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Aleph J illustrated build guide
Aleph J illustrated build guide
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Old 7th April 2020, 08:12 PM   #4961
6L6 is offline 6L6  United States
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Aleph J illustrated build guide
...where, specifically? If you are asking about with mica insulators on the power devices, it’s required. As thin as possible with no voids.
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Old 7th April 2020, 08:47 PM   #4962
TungstenAudio is offline TungstenAudio  United States
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Thermal grease is also required for the Aavid 4180G ceramic insulators. These have better thermal conductivity than mica or even (ungreased) Keratherm.
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Old 7th April 2020, 10:09 PM   #4963
Eric is offline Eric  United States
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Quote:
Originally Posted by TungstenAudio View Post
Thermal grease is also required for the Aavid 4180G ceramic insulators. These have better thermal conductivity than mica or even (ungreased) Keratherm.
I couldn't agree more! Ceramic + grease is WAAAAY cheaper than Keratherm as well. Ceramic also resists those pesky little slivers of aluminum that can easily pierce Kerathem and ground your output mosfets.
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Old 8th April 2020, 01:43 AM   #4964
Mark Johnson is online now Mark Johnson  United States
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Yet that crotchety old curmudgeon from Auburn California stubbornly keeps shipping world beating audio electronics gear that includes Keratherm. Why IS that? Why would he DO such a thing?
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Old 8th April 2020, 01:51 AM   #4965
Zen Mod is offline Zen Mod  Serbia
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Aleph J illustrated build guide
and yet, he even more likes mica and goop, smeared with fingers

addiction, I suppose

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Old 9th April 2020, 10:11 AM   #4966
mpa is offline mpa  United Kingdom
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Hi all, I have a quick question regarding grounding of the XLR inputs on Aleph J. I have two Alephs with balanced inputs only (no rca's) and have simply connected Pin1:Gnd Pin2:+in and Pin3:-in which seems to work just fine (only a slight hum if I stick my head in the speaker!) however I found a post on page 88 of this thread whilst browsing as a refresher (I'm about to build a 3rd Aleph J ) which seems to indicate that I should have my Gnd connected to the chassis and not to the board?

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Originally Posted by claudio52 View Post
Hi krath, the pin 1 is the shield of the XLR connector, must be connected to the chassis and not to the circuit ground. See: 3-1 Balanced Interconnections: Grounding ( Audio Component Grounding and Interconnection )
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Old 11th April 2020, 10:46 PM   #4967
quackers is offline quackers
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Why any manufacturer does anything does not help a DIYer understand or anyone learn.

Isn't thermal conductivity added like parallel resistors? From the manufacturers datasheets, a Kerathem pad it has a thermal conductivity of 6.5 W/mK. The Avvid 4180g has a thermal conductivity of 15 W/mK. High performance grease is about 2 W/mK. Assuming one layer of grease (correctly applied) and one 4180g together is equal to one Keratherm, the Keratherm is a better thermal conductor by 4.7 W/mK. The grease is the limiting factor.

Regardless, if a solution works for you, it works.
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Old 11th April 2020, 11:38 PM   #4968
TungstenAudio is offline TungstenAudio  United States
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If the units are W/mK, then larger numbers are better. If *C/W then you want smaller numbers.
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Old 11th April 2020, 11:38 PM   #4969
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Quote:
Originally Posted by quackers View Post
Isn't thermal conductivity added like parallel resistors?
You don't add thermal conductivity directly - it's just a material property - but thermal resistances are added like series resistors.

Here's a helpful explanation: 16.4 Thermal Resistance Circuits
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Old 12th April 2020, 06:40 PM   #4970
folkdeath95 is offline folkdeath95  France
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Today, I took the opportunity of the containment to open my AlephJ to clean the dust inside (after five years of service, there was some).
I noticed that the sticker on the Torody transformer slipped because it seemed that the glue melted. So, after checking bias and offset settings (both were still OK, no drifting after 5 years), I decided to checked the temperatures in my amplifier.
After 1 one hour (the time to check the settings), the transformer suface temperature was 50C and inside air temperature was 39C (measured with a cooking thermometer).
After 7 hours, I measured 66C on the transformer and 43C inside the amplifier.


My amp is a "classic" DIY AlephJ, nothing fancy, I just followed the BoM given in the first message of this thread. Same with the PSU:
Click the image to open in full size.
The transformer is a 300VA Torody Supreme Grade (so it's encapsulated in epoxy and have a metal case).
Diode bridges are 35A Vishay (GBPC3502-E4/51 Vishay Semiconductors | Mouser France)
Here's a picture of the inside:
fini V2 mini.jpg


Do you think I have to worry about the transformer's temperature?
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