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Dynaco MkIII Kit sellers

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Posted on October 29, 2009 at 13:24:59
Frihed89
Audiophile

Posts: 8445
Location: Copenhagen
Joined: March 21, 2005
 I know about Dynaco kits and Triode Electronics. MapleTree Audio Design sells a finished modle, but it's 4x the price of the kits and won't take a 6550 due to higher voltage.

Are there others?

Does anyone know how far into class A the original amp ran?
"What did the Romans ever do for us?"
RE: Dynaco MkIII Kit sellers, posted on November 2, 2009 at 07:03:30
PakProtector
Audiophile

Posts: 9953
Joined: May 14, 2002
 hey-Hey!!!,
FWIW, I have installed 6k6 a-a output TX's in my Mk.iii's and like it much better than the lower plate-to-plate load originally delivered by the A431's. They've also got U-L taps at 50% and I am running 8417 so it isn't a good apples-apples( though I do prefer the 8417 over the KT88/6550 in any case. I am sure Heyboer could wind up a pair of these outputs at reasonable cost for your project too.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Also consider ..., posted on October 29, 2009 at 16:35:46
RockyAM01
Audiophile

Posts: 33
Joined: July 14, 2008
 If you are interested in a pair of Dynaco Mark III's then you should consider Bob Latino's 60 watt per channel Dynaco ST-120 which is the equivalent of two Mark III's with VTA driver boards but on one chassis. You can buy this amp as a kit or as a wired amp. You can use KT88, 6550 or KT90 output tubes in this amp. I have one of his ST-70's that I built from a kit. The parts set is top notch and the sound quality IMHO is competetive with amps costing much more. RockyAM

How far does it run into class A (how many watts)? NT, posted on October 30, 2009 at 02:02:48
Frihed89
Audiophile

Posts: 8445
Location: Copenhagen
Joined: March 21, 2005
 NT
"What did the Romans ever do for us?"
RE: How far does it run into class A (how many watts)? NT, posted on October 30, 2009 at 03:14:40
PakProtector
Audiophile

Posts: 9953
Joined: May 14, 2002
 What's with this marketing-based claim of power under Class A? The amp is AB, and as such makes some power with both tubes conducting. That is the nature of AB operation; it is not class A. That is rserved for biasing/loading that delivers both phases conducting at maximum power. In any case, the amp will run to ~10W before it starts cutting off one tube.
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
RE: How far does it run into class A (how many watts)? NT, posted on October 30, 2009 at 05:30:40
Frihed89
Audiophile

Posts: 8445
Location: Copenhagen
Joined: March 21, 2005
 Class AB: It runs in class A up to some power output and then switches to B. Where did I go wrong?
"What did the Romans ever do for us?"
RE: How far does it run into class A (how many watts)? NT, posted on October 30, 2009 at 12:57:13
Tre'
Industry Professional

Posts: 4851
Joined: February 9, 2002
 Class A/B is a class of operation. Both tubes conducting up to a point and then some cutoff and then cutoff, as the output power goes up.

Class A has both tubes conducting all the time.

So even though Class A/B "looks" like Class A, up to a point, it's not.

Class A/B does have one attribute of Class A, until a certain power is reached (namely conduction through both tubes), that does not make it Class A. That's why it has it's own name, Class A/B

In a Class A circuit the bias and load is different. A Class A amplifier will have a larger impedance load and the bias point will be at the mid-point, between cutoff and saturation. This is a much more linear way to operate a tube.

A true Class A, push pull amplifier will operate each output tube (in terms of bias and load) just like they would be operated in a single ended amplifier.

In a Class A/B amplifier, running in the range where the tubes are not being cutoff, the tubes are not being run at Class A biases or loads. The only thing that is like Class A is that the tubes are not being cutoff. But that's all. So the so called "Class A" portion of Class A/B operation is not Class A operation at all.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
RE: How far does it run into class A (how many watts)? NT, posted on October 30, 2009 at 05:36:16
PakProtector
Audiophile

Posts: 9953
Joined: May 14, 2002
 calling low power operation from an AB operating point class A. Class A operation is *NOT* defined simply as both phases conducting. It is a combination of conditions, all of which must be met.
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
what would those conditions be? Nt, posted on October 30, 2009 at 08:13:48
Frihed89
Audiophile

Posts: 8445
Location: Copenhagen
Joined: March 21, 2005
 Nt
"What did the Romans ever do for us?"
RE: Dynaco MkIII Kit sellers, posted on October 29, 2009 at 14:39:58
Francois G
Audiophile

Posts: 106
Joined: July 31, 2002
 Check http://www.diytube.com
I have a pair of MkIII's with the poseidon kits and they sound VERY good.

RE: Dynaco MkIII Kit sellers, posted on October 29, 2009 at 14:34:04
PakProtector
Audiophile

Posts: 9953
Joined: May 14, 2002
 hey-Hey!!!,
The amps never ran in class A. The two-tube conduction can be approximated by looking at idle current and load. 4k3 a-a leaves 2k15 Ohms per tube( a-a/2), and about 65 mA...soooo, with Ohm's Law the voltage swing is +/- 140V give or take.
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

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