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    Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

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    Roy

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    Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Roy on Sun Jan 14, 2018 2:50 pm

    Hello everyone,

    Me and my wife would appreciate the chance to listen to a Dynaco ST-70 or ST-120 build, hopefully near where we live in the Netherlands.
    I have some fond memories of tube amps when I was a kid, but in my adult life have only enjoyed solid state amplifiers.
    We would very much appreciate it if someone out there could give us the oppertunity to listen to one of these amps before we make te decision to
    go ahead and get one of these kits to build one!


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    MarcVBelgium

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    Age : 64
    Location : Antwerp, BELGIUM

    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by MarcVBelgium on Sun Jan 14, 2018 4:11 pm

    Welcome in Antwerp (Belgium) if you wish. It is a ST-120 on Tannoy speakers.
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    Roy

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Roy on Sun Jan 14, 2018 4:36 pm

    MarcVBelgium wrote:Welcome in Antwerp (Belgium) if you wish. It is a ST-120 on Tannoy speakers.  
    Thank you very much Marc! - do believe we already spoke on FB =]

    I sent mr. Latino some mail for information on the ST-120 and got speedy replies - he knew he has sold some kits to people in Amsterdam and Utrecht which is more around the corner for us.
    Did talk to my wife about Antwerp but for the foreseable future her work schedule rules out any weekend trips and weekends is what we got to use for that distance, and the little one would need to come along too ^^

    Maybe exchange skypes? Would love to chat and hear what got you to pick thís amp and how the build fared etc



    Dale Stevens

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Dale Stevens on Sun Jan 14, 2018 6:27 pm

    Roy, welcome to our group. Mr L's ST120 is spot on, the build is forward and you'll get lots of support
    from all here. The ST120 has lots of head room over the 70 which I like. My 120 powering the
    K-horns is splendid! And that amp will probably outlive my new Corvette!! Dale
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    Roy

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Roy on Mon Jan 15, 2018 4:43 am

    Thank you Dale ^^  Have been reading the various build stories here and elsewhere on the forum with much interest. A little hesitant about the actual electronics soldering lol..  Going to dig up my soldering station and do some practising in the coming time.

    One of the 'issues' I have been pondering over is the use of a cage on the ST-120.
    Have read many comments on the ST-70 running with or without the cage and  heat seems an issue wíth.
    Considoring the ST-120 has even beefier transformers and a much higher output I imagine this heat issue to be more acute with this amp.  
    In our case, with both a pet and a small child I think I would very much appreciate a cage over the amp.  Am looking at various ( stainless ) meshes available here to construct one out of but I wonder if ány cage would not constrict airflow too much for the ST-120?
    I see meshes with circular openings up from 20-50%  open - also honeycomb meshing that is 90% and more open.. Does anyone know the mesh specs of the (ST-70) cages?
    Certainly I suppose having the sides nót closed as with the original ST-70 cage would be a must I reckon with the ST-120 if some ST-70 users already comment these closed sides are what is hindering airflow already..  The newly released ST-70 incarnation from Dynaco has its cage perforated on all sides, though the curvature does not really please my eyes - perhaps done for strength, and economics of construction.


    Last edited by Roy D on Mon Jan 15, 2018 11:04 am; edited 1 time in total
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    Bob Latino
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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Bob Latino on Mon Jan 15, 2018 11:00 am

    Roy,

    You can use a Dynaco ST-70 tube cage on the VTA ST-120 and the amp will still have enough air flow to keep it cool. The key thing with the ST-70/ST-120 is that the top of the amp should "look at the ceiling" of your home so that the amp can get rid of the heat through natural air circulation. Tube amps do not have heat sinks for cooling like solid state amps and they depend on natural air circulation for cooling. The one thing you should NOT do is place a tube amp inside a cabinet where air circulation would be inhibited. Below is a photo I have posted before here on the forum. This is an earlier version of the VTA ST-120 and the temperatures on various areas of the amp after the amp has been on for 3 1/2 hours. The temperatures derived were from a Cason infrared thermometer seen on the right of the photo. These infrared thermometers can be had for $20 or so on Ebay and are nice to have if you want to know the temperature of something quickly. You just point at the object and pull the trigger. The temperature reads out in about a second on a small LCD screen. It is interesting to note that the temperatures on the LEFT side of the amp are slightly higher than the RIGHT side. The rectifier (in this case a Weber WZ68 but the same holds true of a tube rectifier) is on the left side and the rectifier gets pretty hot although I did forget in this case to take the Weber's temperature. That hot object on the left side of the amp makes it more difficult for the left side components to get rid of their heat. Note also that the two rear output tubes run warmer than the two front output tubes. The rear output tubes are "trapped" between the heat of the output transformer and the front output tube's heat.

    Bob


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    Dave_in_Va

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Dave_in_Va on Mon Jan 15, 2018 11:15 am

    I bought my cover for my VTA ST-70 from Dynakits and it fit perfectly. NO problem with heat that I can tell.

    http://www.dynakitparts.com/DYNAKIT-ST-70-COVER

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    MarcVBelgium

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by MarcVBelgium on Mon Jan 15, 2018 11:19 am

    Roy D keep in mind that these temperatures are Fahrenheit, not Celsius..... you have to do the math ;-)
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    Roy

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Roy on Mon Jan 15, 2018 11:22 am

    Thank you Bob, or mr. Latino    for the replyh and photo of the thermals ! Just showed it to my 4 year old and he pointed out the black things were transformers =)       His dad had been watching some videos on youtube on transformer basics and all through that he kept asking questions on the subject lol..

