Nope... Not College Basketball.... This is Head-Fi

Up until now every single OTL Tube headphone amp made by
anyone (commercially at least) had one thing in common. A
nasty electrolytic output cap. Everyone by now should know
my opinion on such devices.

The holy grail of course is a fully direct coupled all Tube OTL
amplifier. Not so easy. Requires trickery, many different power
supply voltages, and practices that some may consider unacceptable.
(like lifting ground 150 volts high)

So I've been working on this holy grail for some time. And i have
something that works, but it is brutally complicated. About 2 weeks
ago i came up with something a whole bunch simpler. It is DC coupled
input. It is DC coupled output too. Yes it does have one cap
but it is in a place where the impedances are high and thus you
can use one of the silver foil/teflon ones...

Obligatory Warning:
Uses high voltages and high currents. As simple as this might look
this is not a beginners project.

http://gilmore.chem.northwestern.edu/dynatoob.gif (1 megabyte)

Yes there are 5 power supplies.
All of which need to be well regulated. I'm still running this thing
on bench supplies and it tests very well.
At 2 volts RMS into 32 ohm load, Thd is .03%

The power supplies will be based on the blue hawaii supply scaled
down for voltage and up for current.

Power supply voltages are
+250 volts at 25 milliamps
+150 volts at 300 milliamps
-150 volts at 300 milliamps
+ and - 15 volts at 50 milliamps REFERENCED TO -150 VOLTS!

Each output tube dissipates 25 watts.
Each cathode resistor actually dissipates about 5 watts.
Make sure you build these up with many high quality resistors in parallel.
Overall the power supply is going to put out about 100 watts including
fillament power.

This is NOT a WCF. The top tube is a low impedance constant current
source. Think of it as an upside down woo audio.
ON STEROIDS... Lots of STEROIDS...

I'm planning on board layouts in the near future.

For those of you not on a network connection...

LOL. Wow.


OK, raise your hand if you still haven't finished making a Dynahi yet.

[size=xx-small]*Sheepishly raises hand*[/size]

-Ed

There's a Dynahi? I just finished a Dynalo

This looks great however as much as I want to get into tubes I don't like the idea. Thoes voltages scare me despite how careful I am.

Quote:




HA HA HA!!!

Quote:






Sweet!

So what's the ETA on boards?




Just kidding

Compared to your other amps how does this stack up in terms of power? Any particular headphones that this amp will be ideal for? How much will it cost to make approximately?

Ok, thats enough questions for now.

5 power supplies...

Cool...

$2000.00 in parts mebbe

A few dozen heatsink bits

Fun crap

PSU floated at 150? Hell, thats nothing, my preamp has a 555 timer circuit floating at 275 or so

Looks cool! Now for that Dynahi...

BTW, what are you gonna call this one... DynaValve?

I haven't started my Dynahi yet either. I will be starting a Dynalo soon. I am very interested in this tube amp. Especially if there are boards for it.

Is this another amp that will be able to drive speakers? Just curious. Those high voltages and currents truly don't look like anything for beginners, so I won't be attempting this. All my DIY equipment is in storage in the US right now anyway (together with my Dynahi )

Looks fun.

100W consumption ? Nice, let's go overkill for headphones, my rkv only eats 45W.

Something in me tells me this one requires an output protection system.

LOL.

C'mon people.

Dr. Gilmore = Overkill.

Are we forgetting about the solid gold volume knob?

Will be interesting to see what crazy setup the first prototype DynaToob will be.

Hey, Kevin, was this schematic at all liquid inspired like the Blue Hawaii?

-Ed

I suppose the regulation of the second stage has to be solid state to avoid it to vary too much. Something like a bipolar, a mosfet and a few zener ? First stage could use tube regulation and a choke... hum... yummy.

ETA on the boards. First i have to lay them out. Then the
rest is easy. I'll be finished with the massive crunch that has
been eating up much of my free time no later than 3/21
after which time i will get to work on this at a reasonable rate.

I don't have any idea how much this will cost, the most
expensive item will be the multi tap power transformer which
i figure at about $120 or so. Will have victoriamagnetics quote
me one once i figure it out. Definitely no more than 1000 in
parts, probably a lot lower unless you stuff the power supply
with black gates.

This amp has a sweetness and powerful presentation that no
other tube amp i have listened to can match.

No it will not drive speakers. But if you put say 8 output tubes
in parallel, and beef up the power supply it will. And then
it looks like an unbalanced version of an atmasphere.

100 watts consumption is really not out of line for an item like this.
Tubes are generally high voltage low current devices. To make
them work the other way requires special tubes and stacks of
power supplies.

Output protection system is a good idea. However since each
tube is both the high and low driver for a specific channel, It warms
up equally and i have not seen the output voltage stray more than
a volt or two on power up from dead cold.

No liquids involved in the design of this. Well maybe...
I gave Tyson a list of the various scotch's in my special cabinet
and he insists that once they have been opened that they start
to degrade, and i should be drinking the expensive ones first, and
soon. Who am i to argue. Claret finish 50 year old glenmorangie YUM.

Power supplies. + and -150 will definitely be current source driven
zeners with a big mosfet pass transistor. In addition i may also make
it dual tracking. The +250 can be built the normal way (even tubes)
The +/-15 is trivial.