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    Read 'em and Weep

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    pmarcin

    Posts : 131
    Join date : 2009-01-20
    Age : 69

    Read 'em and Weep

    Post by pmarcin on Wed Jan 27, 2016 1:30 pm

    For all fellow tube nerds:
    Review of Poseidon vs vanilla

    Enjoyable zoning out.

    PeterCapo

    Posts : 386
    Join date : 2008-12-05

    Re: Read 'em and Weep

    Post by PeterCapo on Wed Jan 27, 2016 3:38 pm

    He followed-up here: https://youtu.be/RlQgfETQVEs

    peterh

    Posts : 680
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Read 'em and Weep

    Post by peterh on Wed Jan 27, 2016 3:51 pm

    pmarcin wrote:For all fellow tube nerds:
       Review  of Poseidon vs vanilla

    Enjoyable zoning out.
    I have two comments :
    1 - i do not use 50w at 20khz in my music listening, the diffs at lower power levels were close to none. The main reason to replace 6an8 is to use some new production tubes imho

    2 - nice to se that he likes JJ KT88 , i have been selling them for 2 years now. And yes,
    JJ is made in slovakia, not china!

    PeterCapo

    Posts : 386
    Join date : 2008-12-05

    Re: Read 'em and Weep

    Post by PeterCapo on Wed Jan 27, 2016 4:36 pm

    In the videos there is no mention of the importance of matching the two 47KΩ resistors found at the phase splitter.  The original Dynaco schematics for the Mark II, Mark III, Mark IV and Stereo 7o asterisked these resistors as needing to be a matched pair, and, for instance, on the Stereo 7o schematic it specifically says a 1% match.  The same goes for the two 100KΩ resistors off of E2 on the original Mark III PC board pertaining to the original biasing scheme, which did not include individual bias adjustment for each power tube.

    There’s a third video in this series where respondent "sporadic –Z" mentions the importance of the 47KΩ phase splitter resistors being matched.  In Dynaco Doctor forum, Bill Thomas mentioned it in regard to the Stereo 7o but the same applies to the Mark III http://www.audioasylum.com/forums/dynaco/messages/12/1683.html

    In ElPaso TubeAmps’ third video, he whipped up his own bias balance for the power tubes plus a different method of balancing the phase splitter.  Bias balance kits are available from Dynakitparts.com and [last I knew] Triode USA.  And, to keep the phase splitter balanced, all you need, per the original design, are closely matched pairs of 47KΩ resistors, which should be obtainable without too much difficulty.

    His videos are informative and valuable but in this series I think he needed to point out the need for the key matched resistor pairs as shown on the original schematic.

    Here’s the third video: https://youtu.be/OUbnQc_zcFI

    PeterCapo

    Posts : 386
    Join date : 2008-12-05

    Re: Read 'em and Weep

    Post by PeterCapo on Wed Jan 27, 2016 6:37 pm

    Here's another thought.  He said that for his test he hand-selected the very best 12AX7 and 12AU7 tubes he had available, for the substitute driver board.  Granted 6AN8 tubes are no longer made, but you can also buy a 12AX7 or 12AU7 that’s not up to par, and without his kind of equipment most of us might not ever know it unless it were a pretty serious deficiency.

    If a 6AN8 were significantly out of whack, it would be interesting to see what the Mark III’s internal voltage readings would look like.  I am referring to the voltage chart in the Dynaco manual that is available as a reference for establishing the baseline health of the amp.  If the problem were significant enough, maybe the readings would be off and this could be a way for the average DIYer to know there is a problem.

    In any case, when all was said and done I think the original Mark III did quite well.

