I have found a special amplifier, am trying to contact the designer

[jacco vermeulen]

One crazy day I ll take the lid off the Nemo and see what exactly is inside.

Take a guess.

 

[gaetan8888]

Hello

About class A bias.

Nelson Pass did a very interesting graph of distortions versus bias of a mosfet amp.

The graph do show that the change are not abrupt wen we go from class A to AB mode, and a higher bias improves the linearity at all power levels.

I've edited the graph image to included the explanations from mr Pass.

Bye

Gaetan

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

 

[destroyer X]

It is pleasure to have you around Gaetan

Your presence is always a helping hand, a support, a friendly advice, you are a very special spirit.

"Votre présence, cher ami Gaétan, apporte le confort de leur esprit amical, à savoir élevé, le soutien moral, soutien fraternel et de dévouement"

regards,

Carlos

 

[destroyer X]

As we cannot listen to the books Mr. AndrewT

Thank you all folks... while we wait by Mr. Dunlap...we are trying to discover things...well...he will fast present something will kill our curiosity.

Unfortunattely Thomas wife had problems..but soon life will return to normal once again.

thank you:

Darian
Lumanauw
Analog-sa
Sakis
AndrewT
Jacco Vermeulen
Gaetan

........................................................................................................

Mr. AndrewT

Not sure if you read my posts.... i hope not, but if you are reading them, please do a favor for me and for forum folks....we are DIY folks, it seems you are too, as you are into a DIY forum...the favor is bellow:

Can you show some real amplifiers you have made, some pictures showing stages of building for us...some schematics and so on?

I would be happy to see the latter amplifiers you have made those years....maybe the last three build by yourself, or designed.

Also will be lovely to know the result of a wise man knowledge applied to real world.

Can you post some DIY products you have made Mr. AndrewT?

regards,

Carlos

 

[gaetan8888]

Can I ask a question ? In the US and places on 110 volts, how much current can you draw from a single outlet ? In the UK it's 13 amps nominally.

Hello

Here in Canada it's 13 amps nominally, USA should be quite same, in Canada we use gage no. 14 electrical wire in the wall and it should be quite same in USA. I presume that UK use quite same wire gage, and so same nominal amps than us and USA.

Bye

Gaetan

 

[Mooly]

Thanks,
Just curious what wattage you could pull, that's all ? ( 3Kw here )
Some of these monster amps and all that.

 

[destroyer X]

My place is two wires, 220 VAC and 15 amperes

Wire is fire resistant and 12 gauge.

Some appartments have the third wire using real ground, and the one is different related the other one used to atmospheric discharges.

The third wire is heavy gauge and runs outside the building, having not insulators to the building wall.... down the building there are 12 copper bars disposed into a circle,...bars are deep into the soil... the circle made is 2 meter diameter, the ground is prepared with salt and have humidity as colect some watter througth holes into the cement surface...this is the grounding used down here....those copper bars are 3 meters long and 20 milimeters diameter, they are all interconected using solder and other copper cables, those ones not so sick..the interconection ones are radial and uses reduced diameter rods.

Higher power is needed because of Air conditioned equipment used into our walls during 2/3 of the year.... only may, june, july and august the temperature goes to 22 degrées celsius...the rest of the year goes 31 degrées celsius.

regards,

Carlos

 

[gaetan8888]

Thanks,
Just curious what wattage you could pull, that's all ? ( 3Kw here )
Some of these monster amps and all that.

Hello

Canada and USA are limited to 1500 watt max that you can draw from a single outlet.

That's the limitation of 110volt or we would need much bigger wire in the wall and that would cost more.

Bye

Gaetan

 

[AndrewT]

Re: As we cannot listen to the books Mr. AndrewT

Mr. AndrewT

Not sure if you read my posts.... i hope not,

of course I do.

 

[darian]

About the Mosfet biasing.

To my knowledge, there is a different behavior of the mosfets concerning the 3 types of distortion :

1) Crossover distortion in mosfets is very high compared to bipolars, raising the bias will obviously improve it to a certain extent, within a limit.

2) Switching distortion is better than bipolars because the mosfets are fast and need less to be quickly reverse biased. Working at high bias in the driver stage may help and higher bias in this stage is linked to higher output bias unless you change some components hence the better switching at high output bias.

3) Gm doubling transition can be less abrupt because their response curve is more asymptotic in behavior (quadratic versus the exponential of the bipolars)

I think it can complete somehow the curve Gaetan submitted. They behave differently compared to bipolars.

 

[destroyer X]

It seems to me they have a very low resistance when saturated

This reduces resistance in series with the load.... i found this very good to bass reproduction.

About Fets... i have tried some.... but i am not experienced with them.

I see that in Italy and France people loves FET amplifiers, i was into the internet searching for French and Italian designs and i could see that...and this happens since many years ago.

