The Dynaco Tube Audio Forum

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The Dynaco Tube Audio Forum

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


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    caferacer59


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    Post by caferacer59 Fri May 22, 2020 9:02 am

    great forum and i hope to learn a lot. My name is Jerry and I have gotten back into 2 channel HiFI after a long hiatus. Long Story short, i picked up a Dynaco ST-70 and a PAS 3 a couple of weeks ago and know nothing about them really, however, I am pretty thrilled with the sound. I do not have fancy stuff and i was running a Pioneer sx-750 with a pair of KG-4's that I have had forever. Sensitive Speakers and I like them however, they could get fatiguing with the SX-750 and those Horns. My local record store friend sold me the Dynaco stuff very inexpensively because he said they worked but that was about it. Now that being said, here are some dumb questions, the biasing sockets on the front of the amp have been removed, does that mean that inside the amp is a self biasing board ? It sounds good, the balance is nice and tone also, everything on the pass 3 is set to neutral and frankly aren't needed at all. I have just bought a quad of gold lion KT77's and want to pop them in to see what characteristics change. Is there any problem with doing so, I am a little concerned that I don't understand if the mod on my st -70 presents any danger of taking the perfectly working el 34's out and popping the new tubes right in.

    I will say that the amp and pre, rolled off the highs on my KG4s perfectly, my sources are an Akai 201d rtr, a music hall 1.5 and a sonus zp-120, all sources sound great.

    I am not a tech, but I am chasing good sound, this stuff is getting me damn close.

    Best regards,

    Jerry
    peterh
    peterh


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    Post by peterh Fri May 22, 2020 9:50 am

    caferacer59 wrote:great forum and i hope to learn a lot.  My name is Jerry and I have gotten back into 2 channel HiFI after a long hiatus. Long Story short, i picked up a Dynaco ST-70 and a PAS 3 a couple of weeks ago and know nothing about them really, however, I am pretty thrilled with the sound.  I do not have fancy stuff and i was running a Pioneer sx-750 with a pair of KG-4's that I have had forever.  Sensitive Speakers and I like them however, they could get fatiguing with the SX-750 and those Horns.  My local record store friend sold me the Dynaco stuff very inexpensively because he said they worked but that was about it.  Now that being said, here are some dumb questions, the biasing sockets on the front of the amp have been removed, does that mean that inside the amp is a self biasing board ?  It sounds good, the balance is nice and tone also, everything on the pass 3 is set to neutral and frankly aren't needed at all.  I have just bought a quad of gold lion KT77's and want to pop them in to see what characteristics change.  Is there any problem with doing so, I am a little concerned that I don't understand if the mod on my st -70 presents any danger of taking the perfectly working el 34's out and popping the new tubes right in.

    I will say that the amp and pre, rolled off the highs on my KG4s perfectly, my sources are an Akai 201d rtr, a music hall 1.5 and a sonus zp-120, all sources sound great.

    I am not a tech, but I am chasing good sound, this stuff is getting me damn close.  

    Best regards,

    Jerry
    It was a very stupid thing of previous owner to remove the fron octal sockets, it's here
    one measure bias, something you MUST do from time to time, and especially when
    installing new tubes.

    Self biased ? Unlikely. You must open up and compare with the manual.

    Is this stupid owner have removed the sockets, is there any other external measuring points ?
    if not you need to turn the amp on it's side and open it to be able to measure bias on
    the output tube sockets.

    I recommend you get the manual ( can be found at this site ) and start examining
    what the (stupid?) previous owner has done more. It should have been proper documentation
    with the amp that could clear up this issues. If not i suggest you locate a technician  that
    can help you restore the amp.

    Sorry to deliver bad news but i think it's better to know then sat in the dark.


    Last edited by peterh on Fri May 22, 2020 9:52 am; edited 1 time in total (Reason for editing : Spelling)
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    caferacer59


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    Post by caferacer59 Fri May 22, 2020 9:56 am

    Thanks, I am not sure this is answering my inquiry directly. It sounds very good. I assume if the autobias is working correctly then the octal sockets are superfluous. But again thanks for your response. I have a tech, but it aint broke. Bill Evans Sunday at the village vanguard sounds sublime.
    peterh
    peterh


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    Post by peterh Fri May 22, 2020 10:18 am

    caferacer59 wrote:Thanks, I am not sure this is answering my inquiry directly.  It sounds very good.  I assume if the autobias is working correctly then the octal sockets are superfluous.   But again thanks for your response.  I have a tech, but it aint broke.   Bill Evans Sunday at the village vanguard sounds sublime.
    Are you sure it has an autobias card ? Or are you guessing ?
    In that case you should have documentation.
    If there is no autobias there is a danger to destroy both tubes and amp if you ignore bias adjustment. Have it checked asap !
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    caferacer59


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    Post by caferacer59 Fri May 22, 2020 10:48 am

    I am in the office but I googled some images of autobias cards, and I am pretty sure from memory, it looks similar, but thank you , when I get home i will confirm.
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    Post by Dave_in_Va Fri May 22, 2020 11:08 am

    If you're going to swap in some different power tubes, make sure you clean and re-tension each socket.
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    Post by Guest Fri May 22, 2020 5:42 pm

    .


    Last edited by PeterCapo on Mon Nov 30, 2020 7:55 pm; edited 1 time in total
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    caferacer59


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    Post by caferacer59 Fri May 22, 2020 6:07 pm

    Here are a couple pics
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    caferacer59


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    Post by caferacer59 Fri May 22, 2020 6:09 pm

    New Guy here  0ae08010New Guy here  0ae08010
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    Post by Guest Fri May 22, 2020 6:55 pm

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    Last edited by PeterCapo on Mon Nov 30, 2020 7:55 pm; edited 1 time in total
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    caferacer59


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    Post by caferacer59 Fri May 22, 2020 8:12 pm

    Thanks. I’ll get more pics. All I can say is I have had it for a month and under heavy use it sounds really nice. A big step up from my ss amp and it was no slouch either.
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    Post by Guest Fri May 22, 2020 8:18 pm

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    Last edited by PeterCapo on Mon Nov 30, 2020 7:55 pm; edited 1 time in total
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    caferacer59


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    Post by caferacer59 Fri May 22, 2020 8:20 pm

    Especially with my kg4s. My buddies were very impressed with the sound stage and detail. I’m just not sure what I got here
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    Post by Guest Fri May 22, 2020 9:07 pm

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    Last edited by PeterCapo on Mon Nov 30, 2020 7:53 pm; edited 1 time in total
    peterh
    peterh


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    Post by peterh Sat May 23, 2020 4:39 am

    caferacer59 wrote:Here are a couple pics
    Any autobias board is located inside, you have to open the bottom to show this.

    What we have seen so far shows that this is an ex-dynaco , it has very little in
    common with a dynaco amp. Unless you have got proper documentation you are on
    your own here. Sorry.
    You could contact the seller and ask for documentation.


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