tomorrow i want a buy st70 !!! but i need many info:

knowledge base for the classic Dynaco ST70

tomorrow i want a buy st70 !!! but i need many info:

Postby mati1979 » Thu Apr 09, 2009 10:33 pm

i see, i have many choises:

DriverBoard: newEF86 or 6AU6 (???)
Caps: Xicon or Solen +u$10 ? (is recomendable solen for 10 u$ + ? )
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Postby mati1979 » Thu Apr 09, 2009 10:48 pm

i see:

with

* "EF86 board" i can use tubes: 6922, 6DJ8, 7308, 6CG7 in addition to the 12AU7, 12BH7, ECC99

* with "6AU6 board" only i use tubes: 12AU7, 12BH7, or ECC99

this is correct ?

For my convenience it(he,she) is better to buy the first ? (EF86)
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Postby kheper » Fri Apr 10, 2009 12:26 am

I would go with newEF86 and Solen. This is just my opinion.
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Postby mati1979 » Sat Apr 11, 2009 3:58 pm

i have more questions :(
I see 2 model of st-70
1 with 7 tubes : 4 el34 + 2EF86 + 1 5AR
and another with 8 tubes 4EL34 + xx + xx ?

A model with 7 tubes comes with board EF86 and 8 tubes with board 6ua6 ?

.

Image

Image

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Postby TomMcNally » Sat Apr 11, 2009 5:11 pm

The original Dynaco ST-70 driver board used two 7199's ...
they are hard to find, and weren't all that great to begin with.

New amps, and rebuilds, use one of the many replacement
driver boards, like the diytube ST-70, and about ten other
boards available. If you are building a kit, the supplier
will use their favorite board, or let you choose your own.
Most new boards use three tubes, amps and phase inverter.
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Postby mati1979 » Sat Apr 11, 2009 5:27 pm

TomMcNally wrote: If you are building a kit, the supplier
will use their favorite board, or let you choose your own.
Most new boards use three tubes, amps and phase inverter.


i have putted order here:

http://store.triodestore.com/st70buildkit.html

DriverBoard : newEF86
Transformers : Standard 120VAC
Caps : Solen (+$10
Tubes : With Tubes (+$100)
$685.00


wich are the "default" board ? :(
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Postby mati1979 » Sat Apr 11, 2009 5:31 pm

The question should be: what is the most suitable thing to buy for me?
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Postby TomMcNally » Sat Apr 11, 2009 5:49 pm

There is no "default board" since Dynaco hasn't made amps
for like 25 years ... the board you ordered will be fine.
I have one of those Triode boards in my ST-70 that I
built about 10 years ago.
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Postby burnedfingers » Sun Apr 12, 2009 5:58 am

one reason of the popularity of the Dynaco is that you can customize it to suite your needs and ears.

picture of one of my Dynaco's that I will be selling shortly.

Image

This one had the nickle stripped off and an aftermarket Chrome plating from a good plating shop. A good aftermarket driver board, power supply board, power transformer, and bias controls added just to name a few tweaks. Cost of my tweaks is $685 So there are a number of options available to someone wanting a toy to play with. You can build it anyway you want and you don't have to purchase a kit to have something nice.
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Postby SDS-PAGE » Sun Apr 12, 2009 3:56 pm

Hey, are those 5693s (red RCAs)? Those are one of my favorite pentodes ever. I like them especially in my WE91A.
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Postby burnedfingers » Sun Apr 12, 2009 6:18 pm

Yes, those are 5693's and also my favorite. The driver board is a Mapletree and it uses 6Sj7/5693's and 6SL7/5691's. It is my favorite driver board for a Dynaco and I have used and or listened to them all.
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Postby mati1979 » Sun Apr 12, 2009 9:30 pm

Hi, another quest :))

i see many differences between chassis in sales.
for example in triodestore sales a st-70 kit without labels or anythings printed in chassis ? and in dynakitsparts i see switch mono-stereo in front and i see labels and printed in the chassis "dynakits stereo 70" etc.
They are the same kits or are different ?

http://store.triodestore.com/st70buildkit.html

http://www.dynakitparts.com/store/product.aspx?id=2

.

Image

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Postby burnedfingers » Mon Apr 13, 2009 4:46 am

It looks to me like the Dynakitparts amp is a remake of the original Dynaco but with a better power transformer and better driver board. The driver board is a remake of the original board but features a fibreglass board and better caps and resistors. The original chassis is punched for the octal sockets on the front which provide the power for the Dynaco preamp.

The Triode chassis doesn't have the octal sockets on the front and will not power up a Dynaco preamp without having to make a special adapter. The Triode board gives you a choice of newer and better driver boards than the Dynakitparts unit.

I personally don't see a need to run any tube amplifier in mono bridge mode. The distortion will go up and you will find that you need one amplifier for each channel.

If you don't plan on using a Dynaco preamp but rather a conventional preamp than the Triode unit would be my choice if I were wanting to buy one.

These are the difference that I see and there could be something that I missed.
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Postby mati1979 » Mon Apr 13, 2009 7:56 am

Thank you Burnedfingers !.
I see, a chassis dynakit have more sheen than triode chassis.
this is pulished stainless steel or chrome ?
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Postby burnedfingers » Tue Apr 14, 2009 4:42 am

I haven't seen the Dynakit chassis up close so I cannot tell you if it is polished nickle or chrome. The other chassis is stainless steel and I cannot tell you what alloy it is either. Some stainless will rust and it all depends on the alloy.

My preference is to get a original chassis and send it to a plating shop and have it stripped of the nickle and then have a good chrome plate job. It usually runs $85 per piece plus shipping but the result is far better in my opinion than an aftermarket piece.
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