Rod Elliott Project 36 Death of Zen (DoZ) build

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arkay

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Joined 2001
#1
I am getting back into amplifier diy after a very long time. I am beginning construction of Rod Elliott's project 36 Death Of Zen amplifier.
Death of Zen - A new Class-A power amp
I'll use this thread to track the progress of the build and to get answers to my doubts and questions regarding this build. Need all of your help in this.

I will be using the Dual Capacitance Multiplier For DoZ Amp
Capacitance Multiplier Power Supply Filter with a transformer 2 x 25V, 300VA secondary.

Will any of these heatsinks be suitable for each channel of this amp?

1. Specifications :
Rth 1 K/W
External Height - Metric: 33mm
External Width - Metric: 196mm
External Length - Metric: 100mm
Heat Sink Material: Aluminum
SVHC: No SVHC
Mounting Type: Adhesive
Surface Finish: Black Anodized

2. Technical Specifications:
Material: Aluminium
Height: 80mm
Width: 53mm
Length: 200mm (+/- 9mm)
Weight: 4.5Kg/M
External Perimeter: 1020mm
Area: 1667.96mm2
Corner Radius: 0.30mm

Thanks,
rk
 
#3
Each DoZ amplifier is rated for 1.7A idling current @ 40V, for 15W max. output to an 8 ohm speaker. If you calculate the idling power consumption, that is 68W dissipation each channel - a lot of heat.

To keep the heatsink at a safe temperature, it would need to be maintained below 55C. That means at say, 25C ambient, the differential is 30C so each heatsink has to be rated at about 0.4C/W or lower. That's a heavy heatsink, a little larger than your second option though I don't know what you mean by "external perimeter" of 1020mm.

I assume that heatsink is much like a conventional rectangular type of 200 x 80 x 53mm overall. If that is so and the thickness of the backplate and fins is say, 7mm or more, 2 of these should be OK for stereo in cool weather. At 40C in summer, all bets are definitely off :hot: Then it's time to add noisy fans.
 
#4
Ian Finch said:
Each DoZ amplifier is rated for 1.7A idling current @ 40V, for 15W max. output to an 8 ohm speaker. If you calculate the idling power consumption, that is 68W dissipation each channel - a lot of heat.
Click to expand...

@Ian Finch, I am planning to use the schematic version with Iq Stabilisation using 2 x 12V zeners. So I presume the idle power consumption to be slightly lower (41W ?). In this scenario would a 1 K/W heatsink suffice per channel?
 
#5
Arkay,

If you truly have lower current of 1A bias, I would not go above 0.6-0.7 deg C/watt if your rail voltage is 40V. That would be just under a max of 30 degC increase over 25 deg C ambient =~ 55 deg C.

Better yet, a 3U/300 from the diyaudio store at 0.5 degC/watt (or equivalent) would keep the amp nice and cool which you really want in Secunderabad 😉

At the lower bias it most definitely will be less than 15 watts, more like 10-12 watts.

Best,
Anand.
 
#9
with all due respect to Rod (a great contributor to diy audio): it should have been called LessonofZen rather than DeathofZen. By the time he was done I think Rod got a taste of how much knowledge it took to play in Papa's sandbox with a seemingly trivial circuit.

He missed a point though of designing for a distortion pattern which sounds good when playing music rather than designing for the measurements of signal generator outputs which mean little for psycho acoustic outcomes.

And I love the "HiFi" misnomer aimed at a truthful reproduction of what?: an engineered file with mixed individually recorded instruments captured by a non-standard microphone arrangement listened to on some tbd headphones or monitor speakers and equalized to someone's personal taste. And that on a different set of speakers and in a different room is supposed to sound good how? So everything else is allowed to introduce distortion but the amp is to cancel any harmonics?