Anthony Holton 150 amplifier, using Lateral fets sounded nice, despite i had to adjust it with more current than i was intending to use as iddle.

regards,

Carlos

 

[Wavebourn]

Thanks;
this curves show that made for class A and biased in class A are different animals.

However, in the vacuum tube era it was the same but with transistors we have now give us more freedom. Though, getting unbelievable results from transistors I decided to try the same approach with more linear devices, and got equally beautiful results, both using PP with triode VS modulated SS CCS, and with triode VS pentode with local feedback by current. All of them can't wotk in class AB, or B, because they are designed for class A, to get the less THD the quieter is the sound.

Definitions of classes come from push-pull tube amplifiers that had almost the same output stages, and reflect less of properties than are needed to describe the topology.

There are some definition of "non turn off" output stage. Some say never turn off (every output transistor has a certain bias current flowing all the time) is enough. Many patents like from Japan are about this.

But some give "harder" requirement, that is the continuity of Gm. In classA, Gm is relatively constant even in handover (crossover) around 0V from PNP to NPN vice versa. In lower than classA bias, there will be dip or valley for Gm curve around 0V. Douglas Self book shows these graphs.

Many "Non turn off" output stage cannot fit into this 2nd criterion, even all output stage transistors never turn off.

 

[planet10]

I pointed out that if the inactive side could always remain on, then one important source of HF artefacts would no longer be injected into the speaker line. This is one very important source of HF distortion in push pull Class AB amplifiers, as you know.

Actually, I said it was Class AB doing Class A tricks. I would not regard it as anything more than quasi-Class A

Technics built a series of amps called New ClassA using this kind of trick. They are quite decent sounding...

dave

 

[homemodder]

Hi Analog, back in 88 I was still in highschool in secunda (sasol2 and 3 highveld town). I moved here in 2004. How I miss SA, but untill SA doesnt get a grip on crime, it wont see me again, well maybe next year just for the soccer worldcup. In 13 years of adult life there I went through 10 stolen cars, 6 by hijack at gunpoint and 3 house breakins living in a suburb of alberton. In the last attempt I was shot in the a*s, that was it for me. 88 is also the time I built second amp, kit from Rs electronics in mooi street KWmos250 maybe you familiar with it.

Thanks jacco, looks like 2 aw180s to me, would like to see schematics of the floating supplies. Gosh you must have a couple of gigabytes of pics on your harddrive 😀 😀.

Carlos how did you find the mosfet outputs bass slam, as good as BJT,s??

 

[Wavebourn]

Technics built a series of amps called New ClassA using this kind of trick. They are quite decent sounding...

Also, Walker patented an amp with A+C approximation, that he called very strange, and surrounded by a cloud of non-significant "scientific" details... It was a very genial way to patent an obvious solution.

Edit: Homemodder, the main problem was, illegal immigrants did not have a chance to get a legal job. A first, they did not have work permits, and could not get them staying inside of the country. Can you imagine somebody going back to Zimbabwe to get a work permit for a job of a gardener or a maid that may be given to a local citizen recently coming from own bantustan for a Western-like life?
But they managed to isolate themselves from a worldwide economical crisis, they even had a shortage of electricity so quickly their economics is growing up... I'm seriously thinking of organizing of manufacturing of my audio stuff there...

 

[gaetan8888]

Also, Walker patented an amp with A+C approximation, that he called very strange, and surrounded by a cloud of non-significant "scientific" details... It was a very genial way to patent an obvious solution.

Hello

You mean those current dumping amp like the Quad 405 ?

Gaetan

 

[tinitus]

Arent Gryphon too using some kind of "sliding" bias so that bias is just enough fore classA at any output

 

[Wavebourn]

Hello

You mean those current dumping amp like the Quad 405 ?

Yes. I mean so called current dumping that guarantees class A operation on fine details.

Arent Gryphon too using some kind of "sliding" bias so that bias is just enough fore classA at any output

Class A bias is not needed on any output. What is needed, the less distortions the less is the power. Single ended class A is the way to get such behavior. Class A itself is not a panacea.

 

[analog_sa]

In 13 years of adult life there I went through 10 stolen cars

And never got caught? Sorry, couldn't resist it. Only lost one car in '91 at Bruma and swore to never let the bas***** get anything free out of me again but bullets. So far this arrangement has been working well.

 

[Wavebourn]

And never got caught? Sorry, couldn't resist it. Only lost one car in '91 at Bruma and swore to never let the bas***** get anything free out of me again but bullets. So far this arrangement has been working well.

Coming to California I kept the habit of locking doors and windows getting to the car for about an year... Approached red lights slowly, and during the night was afraid to stop on intersections. Also, once I drove on the left side of the road until realized that it's wrong. 😀