kevin gilmore
Señor Stax. Señor MAXX.
Can Jam '10 Organizer
- Joined
- Jun 21, 2001
- Posts
- 3,019
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- 996
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.
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.