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Old 1st February 2001, 03:55 PM   #1
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Location: Austin, Texas, USA
I just did some measurements of my Zen connected to my pre-amp.

The pre-amp could only deliver 2.0V p-p before clipping itself. Which was not enough to drive the Zen to clipping.

The calculation for wattage I have is:

W = V^2 / sqrt(2) * ohms

At 2 volts in I only got 6 volts out into 8 ohms. That's 3.18 Watts.
I plotted the output for 1V, 1.25V, etc... and the output was linear. So, assuming this thing peaks at 10 Watts, I will need 3.54V at the input. Mr. Pass says it should only be 2.5V. So, my Zen is slightly under powered. It's only about 5 Watts if 2.5V is all it will handle before clipping.
I still need to figure out some way to drive it to clipping to get a real number.

Still, connecting this thing to my Klipsch Forte II's puts out some serious volume! The only problem is the tweeter must need more power because it didn't give quite the solid highs my McIntosh gives.

Someone, please respond and tell me my calculations are wrong, and read "Zen Enlightenment Attained" and give some ideas and answers to what I said in there.

Thanks guys,
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Old 1st February 2001, 07:09 PM   #2
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Lightbulb Zen input to output

What's up Pixie,

In the original article, the "operation" section states you can increase or decrease R5 to suite your input needs. Your preamp may not provide enough voltage or it may not provide enough current. Which ever it is, you may be able to get a better balance by adjusting accordingly.

Also, read about the BOZ preamp project on Pass Labs. It might give better insight on exactly what you need.

I have a question that has nothing to do w/ your question. Are you using just one channel? Just curious.

Good Luck.

p.s. ...god forbid, maybe your Mac is a bit ruff on the highs and the Zen is a bit soft?? Just a thought.

[Edited by vdi_nenna on 02-01-2001 at 02:12 PM]
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Old 1st February 2001, 09:03 PM   #3
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Having fun Vince

I only have one channel.

There is no R5 in the revisited design. R10 and R11 control the gain. I just re-read both articles. So, I'll mess with those two. Increasing the gain will increase the distortion. So, I think I will go to the .22ohm R1 to reduce the distortion a little.

Remember from our old conversation: the Zen only goes up to 15,000 Hz. I just re-remembered that. So, that's what I'm hearing. I was listening to Star Trek music which is basically sensational orchestral music. So, the highs of the trumpets, flutes, and violins were missing.

I once heard that most adults can't hear above 15kHz. I tested this between my wife and I. I can hear clearly up to 20kHz, she does indeed drop off at about 16kHz. It didn't matter how loudly I played the 16kHz tone, she couldn't hear it. I had it up to 80dB before I had to stop my own pain. My amp/CD/speakers don't go higher than 20kHz. I wonder how high I can hear?

OK, enough of that. I just got a response from Wayne Colburn at Pass Labs. He said they had 4 Zens bridged together and they sounded great! So, I'm asking for the details of the connections so I don't fry my $300+ investment when I'm done. I'm assuming they bridged two sets of two Zens in parallel. But, I wasn't sure if because the Zen is inverting, do I need to invert the way I bridge them? All he said they paralleled them and then bridged them. So, I need some details before I try it. I also asked him if I need more than 5amps out of each power supply to drive a 4 ohm load with that configuration.

I'll let you know what he says. He's responded to me twice. So, he's a nice guy and I expect an answer.

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Old 2nd February 2001, 04:39 PM   #4
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OK. I got a response from Wayne. He told me I was right about the connections. But, he told me I need a balanced source to drive it. Is the BOZ a balanced source?

This is the connection scheme I came up with:

+===+===+speaker (These three +'s connected together)
Z1 Z2 (Zen one and two)
-===- (All -'s connected together.)
Z3 Z4
+===+ -speaker (These two +'s connected to the - speaker connection)

The inputs are connected the same way.
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Old 5th February 2001, 09:14 PM   #5
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I have finally figured this thing out. I have the feedback resistor set so I have enough gain, but it doesn't pop my speakers!

At ~90dB, which is about as loud as I ever listen to my stereo, my center channel is about .5 - 1dB lower than my mains. I happy for now with that.

I've ordered the parts for a Bride of Zen. I'm going to put it in the same box. Then I'm done.

Then I'm on to my next project. Three more amps for a stereo system with a sub. Any suggestions on a good DIY amp for a sub? I'm guessing the Zen wouldn't do very well. I'm thinking about 200W.

Thanks again for all you guys' help. This has been fun!
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Old 6th February 2001, 03:32 PM   #6
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Location: Austin, Texas, USA
Well, maybe not...

At 20W or so it only lasted a few days. Now it's putting static out to my speaker. Something is a little fried.

I guess I will build at least one more Zen on top of the Bride.

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