joeBerlin
New Head-Fier
- Joined
- Jul 24, 2013
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Hi, I join this forum because plan to build a Kevin Gilmore's Blue Hawaii for myself. Starting out from
the original __ I have a few questions:
For replacing the 2SA1968-CCS I'm thinking about the following Possibilities (see schematic):
1a) Plain+simple: ANODE---R 10k---L (choke)---PLUS. Wehre L can be something between 0 (as prosponed in the original Document) and so that R*L goes << 20 Hz. Seriously: For me it's just simplicity at the right places which makes the difference from fancy to excellent. But: is that the right place?
1b) IXYS 10m90s (hard to get here in Germany, don't wanna wait at import customs, but maybe Mouser+Fedex have agreement so that it could work without waiting ... not sure...)
1c) Simulation AM1 or AM2 (just for orientation, T4 could be omitted) - can't find a 900V PNP (btw: 2SA1968 is documented as
NPN what does that mean?)
1d) AM4 Simulation: Gives promising result
1e) AM4 again, but take "mu follower Output" after the 1st MOSFET to decouple capacitive load from the tube - see http://www.pimmlabs.com/web/Active_loads_and_signal_current_control.html
1f) AM5 not realistic, I think
1g) AM6 promising result
Power Supply: Is it possible to simply omit the 2SA1968, i.e. Rectifier+---Some R 30Ohm--+--Some 100W MOSFET with Gate directly
connected to the Zehner Diodes--+--o
(+ goes to C's). I don't konw much about tubes - so:
2a) Is it REALLY somehow destructive for EL34's if anode voltage is there before they are heated up?
2b) Can one expect an audible advantage when using a 400-Volt Version of the much more advanced KGSS PS?
I mean 60 years ago they treated transistors like tubes, I don't wanna start to threat tubes like transistors now -
maybe voltage deviations are not important...
2c) did someone REALLY find an improvement when using DC filament heating?
3) The amp will stand 10 cm aside the source, so symmetrical connection is only an option, but not crucial.
So: Replace the 2SK389 with 2 * 2SK170? They are pretty cheap, so I could buy 10 or 20 and try to pair it
DIY - but is that possible without a 6.5 digit multimeter?
Btw: I have an understanding problem: Why is symmetry so important in this case? In a "normal" B-class
Amp where each side is responsible for a half-wave that's clear. But here, as I understand, it's different: A small
section of the diaphragm with the charge q which depends only(?) on the bias is moved by the force
F = q*E where E comes only form the voltage difference between the stators. So if the input of say 0V...500mV
ends up on both stators as 0V/0v...-100V/+100V or 0V/0V...-90V/+110V shoudn't affect the result!?
In both cases is E = 200V / distance_of_the_stators.
4) Are there newer Versions or bugfixes of the original version? What about the schematic in this thread?
the original __ I have a few questions:
For replacing the 2SA1968-CCS I'm thinking about the following Possibilities (see schematic):
1a) Plain+simple: ANODE---R 10k---L (choke)---PLUS. Wehre L can be something between 0 (as prosponed in the original Document) and so that R*L goes << 20 Hz. Seriously: For me it's just simplicity at the right places which makes the difference from fancy to excellent. But: is that the right place?
1b) IXYS 10m90s (hard to get here in Germany, don't wanna wait at import customs, but maybe Mouser+Fedex have agreement so that it could work without waiting ... not sure...)
1c) Simulation AM1 or AM2 (just for orientation, T4 could be omitted) - can't find a 900V PNP (btw: 2SA1968 is documented as
NPN what does that mean?)
1d) AM4 Simulation: Gives promising result
1e) AM4 again, but take "mu follower Output" after the 1st MOSFET to decouple capacitive load from the tube - see http://www.pimmlabs.com/web/Active_loads_and_signal_current_control.html
1f) AM5 not realistic, I think
1g) AM6 promising result
Power Supply: Is it possible to simply omit the 2SA1968, i.e. Rectifier+---Some R 30Ohm--+--Some 100W MOSFET with Gate directly
connected to the Zehner Diodes--+--o
(+ goes to C's). I don't konw much about tubes - so:
2a) Is it REALLY somehow destructive for EL34's if anode voltage is there before they are heated up?
2b) Can one expect an audible advantage when using a 400-Volt Version of the much more advanced KGSS PS?
I mean 60 years ago they treated transistors like tubes, I don't wanna start to threat tubes like transistors now -
maybe voltage deviations are not important...
2c) did someone REALLY find an improvement when using DC filament heating?
3) The amp will stand 10 cm aside the source, so symmetrical connection is only an option, but not crucial.
So: Replace the 2SK389 with 2 * 2SK170? They are pretty cheap, so I could buy 10 or 20 and try to pair it
DIY - but is that possible without a 6.5 digit multimeter?
Btw: I have an understanding problem: Why is symmetry so important in this case? In a "normal" B-class
Amp where each side is responsible for a half-wave that's clear. But here, as I understand, it's different: A small
section of the diaphragm with the charge q which depends only(?) on the bias is moved by the force
F = q*E where E comes only form the voltage difference between the stators. So if the input of say 0V...500mV
ends up on both stators as 0V/0v...-100V/+100V or 0V/0V...-90V/+110V shoudn't affect the result!?
In both cases is E = 200V / distance_of_the_stators.
4) Are there newer Versions or bugfixes of the original version? What about the schematic in this thread?