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Old 22nd July 2001, 09:16 AM   #1
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I'm going Class-A

I still plan to build the ESP 60w, but i won't need that much power on my bedroom, and what the hell, i want to do something "different". The idea is to have the amp sitting high with my speakers, staying on standby until activated by a remote signal (on my preamp, low on the desk ).

Now, i'm kinda biased to the JLH '96... 15w, simple, relatively cheap, and, reputed to sound amazing. The power supply would be a capacitance multiplier (been simulating those; why aren't they more widely used?), and the aditional circuitery would be the standby, led vumeters and perhaps a small fan to keep things cool inside. My main concern is the dissipated power, i'll go shopping for aluminium this monday and have that item covered before even soldering.

So, any comments? Things i should know (besides one cap being incorrectly conected to the -V on the schematic, know that)? How it compares to other low power class A amps?
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Old 22nd July 2001, 10:55 AM   #2
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Hi Lisandro.
Try to avoid the fan. I'm (still)using one in my Pass ClassA amp, and it's kind of irritating, when You know it's there.
I'd spend some more money on heatsink if I were You.
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Old 22nd July 2001, 05:58 PM   #3
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Quote:
Originally posted by Lisandro_P
The power supply would be a capacitance multiplier (been simulating those; why aren't they more widely used?), and the aditional circuitery would be the standby, led vumeters and perhaps a small fan to keep things cool inside.
The ESP Capacitance Multiplier drops the voltage by 1-2 volts (even more, sometimes). That voltage drop creates quite a bit of heat. If you intend to use this, only put it on the unregulated side. DON'T put it on the regulated side. Also, you mught need to bump the transformer voltage; I suggest you do a simulation.

Why are you bothering with this? At +/-28V, the capacitors are easy to get, and relatively inexpensive. Check the prices of ALL the parts, before you commit yourself.

If this were a high-power amp, I'd consider the Capacitance Multiplier, but not for 15WPC.

Good luck.
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Old 22nd July 2001, 09:58 PM   #4
paulb is offline paulb  Canada
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Hi Lisandro,
I have decided to go ahead with the ESP 60W, but my plan is to eventually use this as the woofer driver for a biamp setup. I'll be deciding on a Class A design sometime in the next year or so to drive the midrange / tweeters.
Please keep us all posted on your progress. Are you buying the PCB?
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Old 23rd July 2001, 06:12 AM   #5
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Quote:
Originally posted by Thoth
The ESP Capacitance Multiplier drops the voltage by 1-2 volts (even more, sometimes). That voltage drop creates quite a bit of heat. If you intend to use this, only put it on the unregulated side. DON'T put it on the regulated side. Also, you mught need to bump the transformer voltage; I suggest you do a simulation.

Why are you bothering with this? At +/-28V, the capacitors are easy to get, and relatively inexpensive. Check the prices of ALL the parts, before you commit yourself.

If this were a high-power amp, I'd consider the Capacitance Multiplier, but not for 15WPC.
Well, the power lost in the cap. multiplier is something to take care of, but a modest heatsink would do ok i beleive. I thought about a regular bridge rectifier/capacitor psu, because as you said, in that voltage range caps are not that expensive, but even then, the capacitance multiplier is STILL cheaper, and will outperform it. And cheaper means more money for heatsinking
By the way, a regulated psu is out of the question. I already have too much power to dissipate.
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Old 23rd July 2001, 06:16 AM   #6
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Quote:
Originally posted by paulb
Hi Lisandro,
I have decided to go ahead with the ESP 60W, but my plan is to eventually use this as the woofer driver for a biamp setup. I'll be deciding on a Class A design sometime in the next year or so to drive the midrange / tweeters.
Please keep us all posted on your progress. Are you buying the PCB?
No, i think i'll do the PCB myself. I don't have a lot of practice with them and it's a simple circuit anyway. I'll keep you briefed!
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Old 23rd July 2001, 03:35 PM   #7
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Quote:
[i]
Well, the power lost in the cap. multiplier is something to take care of, but a modest heatsink would do ok i beleive. I thought about a regular bridge rectifier/capacitor psu, because as you said, in that voltage range caps are not that expensive, but even then, the capacitance multiplier is STILL cheaper, and will outperform it. And cheaper means more money for heatsinking
By the way, a regulated psu is out of the question. I already have too much power to dissipate. [/B]
I forgot that you're only drawing 2A. I think this would give a power disipation of only about 3-5WPC. Not much of a problem. You will need to have a power supply for each amplifier (at least everything after the multiplier).

Without the regulator, the capacitance multiplier would definately be worth it. Make sure you put good sized caps on both the input and output. If the regulator helps, then it's because the PSRR of this amp is poor.

Good luck.

[Edited by thoth on 07-23-2001 at 09:16 PM]
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Old 24th July 2001, 02:10 AM   #8
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Thanks for the help. Today i went shopping and found some 0.6 °C/W heatsinks for about $20 each (heavy, but not too big); four of those (one for each output pair in the push-pull output) would dissipate the 180 watts without raising more than 25-30°C. Hope those $100 are worth it...
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