Hey guys,
i just need some basic info on my NAD 310 integrated amplifier, which by the way serves me well, since i began very interested in it`s circuit topology.. i know that it`s a hybrid (NMOSFET w bipolar) design but i cant` really understand how it operaters in this particular model.. is it like a class AB or something else.. so if anyone here could give me some info about this "strange" transistor implementation, i would be very happy..
Here`s the schematics picture..
http://img526.imageshack.us/img526/9905/nad310schxb3.jpg
Cheers,
Filip
i just need some basic info on my NAD 310 integrated amplifier, which by the way serves me well, since i began very interested in it`s circuit topology.. i know that it`s a hybrid (NMOSFET w bipolar) design but i cant` really understand how it operaters in this particular model.. is it like a class AB or something else.. so if anyone here could give me some info about this "strange" transistor implementation, i would be very happy..
Here`s the schematics picture..
http://img526.imageshack.us/img526/9905/nad310schxb3.jpg
Cheers,
Filip
This is a very interesting circuit... it's single ended AC coupled which is the obvious feature... less obvious is the fact that this "single ended" input stage, as opposed to a long tailed pair generates even harmonic distortion... which is great for sound quality.
The output stage is class ab and very unusual in that it eliminates a push pull driver stage... I think that's the reason for "having" to use a FET as the top device, as it's drive requirements are modest. Again this will generate distortion... but it's the "right" sort. I imagine it sounds fantastic... very musical.
Even more unusual... I might post a link to this is the "cross coupling" between channels. Look at the output and R255 and C225 and R256 and C226... why ?
Edit... have linked another thread to this one. It's worth discussing
The output stage is class ab and very unusual in that it eliminates a push pull driver stage... I think that's the reason for "having" to use a FET as the top device, as it's drive requirements are modest. Again this will generate distortion... but it's the "right" sort. I imagine it sounds fantastic... very musical.
Even more unusual... I might post a link to this
is the "cross coupling" between channels. Look at the output and R255 and C225 and R256 and C226... why ?Edit... have linked another thread to this one. It's worth discussing
Last edited:
The link is now showing up for me. But going by what you have said in the other linked post, I wonder if only HF is cross-coupled between left and right channels, not having seen the schematic, then it might be for the "wide-stereo" effect which was prevailent in some Japanese equipment of the early 1990s.
It's very strange for sure...
I know the "wide stereo" effect you mean, isn't that done with out of phase signals though, this is more like deliberately introducing a known level of crosstalk, which in itself should be inaudible.
I have wondered how important having the same level of crosstalk between L-R and R-L is for image stability. Could this be something to do with that, to reinforce the stereo image although the effect at those frequencies would be minute I would think.
I know the "wide stereo" effect you mean, isn't that done with out of phase signals though, this is more like deliberately introducing a known level of crosstalk, which in itself should be inaudible.
I have wondered how important having the same level of crosstalk between L-R and R-L is for image stability. Could this be something to do with that, to reinforce the stereo image although the effect at those frequencies would be minute I would think.
I`ve found something interesting on net.. Review | NAD 310 integrated amplifier Geoffrey Horn for themselves and a considerable number of friends, particularly amongst the student community, by marketing a range of high fidelity units, or 'separates' at very low prices. These units invariabl
it`s a 310`s review in which there is the original NAD`s quote about little 310 :
"(Previous) circuitry, being the most limiting factor, was disposed of, to be replaced with a single ended, pure 'Class A' driver stage. This in turn drives a complementary set of output transistors, one N channel MosFet and the other a state-of-the-art PNP bipolar transistor. Through careful and limited local feedback around these transistors their characteristics are accurately matched. The result is an amplifier with approximately half theumber of components and an increase in efficiency of almost 20% when compared to other amplifiers of similar price or specification. This reduction permits the use of higher quality cornponents ..."
it`s a 310`s review in which there is the original NAD`s quote about little 310 :
"(Previous) circuitry, being the most limiting factor, was disposed of, to be replaced with a single ended, pure 'Class A' driver stage. This in turn drives a complementary set of output transistors, one N channel MosFet and the other a state-of-the-art PNP bipolar transistor. Through careful and limited local feedback around these transistors their characteristics are accurately matched. The result is an amplifier with approximately half theumber of components and an increase in efficiency of almost 20% when compared to other amplifiers of similar price or specification. This reduction permits the use of higher quality cornponents ..."
