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Old 11th February 2013, 01:25 PM   #291
Zen Mod is offline Zen Mod  Serbia
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well - that's sometimes happening - ppl are either not seeing someone's question , or they just don't have enough time to invest , to reply properly

in this moment I don't have enough headtime - to find BA-1 sch , blast it on secondary display and read what you asked

maybe tomorrow , if nobody else jump in
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Old 11th February 2013, 03:57 PM   #292
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Hi Zen Mod

thanks I will for sure be checking the forum tomorrow....
To make your life easier here is the schematic.

BTW I only build the powerstage/bufferstage which I hooked up with the front end of an old Beard p100 tube amp
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File Type: jpg BA1%20OS%20sm.jpg (4.1 KB, 167 views)

Last edited by Alettagla; 11th February 2013 at 04:03 PM.
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Old 12th February 2013, 08:24 AM   #293
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Quote:
Originally Posted by Alettagla View Post
I tried to add an Aleph current source as it is implemented and explained in one of the ZEN papers.
(or at least what I understood from it)
That means from the output with a capacitor and resistor back to the base of the ztx450 biasing transistor. This resulted in a very unpleasant screaming occilation which, despite of several attemts I couldn´t stop.
Can you post a schematic of your modification and some photos of the boards.
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Old 12th February 2013, 08:59 AM   #294
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Here are the pics. Everything is functioning perfect. Apart from the fact that I need more efficiency out of it.
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File Type: jpg DSC_0238.jpg (764.6 KB, 121 views)
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Old 12th February 2013, 09:19 AM   #295
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Running the FE balanced and addint to output bias will give you more power. Increasing bias, improves linearity and gives more current for low ohm loads. In order to get more more power into higher ohmic load, you need to increase rail voltage or use balanced FE. This turns output stage into a bridged topology, effectively doubling the current into the double the load....assuming you have the current to support that load. In other words, an amp capable of 50W into 4 ohms will do 100W into 8 ohms, as balanced/bridged amp. BA3B FE has BIG potential.
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Old 12th February 2013, 10:26 AM   #296
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Hi Buzzforb,

Thanks for your help.
I know that increasing bias will give more power and this will indeed become a balanced version. I also think that together with BBA3 and doubbling the efficiency this this can become a monster amp.

But the first two actions do not improve efficiency.
Nelson hinted that he will double the efficiency in a later version. (withoud turning it into an aleph)

Since this is DIY and because I want to get better understanding of these circuits I also like to experiment and find out things for myself by trial and error .

So my ( for the experienced probably simpel) question of why my Aleph current source experiment didn´t work remains.
And heh wouldn´t it be nice If someone could come up wth a nice sollution to improve efficiency before Nelson does...

Alltough I would very much appreciate it if he jumped in

Last edited by Alettagla; 12th February 2013 at 10:28 AM.
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Old 12th February 2013, 12:07 PM   #297
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Generally single ended class A and efficiency do not go hand in hand.
An Aleph current source will increase efficiency, but if you want more - for an all N output you will need to change topology to a quasi push pull output, and the most efficient is to bias in class AB.
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Old 12th February 2013, 12:23 PM   #298
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Quote:
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Generally single ended class A and efficiency do not go hand in hand.
Generally ? You likely meant Totally !
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Old 12th February 2013, 12:58 PM   #299
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I tihnk the efficiency that Nelson was talking about, was just that. The PP stage of BA2.
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Old 12th February 2013, 01:46 PM   #300
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I know teh general inefficiency of single ended amps. But in balanced configuration and double the efficiency this will be a killer amp

But can anyone help me out on the original questions
=why adding an aleph current source to just the buffer stage doesn´t work and results in an occilation?
=Which other options there are for increasing efficiency?

If Nelson knows how to do it there surely must be a way to do it
By the way here the quote from Nelson.

Quote:
Originally Posted by Nelson Pass View Post
They are pure heat. This is a Burning Amp.

You will get a lot more efficiency out of BA#2, which is push-pull
instead of single-ended/constant current source.

If you want more efficiency out of the all-N channel output stages,
we will expect to be doubling the efficiency in a later version.

Later on Nelson said that turning it into an aleph would lack Novelty. ......

Last edited by Alettagla; 12th February 2013 at 02:02 PM.
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