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    Prototype 125 watt monoblock tube amplifier KIT

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    Bob Latino

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    • Post n°1

    Prototype 125 watt monoblock tube amplifier KIT

    Post by Bob Latino on Sat Jun 05, 2010 12:07 pm

    Since business slows down during the summer I will be experimenting with a prototype monoblock tube amplifier which should be capable of 125+ watts. I don't want to give the details of the circuit right now because the circuit is still in the development stage. I had a pair of larger output transformers made for me by my transformer company (see photo comparisons below). This 11.5 pound output transformer has a very large core so it won't saturate at higher current flow levels. The manufacturer assured me that these have been tested up to 200 watts (continuous power) with no core saturation. The plates are M6 grain oriented silicon steel like the VTA ST-70/ST-120 output transformers. The primary and secondaries are interleaved/layer wound just like the VTA ST-70/ST-120 output transformers. The primary impedance is 1800 ohms. I won't be able to work on this for a couple of weeks but will let you know in this thread how (if any?) progress is being made on the project.

    Bob



    Last edited by Bob Latino on Fri Jul 29, 2011 10:54 am; edited 7 times in total
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    PeterCapo

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    • Post n°2

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by PeterCapo on Sat Jun 05, 2010 8:51 pm

    Hey Bob,

    Pretty exciting possibility there! It could be a successor of sorts to the Dynaco Mk-VI.

    Suggestion: make the amp user-configurable for either the new KT-120 as well as KT-88/KT90/KT98/KT100 (in the event KT-120 ever ceases production).

    Good luck.
    Peter
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    baddog1946

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    • Post n°3

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by baddog1946 on Sun Jun 06, 2010 8:35 am

    Hi Bob:
    What are the specs on that transformer? What voltages does it have output, bias etc.
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    baddog1946

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    • Post n°4

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by baddog1946 on Sun Jun 06, 2010 8:38 am

    Oh yes! Can we buy them soon?
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    Bob Latino

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    • Post n°5

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Bob Latino on Sun Jun 06, 2010 8:56 am

    baddog1946 wrote:Oh yes! Can we buy them soon?


    Right now all I can tell you is that the primary impedance of the OUTPUT transformer is 1800 ohms CT. The POWER transformer secondaries will be able to deliver 415-0-415 VAC @ 450 milliamps.

    Re: "Can we buy them soon?". These amps may or may not see the light of day as a production amp kit? I am having two prototype chassis made which I won't see until the end of this month. I will post some photos of the chassis when they arrive ..

    Bob


    Last edited by Bob Latino on Wed Jul 20, 2011 8:03 am; edited 5 times in total
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    JunkyJan

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    • Post n°6

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by JunkyJan on Wed Jun 09, 2010 3:55 pm

    Hi Bob

    I assume to get that kind of power output, you'd be looking at running 4 X KT88 in a PP configuration (per monoblock)? I admit to being very curious and even more so VERY interested - that would be serious fun building it (assuming you'd have it available as a kit).

    The power levels would right up there ("Oh-my-gawd-I'm-calling-the-police")...

    -- JunkyJan
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    Falcon4646

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    • Post n°7

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Falcon4646 on Tue Jun 29, 2010 11:23 am

    Bob,

    Very interested in your 125-150 watt monoblock effort. My 4 ohm floorstanders go from 20-400 watts of power handling capability. Had been considering the ST120 but your new effort seems more suitable to my needs.
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    natoe

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    • Post n°8

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by natoe on Tue Jun 29, 2010 12:17 pm

    Bob, I think it might be interesting just to buy the parts off of you for the mono blocks and do your own chasis.I have had some ideas for a chasis for a while and I think this would be the proper platform to do them. Almost the same is Jim McShane and the pre-amps he will be offering up when he gets the r&d done on them.They will come with no chasis, kit form to keep the cost down.

    always,thank you
    pete
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    davidnes

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    • Post n°9

    Any update on the new amp project?

    Post by davidnes on Wed Sep 01, 2010 9:05 am

    Bob,

    Any update on the status of this project?
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    Bob Latino

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    • Post n°10

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Bob Latino on Wed Sep 01, 2010 9:09 am

    davidnes wrote:Bob,

    Any update on the status of this project?


    Hi,

    Yes - I should have the two prototype chassis by the end of this week. I will post photos of the chassis when I get them ...

    Bob
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    Bob Latino

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    • Post n°11

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Bob Latino on Thu Sep 02, 2010 11:17 am

    Hi All,

    I have one of the two prototype chassis for the VTA M-125 power amp. The photos are below. The chassis will be 10" by 12" and made of 16 gauge brushed stainless steel as seen in the photos. The chassis will have no silk screening. The amp will have a parallel push pull circuit using a modified VTA Mark III driver board. The complete circuit details have not as yet been worked out. The chassis will have on the front face three bias test pins - one grounded to the chassis and the other two for biasing one pair of the 4 output tubes. The ON/OFF power switch will be on the front. On the rear face will be the input jack, fuse post, IEC AC connector and a single output binding post terminal. The amp will use four KT88, 6550, KT-90 or KT-120 output tubes. The amp should be capable of 120 to 140 watts ...

    I will not be able to really work on this until Monday Sept 20th. I am helping someone with a project all next week and and will be on vacation the week of Sept 12 to Sept 18.

    Chassis photos below ..

    Bob

    Chassis top and front face



    Chassis top and rear face

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    PeterCapo

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    • Post n°12

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by PeterCapo on Thu Sep 02, 2010 7:11 pm


    Outstanding! Looking forward to hearing more about it.
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    Corona

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    • Post n°13

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Corona on Thu Sep 02, 2010 8:13 pm

    Nice can't wait to see this project come together What a Face
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    Bob Latino

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    • Post n°14

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Bob Latino on Fri Sep 03, 2010 7:34 am

    Hi,

    I found some minor "glitches" in the translation of what I wanted as to spacing of certain parts on the chassis. The IEC connector is too close to one of the mount screws for the power transformer. On this prototype it's no real problem because I will just shorten the screw about 1/4 inch and it will go in there fine. The IEC connector will have to be moved 1/4 inch toward the fuse post and the fuse post will be moved 1/8 further towards the input jack.

    Also, the four holes that mount the SCM, main grounding tabs, 3 lug and two lug terminal strip were too small. I told them that I wanted a hole for a 4-40 screw. What they gave me was 4 holes that could be TAPPED for a 4-40 screw. I just drilled the 4 holes out. They also got one dimension wrong by 3/8 of an inch. The triode/pentode switch is too close to the mount screw for the SCM module. It will be moved 3/8 of an inch towards the two lug terminal strip. On production models a heavier duty DPDT triode/pentode ultralinear switch will be used. On production models a 15 amp rated SPST ON/OFF switch will be used. I just used some smaller switches I had around the shop here on the prototypes.

    Photo below of progress so far. I will be able to work more on the amp next week because the project that I was going to help someone with has been postponed.

    Bob



    Last edited by Bob Latino on Sat Nov 06, 2010 5:13 pm; edited 1 time in total
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    baddog1946

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    • Post n°15

    new amp

    Post by baddog1946 on Fri Sep 03, 2010 9:01 am

    Hi Bob:
    The new project looks like it is coming along quickly. I noticed you are sticking with the quad cap on this one. Is there a particular reason you are doing so?
    I would think that a board with the option of modifications and swapping out better caps would have been the call. Got any other specs for that thing yet?
    I hope to see the completed project soon. Will it be a kit or a complete amp?
    a very curious
    Baddog1946
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