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    Poseidon driver boards for MKIII, IV & ST70

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    MontanaWay

    Posts : 767
    Join date : 2014-02-06
    Age : 58
    Location : Cameron, Montana

    Poseidon driver boards for MKIII, IV & ST70

    Post by MontanaWay on Fri Mar 28, 2014 8:19 pm

    has anyone here had any experience with the Poseidon driver boards from DIYTUBE for the above mentioned amps?

    stewdan

    Posts : 160
    Join date : 2010-03-07
    Age : 78
    Location : Houston Texas

    Re: Poseidon driver boards for MKIII, IV & ST70

    Post by stewdan on Fri Mar 28, 2014 10:15 pm

    Hi -- I built a pair of Mk III Poseidon's and I was impressed.  

    (1) The blank PCBs are beautiful, excellent silk screening, easy to see where parts go and the parts were easy to come by.

    (2) To me, they were easier to wireup to the MKIII than the Tubes4HiFi pcbs.

    (3) Soundwise, if I had to pick a performance order (best sound to worst):
       
         a) Tubes4HiFi PCBs
         b) Poseidon PCBs
         c) Triode's PCBs
         d) Stock Dynaco but with Modern PCB and Parts
         e) Original Dynaco with old PCB and parts

    The a) thru e) are my order based upon the MKIII pairs that I put together.

    IMHO a) and b) are very close, c) is good and much better than d) and e).

    Hope this helps, but remember it is all subjective and based upon listening area and speakers.
    Stew

    MontanaWay

    Posts : 767
    Join date : 2014-02-06
    Age : 58
    Location : Cameron, Montana

    Re: Poseidon driver boards for MKIII, IV & ST70

    Post by MontanaWay on Fri Mar 28, 2014 10:22 pm

    great info, thank you very much.

    Now on a somewhat different note...am always thinking, which could be dangerous!!

    I am playing with the idea of combining 2x MKIII's into one chassis. I know, why not just got for the ST120, but hey, its all about having fun!
    With regards to transformers, I am pretty sure I have found suitable units to handle the load, that is, one power transformer for B+ and 6VAC filament, plus a separate unit for the 5VAC for the rectifier.
    Now, with regards to the rectifier tube, what is a recommended unit that could handle the demand of two MKIII?

    DynakitParts
    Admin

    Posts : 181
    Join date : 2008-11-30

    Re: Poseidon driver boards for MKIII, IV & ST70

    Post by DynakitParts on Fri Mar 28, 2014 10:39 pm

    Montana,
    Use two (2) rectifier tubes.....5AR4's or go with solid state rectification. Retain separate power supplies if possible.

    Just my suggesetion.

    Kevin

    MontanaWay

    Posts : 767
    Join date : 2014-02-06
    Age : 58
    Location : Cameron, Montana

    Re: Poseidon driver boards for MKIII, IV & ST70

    Post by MontanaWay on Fri Mar 28, 2014 10:42 pm

    DynakitParts wrote:Montana,
                Use two (2) rectifier tubes.....5AR4's or go with solid state rectification. Retain separate power supplies if possible.

    Just my suggesetion.

    Kevin

    thank you.What is your main reasoning for two separate power supplies, I would think that one would give more stable and even supplies.

    stewdan

    Posts : 160
    Join date : 2010-03-07
    Age : 78
    Location : Houston Texas

    Re: Poseidon driver boards for MKIII, IV & ST70

    Post by stewdan on Fri Mar 28, 2014 10:49 pm

    Hi again --

    Since you are combining two MK III's on 1 chassis, the configuration is somewhat like one of Bob's ST-120's and you are probably going to achieve 50-60 WPC on your project and use 6650 or KT88 type tubes.

    So, I would go with a GZ37 or maybe the larger Weber Copper-top which they use on the ST-120 and also on Bob's M-125.  It seems like Skizo is very happy with the GZ37 on his ST-120 which is probably a 75 WPC amplifier.  He made a comment about the Copper-top sagging the output on his speakers.

    Again, performance would probably be dependent on the listening room and the speakers you use.

    My main listening area is 20 by 24 feet with a 20 foot high peaked ceiling....lots of open space. I am driving Vandersteen 2CI's and an assortment of other selectable speakers with a pair of Roy's VTA MK III's using 12AU7s and GZ34's.  Most of the speakers are of the low efficiency type.  To my ears, the sound is very smooth and has an excellent mid range presence, but I can't push the volume up before it starts to get harsh.....hmmm, wonder what it would sound like with GZ37's or GZ33's??

    Oh well, hope I don't shoot myself in the foot!!!

    Stew

    MontanaWay

    Posts : 767
    Join date : 2014-02-06
    Age : 58
    Location : Cameron, Montana

    Re: Poseidon driver boards for MKIII, IV & ST70

    Post by MontanaWay on Fri Mar 28, 2014 11:05 pm

    I see that the GZ34 is rated at 1.9A and the GZ37 at 2.8A. I think a single GZ37 should be OK driving 2x MKIII's. Of course I will need to up the capacitor as well, but that is easy to do. It would also be wise to up the wattage on the power supply resistor as well. Another question is the choke, will need to look into that.

    pmarcin

    Posts : 131
    Join date : 2009-01-20
    Age : 68

    Re: Poseidon driver boards for MKIII, IV & ST70

    Post by pmarcin on Sat Mar 29, 2014 12:21 pm

    I also mated Mundorf Supreme coupling caps and Chart Chong's excellent cap board to the Poseidon. Those took the sound up a notch.

    Chart is off the chart, so to speak, but you may reach him at: tubes4pro@yahoo.com. His silk screening is so informative you may not need instructions. Smile

    Good luck on your cabinet quest over at diytube.


    Last edited by pmarcin on Sat Mar 29, 2014 1:03 pm; edited 3 times in total (Reason for editing : added)

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