When Linkwitz started dispersing the sound in a pattern never experienced at the mixing table and in the perception department it beat the hell out of anything else, he proved the same point which Papa has been advocating in amp design that: "all means to a good subjective perception are allowed". Moreover if you read the latest standards dealing with the sound tonality (for regulating the tonal noise of industry products) by introducing prominence ratio etc. one can see that designing for one-freq-at-a-time does not cut it for the human brain.

btw ACA is a good recommendation if the speaker application is matching.
 
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#10
Koja,

I think that the Zen variations, ACA, and DOZ all seem like fun and worthwhile projects.

koja said:
1)I think Rod got a taste of how much knowledge it took to play in Papa's sandbox with a seemingly trivial circuit.
Click to expand...
It is an art for sure. I know I struggle with this myself.
koja said:
2)He missed a point though of designing for a distortion pattern which sounds good when playing music rather than designing for the measurements of signal generator outputs which mean little for psycho acoustic outcomes.
Click to expand...
That all depends on what goal is in mind. Some people would rather hear the audio/distortion as it was recorded, without changing the sound. Or perhaps use a pre-amp to "color" the music. This is the method I prefer myself, but whatever provides the best listening experience to the end user is the most important goal IMHO.
koja said:
3)So everything else is allowed to introduce distortion but the amp is to cancel any harmonics?
Click to expand...
As stated above, in my opinion, if an amplifiers(instrument amplifiers excluded, I love my JCM 900 🙂 ) job is to amplify the signal, then yes. I would like it to recreate the original recording as close to original as possible.

You can always use a preamp, or some type of equalization circuit to fine tune/adjust to taste. This also has the added benefit of changing the sound signature for different recordings.

Just my 2 cents! 🙂

Cheers,
Tim
 
#12
I've found a heatsink which is available locally with the following specifications:
Rth 0.65 K/W
External Height - Metric: 33.0mm
External Width - Metric: 196.0mm
External Length - Metric: 150mm
Heat Sink Material: Aluminum



I hope one of these for each channel would suffice.
Comments and suggestions please..
 

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#14
helitim said:
Apologies arkay. Looking forward to seeing your completed project!
Click to expand...
No need to apologise sir...I appreciate your response, but want to keep this thread on subject.
I'm sure you can help me a lot with your knowledge and experience in getting this project completed.

This is just the beginning, I've to select components, design and fabricate the pcb, the layout both electrical and mechanical, putting it all together...would really appreciate your help.
Thanks.
 
#15
arkay said:
....I am planning to use the schematic version with Iq Stabilisation using 2 x 12V zeners. So I presume the idle power consumption to be slightly lower (41W ?). In this scenario would a 1 K/W heatsink suffice per channel?
Click to expand...
Think about it; 0.4K/W is barely adequate for 68W dissipation. For the same temperature rise, 41W dissipation is going to require 68/41 multiplied by the the existing heatsink rating of 0.4K/W - meaning the heatsink rating should not exceed 0.66K/W.

I would adopt more conservative ratings if you want the amplifier to run safely in all conditions, as nycavsr2000 suggests. Don't skimp on heatsinking unless you are going to use a lower voltage transformer as well as reduce power output to below 10W.

You don't tell us how you intend to apply zener diodes as regulators but remember that if you use regulation to drop the voltage supply, you still have to dissipate extra heat from that voltage drop in the regulation devices as well as the heat still dissipated in the output devices. The current requirement may be less for a lower amplifier supply voltage but the inefficiency of regulation for class A amplifiers means you get a poor return.

re heatsink: - deep fins and less height are the most efficient combination of sizes
 
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#20
Ian Finch said:
You don't tell us how you intend to apply zener diodes as regulators but remember that if you use regulation to drop the voltage supply, you still have to dissipate extra heat from that voltage drop in the regulation devices as well as the heat still dissipated in the output devices.
Click to expand...

I don't know whether I will be breaking any IPR if I post the schematics from Rod's site.

In this link Death of Zen - A new Class-A power amp figure 5 is the schematic I am using.
 
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