More Power for ZEN

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Hi you all!

I’ve recently finished my version of ZEN Revisited. It worked great first time started and I enjoy its sound almost every day. No hum. Very stable. Sounds good to! Thanks to Mr. Pass I’ve also got rid of that noisy bump in the speakers when powering on.
I‘ve placed the transistors on very large heat sinks, which are at the same time the sides of the Al box. Large enough to comfortably keep my hands on them.
Since there is some extra room for heating I was thinking about adding some power to the amp. Is this possible? And if it is, how can be done?

Regards
 
The one and only
Joined 2001
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The stock Zen amp runs the output transistors at
about 25 watts, which is a figure that I have found
over the years to be absolutely reliable. The
manufacturers of these devices tout figures up to 150
watts or so, which I find to result in very unreliable
operation. Somewhere in between is a region where you
might find acceptable reliability with only an occasional
failure.

Given good heat sinking, I think you could probably
take the devices up to 50 watts, resulting in 20
watts worth of output for the amp, without seriously
compromising reliability.

Alternatively, you can parallel (matched) devices and
take the power up arbitrarily, which will be the subject
of a future Zen project.

Also alternatively, you can use the Aleph current source
and double the efficiency of the circuit, which would
double the output with the same dissipation, and if you
also allowed for 50 watts per device, you could easily
get 40 watts. This project has already been done, and
is being prepared for publishing.

There are yet other ways to increase power, many of
which are on a schedule for projects, but we don't want
to overlook an easy and very good sounding one: Build
4 stock Zen channels, and run them as two set of parallel
bridged into the load. This has to be driven balanced,
but it gets you 40 watts and sounds just terrific.
 
Gema, my Zen Revisited does 50W/chan into 4ohm - parallel channels. Nelson (thanks due again) is taking this to the next level - fully balanced - nice :)

I established current and voltage swing requirements into my speakers (by listening to real music & scoping), turned out it needed 50V rail, 4A bias per stage. It'll be less into 8ohm. And (this is the fun bit!) BIG heatsinks. I'm using 250W Exicon MOSFETs from Profusion. These are twin chipped versions of their 125W devices and so far seem happy at 128W - heatsinking is everything with these desgins. The high bias also brings down distortion.

The result manages to both play loud and sound nice. Heating bill will be lower too this winter I'm sure!

Check my site for the rest of the story.

Cheers

Pete
 
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Joined 2000
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Yes, but if you look at what NP wrote:

but we don't want to overlook an easy and very good sounding one: Build 4 stock Zen channels, and run them as two set of parallel bridged into the load. This has to be driven balanced,

2 sets of parallel bridged...that sounds like 4 amps for one stereo channel. Parallel one stereo Zen, then bridge another set, right? Is that 8 channels for a stereo setup?

I don't know, someone learn me right here! ;)

Vince
 
Nelson Pass said:
<snip>but we don't want
to overlook an easy and very good sounding one: Build
4 stock Zen channels, and run them as two set of parallel
bridged into the load. This has to be driven balanced,
but it gets you 40 watts and sounds just terrific.

Vince, ref NP above: I think Nelson means 4 Zens per channel, i.e. bridged paralleled stages, for double the votlage swing but that means you also need double the current capability. A lot of hardware indeed! Guess it comes down to how easily you can create the heatsinks!

I went parallel (still unbalanced) only to drive a 4ohm load - built 4 of the critters - amazing how much quicker the last ones are to build over the first one!

Pete
 
Member
Joined 2000
Paid Member
Man. That's what I thought. How's the bridge/parallel sound over a single set? Probably a better lower freq.

You guys ever hear of Bob Lubwig? His main mastering room uses something simular, but his Cello amp's put out 1000w for the neg. side and 1000w for the pos. signal. All going to a set of very large EgglestonWorks monitors. They stand on a concrete slab that goes down to granite. A really sick room!

Some other guy heard about it too.
http://www.audioreview.com/reviews/Speaker/product_7220.shtml

Thanks for the info.

Vince
 
There's no reason you have to build 4 discrete Zens. Just parallel the circuit from the start; build all four into one chassis, with one power supply, etc. No sense in making a rat's nest of cabling if you don't need to, as the Zen should parallel very easily. If nothing else, you'd save money on the DC blocking caps, as you'd only need one set per bank.

Grey
 
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