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|14th February 2012, 10:28 PM||#121|
Join Date: Jul 2007
Bentoronto's comments are well received here. I, too long to build a direct drive amp, and am not at all put off by the high voltages. I worked in a neon shop where 2 KV to 15 KV were the norm. Unfortunately, the cost of the components is prohibitive for most of us. As well, the availability of high voltage components is getting to be a real challenge in this low voltage digital age.
Some years back, I visited a large electronics surplus outlet in Dayton, OH looking for oil HV caps and HV trafos for such a project. I was dismayed to find they were scrapping the trafos for copper, and recycling the caps. They were scooping the parts up with a front loader and dumping them in huge bins. Alas.
|15th February 2012, 12:10 AM||#122|
Join Date: Feb 2008
Thank You, Ben!
I have giving very much thought about Direct drive amps through the years.
I personaly know the rules of H.V. and don't have any issues with them.
I have some idea's for a direct drive bass amp system and I think that this might be the key to good performance of such a system.
Since building my variable H.V bias supply I have found that I can have full DC control over the movement of the diagphram.
Yes it does output a full 13.8kv and it is very hard to contain at times.
And to get nailed by it is no joke.
The other day I got nailed by 10Kv across the palm when I got to close to leads while I was confirming a measurement distance of 1 meter to the microphone.
But a bass system will not require anywhere's near the amount of current that the high frequency's do.
Possibly giving the idea of a direct drive amplifier for bass only application very feasible and safely possible within the limits of the current ESL technology.
Let us say you had a very large panel and it had a capacitance of 1000pf (.001uf) and to fully drive this panel at 20khz would take over 3125 watts peak (1562 watts rms) at 5kv peak.
Well we all know that a panel this size has its issues and is not suitable for high frequency's.
But a panel this same size would only require 78.5 watts peak at 39.25 watts rms to drive at it at a full 5kv peak (10kv p-p) level.
This is a very great reduction in the current driving requirements and to a safer level of only 16 ma. as well as half of that at 250hz.
This is more around near the typical output of a non limited bias supply.
Mine certainly outputs some where around half of this I have only measured the input current at around 4 amps peak at 18V when pulling arcs at 13.8Kv.
That it is not a very accurate example and a bit of an exaggeration but it least it might give you an idea.
By my calculations it takes about 1kw to fully drive a 1' X 4' panel to its limitations at 20khz.
Even my little 3.25" X 9.75" panels when driven to the level of 5Kv peak is more than enough for comfortable listening and you (I) could only imagine what a large panel would sound like.
glorocks, I can certainly feel your dismay.
I have been found of H.V. since I was old enough to hold a soldering iron back when tubes were still prevailent in the early 70's.
I have lost through the years some very fine ole' H.V. stuff (mainly because moms thought it was a bunch of junk)tubes,Transformers and chassis.
it was alot of stuff to keep hualing around and store as well.
But I did manage to save my 2.5Kv 10mfd oil filled capacitor.
I had a few others but I don't know if I still have them or not.
If I still had all of it, I certainly would have been rich by the replacement value at today's prices,So I guess that means that I am in the hole big time! He,he,he
I am always looking for MOT's and I had a few of them but strangely enough I now can only find one of them right now,But I do have 3 or 4 neon transformers though.
|15th February 2012, 10:18 PM||#123|
Join Date: Jun 2005
Location: Fort Worth, Texas
Segmented Wire Stator ESL simulator (esl_seg_ui)
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