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Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
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Old 30th January 2018, 01:11 AM   #31
Vunce is offline Vunce  United States
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Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
The 50w version can really get creative, I'm thinking V4 motorcycle engine with the exposed cpu sinks.
I've got my Dells on their way:-)
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Old 30th January 2018, 03:20 AM   #32
xrk971 is online now xrk971  United States
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Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
Ooohh, nice an antique motorcycle air cooled head (or even airplane engine head). I saw a guys use an aluminum wheel from a car. I have some old thick non stick aluminum fry pans that have lost their coating and destined for the trash/recycle. Drill and tap a few holes and you can have a coffee warmer perhaps?

I just measured the copper area of the Dell FD841 heatsink at 61mm x 42mm. TO-247 devices are 16mm wide, so 3 would fit quite comfortably.
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Old 30th January 2018, 03:26 AM   #33
ammel68 is offline ammel68  United States
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Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier
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Originally Posted by xrk971 View Post
Ah, the 29 transistor amp!
I wouldn't build a preamp either that required 29 transistors.
If one of them decided to take a dump, it would be hell trying to figure out which one it was.
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Old 30th January 2018, 03:43 AM   #34
xrk971 is online now xrk971  United States
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Originally Posted by ammel68 View Post
I wouldn't build a preamp either that required 29 transistors.
If one of them decided to take a dump, it would be hell trying to figure out which one it was.
Well, I will do it just out of sheer will power - once I get the will I need to because I will also be building SuzyJ's 32 transistor 5w sub-ppm THD amp - as a headphone amp. She did not say any matching is needed though.

Cascading diamond buffers - a cheap low THD 10W amp with TIP41C

I am going to do another headphone amp comparison thread so would like some super low THD options to compare the SE Class A amps against.
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Old 30th January 2018, 03:44 AM   #35
xrk971 is online now xrk971  United States
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Wow, some serious firepower!!
PC liquid cooling kits may just be the ticket here...
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Old 30th January 2018, 04:48 AM   #36
indra1 is offline indra1  Indonesia
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Originally Posted by xrk971 View Post
... no fancy unobtanium JFETs, SITs, hockey pucks, ...
Hi X,
I'd have to clarify your statement on the hockey pucks, the SOT227 parts are active current production that offer higher power handling capability and superior junction to sink heat transfer compared to smaller packages. I feel it could be misinterpreted by others and create unnecessary misunderstanding.
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Old 30th January 2018, 05:14 AM   #37
xrk971 is online now xrk971  United States
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Hi X,
I'd have to clarify your statement on the hockey pucks, the SOT227 parts are active current production that offer higher power handling capability and superior junction to sink heat transfer compared to smaller packages. I feel it could be misinterpreted by others and create unnecessary misunderstanding.
You are right, perhaps I should be using these for this amp as it really does put out some heat.

90amps and 1.5kW dissipation - definitely heat pipe territory. You could use it as a heating element of a stove

$25 ea though.

https://www.mouser.com/ds/2/205/Viewer-738438.pdf
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Old 30th January 2018, 05:26 AM   #38
dadod is offline dadod  Croatia
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Originally Posted by ammel68 View Post
I wouldn't build a preamp either that required 29 transistors.
If one of them decided to take a dump, it would be hell trying to figure out which one it was.
It is actually together with shunt regulator power supply.
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Old 30th January 2018, 05:43 AM   #39
Tibouchina is offline Tibouchina  Australia
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Default No global feedback at DC?

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Originally Posted by xrk971 View Post
Here is the Big Boy version
A quick look at the circuit. The Big Boy has no global feedback at DC? Could be interesting to see what happens to the offset at the output as the amplifier warms up. Might share some of that excess heat with the speaker.

And just to remind everyone, have a look at the Pass Aleph 5 schematic.
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Old 30th January 2018, 06:02 AM   #40
xrk971 is online now xrk971  United States
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Hugh may have a more concise answer, but yes, that was a conscious decision for moderate amounts of global feedback to be applied at only higher frequencies. Regarding the Aleph 5 schematic - that’s why attribution for this amp goes in part Mr Pass. But notice that the front end is very different. BJTs, no CCS, and a modified Lender topology with KSC1845 straddling the “long neck pair.” And the outputs are P-channel MOSFETs.
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