Ok.. thank you Mooly!
Anyway, i was thinking about refreshing this little gem with some new capacitors.. the original values for 4 main caps are 4700/63v/85 c .. do you think i should better get some increased values caps? I also think they should be upgraded with some 105 c values because the one cap that sits close to the transistor layout gets hotter than the other (because of the unusual caps design in the preamp section)... what do you think about all of this?
Cheers,
Filip
Anyway, i was thinking about refreshing this little gem with some new capacitors.. the original values for 4 main caps are 4700/63v/85 c .. do you think i should better get some increased values caps? I also think they should be upgraded with some 105 c values because the one cap that sits close to the transistor layout gets hotter than the other (because of the unusual caps design in the preamp section)... what do you think about all of this?
Cheers,
Filip
It's worth changing electroylitics on anything that's over a few years old... particularly if they run hot.
Increasing the value of the caps isn't always a good idea. Like in everything there are trade offs. The larger the cap the less they discharge "between" cycles as the bridge rectifier "top up" the caps.... in some ways a good thing as the ripple will be slightly less. The problem is the same amount of energy has to be put back in those caps and so the conduction angle of the bridge is now less, and that means the charging current are now much higher. That increases power dissipation in any wiring, and the transformer etc so on balance it's probably best to leave them as they are value wise...
Having said that it's a case of finding what will fit... there's nothing worse than parts with wires tagged on etc because they don't fit... so although I wouldn't go below 4700uf a 6800 would be OK... but I wouldn't go any higher for the reasons given.
Look out for 105 degree caps with a low E.S.R. rating... the equivalent series resistance.
I would replace all the electroylitics in the amp tbh with 105 degree types, but do make sure you choose physically similar parts so that they fit perfectly... most suppliers give the lead spacings and size so have a measure and get some ordered. Choose good quality parts such as Panasonics or Nichicons Rubycons etc
Increasing the value of the caps isn't always a good idea. Like in everything there are trade offs. The larger the cap the less they discharge "between" cycles as the bridge rectifier "top up" the caps.... in some ways a good thing as the ripple will be slightly less. The problem is the same amount of energy has to be put back in those caps and so the conduction angle of the bridge is now less, and that means the charging current are now much higher. That increases power dissipation in any wiring, and the transformer etc so on balance it's probably best to leave them as they are value wise...
Having said that it's a case of finding what will fit... there's nothing worse than parts with wires tagged on etc because they don't fit... so although I wouldn't go below 4700uf a 6800 would be OK... but I wouldn't go any higher for the reasons given.
Look out for 105 degree caps with a low E.S.R. rating... the equivalent series resistance.
I would replace all the electroylitics in the amp tbh with 105 degree types, but do make sure you choose physically similar parts so that they fit perfectly... most suppliers give the lead spacings and size so have a measure and get some ordered. Choose good quality parts such as Panasonics or Nichicons Rubycons etc
310
Hi !
I've got one. Like it very much. Simple, and functional. Sounds great.
He's the "piece of resitánce" from an insane audiophile era!
But I have an idea about this amp, since the day I got it....
- remove the pre-amp, and turn it into an amp. Swap some components with ones with better quality.
It's possible??
best regards
Hi !
I've got one. Like it very much. Simple, and functional. Sounds great.
He's the "piece of resitánce" from an insane audiophile era!
But I have an idea about this amp, since the day I got it....
- remove the pre-amp, and turn it into an amp. Swap some components with ones with better quality.
It's possible??
best regards
I have start a new thread concerning the actually subject:
http://www.diyaudio.com/forums/soli...l-kind-thd-mosfet-bjt-new-me.html#post2140251
http://www.diyaudio.com/forums/soli...l-kind-thd-mosfet-bjt-new-me.html#post2140251
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