    Bob Latino
    Admin

    Posts : 2414
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Read 'em and Weep

    Post by Bob Latino on Wed Jan 27, 2016 9:06 pm

    That El Paso Tube amp video does not tell the whole story about the SOUND of a tube (or a solid state) amp. There are many amps that MEASURE GOOD but do not necessarily SOUND GOOD. As an example, most solid state amps will measure with respect to their distortion and bandwidth figures better than most tube amps. The better measurements do not necessarily correlate with better sound. One of the best examples of all time is the solid state Dynaco Stereo 120 that came out in the mid '60's. This amp was hyped in many audio magazines at the time as "the future of amplifiers" and writers in these mags made statements like >"Sell your tube gear now while they still have some value because solid state is going to completely take over" Kinda reminds me of what the Hi-Fi mags said in the early '80's about CD's completely replacing vinyl records as a signal source - lol...

    About a month after the solid state Dynaco Stereo 120 came out, my local Hi-Fi dealer got one in as a demo model. I stopped in and listened to this amp. Being blunt and honest, although they claimed great distortion figures for the Stereo 120, this amp was and still is the WORST SOUNDING audio amp I have ever heard in my life .. harsh, brittle, annoying sounding.

    Moral of the story > You should never buy anything on the basis of distortion or bandwidth figures. Go and listen for yourself and let your ears help you make your choices ..

    Bob

    10-E-C

    Posts : 87
    Join date : 2014-02-12
    Age : 63
    Location : upper east tn

    Re: Read 'em and Weep

    Post by 10-E-C on Wed Jan 27, 2016 9:47 pm

    Bob Latino wrote:That El Paso Tube amp video does not tell the whole story about the SOUND of a tube (or a solid state) amp. There are many amps that MEASURE GOOD but do not necessarily SOUND GOOD. As an example, most solid state amps will measure with respect to their distortion and bandwidth figures better than most tube amps. The better measurements do not necessarily correlate with better sound. One of the best examples of all time is the solid state Dynaco Stereo 120 that came out in the mid '60's. This amp was hyped in many audio magazines at the time as "the future of amplifiers" and writers in these mags made statements like >"Sell your tube gear now while they still have some value because solid state is going to completely take over" Kinda reminds me of what the Hi-Fi mags said in the early '80's about CD's completely replacing vinyl records as a signal source - lol...

    About a month after the solid state Dynaco Stereo 120 came out, my local Hi-Fi dealer got one in as a demo model. I stopped in and listened to this amp. Being blunt and honest, although they claimed great distortion figures for the Stereo 120, this amp was and still is the WORST SOUNDING audio amp I have ever heard in my life .. harsh, brittle, annoying sounding.

    Moral of the story > You should never buy anything on the basis of distortion or bandwidth figures. Go and listen for yourself and let your ears help you make your choices ..

    Bob


    I think you are spot on Bob, I worked many years as an electronic maints tech in manufacturing, and seen many plans from engineering that looked good on paper but wasn't practical on the shop floor.

    TM

    GP49

    Posts : 735
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: Read 'em and Weep

    Post by GP49 on Thu Jan 28, 2016 1:11 am

    Add to that...different samples of the Dynaco Stereo 120 sounded different from each other! In some cases, it was like listening to a completely different model of amplifier. The variations probably also explained why some of them blew up if you looked at them funny, while others perked along with no problems for decades.

    The audio perfectionist magazine that reviewed the Dynaco Stereo 120 as sounding better than a pair of Mk IIIs may have had a specially-tweaked sample. Such things can happen when review samples are provided by the manufacturer.

    zx

    Posts : 194
    Join date : 2011-08-05

    Re: Read 'em and Weep

    Post by zx on Thu Jan 28, 2016 12:31 pm

    As for myself....M3s have always been the Dynaco amps for me.....any of the new boards I have used an heard..6922...12x..12au....6SN7 the best of all too me....all sound darker to my old ears....
    that's why I have stayed with the 6AN8s..... big 6550s fan... ....even with the 6AN8 the KT88 make things darker....but that's me....I let the tube preamp add my color
    I only payed $4.ea for my NOS 6AN8s a year ago....finding good sounding one never been a prob......
    I like this guy...lot of good info...thanks for posting this one....but yes your ears... well tell you what tone you like...better stick with that.....have fun with tube sound




    Thanks for the site Bob..................

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