Right. Wayne you asked my question right out of your hands.
Would like to know which one is better for 90 db 8 ohm speakers.
Standard, double output, cascode version.
Thanks
Pandu
Biasing does two things with the F5 - this does not hold true for all amps - it alters the sonic presentation and it sets the maximum current which in turn sets the lowest Z load that will still be in class A all the time.
Regarding the sonics, I am sad to report that on this one I am mostly an "armchair general". While I have a complete amp waiting to be built (actually 4) my personal situation had precluded my taking any action. Drat!
However, my audio friend Rick built one pretty early on and showed me what he did. He did it all, but he used my system as the "reference" so we talked about what was what and he brought it over after each change.
That's in another thread that I started on the F5 that would be here:
F5 Listening Impressions Thread
In general terms the amp is something of a chameleon - it comes out differently depending on how it is built. It seems to range from a bit dull and muddy up through a bit bright. However I did personally find that Rick was able to present a version that on my compression drivers had tremendous HF energy but with NO sibilance. Quite a feat.
Pretty incredible for an amp with no parts and that I dismissed early on as another NP "throwaway DIYer design".
Bias, output devices, matching, resistors and power supply all factor in directly.
_-_-bear
Regarding the sonics, I am sad to report that on this one I am mostly an "armchair general". While I have a complete amp waiting to be built (actually 4) my personal situation had precluded my taking any action. Drat!
However, my audio friend Rick built one pretty early on and showed me what he did. He did it all, but he used my system as the "reference" so we talked about what was what and he brought it over after each change.
That's in another thread that I started on the F5 that would be here:
F5 Listening Impressions Thread
In general terms the amp is something of a chameleon - it comes out differently depending on how it is built. It seems to range from a bit dull and muddy up through a bit bright. However I did personally find that Rick was able to present a version that on my compression drivers had tremendous HF energy but with NO sibilance. Quite a feat.
Pretty incredible for an amp with no parts and that I dismissed early on as another NP "throwaway DIYer design".
Bias, output devices, matching, resistors and power supply all factor in directly.
_-_-bear
Makes no real difference into 8ohms EXCEPT that they may sound a bit different.
The cascode version can run slightly higher rail voltages, but that means more heat.
Doubled up outputs may sound different again, and are best for situations where the load drops below 8 ohms (or whatever ur bias point is...). But matching IS important.
There are some boards that permit both the cascode and the double outputs, or NOT (CViller does...). So you can build with whatever options you want to try, or try them all eventually.
This is where ur layout will count in terms of how easy it is to work on it and change things. You can socket the JFets for example...
I would not think too hard about these things.
Just go ahead an build a version.
Don't make the first version the "final" and fancy one, make it so that the amp works, and get a feel for it before you commit to a fixed package.
Rick built his on wood pieces. Looks like hell, works great!
Maybe the "good chassis" will ruin the sound? Dunno, could happen.
_-_-bear
You need to read the original article again, not the thread. First Watt's article. It explains the biasing.
The short answer is that the biasing is going to vary a small amount around a particular current that sets the amp up for Class A operation.
_-_-bear
Quite of a load? If ur speakers are below a particular Z then this amp is not suitable without extensive modifications, in which case it is not an F5 any longer...
Could you please tell me where to find the original article?
I think it will handle them ok, they're just not super - easy...
(Spendor S8e)
In the DIY world, playing is the game.
Personally the F5 didn't do it for me, that is MY decision and I opted for the more powerful Aleph 4.
If you think ahead you can build both at minimal loss / wastage.
Buy or build a case that is suitable for both and buy heatsinks that can be added to at a later date.
The only expensive components that cannot be re-used are the transformer(s).
You can build the F5 with 63V caps so that they could be re-used in a more powerful amp.
The only wastage is the PCBs and the components - I'm sure if you are not happy with the F5 you could EASILY sell them here. They only cost about 40 Euros to put together. You'd need to sell the transformers too and increase their voltage but again there are lots of F5 fans that would SNAP them up.
Personally the F5 didn't do it for me, that is MY decision and I opted for the more powerful Aleph 4.
If you think ahead you can build both at minimal loss / wastage.
Buy or build a case that is suitable for both and buy heatsinks that can be added to at a later date.
