High Voltage SE amp

[JC951t]

Hello everyone,
This is my first post over here.
Am wondering if anyone has build
any of Mr. Pass circuit running at higher
dc voltage like 50-60 vdc or more.
I understand that you can run lower
voltage with lots of parallel output
devices to get more power but ???

Thanks in advance

[GRollins]

Sounds like you need an Aleph 1.2

Grey

[Nelson Pass]

Are you looking for just high voltage, or high voltage
with high power?

Just High voltage is easy enough.

[flg]

Put even another way are you interested in 200 Watts into 8 ohms? Or possibly driving 16 or more ohms?

[JC951t]

Hi,
Thanks for the reply.
I'm actually looking at 50 watts.
I have build a few variations of
the zen pre-amp just for experiment.
The last one I tried was with a pair
of 6X4 rectifying tube for DC supply.
As Mr. Pass mentioned that higher
voltage will make the circuit more linear,
I was wondering why this principal is not
applied on the amplifiers as well.
I am no designer but rather a compulsive
tweeker & experimenter & am always
trying to learn more about audio electronics.

Mr. Pass, thanks for the wonderful articles that
you've provided for us the diy community

Many thanks again Gentleman for the reply

[ed2005]

Hello:

I am running Zen Lite at 100 VDC with one 300 Watts lamps per channel. I installed the lamps away from the amplifier, in normal living room lamps, so I use the lamps for normal illumination when I am listen music. The system works fine, you must be careful with these voltage level though. If you have specific question about my system, don´t hesitate to ask.

[GRollins]

50W on 50-60V rails?
Hmmm...that's an unusual combination.
You didn't answer as to what load, so for the time being, I'll assume 8 Ohms.
First off, you need to realize that there's a natural ratio between output wattage and rail voltage. A "normal" 50W amp might have something along the lines of, say, 28-30V rails. 50-60V rails will generally put you in the range of 200-250W.
The rail voltage sets the wattage; the bias current tells you how low an impedance you can drive.
Hand in hand with this is the choice of operating class. Do you want class A, class AB, or class B?
But you want 50W...
Well, okay, you can swing the full 50V rails, but to make it a 50W amp you'll have to starve the bias such that the poor thing current limits before it reaches the rails. This is not a good design choice, for any number of reasons.
So you need to burn some volts, but do so in a way that makes sense. Using a cascoded output stage is a good way to use up volts. Look at the last couple of Zen projects for examples. Another possibility is to use a current source to bias a differential.
Things get more complicated if you're looking at +-50V rails rather than a single rail. I've got some things I've done here that set differentials against one another, but they're transconductance amps--not part of the normal stream of things. I've also got cascode output amps using Lovoltech JFETs (a new one almost ready for prime time), but that may or may not be to your liking.
Yes, voltage increases linearity, but it has to be viewed in context. You can't just toss voltage at a circuit without looking at the larger picture. Sit down, think about exactly what you're trying to accomplish, and try to come up with an overall strategy for using that voltage to good effect. Start with your speakers. What impedance are they? Then work backwards from there. Amps are designed from the output first, then the front end. One you've got an output stage that will deliver your target wattage, then you can look at the front end.
At all times, keep a calculator handy. Stop and punch in some numbers. Ohm's Law is a good starting point (IR=E). Look at the consequences of 50-60V rails vs. something more like 30V rails. If you want to stick with your 50W output target, you're going to need a plan for burning the extra volts. You'll either end up with an amp more along the lines of 200W or you'll need to use up rail voltage. It's just one of those inescapable math things.

Grey

[JC951t]

Hi Guys,
Thanks for the reply. Actually I'm not sure
what voltage is appropriate for the ZEN amps.
The reason that I'm asking this question is that
it does not sound logical. Why parallel so many output devices to get to the output that one ones.
Why not use less output devices & increase the
voltage to get to the target power output ?
To me it looks like low voltage with lots of output
devices = Truck Engine. Lots of torque but at low rpm
range. Why not build it where it looks like a Chevy
V8 with lots of torque & able to rev as well.
With lots of output devices, it would call for lots's of capacitance.
From personal experience, it kill's the pace of the amp.

[Zen Mod]

Originally posted by JC951t
Hi Guys,
Thanks for the reply. Actually I'm not sure
what voltage is appropriate for the ZEN amps.
The reason that I'm asking this question is that
it does not sound logical. Why parallel so many output devices to get to the output that one ones.
Why not use less output devices & increase the
voltage to get to the target power output ?
To me it looks like low voltage with lots of output
devices = Truck Engine. Lots of torque but at low rpm
range. Why not build it where it looks like a Chevy
V8 with lots of torque & able to rev as well.
With lots of output devices, it would call for lots's of capacitance.
From personal experience, it kill's the pace of the amp.

P=UI
I=U/R............

if you have 800 Ohms speakers,than your thinking is OK;
if you dont,with high voltage/low amperage amp you must use output xformer

so-what you really need is-tube amp

[Nelson Pass]

There's nothing intrinisically wrong with using higher voltage,
it's just that your dissipation goes up proportionately. The
distortion and bandwidth characteristics are better with higher
voltages, but there is a matter of diminishing returns.