what the best kit for Dynaco

[tony Ma]

Hi there,

Any one can suggest me what is the best KIT Dynaco (looking either st-120 or mk4)

I found couple interesting one like welborne labs, dynakitpart and bob latino...

Which one you think is the best for bucks

tks

[Bob01605]

Originally Posted by tony Ma

Hi there,

Any one can suggest me what is the best KIT Dynaco (looking either st-120 or mk4)

I found couple interesting one like welborne labs, dynakitpart and bob latino...

Which one you think is the best for bucks

tks

Disclaimer - I sell one of the kits mentioned ...

Your questions about comparing the Dynaco Mark IV monoblock kits to the VTA ST-120 amp kit is a difficult one. The reason is that the Mark IV's are 35 watt monoblocks - essentially half of an ST-70 but with a larger power supply. The ST-120 is a 60 watt per channel stereo amplifier and has more power.

Some differences between the two amps ...

The Mark IV's use the original Dynaco circuit with 7199 driver tubes which are not made anymore. The Mark IV may, however, be retrofitted with adapters to use 6GH8A driver tubes. 6GH8A tubes are more easily sourced than 7199's. The ST-120 uses 12AT7 driver tubes which are less expensive and more easily sourced than either 7199 or 6GH8A tubes.

The Mark IV uses EL34 output tubes and may also use 6L6, KT66 or KT77 output tubes. The ST-120 uses KT88, 6550, KT90, KT100 or the new Tung-Sol KT120 output tube. The tube set on the ST-120 will be more expensive than outfitting two Mark IV's with tubes.

Each Mark IV uses one bias pot on each amp to bias a pair of output tubes. The ST-120 has individual bias pots for each of the four output tubes.

The Mark IV operates in ultralinear mode only. The VTA ST-120 has a switch which allows operation in ultralinear mode or triode mode.

The Mark IV is built on an .048 inch thick 18 gauge stainless steel chassis. The ST-120 is built on a heavier .060 inch 16 gauge stainless steel chassis.

Bob Latino

[indianajo]

The master himself. Mr. Latino, I think your "dynaco stereo 120" is a nice looking tube kit. I think calling it a "dynaco stereo 120" is silly, because the dynaco st120 is a transistor amp. I'm listening to mine tonight, a 1970 ST120 with djoffe bias mod and cooling fan mod. Call yours a stereo 115 or 125 or something, please. I gave Mr Ma a lot of stupid advice about not building the transistor amp before I found your website.

[quinnling]

Mr Latino did call his amp VTA-120 on his post not Dynaco 120. Some of his potential customer or current customer do call it Dynaco 120 which is very confusing. A Dynaco 120 is a Transistor amp, but Mr Latino built a 60 watt tube amp on a Dynaco styled ST-70 chassis.

[indianajo]

Mr. Latino's website today (Mar 19 2011) reads "ST120-VTA120" on its home page, with a picture of a nice tube amp with bulgy bulb output tubes. The amp page leads off with "ST120 stereo amp" with the picture at the top. He should put a modifier ahead of ST120 every time he uses it, because the Dynaco ST120 was a transistor amp. His may be a more reliable amp than the Dynaco, but it is different.

[Sal Brisindi]

I've always thought the Dynaco Mark IV was rated at 40 watts per channel. Also since the Mark IV is a mono-block, it has its own transformer/power supply per channel.

Sal

[Bob01605]

Sal is correct. the Dynaco Mark IV's were rated at 40 watts per monoblock - not the 35 watts that I mentioned in an above post. The 5 extra watts is due, as Sal has mentioned, to the just ONE channel.

As to power ratings of these older amps .. In general, most power ratings were (to say the least), somewhat inflated. In November 1974 the FTC got after all amp makers to give a more realistic rating of power output and bandwidth. Dynaco and other amp makers had to revise their power and bandwidth ratings to comply with the new ratings systems. All of a sudden that Dynaco ST-70 which was rated at 35 WPC from 20 Hz to 20,000 Hz at less than 1 % distortion was now a 20 WPC amp from 50 Hz to 10,000 Hz at 1 % distortion. See ratings page from the 1975 Dynaco brochure below ..

Bob Latino

[tony Ma]

2nd thought on the KT88 Tube amp
I found MUSIC ANGEL XD-800MKIII seems so cheap and nice looking. Also I found how to modify it. Any comment and suggestions???

[indianajo]

Here is a link from 2005 about one of the products. http://www.diyaudio.com/forums/tubes-valves/59070-my-experience-music-angel-el34-pp-5.html
Personally I think the vendor is in an economy that is growing fast enough, but join the crowd, we can import everything all the time, the party will never end.
After I installed new caps and new GE output tubes & rectifier tube & selenioum rectifier in 1971, the McIntosh salesman got 35 watts/ch on my ST70, but I don't remember what distortion level he was using.