Just to throw a spanner in the works... and I have only skimmed through this thread...
If you are going down the Class A route because you feel it will offer a very different musical presentation or offer somehow "smoother" sound then you might be disappointed.
While Class A offers the promise of the best possible technical performance, that only applies if it's done correctly. Many a Class AB can out-perform a Class A on specs.
If you really are looking for something different then I would suggest knocking together a version of JLH's original 10watt Class A, not because it is just Class A but because it uses a different topology to more modern stuff in that it uses a single ended input stage. It will give you an idea on something different, a genuinely different kind of sound.
Forums etc are awash with folk with equipment that is technically pretty much beyond reproach... but they don't like the way it sounds. That's not always the fault of the equipment but more to do with the way we perceive sound and what we actually like to hear.
If you are going down the Class A route because you feel it will offer a very different musical presentation or offer somehow "smoother" sound then you might be disappointed.
While Class A offers the promise of the best possible technical performance, that only applies if it's done correctly. Many a Class AB can out-perform a Class A on specs.
If you really are looking for something different then I would suggest knocking together a version of JLH's original 10watt Class A, not because it is just Class A but because it uses a different topology to more modern stuff in that it uses a single ended input stage. It will give you an idea on something different, a genuinely different kind of sound.
Forums etc are awash with folk with equipment that is technically pretty much beyond reproach... but they don't like the way it sounds. That's not always the fault of the equipment but more to do with the way we perceive sound and what we actually like to hear.
What's that saying about a little bit of knowledge....
Most of your suggestions above would result in instant smoke release! maybe from the voice coils of your speakers as well when the amp goes DC.
There is no issue with the output from the NAD. It's fine.
Whatever design you settle on you need to follow it exactly and not be tempted to "modify" anything.
If you don't know why your above ideas are doomed to failure then you shouldn't mess with changing anything until you do!
Alright mate,
I see where you are coming from. I wasn't sure what the situation was when I go from the pre-amp's out's to the input of the power amp. Valid question (to me at least) and I am glad you have pointed me in the right direction. So thank you very much for that.
OK, so I can just go ahead and build the design and all will be fine. Slone says that this particular design works right every time, plug and play of the amplifier world I guess. He says it is a completely repeatable design time after time and doesn't fail.....provided I follow the schematic correctly and don't get the components the wrong way around. It has many inherent fail-safe's regarding the output devices and the THD, 2nd and 3rd harmonic spec's (I love the numbers game) are pretty fantastic. It is basically an op-amp buillt large from discrete components !!!!
I asked this question partly because of the output impedance of my pre-amp and the input impedance of the power amp and wasn't sure if matching these impedances was critical.
OK, just follow exactly and see where it goes. I would like to see if there are PCB's made for this particular design. In the back of Slone's book there are templates for the copper tracks of the PCB so I would need to find somewhere that could make these up for me, I would need two of them. The power supply is just a raw +- 50v affair, 500VA I think is suggested. Any ideas as to where I could get these PCB's made for a decent price Jez ??
Cheers mate
I see where you are coming from. I wasn't sure what the situation was when I go from the pre-amp's out's to the input of the power amp. Valid question (to me at least) and I am glad you have pointed me in the right direction. So thank you very much for that.
OK, so I can just go ahead and build the design and all will be fine. Slone says that this particular design works right every time, plug and play of the amplifier world I guess. He says it is a completely repeatable design time after time and doesn't fail.....provided I follow the schematic correctly and don't get the components the wrong way around. It has many inherent fail-safe's regarding the output devices and the THD, 2nd and 3rd harmonic spec's (I love the numbers game) are pretty fantastic. It is basically an op-amp buillt large from discrete components !!!!
I asked this question partly because of the output impedance of my pre-amp and the input impedance of the power amp and wasn't sure if matching these impedances was critical.
OK, just follow exactly and see where it goes. I would like to see if there are PCB's made for this particular design. In the back of Slone's book there are templates for the copper tracks of the PCB so I would need to find somewhere that could make these up for me, I would need two of them. The power supply is just a raw +- 50v affair, 500VA I think is suggested. Any ideas as to where I could get these PCB's made for a decent price Jez ??
Cheers mate
Well there is always the option of making the pcb's yourself.... plenty of info on this site and the interweb thing.
Or there are many specialist companies who just make pcb's. Try the yellow pages for a local one. Or you may well find pcb's for Sloanes designs on the likes of ebay as they are well known and widely copied... this would be the cheapest, easiest route! If you can't get ready-made pcb's then maybe another design that does have pcb's available would be better to start of with?
If making them yourself think in terms of at least £100+ in equipment plus a learning curve.
If getting a local specialist to do the job then you will probably be charged extra for taking the layout from a book and then making it into a form they can deal with. And you only want two of them..... £90 - 200 ? A lot of the cost is the setting up etc. If you then wanted more of them you would pay around £10 each.
Or there are many specialist companies who just make pcb's. Try the yellow pages for a local one. Or you may well find pcb's for Sloanes designs on the likes of ebay as they are well known and widely copied... this would be the cheapest, easiest route! If you can't get ready-made pcb's then maybe another design that does have pcb's available would be better to start of with?
If making them yourself think in terms of at least £100+ in equipment plus a learning curve.
If getting a local specialist to do the job then you will probably be charged extra for taking the layout from a book and then making it into a form they can deal with. And you only want two of them..... £90 - 200 ? A lot of the cost is the setting up etc. If you then wanted more of them you would pay around £10 each.
Well I have an inkjet printer and you can print the supplied PCB drawings onto some overhead projector acetates but I would have to make my own lightbox to expose the photo-sensitive copper board. Making the lightbox would be a doddle and far cheaper than to buy one. I wonder if it is worth my while doing this from the off because I am sure to be using it again in the future. I have priced a lightbox and it was about £150 to £200 with a timer built in for correct exposure. There is not much to one of these and I can build it easily (I think.. !!??!!) so what do you reckon ? I might aswell after looking at the prices you mention for PCB's and I am not sure if there are any places around here that offer those facilities.....it's grand living in the sticks !!
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