The only expensive components that cannot be re-used are the transformer(s).
You can build the F5 with 63V caps so that they could be re-used in a more powerful amp.
The only wastage is the PCBs and the components - I'm sure if you are not happy with the F5 you could EASILY sell them here. They only cost about 40 Euros to put together. You'd need to sell the transformers too and increase their voltage but again there are lots of F5 fans that would SNAP them up.
If you listen at LOW VOLUME and have VERY EFFICIENT speakers then the reviews are VERY encouraging.
If you listen at HIGH VOLUME and your speakers are VERY INEFFICIENT then the reviews are less encouraging.
There are a lot of VERY impressed builders out there. What they are comparing their builds to is unknown.
I compare my Aleph 4 to my Highly Modified Arcam AVR350. PRAISE Nelson Pass, the Aleph 4 is ABSOLUTELY STUNNING compared to the "run-of-the-mill" sound from the Arcam.
Pass do make BEAUTIFUL sounding amplifiers.
In High-End Hi-Fi you often start to have to match the components together. Is it this level that you can start to hear the differences between interconnects that the fanatics are talking about.
If you listen at HIGH VOLUME and your speakers are VERY INEFFICIENT then the reviews are less encouraging.
There are a lot of VERY impressed builders out there. What they are comparing their builds to is unknown.
I compare my Aleph 4 to my Highly Modified Arcam AVR350. PRAISE Nelson Pass, the Aleph 4 is ABSOLUTELY STUNNING compared to the "run-of-the-mill" sound from the Arcam.
Pass do make BEAUTIFUL sounding amplifiers.
In High-End Hi-Fi you often start to have to match the components together. Is it this level that you can start to hear the differences between interconnects that the fanatics are talking about.
I get your point. I feel Alpeh4 is little too much for my place. It will turn out be a furnace generating about 600 to 800 watts of heat continously.
My place has 9 months of summer to 3 months of winter. Is there any other design which will get me 50 W class A.
Thanks
Pandu
The Aleph 4 pumps out about 400 W of heat. Mine actually measures 350W in its bi-mono version.
I've calculated my heatsinks to run at 45 Degrees during the winter months. During the summer they run at closer to 60 Degrees.
I believe that the production version runs between 80 and 85 Degrees C.
Hopefully my caps will last a bit longer than a production version.
In high ambient temperatures you may have to consider adding fans. they can be relatively quiet if run at lower voltages than they are rated at - you can always be clever and feed the fans from a temperature controller.
I've calculated my heatsinks to run at 45 Degrees during the winter months. During the summer they run at closer to 60 Degrees.
I believe that the production version runs between 80 and 85 Degrees C.
Hopefully my caps will last a bit longer than a production version.
In high ambient temperatures you may have to consider adding fans. they can be relatively quiet if run at lower voltages than they are rated at - you can always be clever and feed the fans from a temperature controller.
Please don't get blinded by the fact that my speakers are horribly INEFFICIENT and are POWER HUNGRY. They also drop to less than 2 Ohms as a load - hence the 6 x MOS-FETs (12 if you count the current sources) in each output stage of the Aleph suit them down to the ground.
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Have a look at http:\\www.kk-pcb.com
Although his PCBs don't get good press, you can see some of the other Pass DIY amplifiers that are available to build.
Then just do a search for each amp on Google to see if anyone has posted a build and their experiences.
The Pass amps are beautiful in their simplicity and Nelson supports each and every build (I hope).
There is a Pass amplifier for everybody.
The Aleph 5 is a scaled down version of the Aleph 4. (Not sure of the exact maths but it looks about 75W RMS) and there is the Aleph 3 which is scaled down even further.
The beauty of these designs is that they (largely) share the same drive electronics (with minor modifications)
Although his PCBs don't get good press, you can see some of the other Pass DIY amplifiers that are available to build.
Then just do a search for each amp on Google to see if anyone has posted a build and their experiences.
The Pass amps are beautiful in their simplicity and Nelson supports each and every build (I hope).
There is a Pass amplifier for everybody.
The Aleph 5 is a scaled down version of the Aleph 4. (Not sure of the exact maths but it looks about 75W RMS) and there is the Aleph 3 which is scaled down even further.
The beauty of these designs is that they (largely) share the same drive electronics (with minor modifications)
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