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Best SE output transformer for 300B - shootout
Best SE output transformer for 300B - shootout
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Old 14th February 2018, 03:33 PM   #231
RajkoM is offline RajkoM  Bosnia and Herzegovina
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Quote:
Originally Posted by Perfectusaudio View Post
NP2.5SE8F60 T from NP Acoustics look good value for money but the current price list is way out of date.
Current price list is still active.
Maybee that model of OPT is out of production.
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Old 14th February 2018, 06:52 PM   #232
Perfectusaudio is offline Perfectusaudio  Australia
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Hi Hanze,
It is just another square black metal box, it may sound great but try and get it into the house and you other 1/2 says , just another ugly square metal black box.
Aesthetics do count , I have determined not to build big black metal boxes from the last 1/2 of the previous millennium
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Old 14th February 2018, 07:24 PM   #233
audiowize is offline audiowize  United States
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Quote:
Originally Posted by Hanze Khronye View Post
a) Would you consider a filament biased filamentary triode tube as fixed bias
Yes, provided we are talking about amps biased in A1.
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Originally Posted by Hanze Khronye View Post
b) Would you consider a resistively plate loaded triode with cathode bias resistor as fixed bias?.
No.
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Originally Posted by Hanze Khronye View Post
c) Would you consider a gyrator plate loaded triode with cathode bias resistor as fixed bias?.
No.
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Originally Posted by Hanze Khronye View Post
d) Would you consider a CCS loaded triode tube with cathode bias resistor as fixed bias?.
Yes, provided grid current doesn't enter the equation.
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Old 14th February 2018, 09:59 PM   #234
kaputt is offline kaputt  Germany
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Originally Posted by audiowize View Post
If you want to use filament bias, then you're stuck using something like the 4P1L.

Fixed bias and direct coupling don't go together.
In my power amp I use a LED biased input tube (voltage amplification stage) dc coupled to the driver tube. Cathode of the driver is connected to ground with a piece of wire. Stacked supplies make life really easy. At least sometimes.
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Old 14th February 2018, 10:13 PM   #235
audiowize is offline audiowize  United States
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Stacked supplies can put more caps in the signal path too!
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Old 15th February 2018, 10:18 AM   #236
andyjevans is offline andyjevans  United Kingdom
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Originally Posted by audiowize View Post
If you want to use filament bias, then you're stuck using something like the 4P1L.
I wouldn't call this "stuck" - it's a great tube, in fact ex German military design. But you also have 26, 01A, 2P29L, 10Y and a bunch of others. These are some of the best DHTs ever made.

In response to OPTs as "big black boxes" I frankly don't see the issue, and it's a stereotype to think that the "other half" dictates aesthetics. Mind, I have to say that my ex's definition of a good loudspeaker was one she could put a plant pot on.....
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Old 16th February 2018, 03:29 AM   #237
Hanze Khronye is offline Hanze Khronye  Australia
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Quote:
Originally Posted by Perfectusaudio View Post
Hi Hanze,
It is just another square black metal box, it may sound great but try and get it into the house and you other 1/2 says , just another ugly square metal black box.
Aesthetics do count , I have determined not to build big black metal boxes from the last 1/2 of the previous millennium

Hi Perfectusaudio,

Black boxes is all I have... I use constrained layers of ply and cork to mount stuff to and help dampen the enclosure, but at the end of the day its a black box.

Nothing wrong with LW, please excuse me for that.. I was out of line.

Cheers,
Hanze.
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Old 16th February 2018, 03:30 AM   #238
Hanze Khronye is offline Hanze Khronye  Australia
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Originally Posted by audiowize View Post
Stacked supplies can put more caps in the signal path too!
They can, but have you seen a stacked supply run from a single B supply?..

;-)

Hanze.
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Old 16th February 2018, 03:41 AM   #239
Hanze Khronye is offline Hanze Khronye  Australia
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Originally Posted by andyjevans View Post
I wouldn't call this "stuck" - it's a great tube, in fact ex German military design. But you also have 26, 01A, 2P29L, 10Y and a bunch of others. These are some of the best DHTs ever made.

In response to OPTs as "big black boxes" I frankly don't see the issue, and it's a stereotype to think that the "other half" dictates aesthetics. Mind, I have to say that my ex's definition of a good loudspeaker was one she could put a plant pot on.....
I wouldn't say 'stuck' at all. You can bias any filamentary triode tube you like with a low value filament bias resistor, you just might need that current source to be external from the filament circuit.

OPT big black boxes?.. I like ones with silver flecks into mattish sort of dark grey :-).. Not a fan on Lundahl OPT aesthetics, nor their covers. Hey, maybe they sound better if potted.. I dunno if thats possible, maybe potting them is the way to go !! There's a thought, wooden box and some beez wax.

Hanze.

Last edited by Hanze Khronye; 16th February 2018 at 04:11 AM.
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Old 16th February 2018, 03:50 AM   #240
Hanze Khronye is offline Hanze Khronye  Australia
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Originally Posted by audiowize View Post
Yes, provided we are talking about amps biased in A1.
Hi Audiowize, excuse if you will my lack of formatting skills.. but I would like to ask if you would now consider any plate loaded triode, loaded with any type of load, but not CCS loaded, and biased with a cathode resistor, as fixed bias, if the B supply was series CCS filter fed and decoupled by a suitable shunt capacitor in the plate circuit?.

Can your picture it, and if so - what are your thoughts with regard to AC current loop and stability of the circuit wrt to potentially direct coupling?.


Hanze.

Last edited by Hanze Khronye; 16th February 2018 at 04:13 AM.
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