we have duplicated the circuit from our ST70 modification onto a PCB that will fit the Dynaco MK3 mono amplifiers.
(this is the same board used in our M125 monoblocks)
optional - upgrade to K42Y russian PIO mil-spec capacitors
these are preferred by many for better sound quality
$25 for a set of four
optional - upgrade the on board power supply caps
this is 4 - 100uF 400v caps instead of standard 4 - 47uF caps
new speaker posts $19 pair
new TRIPLE speaker posts $25 pair - note these do NOT use standard 3/4" spacing
and must be used with single plugs or terminals, fits ST70 and MK3 only
here's a review from one of our many customers . . .
This is a great-sounding circuit.
With your circuit, one of the first things I noticed was that different recordings are clearly different,
indicating to me that the amplifier is neutral, rather than colored. I was surprised by dynamics in music
that I hadn't noticed before, especially in classical music.
This circuit seems able to render complex passages and dynamic variations that made the original circuit
sound sluggish. I am a trained classical pianist, and I also play Hammond Organ, other vintage keyboards,
and trumpet, so I know what instruments sound like in real space. The original Dyna circuit made acoustic
guitar sound "good," but also a bit unnatural--as if the player were playing an acoustic guitar that was
twenty feet wide. With your circuit, it sounds like someone playing an acoustic guitar right in front of me.
Your circuit is especially wonderful for the MkIII, which I've never thought was a very good-sounding amp
to begin with. It always seemed kind of grainy/grungy even with upgraded parts.
The new circuit cleans up the highs and gives the midrange both clarity and natural richness.
I did do a little tube-rolling last night. I swapped some Telefunken ECC81s in place of the Mullards.
It's hard to say which I like best. The Mullards seem more dynamic, the Telefunkens, a bit smoother.
My brother, for whom I built these, was wowed by them. He says he's going to have to get some speakers
that will do them justice. I'm playing them into a pair of KEF 104/2s that I think are one of the best speakers
for tube amps. This new MkIII is very well matched to them and drives them with apparent effortlessness.
here's some photos of a newly built MK3-octal
tubes 4 hifi |
"the path of least resistance is through a vacuum"