitivities at least in the high nineties for sensitivity (@ 1 meter driven with 1 wattt) to do it justice - or use it as a HF or MR/HF amplifier in a bi- or tri-amp system.

    Da applications **** on the EL84/6BQ5 http://www.retrovox.com.au/STC6BQ5.pdf

    EDIT: You can see a more typical re-implementation of a very similar amp chassis (if not identical) at:
    http://www.polkaudio.com/forums/showthread.php?113687-Have-You-Listened-to-a-Low-Power-Amplifier&p=1512993&viewfull=1#post1512993
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  • halo71
    halo71 Posts: 4,603
    edited December 2013
    Skip which one would you suggest? Mark thanks for the info! I believe I have some speakers that would work with this amp. The main reason I am looking at this one is because of its price. Pretty damn cheap. If anyone has something laying around in the $150 range let me know please. Or a cheap way for me to get into tubes. :)
    --Gary--
    Onkyo Integra M504, Bottlehead Foreplay III, Denon SACD, Thiel CS2.3, NHT VT-2, VT-3 and Evolution T6, Infinity RSIIIa, SDA1C and a few dozen other speakers around the house I change in and out.
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  • mhardy6647
    mhardy6647 Posts: 33,806
    edited December 2013
    Tell us what speakers you're thinkin' about ;-)
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  • halo71
    halo71 Posts: 4,603
    edited December 2013
    A pair of Cannon TLS-1232TLS. I do not know the specs on them but they are very efficient. These in the pic are not mine, but they look just like them. I restored mine last year sometime. They are from 1978 or so. They were built by ESS.

    attachment.php?attachmentid=291040&d=1312409144
    --Gary--
    Onkyo Integra M504, Bottlehead Foreplay III, Denon SACD, Thiel CS2.3, NHT VT-2, VT-3 and Evolution T6, Infinity RSIIIa, SDA1C and a few dozen other speakers around the house I change in and out.
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  • mhardy6647
    mhardy6647 Posts: 33,806
    edited December 2013
    openvalencia.jpg


    Too bad you don't live a little further north ;-)



    Those little Maggotbox amp punch way beyond their weight - they were stoopit simple and made to conserve costs... but they had some sort of synergy goin' on that makes them genuinely hifi amplifiers; easy to rehab and (usually) cheap to obtain.

    I have only one any more (a push-pull stereo EL84) but it was a freebie (dump find) and I have no complaints :-)
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  • halo71
    halo71 Posts: 4,603
    edited December 2013
    Seems the seller decided he wants more now for the amp than what he had listed it for. So that one is out! I told him he should have listed it on eBay if he was gonna take bids on the damn thing!
    --Gary--
    Onkyo Integra M504, Bottlehead Foreplay III, Denon SACD, Thiel CS2.3, NHT VT-2, VT-3 and Evolution T6, Infinity RSIIIa, SDA1C and a few dozen other speakers around the house I change in and out.
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  • Summerwind2
    Summerwind2 Posts: 98
    edited December 2013
    halo71 wrote: »
    Seems the seller decided he wants more now for the amp than what he had listed it for. So that one is out! I told him he should have listed it on eBay if he was gonna take bids on the damn thing![/QUO

    Agreed and bad karma.
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  • pumpkinman
    pumpkinman Posts: 9,826
    edited December 2013
    DSkip wrote: »
    What are you trying to drive with that little thing? I'd honestly suggest you look at Yaqin for a starter tube amp. Great build quality and can be had new for a nickel.

    I heard a Yaqin at a friends house. He bought it used for $300 and I couldn't believe how good it sounded. I believe it was a 10L the only downside was to bias the tubes you had to go inside the case to do it.
    In the newer Yaqins biasing is much easier in that it you can access it the bias points by the tubes.
    lmivdewpnb28.jpg


    Because I am The Pumpkinking


    A Kind Word Is An Easy Gift To Give
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  • halo71
    halo71 Posts: 4,603
    edited December 2013
    I will have to wait. My budget was around $175. Was wanting to get into tubes on the cheap. And I mean CHEAP! lol
    --Gary--
    Onkyo Integra M504, Bottlehead Foreplay III, Denon SACD, Thiel CS2.3, NHT VT-2, VT-3 and Evolution T6, Infinity RSIIIa, SDA1C and a few dozen other speakers around the house I change in and out.
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  • aboroth00
    aboroth00 Posts: 1,106
    edited December 2013
    halo71 wrote: »
    I will have to wait. My budget was around $175. Was wanting to get into tubes on the cheap. And I mean CHEAP! lol

    Best way to start into tubes in my opinion is to start with the preamp, lot less hassle and you can experiment with tube rolling for much cheaper than rolling power tubes.
    2Ch Tube Audio Convert
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  • tonyb
    tonyb Posts: 32,967
    edited December 2013
    aboroth00 wrote: »
    Best way to start into tubes in my opinion is to start with the preamp, lot less hassle and you can experiment with tube rolling for much cheaper than rolling power tubes.

    Exactly....or a tube buffer. Rolling tubes in an amp will cost a buck fifty easily just for the tubes let alone the iron. Tubes is not something to get into on the cheap, especially that cheap. Just sayin'....
    HT SYSTEM-
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  • halo71
    halo71 Posts: 4,603
    edited December 2013
    Well I was thinking a tubed preamp. I've seen some in that price range but don't know enough about them to know what to look for.
    --Gary--
    Onkyo Integra M504, Bottlehead Foreplay III, Denon SACD, Thiel CS2.3, NHT VT-2, VT-3 and Evolution T6, Infinity RSIIIa, SDA1C and a few dozen other speakers around the house I change in and out.
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  • tonyb
    tonyb Posts: 32,967
    edited December 2013
    Doesn't get any cheaper than this. Hows 40 bucks ?

    http://chicago.craigslist.org/chc/ele/4256598406.html
    HT SYSTEM-
    Sony 850c 4k
    Pioneer elite vhx 21
    Sony 4k BRP
    SVS SB-2000
    Polk Sig. 20's
    Polk FX500 surrounds

    Cables-
    Acoustic zen Satori speaker cables
    Acoustic zen Matrix 2 IC's
    Wireworld eclipse 7 ic's
    Audio metallurgy ga-o digital cable

    Kitchen

    Sonos zp90
    Grant Fidelity tube dac
    B&k 1420
    lsi 9's
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