Aleph J Schematic

[bobodioulasso]

Just reading back.

I don't agree that the current through the signal fets decreases with the decrease in Aleph current, they just pull more current through the speakers.

As long as the current into the speaker is the algebric sum of the upper and lower halves currents, Flags is right.
The aleph current source diminushes its current to help the lower half, asking it less current for the same result into the speaker.
Otherwise, we were in the case of a regular single ended amplifier.

On the way, i think 1A bias per leg should be sufficient.
1.3A shoud be right in the case of constant current source.
Though, i never saw the service manual...

 

[samoloko]

Gentelmen

what Is the current per FET
are all 4 fets at 1.3 A
has anybody used MF151-35 heatsinks with this amp

 

[Yunick]

I use Conrad's MF35-151.5 with my Aleph-j. I'll measure the bias when I get home. The heatsinks are around 60 deg C with 24 deg C ambient.

 

[samoloko]

thank you very much

 

[bobodioulasso]

I use Conrad's MF35-151.5 with my Aleph-j. I'll measure the bias when I get home. The heatsinks are around 60 deg C with 24 deg C ambient.

36°c above ambient is too much.
What about summer time?

 

[Bill Fuss]

Hi guys,

My first Aleph J biased to around 1.1A per fet. That worked out to 117 watts/ch, probably a little too much for the 151 Conrads. If they are not black anodized you can help them with a light coat of flat black paint.

 

[Yunick]

36°c above ambient is too much.
What about summer time?

Well 60 deg C is the hottest spot on the heatsink. On the outsides the temperature is around 45 deg C. I dont worry to much about it. I use Peter Daniel's PCB and the mosfets are mounted pretty tight in the middle of the heatsink...

I did build it according to the original schematic from Nelson P but can't remeber what bias I ended up with.. I'll check tonight. it's been running 5-6 month now..

I remeber a few using these heatsinks to build Aleph 3/30 a few years ago...

 

[Bill Fuss]

As long as the current into the speaker is the algebric sum of the upper and lower halves currents, Flags is right.
The aleph current source diminushes its current to help the lower half, asking it less current for the same result into the speaker.
Otherwise, we were in the case of a regular single ended amplifier.

On the way, i think 1A bias per leg should be sufficient.
1.3A shoud be right in the case of constant current source.
Though, i never saw the service manual...

In an Aleph J the current through the speaker will never equal the algebraic sum, the bias must be subtracted. And because it is dynamically biased, the bias is constantly changing.

 

[Bill Fuss]

The Aleph 30 runs at around 90-100 watts/ch, a little cooler than the Aleph J.

 

[frags]

In an Aleph J the current through the speaker will never equal the algebraic sum, the bias must be subtracted.

Please read about Kirchhoff's laws:
Kirchhoff's circuit laws - Wikipedia, the free encyclopedia
The currents in circuits have positive or negative values according to their directions.

 

[frags]

Gentelmen

what Is the current per FET

I'm using 1A. So 2A total bias.

 

[samoloko]

Well 60 deg C is the hottest spot on the heatsink. On the outsides the temperature is around 45 deg C. I dont worry to much about it. I use Peter Daniel's PCB and the mosfets are mounted pretty tight in the middle of the heatsink...

I did build it according to the original schematic from Nelson P but can't remeber what bias I ended up with.. I'll check tonight. it's been running 5-6 month now..

I remeber a few using these heatsinks to build Aleph 3/30 a few years ago...

I will use PD boards but think to place FETs at row on center at MF35-151.5
I have F5 which Is Push Pull and FETs In pair run at same current
I like to know Is It same with AlephJ which Is different
also how can I set bias

 

[frags]

36°c above ambient is too much.
What about summer time?

It doesn't matter what temperature of heatsink is.
It does metter what temperatures of FET junctions are.
You may have cold heatsinks but high temperature in a FET because of crappy thermal interface between heatsink and FET

 

[bobodioulasso]

how can I set bias

R27 sets the bias current.
R8 the output offset.

 

[bobodioulasso]

In an Aleph J the current through the speaker will never equal the algebraic sum, the bias must be subtracted. And because it is dynamically biased, the bias is constantly changing.

The difference is vanishing?

 

[frags]

The difference is vanishing?

Poor Mr. Kirchhoff. He did not know that his laws would not work for Aleph J amplifiers.

 

[flg]

Quote:
Originally Posted by Bill Fuss
In an Aleph J the current through the speaker will never equal the algebraic sum, the bias must be subtracted. And because it is dynamically biased, the bias is constantly changing.

Originally Posted by Bobodioulasso
The difference is vanishing?

I think this is somewhat off thread and belongs in the "Favorite Threads and Posts in "Pass Labs"" thread Or???
Who's Poor Mr. Kirchhoff Anyway? Aaarghh!

 

[flg]

That reminds me of something. This is as good a place as any. Been reading some posts lately from a long time (DIY Time) ago. Who P#$%^d off GRollins? I just thought he'd be back next week, maybe next week, but he didn't come back? You can read his stuff on a few other sites, I'm sure you know, but, It's about time he showed his face(maybe that should be A$%^) here again...
Hi Grey

 

[Yunick]

I did some measurements tonight..

My rails are +/- 22.5V and bias 1.22A.

Heatsinks are measured with a IR gun.
Fets are 60 deg C, sinks are 55 deg C behind the fets and 45 deg C at the ends..

 

[Zen Mod]

yeah - good old Mr. Insomnia Ego GR ....

in any case - (that's) not worse than any of us , with incredible talent for helping other ppl

he got pi$$ed in pi$$ing contest Thread of Threads - Blowtorch Amongst Earthlings Again

who pi$$ed him - I mean it's thread itself ....... that thing is alive ..... like Anaconda



it's time for him to be back ...... long ago .