With all that Surface Area i don't think he has anything to worry about or even think about
With all that Surface Area i don't think he has anything to worry about or even think about
audiosan talks about the additional Rth between plate and heatshink...
it s a serious value to deal with...
Hi, after building several class A amplifiers I have learned (the hard way) that dissipating the heat from much more than a 25W class A using passive heat sinks is very difficult. This should never be underestimated.
I know this is not the correct thread to mention this but there does seem to be a lot of interest in Class A, so here goes.
I have collected components to construct a Krell 100mk2, I will now not be in a position to complete this project.
I have P Watts stuffed boards using good quality components
Heat sinks identical to original Krell.
New Papst fans
Original size Mallory / Sprague capacitors
40-0-40 2Kva transformer ( not toroid)
Enclosure
If anyone is interested please PM me and I will supply pictures and more detail
Alan
I know this is not the correct thread to mention this but there does seem to be a lot of interest in Class A, so here goes.
I have collected components to construct a Krell 100mk2, I will now not be in a position to complete this project.
I have P Watts stuffed boards using good quality components
Heat sinks identical to original Krell.
New Papst fans
Original size Mallory / Sprague capacitors
40-0-40 2Kva transformer ( not toroid)
Enclosure
If anyone is interested please PM me and I will supply pictures and more detail
Alan
The reason why the majority of serial manufactured class A amps with passive cooling were only biased to reach the nominal continuous power level in class A, not peak.
An example is the French AudioAnalyse A90, marketed as a 100W class A stereo power amp.
Biased to 1.75A, at continuous output power levels over 50W it went to class AB.
With 45Vdc rails under load, that's 160W dissipation per channel.
80W dissipation is the maximum each of the A90 heatsinks can handle at 25C ambient (see Seifert KL182)
Peak class A power is 100W, which justified advertising it as such.
(same same with Accuphase, Forté Audio, you name it)
FULL 100W class A would require 6 of those thryristor heatsink beasts, instead of 4.
Plus a 50% larger amp case, and a 500VA toroidal per channel instead of the 330VA Frenchy.
The A90 carried an msrp in Europe which was the equivalent of $10k today.
Biased to 200W peak in 8 ohm would have raised the price tag by thousands more.
Do not underestimate the heat of 1 single joule per second.
(example is a 1cm pcb trace from a transistor lead to a resistor, the m in thermal conductivity W/m·K is actually m2/m)
Picture for Jay (feel free to google how those heatsink modules connected to the amp case, pretty unusual)
Attachments
Attachments
yes
I don't know what to say. Standart parts: ADM1485+DIR9001+AD1853+AD8066ARZ (i/v)+LT1468IS8 (LPF). SPDIF transformer H1102NL used as in datasheet. All caps on DAC's PCB - Panasonic FR, in DAC's "filters" - Nichicon FG. Resistors SMD Yageo 1%, 2,67K - C2-29B 0,05% 25 ppm. Ceramic caps on sound stream - 1206 Samsung NP0, in power supply - 1206 Murata X7R. Beads: BLM31PG601SN1L.
PCB - 2 layers (4 layers better, but impossible to make at home).
Maybe AK4113 will be better than DIR9001.
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Aleph 5 in an amplifier chassis
Hello, My first post here- in the past I have done scratch-built tube amps, like 2A3 push-pull and 300B SE monoblocks (Joe Robert's Sound Practices style - huge influence). Lately I have been working on a Pass Aleph 5 amp using built boards from China (eBay), and I installed them with heat sinks and fan into a gutted Kenwood M2 chassis. Listening tests so far - very musical and smooth yet detailed thanks to the class A operation. I have 98 dB efficient speakers so 30 watts / channel is fine. I can add a display using "magic eye tubes" where the original bar graph displays were, the boards just need a little 12vdc power supply. Here is a pic.
Also I found something interesting in the attic- a box from the 90's from Sound Colony with a Borbely stereo Servo 100 kit in it, complete with semiconductors, most passive components, PCBs, toroidal transformers and heat sinks (kinda small). A well regarded design from Borbely, should be a good project, I am already starting on the boards. I am also working on a 2A3 push-pull stereo amp based on a PCB from China (eBay) and also a monoblock version of the all triode 6BX7 push-pull amp from the Eric Carmichael article in Glass Audio- this stereo amp was the first amp I built back in the early 90's... Bob Scates, Springfield, VA
Hello, My first post here- in the past I have done scratch-built tube amps, like 2A3 push-pull and 300B SE monoblocks (Joe Robert's Sound Practices style - huge influence). Lately I have been working on a Pass Aleph 5 amp using built boards from China (eBay), and I installed them with heat sinks and fan into a gutted Kenwood M2 chassis. Listening tests so far - very musical and smooth yet detailed thanks to the class A operation. I have 98 dB efficient speakers so 30 watts / channel is fine. I can add a display using "magic eye tubes" where the original bar graph displays were, the boards just need a little 12vdc power supply. Here is a pic.
Also I found something interesting in the attic- a box from the 90's from Sound Colony with a Borbely stereo Servo 100 kit in it, complete with semiconductors, most passive components, PCBs, toroidal transformers and heat sinks (kinda small). A well regarded design from Borbely, should be a good project, I am already starting on the boards. I am also working on a 2A3 push-pull stereo amp based on a PCB from China (eBay) and also a monoblock version of the all triode 6BX7 push-pull amp from the Eric Carmichael article in Glass Audio- this stereo amp was the first amp I built back in the early 90's... Bob Scates, Springfield, VA
