Dear Rodents,
I have a few Dynacos in storage but need 100w/c. If I wanted to add
another pair of KT88s or 6550s (4 per mono side) to make a double P/P Mark
III, (physical placement considerations not withstanding) what do I need? Do
I need to change the OPTs? How about the Power Xfrs? Will I need more
current capabilities? Maybe I'm just oversimplifying, hope not.
Your opinions will be most appreciated.
Cordially,
west

in article , west at
wrote on 4/18/05 1:07 AM:

Dear Rodents,
I have a few Dynacos in storage but need 100w/c. If I wanted to add
another pair of KT88s or 6550s (4 per mono side) to make a double P/P Mark
III, (physical placement considerations not withstanding) what do I need? Do
I need to change the OPTs? How about the Power Xfrs? Will I need more
current capabilities? Maybe I'm just oversimplifying, hope not.
Your opinions will be most appreciated.
Cordially,
west


West,

To oversimplify, more than all of the current going to the speakers must
pass through the output and input iron. I doubt either the input or output
trannies would handle double the current. No, I know they won't.

Why not find a pair of Citation II amps? They can be bridged for 120W per
channel. You can sell the Dynacos and offset the price of the HKs.

I happen to know a garage trader that bought two Citation IIs to work on,
but hasn't found the time lately . . . .

Jon Yaeger wrote:

in article , west at
wrote on 4/18/05 1:07 AM:

Dear Rodents,
I have a few Dynacos in storage but need 100w/c. If I wanted to add
another pair of KT88s or 6550s (4 per mono side) to make a double P/P Mark
III, (physical placement considerations not withstanding) what do I need? Do
I need to change the OPTs? How about the Power Xfrs? Will I need more
current capabilities? Maybe I'm just oversimplifying, hope not.
Your opinions will be most appreciated.
Cordially,
west

West,

To oversimplify, more than all of the current going to the speakers must
pass through the output and input iron. I doubt either the input or output
trannies would handle double the current. No, I know they won't.

Why not find a pair of Citation II amps? They can be bridged for 120W per
channel. You can sell the Dynacos and offset the price of the HKs.

I happen to know a garage trader that bought two Citation IIs to work on,
but hasn't found the time lately . . . .

I cannot smile about the doubling of output tubes in a design
built for only 2 tubes.

For starters, twice the heater power is needed.

But the 4 tubes could be biased at say 1/2 the present bias current.
Only marginally more power with the same loads would be possible.
The OPTs would cope with the higher signal po, but maybe not
with the extra DC if they were biased high.
With 1/2 the existing bias current the linearity at low levels might be
compromised,
since the tubes wouldn't be optimally biased at all.

I can only suggest that the Dynacos be left alone, and thus they will retain their
value,
and that a better solution is to devote some time to a new pair of mono amps.
The MkIII are a decent PP amp in their own right; ppl will kill to get a pair in
good condition...

Patrick Turner.

In article ,
west wrote:
Dear Rodents,
I have a few Dynacos in storage but need 100w/c. If I wanted to add

One version of this was called the Sovereign 120 and was published in
an article by Halfer in Radio-Electronics magazine in the late 1950's.

It required a different power and output transformer, plus 4 6550's or
KT88's rather than 2. The driver board was the same as the MK III.

The output transformer hasn't been made (at least by Dynaco) since the
1970's; I bought the last 4, 2 which I used and two which went to Bill Conrad
and Lou Johnson when they were building test beds prior to launching their
amplifier line.

If you really want 120 wpc out of a Dyna tube amp then it may be easier to
find some Mark VI's rather than update the MKIII. I don't think you can push
120 pwc through the MK III transformer, certainly not at the frequency
extremes.

If you don't need a low output impedance, and really want a tube amp, I have
seen variants of the Futterman H3 transformerless designs that were capable
of much more than 120wpc output. Since these don't use output transformers
(and sounded very nice driving full range ESL's; I've never heard one driving
anything else) they would be less expensive to build today than designs with
transformers.

The 250wpc Futterman amplifier was made by Lucius Morris in DC, under an
agreement with Futterman. I heard them driving double KLH Nines ca 1975.