    I see the front tube substantially cooler than the middle one stuck between it and the output transformer - no arguing these things get warm and that is how they were designed really - no vacume tube without a heater in it - but I imagine there is some gains to be had having the standard ST-70 cage's sides more vented or also fully perforated. That the original ones were not was probably a form over function   or cost  design decision. Something to worry about later   or perhaps not at all

    Again, the new st-70 released last year - it just does not look right to me ^^

    hehe I know Marc  and Dale - did the math and came to the conclusion  I could make pretty good skewers over this thing if I can solve the grease drip problem!

    Perhaps it is all a bit like heat & wear in harddiskdrives ( a little more my area ) Yes the heat does cause some additional wear on some aspects of the drive, but in practical terms the difference between temp A and temp B operation does not contribute substantially ( within reason ) to their earlier than intended demise.. Going to finish reading up on (tube) amplifier basics, finesse my wife's counter demands in terms of expendatures in other areas and hopefully take the leap some time soon in building an ST-120 kit. Will just order the standard ST-70 cage possibly modify it a little or a lot Or not..




    Last edited by Roy D on Mon Jan 15, 2018 11:45 am; edited 1 time in total
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    MarcVBelgium

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by MarcVBelgium on Mon Jan 15, 2018 11:36 am

    I did use a cage (Dynakitparts - 80$) with my ST-120 without any problem. I no longer use it because I use a Mullard GZ-37 which is too high.........I would NEVER drill holes in the sides..... it works like a chimney, so just leave it the way it is.
    As Bob mentioned, when it faces the ceiling, all is OK... Do not worry about that.
    When having kids or pets in the house, it is also wise to put the amp out of reach (on top of furniture ) AND teach them to keep away from it.......(kindly of course)
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    peterh

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by peterh on Mon Jan 15, 2018 11:38 am

    Dynakitparts and tubes4hifi do speak with each other. Maybe bob could supply
    a st-70 cage in the box to save the extra shipping cost ?

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    Roy

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Roy on Mon Jan 15, 2018 12:03 pm

    That is an idea PeterH - would be nice as my government really likes the idea of adding import tax on goods including the cost of the shipping of the goods =_=

    From what I have seen Marc   the new ST-70 cage  and many of the other cages for other brands of tube amps employ the  as much perforation as possible strategy..  Bernouli or chimney effect doesnt really come into play with two sides closed and the rest open - those closed side walls are not beneficial to cooling but are beneficial to ridigity, and not having toothed edges going near the case when mounting and dismounting damaging it.. The original 50's design was sendzimir steel case  not stainless - having all round perforated cage with perforations at the edges would mean adding some more production to finishing the edges properly to keep it rigid enough to not catch or scratch taking the cage on n off would be an added cost.


    Last edited by Roy D on Mon Jan 15, 2018 12:04 pm; edited 1 time in total (Reason for editing : grammar, always grammar XD)
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    Kentley

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Kentley on Thu Jan 18, 2018 11:46 pm

    I use the "original" Dynakit cage on my ST-120, but only when powered down. How? Simply loosen the four screws in the sides of the chassis enough so that the (rather heavy) cage sits firmly. It's remarkably stable simply placed on the chassis properly. It's prevented many mishaps with felines, including {ick} males spraying. Try it. You'll like it.
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    Roy

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Roy on Fri Jan 19, 2018 2:47 am

    lol Kentley..  I found that   male cats can achieve whatever they've set their mind to do.  One fine morning I woke to that smell in our livingroom and thought  not before my cup of coffee and the news.. Switched on our new 100Hz Philips widescreen CRT and poof  up in smoke it went.  Our beloved cat found he could reach the sensitive electronics inside by squatting up on top of it and misting the insides through the ventilation slits..
    It was the heart of summer and the fella from the tv repair shop I called with the vain hope something could be salvaged had to drive with that burnt cat pee smell next to him for half an hour back to the shop. The misting managed to reach just about every component equally and conduction was excellent.
    Or current cat luckily does not exhibit this behaviour much at all but curious childrens fingers..

    Besides the main cage  I will be making a second cage for the pre amp board to be sure, not only for the child's sake but for mine and my wifes also and curious visitors oblivious to the danger..
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    Roy

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Roy on Sun Jan 21, 2018 4:40 am


    Visual Led Bias Monitor Kit In 4 Colors For The Dynaco Dynakit ST-70
    Has anyhone used one of these?  It looks mighty handy..

    EDIT - for some reason  I can't post the link to this seller with the message new members cannot post links for 7 days etc, but other links work fine..
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    Bob Latino
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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Bob Latino on Sun Jan 21, 2018 10:12 am

    Those bias kits are about $87 USD with shipping. Yes - they look cool but they add nothing to the sound of the amp for the $87.  Once the bias is set, you only need to check it once a month or so. The bias will change slightly as the tubes wear in. You just make an adjustment after the amp is fully warmed up. The bias does not have to be "perfect". If the bias setting on your VTA ST-70 is supposed to be .400 VDC per each output tube, as long as all four output tubes are between .390 and .410 VDC, that is close enough. Note also that since the VTA amps allow bias for each individual output tube, you will need to install some type of switch on each channel to switch between the front and rear output tubes. You will have to drill a hole in the chassis to install two switches, one for each channel. Link below to these visual bias kits on Ebay ..

    Visual Bias kits on Ebay

    Bob
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    Roy

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

    Post by Roy on Sun Jan 21, 2018 5:00 pm

    Thanks Bob,  not one for flashy lights bells whistles and knobs either but having a clear indicator that my wife can read at press of a button and perhaps see an issue before things go bad is some piece of mind for me. Would like it removable - literally plug n play - so was thinking male octal plug, a little round stainless housing..  but yeah  80 bucks..plus the extra bits to make removable, etc etc  

    First things first, some more massaging of the household budget and get the st120 kit home

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    Re: Interested in VTA ST-70 and ST-120 or other builds near us ( Netherlands )

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