Effects of larger plate chokes?

[Jim R.]

I'm trying to decide on how to best pair the various OPTs and plate chokes I have for a couple of different amps and in general, while I know there are other factors involved, what is the general effects of larger plate chokes, and how much difference  would say, a doubling of the inductance have?  My guess is that dynamics and bottom end performance would be better with more stored energy to tap, but it's just a guess as I've never really done any experiments to confirm this.

Thanks,

Jim

[caffeinator]

Your question reminded me of a thread over on the Magnequest forum a while back...check up and down this thread, there is some commentary pretty relevant to your question.

http://db.audioasylum.com/mhtml/m.html?forum=magnequest&n=8632&highlight=fs-100+plate+choke&search_url=%2Fcgi%2Fsearch.mpl%3Fsearchtext%3Dfs-100%2Bplate%2Bchoke%26b%3DAND%26topic%3D%26topics_only%3DN%26author%3D%26date1%3D%26date2%3D%26slowmessage%3D%26sort%3Dscore%26sortOrder%3DDESC%26forum%3Dmagnequest

[Jim R.]

Thanks for the pointer -- what I saw was basiccally "more is better" and confirmation that bass will be better, and it's perhaps wise to consider a lower than normal pf cap size.  Guess that's enough to go on.

Thanks,

Jim

[galyons]

I wonder at what inductance does one venture into the point of diminishing returns?  I can joyfully testify to the benefit of increased inductance on my Paramour 45's going from the 10H C7X to the MQ 50H BCP15.  But where does it stop?  Just wondering!

Cheers,
Geary

[Paul Joppa]

More is better, and you do get diminishing returns. At some point, a current source is a better solution - it has higher impedance than any choke, and does so at all audio frequencies.

A current source means a 50% to 100% higher power supply voltage at the same current, which of course is larger, more complex, dissipates more heat, and is more costly. So when the cost, difficulty, and size of a larger choke exceeds that of the larger power supply and current source, it becomes pointless (in an engineering-economics sense).

[xcortes]

What would be better, shunt regulated ps and a big choke of a c4s?

[Paul Joppa]

Good question. Maybe I'll have an answer some day. Don't forget direct coupling (which oneeds more voltage...)

[Jim R.]

On a somewhat related note to the original question -- what is the thinking behind the stacked opt/choke in the s.e.x. and stereomour?  I understand that in both of those amps, the pc and opt are oriented to be centered on the side of the power transformer and also such that the windings are perpendicular to those of the PT, but if there were no power transformer in the equation (or it was a sufficient distance away), what is the effect of the pc and opt windings being parallel and why does it apparently not matter in this situation?  Is it that the pc is dc and/or is it that the opt is a small signal AC signal only (following the pf cap)?  If the power transformer was not an issue, would there be any benefit to arranging the pc and opt another way?  Also, does any sort of dot configuration between the two have to be considered for best performance/less magnetic "crosstalk"?

I'm in the process of laying out my two new amps and I can build in as much room and suitable dimensions to support just about any configuration of iron and I'm looking for the optimum, quietest configuration possible (within reason).
Thanks,

Jim

[Doc B.]

It's kinda because the screw holes line up and we save 4 screws that way. Basically you have to work this stuff out empirically by moving the iron around and measuring hum.  Within the constraints of the chassis layout that orientation is a good compromise. If you have acres of room, perpendicular core axes and distance are always a good thing.

[johnsonad]

Jim, in my SEX I have four (count them, four) sets of transformers stacked on one another with nearly inaudible  hum pickup though my speakers with my ear next to the driver (and I'm pretty sure the hum is from the BeePre).  From top to bottom they are 1) Sowther IT, SEX chokes (first set under the chassis), Magnequest grid chokes, SEX OPT. This is of course less than ideal but stacking them seems to work! 

[Jim R.]

Thanks Dan and Aaron. I'm pretty sure my layout will be fine -- the paramounts will be similar to the originals but a bit larger, and the sr-45s are looking like they'll be narrow and deep.  I'm also going to keep the same "landscape" orientation of the paramounts but mirror images of each other and with the opts on top and on the power tube side of the plate.

Aaron, that's crazy stuffing that much iron in the s.e.x. -- I like it :-)

-- Jim

[Paul Joppa]

... and why does it apparently not matter in this situation? ...

Because we tried it and - apparently - it didn't matter?!

Sorry, couldn't pass up the thought. :^)

I did measure the interaction between iron in those locations, long ago when Paramount was being developed, and for similar signal levels it is quite small. That plus the fact that both are handling the same signal voltage suggested it was probably OK. There are, after all, not a lot of other locations which reject the power transformer hum without going to larger and costlier chassis plates - and SEX and Stereomour are our "low-priced spread"!.

I would not do this with a power supply choke and audio choke or transformer, due to the different signals and consequent possible hum pickup - at least, not without some careful experimentation and critical listening. Probably not even then, it's just inelegant. I do have my pride!

[Jim R.]

Oh, don't worry, I'm only talking plate choke and opt here, not ps choke or pt.  In the planned sr-45 rebuild the ps choke and pt will be a significantly greater distance from the opt and plate choke, and the grid choke even further than that. I have my pride too ;-).

[tsingle999]

Aaron what is the sowter it used for? I am going to try to stack a triad c7x on a grid choke.

[johnsonad]

Taran they are for the Stax headphones.