The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    My VTA ST-120 is on the way .....and other loose ramblings of an old fart

    Share
    avatar
    jfine

    Posts : 167
    Join date : 2017-06-19

    Re: My VTA ST-120 is on the way .....and other loose ramblings of an old fart

    Post by jfine on Tue Apr 24, 2018 1:04 am

    CletusB wrote:
    Done, and I can detect no sonic difference to the old electrolytics. Glad I did it nonetheless, they'll last and I won't have to worry about them.  Will sweep the frequencies tomorrow and see what the spec analyzer has to say compared to the last sweep  .........yes, I know it's a mess! What a Face

    What are you using this for? Is it a 3 way or what?
    avatar
    CletusB

    Posts : 164
    Join date : 2018-02-11
    Age : 63
    Location : Trinidad & Tobago

    Re: My VTA ST-120 is on the way .....and other loose ramblings of an old fart

    Post by CletusB on Tue Apr 24, 2018 4:49 am

    jfine wrote:
    CletusB wrote:
    Done, and I can detect no sonic difference to the old electrolytics. Glad I did it nonetheless, they'll last and I won't have to worry about them.  Will sweep the frequencies tomorrow and see what the spec analyzer has to say compared to the last sweep  .........yes, I know it's a mess! What a Face

    What are you using this for? Is it a 3 way or what?
    Three way crossovers for my VOTTs,  550Hz and 6KHz
    Cheap units made by Audio Pipe. Typical Linkwitz-Riley networks on a decent PCB, which I've had for like 20-years (think they were originally in my lab at the Samsung factory back then, when we played with some home stereo speaker designs) and they've worked well all along, I've tweaked them quite a bit over the years adding L-pads and such. Just thought the caps could do with a change-out about now. Laughing
    The original electrolytics actually still measure decent


    Last edited by CletusB on Tue Apr 24, 2018 5:21 am; edited 2 times in total
    avatar
    CletusB

    Posts : 164
    Join date : 2018-02-11
    Age : 63
    Location : Trinidad & Tobago

    Re: My VTA ST-120 is on the way .....and other loose ramblings of an old fart

    Post by CletusB on Tue Apr 24, 2018 4:57 am

    jfine wrote:
    CletusB wrote:BTW folks, here's an excellent and inexpensive piece of test instrument kit for the lab.

    And here I thought capacitor ESR testers were spendy. Hmmm....
    Nope!  Multifunction Meter  Can't beat it for $15 and it quickly tests and identifies all sorts of components (bipolars, fets, mosfets, diodes, chokes, caps/esr, resistors)   ....I really use it a lot. Laughing
    avatar
    CletusB

    Posts : 164
    Join date : 2018-02-11
    Age : 63
    Location : Trinidad & Tobago

    Re: My VTA ST-120 is on the way .....and other loose ramblings of an old fart

    Post by CletusB on Tue Apr 24, 2018 6:40 am

    Response with Dayton Poly Capacitors:



    Response with Original Electrolytic Capacitors:


    Maybe the improved ESR of the new caps keep things a little tighter?
    Old Electrolytics   Avg:  32.66uf   0.57ohm ESR
    New Dayton Poly  Avg:  29.87uf   0.023ohm ESR
    avatar
    jfine

    Posts : 167
    Join date : 2017-06-19

    Re: My VTA ST-120 is on the way .....and other loose ramblings of an old fart

    Post by jfine on Tue Apr 24, 2018 4:16 pm

    CletusB wrote:
    Three way crossovers for my VOTTs,  550Hz and 6KHz
    Cheap units made by Audio Pipe. Typical Linkwitz-Riley networks on a decent PCB, which I've had for like 20-years (think they were originally in my lab at the Samsung factory back then, when we played with some home stereo speaker designs) and they've worked well all along, I've tweaked them quite a bit over the years adding L-pads and such. Just thought the caps could do with a change-out about now. Laughing
    The original electrolytics actually still measure decent

    My guess is the those larger value electrolytics are likely on the low frequency circuit, maybe zobel like, probably wouldn't hear much diff changing those, tighter would be about it. The yellow mylars OTOH likely are mids and/or highs, probably would affect sonics much more if changed out (mylar in xover always bothered me JBL uses them a lot, I can't unhear them now), but Dayton for those? Not worth it. Mundorf silver/gold/oil or beeswax jupiters, much better. Smile But if it sounds good then why mess with it, and hey what do I know.
    avatar
    deepee99

    Posts : 1931
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: My VTA ST-120 is on the way .....and other loose ramblings of an old fart

    Post by deepee99 on Tue Apr 24, 2018 4:20 pm

    jfine wrote:
    CletusB wrote:
    Three way crossovers for my VOTTs,  550Hz and 6KHz
    Cheap units made by Audio Pipe. Typical Linkwitz-Riley networks on a decent PCB, which I've had for like 20-years (think they were originally in my lab at the Samsung factory back then, when we played with some home stereo speaker designs) and they've worked well all along, I've tweaked them quite a bit over the years adding L-pads and such. Just thought the caps could do with a change-out about now. Laughing
    The original electrolytics actually still measure decent

    My guess is the those larger value electrolytics are likely on the low frequency circuit, maybe zobel like, probably wouldn't hear much diff changing those, tighter would be about it. The yellow mylars OTOH likely are mids and/or highs, probably would affect sonics much more if changed out (mylar in xover always bothered me JBL uses them a lot, I can't unhear them now), but Dayton for those? Not worth it. Mundorf silver/gold/oil or beeswax jupiters, much better. Smile But if it sounds good then why mess with it, and hey what do I know.
    Precisely. If it sounds good, don't mess with it.
    avatar
    corndog71

    Posts : 622
    Join date : 2013-03-19
    Location : It can get windy here

    Re: My VTA ST-120 is on the way .....and other loose ramblings of an old fart

    Post by corndog71 on Tue Apr 24, 2018 4:46 pm

    For what it's worth, I know a speaker designer who modded a pair of cheap bookshelf speakers and made them so that you could switch between the cheap stock crossover and one with better caps, resistors, and air-core chokes. They measured exactly the same but everyone who heard them could hear the difference immediately. Of course the upgraded crossover sounded better.

    I also agree that if it aint broke don't "fix" it.
    avatar
    CletusB

    Posts : 164
    Join date : 2018-02-11
    Age : 63
    Location : Trinidad & Tobago

    Re: My VTA ST-120 is on the way .....and other loose ramblings of an old fart

    Post by CletusB Yesterday at 3:58 pm

    Have not even looked my bias settings in over a month. Just decided to do a touch up and noticed it has dropped equally on all tubes from 0.550mV to 0.320mV .....decided to just leave it there as it seems to be settling nicely (these are the KT-88s). Readings were taken today at a line voltage of 114vac.

    Sponsored content

    Re: My VTA ST-120 is on the way .....and other loose ramblings of an old fart

    Post by Sponsored content


      Current date/time is Wed May 23, 2018 9:01 am