tubes 4 hifi
 "the path of least resistance is through a vacuum"

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Dyna MK3 mods



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)


MK3 bare PCBs are $55 a pair including shipping

a pair of PCBs with parts kit is $95 (including shipping),
NOT including tubes
If you'd rather have the boards assembled
and ready to install,
it's $50 for our labor
total price $145 the pair


MK4 bare PCBs are $60 a pair including shipping

MK4 pair of PCBs with parts kit is $100 (including shipping),
NOT including tubes
If you'd rather have the boards assembled
and ready to install,
it's $50 for our labor
total price $150 the pair


NEW 6SN7 OCTAL DRIVER - use for Dyna MK3, VTA M125s or VTA M70s
the bare PCBs are $59 a pair including shipping

a pair of MK3 OCTAL PCBs with parts kit is $109 (including shipping),
NOT including tubes

If you'd rather have the boards assembled
and ready to install,
it's $50 for our labor
total price $159 the pair

optional - upgrade to K42Y russian PIO mil-spec capacitors
these are preferred by many for better sound quality
$20 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
$10


dual bias test jacks to replace front octal sockets
also work with ST70 or ST120 amps
$30 per pair


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

add an additional $50 for 4 - JJ 12AU7 tubes

add an additional $90 for 4 - EH 6SN7 tubes

add an additional $140 for 4 - EH KT88 tubes

MK3 KIT (ONE amp) without tubes $575 plus shipping to be determined
MK3 KIT (ONE amp) WITH TUBES $700 plus shipping to be determined
includes 2 EH KT88, 1 Sovtek 5AR4, 2 JJ12AU7,

would you like us to build
a brand new pair
of MK3s for you?

our finished price is $1560 per pair,
(no tubes) PLUS shipping within USA only

finished pair of MK3 amps WITH TUBES is $1800,
PLUS shipping within USA only



here are some photos of an old MK3 with a few of our upgrades installed (triode-pentode switch, bias test points, triple speaker posts

here's a review from one of our many customers . . .

Roy,

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.

Best,
David A.

here's some photos of a newly built MK3-octal

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 tubes 4 hifi
 "the path of least resistance is through a vacuum"