Mike Squires

--

Mike Squires (mikes at cs.indiana.edu) 317 233 9456 (w) 812 333 6564 (h)
mikes at siralan.org 546 N Park Ridge Rd., Bloomington, IN 47408

"west" wrote in message
news
Dear Rodents,
I have a few Dynacos in storage but need 100w/c. If I wanted to add
another pair of KT88s or 6550s (4 per mono side) to make a double P/P Mark
III, (physical placement considerations not withstanding) what do I need?
Do
I need to change the OPTs? How about the Power Xfrs? Will I need more
current capabilities? Maybe I'm just oversimplifying, hope not.
Your opinions will be most appreciated.
Cordially,
west

What would happen if you ...
...."parallel" two units to serve as 1 channel in a, sort of, master/slave
configuration?
....strap speaker ground of the master to speaker ground of the slave.
....strap speaker out of the master to speaker out of the slave.
....unsolder one end of both power tube coupling caps from the slave at the
phase inverter side.
....reconnect the unsoldered ends to the respective points from the master
phase inverter.
....disconnect the slave feedback circuit from the 16 ohm tap.

I'm not sure what to do with the slave's lower KT88 pin 4 feedback, via the
390mmF cap (is that 390pF?), to the 6AN8.
Maybe the master B+ needs to be connected (via a resistor?) to the slave B+
so both are sagging and surging indentical.
I guess the latter won't be necessary when both power stages and power
supplies are "matched" close enough.

.... and if you apply signal to the master unit.....

Now, master as well as slave deliver the same voltage to the load, but, if
master and slave are closely "matched", only half the usual current each.
IOW, master and slave "see" double the speaker impedance each, so to get
double the power to your speakers you'll have to move the speaker connection
one tap up.
So, if the Infinity (was'nt it?) has 4 ohm, you'll have to drive it from the
paralleled 8 ohm tap etc.

BTW, there's a lot of guessing going on here, maybe it's just a crazy idea.
I've never tried this, lacking stacks of Dynaco's or stacks of anything else
:-(
But I reckon it could work, and, if it does, it might save you some iron and
glass.

In history relationship between master and slave has been troublesome.
I wonder, and am curious, about that in this case.
Keep me posted if you give it a go.

Rgds,
Jan.

Other Rodents have already clarified that it is not advisable to do
Frankenstein-like surgery on a glorious Dyna. I'd just suggest to use all
Your amps together in bi/tri-amplification with bi/tri-wiring. I'm sure You
can sort all Your stuff in order of available power to make it fit the
speakers needs in a reasonable way. Say, a SS for bass, the Dynas for mid
and some other one (I'd suggest a SE if available) for highs. This will
provide about the power You're talking about.
As per the preamp/electronic crossover... well, a chance "to boldly go where
no man has been before."

Ciao

Fabio


"west" ha scritto nel messaggio
news
Dear Rodents,
I have a few Dynacos in storage but need 100w/c. If I wanted to add
another pair of KT88s or 6550s (4 per mono side) to make a double P/P Mark
III, (physical placement considerations not withstanding) what do I need?
Do
I need to change the OPTs? How about the Power Xfrs? Will I need more
current capabilities? Maybe I'm just oversimplifying, hope not.
Your opinions will be most appreciated.
Cordially,
west

"Patrick Turner" wrote


snip

I can only suggest that the Dynacos be left alone, and thus they will
retain their
value,
and that a better solution is to devote some time to a new pair of mono
amps.
The MkIII are a decent PP amp in their own right;


Yep.


ppl will kill to get a pair in
good condition...


Well they can kill me then - I've got a pair (240V) in superb, original
condition, working perfectly and sounding great. See halfway down this list:

http://www.apah69.dsl.pipex.com/item...emsforsale.htm

:-)

"Fabio Berutti" wrote in message
...
Other Rodents have already clarified that it is not advisable to do
Frankenstein-like surgery on a glorious Dyna. I'd just suggest to use all
Your amps together in bi/tri-amplification with bi/tri-wiring. I'm sure
You
can sort all Your stuff in order of available power to make it fit the
speakers needs in a reasonable way. Say, a SS for bass, the Dynas for
mid
and some other one (I'd suggest a SE if available) for highs. This will
provide about the power You're talking about.
As per the preamp/electronic crossover... well, a chance "to boldly go
where
no man has been before."

Ciao

Fabio

But Fabio,
I only have 1 input to the speakers. What you are espousing sounds ideal,
but how do I do it practically? Incidentally,
I have a daughter who graduated from West point with a degree in Chemistry &
minor in Nuclear chemistry. She was talking about after her military
obligations to maybe go to the University of Bologna to study medicine. You
went to Univ of Roma for Chemistry?
west


"west" ha scritto nel messaggio
news
Dear Rodents,
I have a few Dynacos in storage but need 100w/c. If I wanted to add
another pair of KT88s or 6550s (4 per mono side) to make a double P/P
Mark
III, (physical placement considerations not withstanding) what do I
need?
Do
I need to change the OPTs? How about the Power Xfrs? Will I need more
current capabilities? Maybe I'm just oversimplifying, hope not.
Your opinions will be most appreciated.
Cordially,
west