A 50W lateral MOSFET amplifier based on David Tilbrook's AEM6000

[itsparks]

Just now, Janus77 said:

Jason, i went bungy jumping in Nanaimo once, nice place..

I love the island! Much different than Vancouver city !

[Janus77]

I'd like to get up to Mt Cain for a ski one day, a long way from everything.

 

(sorry for the OT)

Edited December 16, 2020 by Janus77

[Guest Suzyj]

2 hours ago, Leinster Lad said:

 

Hi Suzy, I must be having an old bloke look, but for the life of me I cannot find the Faston 110 terminals that go into the board.

 

Would it be possible to trouble you for the part number please ??

 

Thanks heaps

David

TE 63756-1

 

https://au.element14.com/amp-te-connectivity/63756-1/terminal-pcb-tab-1-4mm/dp/2841308

[Leinster Lad]

Thanks Suzy, that part number at mouser is in 1000 piece lots !

[andyr]

16 minutes ago, Leinster Lad said:

Thanks Suzy, that part number at mouser is in 1000 piece lots !

 

Maybe try RS Components?  Ask them what spades, 488-1241 connectors fit onto.  (I use these to fit onto SLA battery lugs.)

 

I think the right part number is 719-7031.

 

Andy

 

Edited December 16, 2020 by andyr

[Leinster Lad]

No worries Andy, no need to buy 1000 of them as  I can get them individually at Element14

[itsparks]

Has anyone built the 50watt version of Suzy's amps yet ? I'm ordering PCB's for both soon and just curious !

[soundbyte]

.

Edited December 20, 2020 by soundbyte

[Guest Suzyj]

I look forward to seeing the results of your simulations and measurements of your proposed changes on a board.

[soundbyte]

Why bother, trying to help but your mind is obviously made up that nothing can improve the circuit, nothing I can say or do will change that, a pity.

Moving on.

[Guest Suzyj]

Okay then, I'll go along with this. Here's what I've done:

 

1. In simulation: Insert a 10mV 10KHz AC voltage source in series with the zener, and simulate the circuit. Measured AC on output is 450nV, giving me 87dB rejection of voltage noise at this point. Like I said, good CMRR.

2. In reality: Stick a 12V zener in series with a 1K resistor. put that across my lab supply and put 5mA through the zener. Measure the voltage noise density across the zener with my 3585B. I measure 79nV/√Hz, flat across the band. For reference my 3585B does 11nV/√Hz with it's input shorted. It's a real beast for noise measurements.

 

So, combining these, the noise contribution of the 12V zener used for biasing the first stage cascode is 3.6pV/√Hz output referred, or 220fV/√Hz input referred (gain of 16).

 

Compare this with the 8nV/√Hz input-referred contribution of the input J-FETs.

 

Regarding the 2 -transistor current source oscillation stuff. I've read about this dozens of times, but am yet to see an actual measurement of this happening. I've simulated and measured real versions of these things to death trying to find anything, and cannot.

 

I'm all for making improvements, but they have to be grounded in reality, not lore.

 

There is a lot that can be done to improve this circuit, and I'm all ears for good ideas. Over on DIYAudio there's a thread for just that.

 

Thus far I've found the biggest improvements are to be found by inserting a folded cascode for the first stage load, and using a current-mirror load for the first stage (higher impedance gives better OLG). I've had a play at trying to come up with a current mirror load for the second stage, and it works well in simulation, but I'm not convinced it's anything but a simulation fluke. I use the folded cascode current mirror load on another amplifier (google DIYAudio cascaded diamond) and it's an absolute ripper there - it improves the PSRR, and makes that amplifier work on any power supply from about +/-5V to +/-20V. I've also played a lot with VAS stages. I'm playing with a cool 200W version with a class-H output stage ripped off from a NAD3240PE, but done with FETs, that should make an easy 250W RMS into 8Ω, with ~0.001% THD at 10KHz, with a quiescent dissipation of around 10-12W (vs ~35-60W for a normal class-AB latfet of this power).

