even more lateral fets

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ed
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even more lateral fets

Post by ed » Sat Jun 16, 2018 12:10 pm

overwhelmed I was by the phenominal enthusiasm for the last lateral fet amp, so I am moved to post another.

Voila! The choke loaded source follower lateral fet amplifier. Similar to the MOFO championed by Mike Rothacher on diyaudio but with a leteral fet and a smaller choke. This one has an opamp front end giving a gain of 3 because I don't have any active pre-amp to feed it. it will be powered from half the ps of the other amp and 2 large 24v smps that I had lying around.

because I'm not sure of the heat sink dissipation figures I'm going to start the bias at about 1.1 amps(30ish watts) and hope it will move to 1.6 amps without getting too hot.

fingers crossed.
se latfet40.jpg
and another of the ps
ps dua40l.jpg
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Re: even more lateral fets

Post by ed » Thu Jun 21, 2018 10:38 am

I may have to put this one on hold.
Just testing 1 channel at 1.0 amp the sink got to 50 degrees, and it was still showing signs of climbing, albeit very slowly.
I need bigger sinks for this...oh waily waily...this was supposed to be a cheap experiment.

The meter showed 34 watts out of the wall.
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Re: even more lateral fets

Post by Nick » Thu Jun 21, 2018 12:49 pm

Heat is always the problem with solid state it seems.
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Re: even more lateral fets

Post by pre65 » Thu Jun 21, 2018 12:57 pm

ed wrote:
Thu Jun 21, 2018 10:38 am
I may have to put this one on hold.
Just testing 1 channel at 1.0 amp the sink got to 50 degrees, and it was still showing signs of climbing, albeit very slowly.
I need bigger sinks for this...oh waily waily...this was supposed to be a cheap experiment.

The meter showed 34 watts out of the wall.
What about a fan to cool things like wot I used on my 50W S/E Mosfet amps ?
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Re: even more lateral fets

Post by ed » Thu Jun 21, 2018 5:36 pm

pre65 wrote:
Thu Jun 21, 2018 12:57 pm

What about a fan to cool things like wot I used on my 50W S/E Mosfet amps ?
seriously?

fans are for air conditioning and computers, eny fule know!

I had a fan in an MF A100 back in the eighties, my first and last...the fan didn't stop the A100 sounding awesome but it did stop the music.

I'll just have to wait for my birthday and convince the boss to buy me some...if anybody has a couple lying around please let me know..min 0.75 c/w
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Re: even more lateral fets

Post by ed » Thu Jun 21, 2018 9:22 pm

it's alive
Image
unforunately my poor little sig gen only goes to about 1.6v RMS so I couldn't find the clipping point

but it sings
Image

I could only run it for half an hour but it sounds awesome even hamstrung at 1A bias. This has promise.
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Re: even more lateral fets

Post by Nick » Thu Jun 21, 2018 11:26 pm

unforunately my poor little sig gen only goes to about 1.6v RMS so I couldn't find the clipping point
Improvise man, you must have a mains transformer that you can use as a step up or if its a dual primary an autoformer to give you 6dB of gain.
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Re: even more lateral fets

Post by ed » Fri Jun 22, 2018 10:22 am

you've found a nerve, reminding me how useless I am these days...I have a pot in the workroom where I put details of projects on hold. These are usually mid point when the boy comes in: 'Dad, can you fix this please, it was an accident, honest'...so, about 3 or 4 years ago I was in the middle of a replacement sig gen..I've just found the outline in aforementioned pot...here it is:

Image

I can't bring myself to fiddle with the old one when this is still unfinished.

It did occur to me that the old one had an opamp buffer on the output, I suppose I should have put some gain in at that point...c'est la vie.

the clipping point is one for the future...I was listening to it during my 30 minute window of opportunity before it set fire to the music room, when the mem sahib came in and said 'isn't that a bit loud!!'
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Re: even more lateral fets

Post by IslandPink » Fri Jun 22, 2018 12:56 pm

Good effort Ed.
What's the tone like - different to a Mosfet output ?
Have you got a link to the DIY-A thread ?
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Re: even more lateral fets

Post by ed » Fri Jun 22, 2018 1:36 pm

IslandPink wrote:
Fri Jun 22, 2018 12:56 pm
Good effort Ed.
What's the tone like - different to a Mosfet output ?
Have you got a link to the DIY-A thread ?
far too early to nail it down...the brief listen was fairly bright and ultra revealing of minutae, the bass was profundo..the music was dirt-like, dirt like.

bear in mind I was aiming to see if I could identify the aforementioned difference, I thought no better place than a single stage, single ended, and I also have an ultra simple pp to compare it with....

there will be more, maybe, I'm conscious of posting into a void at the moment....
I'm confident that the large smps are workable though...

just google mofo amplifier for background but imo you must read Mike's 'build this mofo' paper, it's a real hoot.
ecx10n20se.pdf
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Re: even more lateral fets

Post by IslandPink » Fri Jun 22, 2018 7:09 pm

Better than the music being 'dud-like' ( ...and they called that .... tobacco juice .. )

Thanks for the circuit. suspect that 1058 thing can handle a far bit of current. So is the 60mH like the loading on a valve, then ?
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Re: even more lateral fets

Post by IslandPink » Sat Jun 23, 2018 1:05 pm

Had a look at the datasheet.
So, looks like you could run 2 or 3A with more heatsinking ?
Input capacitance looks very flat vs. Vgs from -2V onwards . This seems like a very good thing.
I had a look at the datasheet for IRFP240 used in the Pass F4 and not sure I could find an equivalent graph , but the capacitance vs. Vds was pretty non-linear.
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Re: even more lateral fets

Post by ed » Tue Sep 01, 2020 11:03 am

I've decided to build another one of these...I loved the sound of the first one and all the talk of current mofos has spurred me on..

I'm going to use the exicon fet again though cos I think it's great.
but I've got some changes planned, to wit:

Use the bigger chokes and max out the current
Use a proper case with some Conrad heatsinks
change the opamp to a Muses02 from the original LTC1150, but may up the gain slightly from 3 to 4(it's got rave reveiws from the Topping DAC)
or
replace the opamp with DA6116 which goes to a gain of 15db and integrate an IR remote control.

In regard to the front end I think I’m quite keen to try one of these Muses opamps, and it might be fun to compare with Steve’s valve front end when we finally escape.

Also, I did think the IR remote control and integrated scenario might be a bit OTT as the Topping E3 that I’m looking at has an IR remote for the volume. I miss the armchair control of the SB and the current control via netbook cannot be in range of the listening chair....oh compromise waily
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