aleph 30 schematic

[Chamberman]

A friend of mine found this ebay offer:
Finished Pass A30 Mos Single-ended Class A Power Amplifier Mono 30W HiFi Amp | eBay
resp.
Finished Pass A30 Mos Single-ended Class A Power Amplifier Mono 30W HiFi Amp | eBay

The price is very tempting but I have doubts whether high-quality components are used.

Are there any experiences with this devices from China ?
Thank you for advices.

In the attachment the schematics - first from the offerer and second from the genuine device.

I do not see that chassis having nearly enough heatsink to support an Aleph 30 mono. Maybe they underbiased it or dropped the rail voltage to keep from overheating the thing.

 

[Luciman]

A friend of mine found this ebay offer:
Finished Pass A30 Mos Single-ended Class A Power Amplifier Mono 30W HiFi Amp | eBay
.....

So as not to open a new thread on the subject: does anyone know the manufacturer of the amp board, because the three mosfets opposite each other would suit my chassis planning very well.

 

[koja]

I do not know about the eBay board but I used Peter Daniel pcb (they are all made to the same format). See Aleph30 board here.

p.s. miniAleph boards may be similar (I have to dish them out to check). MegaAMP has those.

 

[Luciman]

@koja:

Thanks for your hint.

This is the chassis I want to use: BRZHIFI BZ2607 series double radiator aluminum case for power amplifier|Amplifier| - AliExpress

I want to distribute the MosFets on both heat sinks - the PCB then in their middle. Since the PCB side length is shorter, I would have to extend the Mosfets connections. How long can the connections PCB -> MOSFET be?
How long can the connections PCB -> MOSFET be?
Would both heat sinks be sufficient?

 

[Zen Mod]

my estimation is that you can squeeze 70W of heat in that one case

leads can go from pcb to mosfets, but put heatshrinked gate resistor for mosfet on end of wire

 

[Luciman]

@Zen Mod

Thanks for the information.
I come more from the tube scene (Hifi- & Guitar amps) and haven't built a semiconductor amplifier for at least 40 years. I am currently building a Chip-Amp with LM3886 and would like to build a Nelson Pass-Amp that is able to drive my Electrostats Audiostatic RS300 + SW1 as well as my TML IMF RSPM MK4.

Since I have little to zero experience with Class A amps, I cannot really assign the statement "... 70W of heat in that one case".
Which Pass-Amp with which power could I fit in the chassis that meets the requirement?

 

[Zen Mod]

Aleph J and most of other FW format amps are in that category

 

[koja]

@ZenM
since we are already talking Alephs: I have those Aleph30 pcbs fully assembled and collecting dust (they were used only for a year). Next Winter I hope to be making a mini Aleph to drive the mid/top section of my new speakers.

I was planning on making AlephJ with SemiSouths but the speaker section will be 4ohm impedance. When I see amp power output into 4ohm dropping below that which it does into 8ohm I kind of have a feeling that the amp is not really suited to drive a 4ohm load even when it comes to distortion (wrong?).

I also kind of remember Generg saying that the Aleph30 would have been his preferred amp to take to a deserted island (in my experience too the midrange was very nice; bass handling was poor). So I thought rather than selling off these A30 boards maybe I modify and try them: What do I need to change?

As I remember my original Aleph30 ran on +/-25.5V rails and had 3 output fets biased at 0.7A each. On say +/-17V rails do I only pull two out and re-bias the one left for something like 2A and then reset AC gain or is there more to it? Can you have a quick look at the schematic or should I move my question to miniA forum? Hvala.

 

[Zen Mod]

move q. to MiniA or open dedicated thread

 

[zintolo]

Referring to the schematics shown in this post: aleph 30 schematic

What is the sonical difference between three IRFP240 ( https://www.vishay.com/docs/91210/91210.pdf ) in parallel, vs one single IRFP244 ( https://www.vishay.com/docs/91211/91211.pdf )
The input capacitance will be lower in the second case, but will the IRFP244 run too much hot, so will their current capability be lower?

Is it possible that the amp will need to be biased colder than needed, so performance ruined? Or the three are just for lower impedance speakers, in order to be able to deliver current even at lowest impedances?

I'd run it on a 8 Ohm Klipsch speaker.

Thank you all in advance.

 

[tiefbassuebertr]

Referring to the schematics shown in this post: aleph 30 schematic

What is the sonical difference between three IRFP240 ( https://www.vishay.com/docs/91210/91210.pdf ) in parallel, vs one single IRFP244 ( https://www.vishay.com/docs/91211/91211.pdf )
The input capacitance will be lower in the second case, but will the IRFP244 run too much hot, so will their current capability be lower?

Is it possible that the amp will need to be biased colder than needed, so performance ruined? Or the three are just for lower impedance speakers, in order to be able to deliver current even at lowest impedances?

I'd run it on a 8 Ohm Klipsch speaker.

Thank you all in advance.

check out this URL's
Difference between IRFP240 & IRFP244
prefer IRFP 240 or 244
https://www.diyaudio.com/forums/pass-labs/9545-transistor.html#post109876
Audio Asylum Thread Printer

 

[zintolo]

Thank you tiefbassuebertr,

I will read this document and report here some more questions for sure will raise.
https://www.infineon.com/dgdl/para.pdf?fileId=5546d462533600a401535744b4583f79

 

[zintolo]

tiefbassuebertr, looking at your last link, I've found:
Re: Good MOSFET For the Pass Zen Revisited? - klaus - Tweakers' Asylum

IRFP244 - 7 A/V (Pass Aleph amps use 3 244's in parallel)
IRFP048 - 20 A/V

so three IRFP244 (https://www.vishay.com/docs/91211/91211.pdf) in parallel compared to a single IRFP048 (https://www.vishay.com/docs/91198/91198.pdf) will have:
- have the same transconductance;
- a total Ciss of 4.2 nF, compared to just 2.4 nF of the latter;
- a total Rds on of 0.28/3=0.1 vs 0.018 Ohm of the latter;
- a total continuous drain current of 9.7x3=30 vs 52 A of the latter.
- in this amp, voltage doesn't seem a limit for Vds of the latter.

What are the reasons to prefer three mosfets in parallel vs one single beefier one?
Are there modern substitutes for the IRFP048?

Thank you all in advance for letting me understand.

Roberto

 

[zintolo]

The only thing that comes to my mind is that the triplet is safer with low impedance amps, and distributes better the heat on the heatsink compared to a single device that locally tries to dissipate all the heat.

So with 8 Ohm speakers with pretty flat impedance curves, a single bigger device could do the job.

Is there anything else?