Now we know...

[Vinyl Grinder]

You should never put standard electrolytics so close to such a high intensity heat source. The tantalums are fine but the electrolytics will dry out over a couple of years and might explode. There are electrolytics designed (especially in computer applications) to take this level of heat but they are about four times more expensive.

Pha! shitty cheap electrolytics..Why not use Elna 'Silmics'/ 'Cerafines' or even Rubycon 'Blackgates' all depending on applications.

[Vinyl Grinder]

(Addenda) If I remember rightly the circuit was designed by Tim P of EAR fame and he always called it class AB, it was just the marketing dept of MF that called it class A. He also designed it *with* the more expensive caps

Yes it was & is only running in class 'A' upto a certain wattage then reverts to 'AB'...MF never claimed it a pure class 'A' amp.I remember reviews of this amp saying it will easily drive the most difficult of speakers.Hated mine, i think the 'M50's were monoblock versions with bigger power supplies.

[greenhomeelectronics]

Didn't they used to say it was "heavily biased towards class a"? Or was that somebody else. That's right about the elecrolytics though, most are rated at 85 degrees but any near heat should be 105 degree rated.
Dave.

[WikiBoy]

Yes it was & is only running in class 'A' upto a certain wattage then reverts to 'AB'...MF never claimed it a pure class 'A' amp.I remember reviews of this amp saying it will easily drive the most difficult of speakers.Hated mine, i think the 'M50's were monoblock versions with bigger power supplies.

wrong!

It is neither class A or B, all class AB means is that it is both, for some of its voltage bandwidth it runs in A and for some it runs in B. It starts in A and you set the quiescent current to bias the circuit. High quiescent current means it stay in Class A longer, in the case of the MF A1 up to about 15w after that it is *pure* class B. Originally the AB circuit design was configured to get over the low level switching characteristics of a class B circuit which induces odd harmonic distortion. Then some bright marketing spark got the idea of creating a poor mans class A amplifier by increasing the bias. But it ain't the real thing. But it is just one aspect of design and it is ony because of the public perception of terms that the marketing men have their day and earn their oats. Well A must be better than AB or B mustn't it!! I mean it is in our language, even from school "getting an A", well that is what marketing is for

[Vinyl Grinder]

wrong!

It is neither class A or B, all class AB means is that it is both, for some of its voltage bandwidth it runs in A and for some it runs in B. It starts in A and you set the quiescent current to bias the circuit. High quiescent current means it stay in Class A longer, in the case of the MF A1 up to about 15w after that it is *pure* class B. Originally the AB circuit design was configured to get over the low level switching characteristics of a class B circuit which induces odd harmonic distortion. Then some bright marketing spark got the idea of creating a poor mans class A amplifier by increasing the bias. But it ain't the real thing. But it is just one aspect of design and it is ony because of the public perception of terms that the marketing men have their day and earn their oats. Well A must be better than AB or B mustn't it!! I mean it is in our language, even from school "getting an A", well that is what marketing is for

It is a class AB design, the quiescent current is set high enough to ensure class 'A' upto a certain wattage which is around 8 watt.

[spendorman]

The high voltage capacitors I bought from him last year were fine and terrific value.

That pre amp looks brilliant, certainly for the money. Are you going to get a power amp boards from him?

If you do, I dont suppose it will be the NAD!!

This guy certainly has some interesting stuff very cheap. He now has assembled copy Quad 405 boards. Not sure what op amps are in them though. I bet the boards will be OK though.

Starange u mention him as i bought one of these:

http://cgi.ebay.co.uk/NE5532-HI-FI-S...742.m153.l1262

I think those pots will hit the rubbish bin first of all..

[WikiBoy]

It is a class AB design, the quiescent current is set high enough to ensure class 'A' upto a certain wattage which is around 8 watt.

You said it was class A and then became class AB, I said you were wrong. Are you saying you are right? If so please explain how an AB works as an entity and what is working in AB, as I think you have discovered something new in the world of elctronics, and I am always open to learn.

[Vinyl Grinder]

You said it was class A and then became class AB, I said you were wrong. Are you saying you are right? If so please explain how an AB works as an entity and what is working in AB, as I think you have discovered something new in the world of elctronics, and I am always open to learn.

