and if you have fixed bias ... no cathode bypass cap.
and if you have psu with tube regulator instead of last capacitors .... no caps
come on guys .... we'll go to sky 😉
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.
Fixed bias and direct coupling don't go together.
for the price they are very very good ! my personnal favorite is Hashimoto and Monolith magnetics because i love their sound but they are expensive.
at the middle i will vote for lundahl if you can put them inside the chassis ( don't like their boxes)
NP Acoustics Amorphous Transformers
NP2.5SE8F60 T from NP Acoustics look good value for money but the current price list is way out of date.
NP2.5SE8F60 T from NP Acoustics look good value for money but the current price list is way out of date.
Thanks very much for all that great info in this thread, ah output transformers possibly the sexiest part for the DIY amplifier builder 😀
I've heard the FirstWatt SIT-1 amp it still has me shaking my head how good it was and I've strongly considered one for my constant directivity midrange/treble K-402 horn, but then there is nothing that beats DIY and being able to tinker with things like OPTs.
I've heard the FirstWatt SIT-1 amp it still has me shaking my head how good it was and I've strongly considered one for my constant directivity midrange/treble K-402 horn, but then there is nothing that beats DIY and being able to tinker with things like OPTs.
Trivial Questionnaire;
a) Would you consider a filament biased filamentary triode tube as fixed bias, if CCS loaded and then at what percentage of Ip to If, and again if inductively or resistor loaded?
b) Would you consider a resistively plate loaded triode with cathode bias resistor as fixed bias?.
c) Would you consider a gyrator plate loaded triode with cathode bias resistor as fixed bias?.
d) Would you consider a CCS loaded triode tube with cathode bias resistor as fixed bias?.
Notably absent is any reference to stage which operates with a separate (actively powered) grid bias supply.
I can think of a three stage DC coupled amplifier which runs all three stages with fixed bias.
And if the goal of filament bias is to simply lower the impedance of the 'cathode' or filament return wrt signal common, so that a bypass capacitor is not required - you are not limited to using the tubes filament current to reducing the bias resistor value.
All of these seemingly definite comments provided by the quoted poster, define just one thing, and that has nothing to do with tube circuit design, application or function.
Hanze.
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🙂Hi Hanze,
Thanks for the response
For all the DIY's it important they discover all the requirements for balancing a DC coupled Single Ended amplifier for themselves
Isamu Asano (1914-1981) the modern father of the rebirth of Single Ended Triode Amplifiers based this design enclosed on the old Loftin-White circuits of old, a good place to start
Thanks for the response
For all the DIY's it important they discover all the requirements for balancing a DC coupled Single Ended amplifier for themselves
Isamu Asano (1914-1981) the modern father of the rebirth of Single Ended Triode Amplifiers based this design enclosed on the old Loftin-White circuits of old, a good place to start
Attachments
?. My response was to 'audiowize'.
Care to comment on post #228?, or more interested in a re-hash of a 100 year old LW schematic??
Care to comment on post #228?, or more interested in a re-hash of a 100 year old LW schematic??
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Current price list is still active.
Maybee that model of OPT is out of production.
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
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
Yes, provided we are talking about amps biased in A1.
No.
No.
Yes, provided grid current doesn't enter the equation.
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.
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.....
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.
They can, but have you seen a stacked supply run from a single B supply?..
;-)
Hanze.
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.
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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.
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