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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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    VTA M-125 in custom chassis

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    • Post n°1

    VTA M-125 in custom chassis Empty VTA M-125 in custom chassis

    Post by Guest Mon Sep 08, 2014 8:49 pm

    My version of the M125 getting close to first power up!
    Front face panel will have a mini retro look VU meter. I will be using 4x KT120's, the transformers are currently being sprayed satin black.

    photo fats2_zps85d4642e.jpg

    photo fats1_zps3bc7fc68.jpg

    photo fats3_zps7a12720a.jpg
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    • Post n°2

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    Post by carpenter Tue Sep 09, 2014 5:06 am

    Lovely! I love how you drilled your vent holes with such precision. Now you need a front/side view of the chassis.

    I've been thinking of using star or hex bolts to avoid that cluttered look of misaligned screw heads.

    I'm also considering placing the speaker ground post in between the 4 ohm and 8 ohm posts. That way, all I have to do is flip the speaker's banana jack 180 degrees to alternate between 4 or 8 ohms.
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    • Post n°3

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    Post by mazeeff Tue Sep 09, 2014 5:40 am

    Tell us more about that little mini-fan. How are you powering it?

    Mike
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    • Post n°4

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    Post by Guest Tue Sep 09, 2014 8:40 am

    carpenter wrote:Lovely! I love how you drilled your vent holes with such precision. Now you need a front/side view of the chassis.

    I've been thinking of using star or hex bolts to avoid that cluttered look of misaligned screw heads.

    I'm also considering placing the speaker ground post in between the 4 ohm and 8 ohm posts. That way, all I have to do is flip the speaker's banana jack 180 degrees to alternate between 4 or 8 ohms.

    I wish I could take credit on the plate drilling....but alas....I cannot, it is all professionally done on a CNC milling machine by Front Panel Express. I could never do such precision work.
    I will take the credit for designing the layout though and laying out the vent holes Smile
    The front panel too is all done, I am still waiting on the gauges etc., once I have those will take more photo's.
    The transformers have been painted and I 'll be able to mount those later today and start on the wiring.
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    • Post n°5

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    Post by Guest Tue Sep 09, 2014 8:47 am

    mazeeff wrote:Tell us more about that little mini-fan. How are you powering it?

    Mike

    the ones I use are a mini 12VDC unit, I buy them in bulk from Hong Kong. At full 12V, they are not the quietest, so I have made up a very simple variable DC power supply using an LM317 regulator, in a TO220 package, and drive them at about 8VDC, I found at that setting they are very quiet and still move plenty of air. Being a variable power supply, I can fine adjust that fan supply voltage to arrive at the best/least 'noise setting'.
    I use a mini fully encapsulated transformer for the 15VAC supply, that same transformer also supplies the VU meter driver board.
    I am using the fans to push air into the chassis. Hot tubes, by the nature of heat, draw air 'out' of a chassis through vent holes, that small fan supplies cooler ambient air into the chassis to aid in the tube cooling.
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    MarcVBelgium
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    • Post n°6

    VTA M-125 in custom chassis Empty M-125 in custom chassis

    Post by MarcVBelgium Tue Sep 09, 2014 11:16 am

    This work is just BEAUTIFUL

    Congrats on the work so far..... it's a great job!
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    Bob Latino
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    • Post n°7

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    Post by Bob Latino Tue Sep 09, 2014 11:27 am

    Holger,

    Excellent work on that custom version of the VTA M-125 monoblock amp. Yes - post up a photo of the wiring when you get the amp wired ..

    Bob
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    • Post n°8

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    Post by audiobill Tue Sep 09, 2014 4:30 pm

    Is that the "soft start" board I see in there?
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    • Post n°9

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    Post by Guest Tue Sep 09, 2014 4:32 pm

    audiobill wrote:Is that the "soft start" board I see in there?

    it is indeed, I believe that is a great addition to any tube amp in extending power tube life, and the extra cost is minimal
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    • Post n°10

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    Post by Guest Mon Sep 15, 2014 9:26 pm

    well, the beasty is alive...and sounds just so wonderful!...I had the volume pot wired the wrong way, nearly blew the test speakers off the wall!!!!!!!...not to mention my eardrums!!
    Powere straight up, no worries.

