Aksa Lender P-MOS Hybrid Aleph (ALPHA) Amplifier

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#2,382
Thanks folks🙂
I’ve got an extended weekend so I’m hoping to power one channel up.

Danny,
I increased R111 on the Alpha 20 to 2k2ohms. I did notice a slight decrease in the gain but I will not go any further. As you know, changing one component affects others down the line....🙄

Tonza,
The red color makes them sound better😀
I’m using these mosfets:

IXTK90P20P IXYS | Mouser

IXTK88N30P IXYS | Mouser

Regards,
Vunce
 
#2,384
Is 4U Dissipante enough for higher bias Alpha 20 (1,93A)??

Today we placed Alpha against Lyngdorf integrated, speakers were JBL 4341 monitors.

Alpha succeeded much better on every area, except Lyngdorf kept better control on bass. Surprisingly Alpha went lower though. Higher register improved most with Alpha, you could hear it in a second.
 
#2,386
Juntuin said:
Is 4U Dissipante enough for higher bias Alpha 20 (1,93A)??

Today we placed Alpha against Lyngdorf integrated, speakers were JBL 4341 monitors.

Alpha succeeded much better on every area, except Lyngdorf kept better control on bass. Surprisingly Alpha went lower though. Higher register improved most with Alpha, you could hear it in a second.
Click to expand...

1.93amp x 24x2v is ~90w per channel which I think a 5U Dissipante would be better. At 1.35amps it is 45C.
 
#2,388
What is your usual temperature °C where your listening.
Calculate heatsink requirements.

With Irfp240 9240 in circuit take account the ~10V dc when they conduct ~ > 200ma in circuit.

Ask yourself how many watts you need vs temp.

There are many options but it's for you to decide.

I been in India a 2 times.

Have Fun.
 
#2,389
Juntuin said:
..Alpha succeeded much better on every area, except Lyngdorf kept better control on bass. Surprisingly Alpha went lower though. Higher register improved most with Alpha, you could hear it in a second.
Click to expand...

If I am not wrong, they are class D amps -> ridiculous output impedance -> more and better controled bass.

Btw, ten years ago, Lyngdorf SDA-2175, I see a RF/EMI filter inlet with class-D.

An externally hosted image should be here but it was not working when we last tested it.


Inside the new Lyngdorf TDAi 2170 Integrated Stereo:

tdai_l_9-large.jpg


Class A amps need a very good PSU -> you need to spend money in this section.
 
Last edited:
#2,394
Danny,

Thanks for the guidance. I have got 511 ohms when ordering parts but will add 10K (had it in parts bin) in parallel to get around 486 ohms. That is the closest we can get to value of 490.

Thanks

danny_66 said:
Hi Balaji,

R128-490ohms gives perfect current balance for R131-0.43ohms, R132-0.11ohms
If you don't have 490ohms a little lower value like 470ohm will do fine (better then 510).
Bias is 1.49A

Regards,
Danny
Click to expand...
 
#2,395
xrk971 said:
You mean the OT excursion to car talk? About how expensive American cars are in Finland...

We are back on topic now, and perhaps a mod can remove all car-related posts if that bothers people.
Click to expand...

I'm agaist drugs illegal ones , when you said that drug dealer use those cars i got the impression you know drug dealers. Well look the the netflix take your pill maybe it gives insight . If you got a presciption all is ok , but then you can't give them to other peolple . Well you got the livepd tv show in amerca. but back to topic.

I don't use amps without loudspeaker protection so i'm putting together one , its not as good looking as alpha boards but functional , you know diy pcb and i done a lot in my days.

There a lot of good loudspeaker and one can enjoy even a 30€ one , but when you get more exp. level you value the ones of your references not so cheap even diy ones.
This is a never ending topic as we all have your own refs. over the decades with this audiophile hobby. High end expos and so on . Maybe munchen next year maybe jps is there. Would be nice.

Economic depression hit hard in the 90 in finland , and cars are expensive here compered to other countries.
Some people are born with richer and with more money . If you own a part of "overexerated" wall street good luck . Not all people are born rich.

Alpha up running, the other one not yet for my liking.

I'm not in a hurry and still haven't got the al2o3 0.635mm insulators they should arrive next week hopefully , in need to get rid of the irfp tubes many amps diffrent topologies .

As said i'm 6bits old and this years become 7bits old.
 
#2,399
In between BBQ’s I managed to power up one channel of my ALPHA BB 😀
I don’t have a properly sized transformer yet, so I used what I had available an Antek AS-3225 (300va/25vac). With the BB powered I got 29.5vdc, and .604mV bias and 2mV offset. Very similar to the ALPHA20 without any power-up drama and settled right in. Since only one channel is operational, it’s far to early for musical impressions but, what I am listening too sounds very clean and without any added noises in the background.
One observation that really stands out is just how good these cpu coolers work! I was expecting a LOT more heat from this amp board. Actually, I’m more concerned with the psu board as it’s much hotter than the BB. The psu rectifier heatsinks are 58°C and the resistors are 55°C, the hottest part on the BB is the aluminum angle used to clamp the mosfet to the cpu cooler at 42°C.
Way to go X, you’ve been right on with the cpu cooler experiment!
 

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