[nikongod]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif Okay, sure the headphones might work at low-ish currents, however the currents in the amp itself are another story! This depends how far into class A you wanna go

so how much current are we talking here in the end? this is a KEY thing. putting a transformer that is speced for 400ma, 800v CT on an amp thats going to draw 75ma at max is somewhat poor practice.

i really think the specific amp should be looked at.

something like the blue hawai has a pretty strong draw at 100mA for the output tubes (combined)

the other tube based electrostatic amp designs i found on a quick glance make 25ma look like water from a fire-hose.
Quote:

Originally Posted by Budgie /img/forum/go_quote.gif Yes, you need fairly large inductors to get much advantage. Size of a power transformer.

you can very easily see an advantage even with a physically smaller inductor. perhaps not as big of an advantage compared to a physically larger one, but an advantage none the less. this is ESPECIALLY true on a preamp, where the total current is likely to be fairly low.

That being said, im not sure if you will find ANY that will fit in that case. If you can mount one to the top of the case, the options RAPIDLY unfold.

 

[Budgie]

The current draw in a class A amp is dependent on the power you want to deliver to the load.

Amplifier Efficiency

 

[luvdunhill]

Quote:

Originally Posted by nikongod /img/forum/go_quote.gif so how much current are we talking here in the end? this is a KEY thing. putting a transformer that is speced for 400ma, 800v CT on an amp thats going to draw 75ma at max is somewhat poor practice. i really think the specific amp should be looked at. something like the blue hawai has a pretty strong draw at 100mA for the output tubes (combined)

are you referring to the OP?

Don't forget in the case of the BH, the EL34 output tubes can be run twice as hard in the BH, nothing stopping you from doing that... If you ditch the EL34, then you can raise the current and rails even higher. Nothing preventing you from doing 400mA combined, if a few more details are taken care of.

I think oversizing a transformer isn't really a bad idea at all. Do you think that the Supra transformers used as an upgrade for the Singlepower MPX3 are poor practice? One advantage that comes to mind is better regulation.

 

[spritzer]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif are you referring to the OP? Don't forget in the case of the BH, the EL34 output tubes can be run twice as hard in the BH, nothing stopping you from doing that... If you ditch the EL34, then you can raise the current and rails even higher. Nothing preventing you from doing 400mA combined, if a few more details are taken care of. I think oversizing a transformer isn't really a bad idea at all. Do you think that the Supra transformers used as an upgrade for the Singlepower MPX3 are poor practice? One advantage that comes to mind is better regulation.

The use of a larger transformer on a prototype preamp once was the spark for PS Audio's work on power supplies (the story was in a recent HFN article) so it's a good idea to have them a bit too big even massively over sized.

 

[nikongod]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif are you referring to the OP?

to a point yes, to a point no.

you mentioned needing BIG caps for PSU's that need to supply hihg currents. it is seriously a waste of effort to design a PSU to supply 0.5A for an amp that will only use all that power in failure-mode.

i think that to really get a solid answer the OP should say what the amp is to be...

all we are really doing at the moment is arguing over the merits of different design ideals...

Quote:

Don't forget in the case of the BH, the EL34 output tubes can be run twice as hard in the BH, nothing stopping you from doing that... If you ditch the EL34, then you can raise the current and rails even higher. Nothing preventing you from doing 400mA combined, if a few more details are taken care of.

to be sure there are a few larger pentodes that are available. the kt88, kt90 and a few others come immediately to mind. you could even go all out and use a triode direct coupled to the stators for the output, the options REALLY unfold when you think of what 4 6238's can do....

a blue hawaii, STOCK can adequately (and then some) drive the capacitance of any 2 electrostatic headphones... why take the effort to make these larger tubes work when you have already exceeded the requirements by a fair margin?
Quote:

I think oversizing a transformer isn't really a bad idea at all. Do you think that the Supra transformers used as an upgrade for the Singlepower MPX3 are poor practice? One advantage that comes to mind is better regulation.

i agree with slightly to mildly oversizing, but i think that is a weak example.

the BIGGEST reason for the supra transformer on an mpx3 is that it can power the heaters on the 6bl7/6bx7 and a couple other tubes. The MPX3 transformer can EASILY handle the HV load with any of the commonly used tubes.

 

[spritzer]

Quote:

Originally Posted by nikongod /img/forum/go_quote.gif a blue hawaii, STOCK can adequately (and then some) drive the capacitance of any 2 electrostatic headphones... why take the effort to make these larger tubes work when you have already exceeded the requirements by a fair margin?

It's quite clear when you listen to the BH that it lacks power and could be much better. Why settle for merely ok when you can have the best?