[andyr]

Wow, formidable (spoken the French way)!  

 

I'm hoping you are also an LTspice whizz (as I have some Qs   ).

 

Andy

[itsparks]

Anyone know where we can get the SST404 dual matched N-JFET units. "Q1" 

[Guest Suzyj]

There are two manufacturers that I know of:

 

CA Logic, distributed by future electronics, and

 

Linear systems, distributed by micross.com

 

[itsparks]

10 hours ago, Suzyj said:

There are two manufacturers that I know of:

 

CA Logic, distributed by future electronics, and

 

Linear systems, distributed by micross.com

 

Yeah i found them at future Electronics,

 

Looking for the EXICON ECW20N20 and EXICON ECW20P20  units are 15$ each Euro.  

 Any substitues for these instead of something that is really hard / expensive to get.

 

 

[Guest Suzyj]

I’m not aware of any substitutes for the Exicon parts. I designed it originally around Hitachi lateral MOSFETs, but they haven’t been available for some years.

[itsparks]

11 minutes ago, Suzyj said:

I’m not aware of any substitutes for the Exicon parts. I designed it originally around Hitachi lateral MOSFETs, but they haven’t been available for some years.

 it's ok, i found some in the UK, going to order enough outputs to build 10 channels.

[acongdon]

Just wanted to say thanks to Suzy for your compendious notes. I've ordered the bits and look forward to building this..

but I really wanted to say that I purchased the tweezers you recommended and used them for the first time and they are a life-changing joy to use, thanks

[itsparks]

1 hour ago, acongdon said:

Just wanted to say thanks to Suzy for your compendious notes. I've ordered the bits and look forward to building this..

but I really wanted to say that I purchased the tweezers you recommended and used them for the first time and they are a life-changing joy to use, thanks

Where did you get your output devices ?

[Guest Suzyj]

6 hours ago, acongdon said:

Just wanted to say thanks to Suzy for your compendious notes. I've ordered the bits and look forward to building this..

but I really wanted to say that I purchased the tweezers you recommended and used them for the first time and they are a life-changing joy to use, thanks

 

A pleasure!

 

I'm getting such great warm and fuzzies reading of people building these. I'm assembling a pair of more uber ones on the bench today with Class G (erroneously referred to as class H on my silkscreens) output stages, in a 100W and 200W flavour. In simulation they show great promise. I can't wait to test them.

[itsparks]

9 hours ago, Suzyj said:

 

A pleasure!

 

I'm getting such great warm and fuzzies reading of people building these. I'm assembling a pair of more uber ones on the bench today with Class G (erroneously referred to as class H on my silkscreens) output stages, in a 100W and 200W flavour. In simulation they show great promise. I can't wait to test them.

Interested in some measurements and pictures  

[acongdon]

On 14/01/2021 at 10:42 AM, itsparks said:

Where did you get your output devices ?

From Suzy's blog:

 

They’re distributed by profusion: http://www.profusionplc.com/type/lateral-mosfet

[itsparks]

Guys I accidently ordered WAY to many of these, I meant to order a handful of the 50watt and 100 watt of the AEM amplifier boards, but instead I screwed up and ordered TONS of the 100 watt boards.

 

Offering them very cheap If any interest please let me know ! 

[acongdon]

I think there is a few small errors in the 100W notes and parts list.

Schematic C23-26, parts list C22-25, overlay C13,15,23,25?

Schematic R44,45,  parts list R44,R45, overlay R44,41.

Schematic R40-43,45, parts list R40-43,46, overlay R18,37,40,42,46 (3W wirewound)

Schematic R36-39, parts list R36-39, overlay R36,38,39,43.

Edited February 2, 2021 by acongdon

[NDHien]

Hi

Any Errata on the 100W please , I can see the post of acongdon  above , before I order parts , thanks for your time .

 

Regards