    The wiring is still somewhat temp, I am waiting for the correct handed front panel, the one in the photo is for a 'left handed' chassis, the amp in the photo is actually a 'right handed' chassis.

    photo bbopper2_zpsaba102cb.jpg

    photo bbopper3_zps5cc3ef0b.jpg

    photo bbopper4_zps184d1187.jpg

    photo bbopper5_zpsa89c8485.jpg

    photo bbopper1_zpsd78beff7.jpg
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    • Post n°11

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    Post by colin86325 Tue Sep 16, 2014 6:43 am

    She's a beauty!
    On a side note, would there be an improvement if you clocked one of the chokes 90 degrees?
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    • Post n°12

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    Post by Bob Latino Tue Sep 16, 2014 9:21 am

    colin86325 wrote:She's a beauty!
    On a side note, would there be an improvement if you clocked one of the chokes 90 degrees?

    The chokes are mainly passing DC .. They are there to "choke off" small amounts of AC riding on the DC before the audio signal is dropped onto the DC B+. Because almost no AC is passing through the choke, there is virtually no interaction either between the two chokes or between the chokes and the power transformer.

    Bob
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    • Post n°13

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    Post by Guest Tue Sep 16, 2014 9:28 am

    Bob Latino wrote:
    colin86325 wrote:She's a beauty!
    On a side note, would there be an improvement if you clocked one of the chokes 90 degrees?

    The chokes are mainly passing DC .. They are there to "choke off" small amounts of AC riding on the DC before the audio signal is dropped onto the DC B+. Because almost no AC is passing through the choke, there is virtually no interaction either between the two chokes or between the chokes and the power transformer.

    Bob

    you took the words right out of my mouth! :-)
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    • Post n°14

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    Post by Guest Tue Sep 16, 2014 3:27 pm

    .


    Last edited by PeterCapo on Thu Dec 03, 2020 11:15 pm; edited 1 time in total
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    • Post n°15

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    Post by colin86325 Tue Sep 16, 2014 4:15 pm

    Ah, good to know Smile
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    • Post n°16

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    Post by mantha3 Tue Sep 16, 2014 7:59 pm

    Excellent Job. Get a shot of the two side by side when you are done
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    • Post n°17

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    Post by Guest Fri Sep 19, 2014 8:24 pm

    OK, here are shots of the finished unit. This is the 'right handed' version, I have added a 'left handed' version, but I cheated, by just 'mirroring' the right hand version.

    photo bbopperrh1_zps17abf83a.jpg

    right handed version

    photo bbopperlh_zpsa9f79d52.jpg

    left handed version

    photo bbopperrh2_zps776956bc.jpg

    photo bbopperrh4_zps7bd53892.jpg

    photo bbopperrh6_zpsd510d0c0.jpg

    photo bbopperrh7_zpsa5d01546.jpg

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    • Post n°18

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    Post by Guest Mon Oct 13, 2014 5:42 pm

    here are 'both' handed versions, in a different wooden chassis

    photo BBopper21_zpsdbade123.jpg
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    • Post n°19

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    Post by Bob Latino Mon Oct 13, 2014 7:20 pm

    Nice work Holger ..
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    • Post n°20

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    Post by mantha3 Mon Oct 13, 2014 7:21 pm

    NICE!!!!
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    • Post n°21

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    Post by mantha3 Mon Oct 13, 2014 7:29 pm

    PS - I have the same VU meter kit in a preamp I built. It is nice. I did have a problem with the body of the meter breaking from the face. I got a replacement and ran a bit of epoxy where the body fits to the face to reinforce.

    You may want buy a back up pair of meters just in case.
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    • Post n°22

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    Post by Guest Mon Oct 13, 2014 11:07 pm

    mantha3 wrote:PS - I have the same VU meter kit in a preamp I built.  It is nice.  I did have a problem with the body of the meter breaking from the face.  I got a replacement and ran a bit of epoxy where the body fits to the face to reinforce.  

    You may want buy a back up pair of meters just in case.  

    thanks for the heads up, will keep an eye on them and yes, I do have plenty of spares!
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    • Post n°23

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    Post by wgallupe Tue Oct 14, 2014 8:20 am

    Those are beautiful!
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    • Post n°24

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    Post by deepee99 Tue Oct 14, 2014 3:13 pm

    wgallupe wrote:Those are beautiful!
    Yup.
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    • Post n°25

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    Post by thompson12 Sun Dec 06, 2015 6:52 pm

    Did you connect the VU meters on you amp if so how

    thanks Mitch
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