Richard:
The 'A1' is around a 20 watter,it runs class 'A' up to around 8watt/8 Ohm, after that it runs into class 'A/B'..You said that ''all class AB means is that it is both'', no it's not..Class 'A' runs at 100% input, Class 'B' 50% input, 'A'/'B' runs more than 50%, less than 100% so it's neither 'A' or 'B', compromise if you like...

[WikiBoy]

Richard:
The 'A1' is around a 20 watter,it runs class 'A' up to around 8watt/8 Ohm, after that it runs into class 'A/B'..You said that ''all class AB means is that it is both'', no it's not..Class 'A' runs at 100% input, Class 'B' 50% input, 'A'/'B' runs more than 50%, less than 100% so it's neither 'A' or 'B', compromise if you like...

Complete nonsense and lack of knowledge in how an amplifier works. There is no such thing as working in AB, it simply doesn't exist.

A little lesson, which may help.

First there was class A, simply called that because it was the first amplifier circuit designed. Then there was class B, simply called that because it was the second type of amplifier circuit designed. Then there was class C - D - E and F, there may even be more. No one designed a class AB as such it is a misnomer it does not exist, it is A sometimes B others, an amplifier *cannot* work in class AB.

Class AB is a compromise. It is normally an amp that is only biased to make a class B amp work up to about a watt or less in double ended class A in order to get the output transistors over the non linear part of their operation i.e. the point where the signal is switched between the two devices (or more if totem poled). The problem occures because transistors have a switch on resistance which gives a time lag between devices and creates distortion. This happens when the signal passes OV or earth ref. By biasing the transistor to work in parallel class A for a few milliwatts you get over that portion of the transistors work where it is non linear. You do this by setting a quiescent (constant) current across the transistor. That is a class AB, it is A until it switches to being B it is never in your fantasy non existing AB mode. All the MF A1 is is a class B amplifier design biased to stay in double ended class A until in theory 15w according to Tim, but maybe they lessened it to account for early failures of the product. Tim de P took the concept further at EAR by producing a single ended transistor class A amplifier, which was very clever and a bit of a bloody miracle it ever worked at all. I never heard it but a few that did said it had much in common (but not the same) with things like the single ended 300B valve amps.

There endeth the lesson, no charge, everything else refered to about amplifier class is marketing bullshit. Professional marketers love it, their oats depend on it, forum amateur marketers thrive on it, their egos depend on it.

PS another marketing BS is that class D means it is digital, 'fraid not it just means it is 4th in line in development timescale. It is a high speed switching amp.

[Vinyl Grinder]

Complete nonsense and lack of knowledge in how an amplifier works. There is no such thing as working in AB, it simply doesn't exist.

A little lesson, which may help.

First there was class A, simply called that because it was the first amplifier circuit designed. Then there was class B, simply called that because it was the second type of amplifier circuit designed. Then there was class C - D - E and F, there may even be more. No one designed a class AB as such it is a misnomer it does not exist, it is A sometimes B others, an amplifier *cannot* work in class AB.

Class AB is a compromise. It is normally an amp that is only biased to make a class B amp work up to about a watt or less in double ended class A in order to get the output transistors over the non linear part of their operation i.e. the point where the signal is switched between the two devices (or more if totem poled). The problem occures because transistors have a switch on resistance which gives a time lag between devices and creates distortion. This happens when the signal passes OV or earth ref. By biasing the transistor to work in parallel class A for a few milliwatts you get over that portion of the transistors work where it is non linear. You do this by setting a quiescent (constant) current across the transistor. That is a class AB, it is A until it switches to being B it is never in your fantasy non existing AB mode. All the MF A1 is is a class B amplifier design biased to stay in double ended class A until in theory 15w according to Tim, but maybe they lessened it to account for early failures of the product. Tim de P took the concept further at EAR by producing a single ended transistor class A amplifier, which was very clever and a bit of a bloody miracle it ever worked at all. I never heard it but a few that did said it had much in common (but not the same) with things like the single ended 300B valve amps.

There endeth the lesson, no charge, everything else refered to about amplifier class is marketing bullshit. Professional marketers love it, their oats depend on it, forum amateur marketers thrive on it, their egos depend on it.

PS another marketing BS is that class D means it is digital, 'fraid not it just means it is 4th in line in development timescale. It is a high speed switching amp.

Richard wtf are you contradicting most everything ive said. I have said the current has been set high enough to allow it to work in class 'A' .The amp is a CLASS AB design, i don't care what you claim it is.If you wanna argue it furthur i will encourgae an 'A1 specialist to come on here & give it how it is.