Guys,
Could we please limit our conversation strictly about this project, and avoid pitfalls from many other threads, where conversation gets derailed with personal attacks, and all kind of nastiness. There is enough excitement in this thread about this project, obviously many people are in need, support and of desire to do it, so PLEASE, lets not loose that momentum. We are going for it so please do not derail it with empty rhetoric. . Quite honestly, I could hardly recall any other effort where the complete solution is presented to people - boards, heatsinks and case. Yes, someone might learn some more by etching, sourcing and machining on his own, but there will be many that might get exhausted with the process.
This might be the chance for someone to learn, to assemble on his own and to complete the project. Than to take it to his living room and all happy to stare at it at some cold December night, all proud that he did it. F5 is the jewel of the amps, and balanced will drive many speakers out there with ease. What better project for someone who is starting?
Because of that, lets not make this 150 pages long, lets be open and concise so that anyone could easily get what they need. I will try to document every step, measurement and technic so that even a caveman could do it. Only that way someone will learn instead of spending more time in search and giving up in frustration. Having case and tapped heatsinks is 90% of the amp and that certainly will more than anything encourage people to do it, experience it and and learn from it.
Thank you
AR2
PS Variak, please keep an eye on this thread
Could we please limit our conversation strictly about this project, and avoid pitfalls from many other threads, where conversation gets derailed with personal attacks, and all kind of nastiness. There is enough excitement in this thread about this project, obviously many people are in need, support and of desire to do it, so PLEASE, lets not loose that momentum. We are going for it so please do not derail it with empty rhetoric. . Quite honestly, I could hardly recall any other effort where the complete solution is presented to people - boards, heatsinks and case. Yes, someone might learn some more by etching, sourcing and machining on his own, but there will be many that might get exhausted with the process.
This might be the chance for someone to learn, to assemble on his own and to complete the project. Than to take it to his living room and all happy to stare at it at some cold December night, all proud that he did it. F5 is the jewel of the amps, and balanced will drive many speakers out there with ease. What better project for someone who is starting?
Because of that, lets not make this 150 pages long, lets be open and concise so that anyone could easily get what they need. I will try to document every step, measurement and technic so that even a caveman could do it. Only that way someone will learn instead of spending more time in search and giving up in frustration. Having case and tapped heatsinks is 90% of the amp and that certainly will more than anything encourage people to do it, experience it and and learn from it.
Thank you
AR2
PS Variak, please keep an eye on this thread
adequacy of Conrad Heatsink
About April of this year I changed my dual mono F5, Fairchilds on Conrad MF35-151 heatsinks, into a balanced F5. Standard F5 voltage and bias currents. Now the sage advice is that if one can hold their hand on the heatsink, comfortably, for five seconds, then the heatsink is adequate. With the balanced F5 I could hold my hand on for two to three seconds. They were very hot. Ambient was 75F. I did take measurements of sinks at various positions and on tabs of mosfets. I did not save those readings, however I recall the temp on the mosfet tabs was in the safe zone, for longevity, as I found recommended somewhere on the F5 thread.
About six weeks ago I reverted back to the dual mono configuration. Well,
sonically there was more detail overall in the sonic picture. The loss just wasn't apparent for me when I went balanced. I venture a guess, that because of mismatches between the two amps in balanced mode, a veiling resulted.
About April of this year I changed my dual mono F5, Fairchilds on Conrad MF35-151 heatsinks, into a balanced F5. Standard F5 voltage and bias currents. Now the sage advice is that if one can hold their hand on the heatsink, comfortably, for five seconds, then the heatsink is adequate. With the balanced F5 I could hold my hand on for two to three seconds. They were very hot. Ambient was 75F. I did take measurements of sinks at various positions and on tabs of mosfets. I did not save those readings, however I recall the temp on the mosfet tabs was in the safe zone, for longevity, as I found recommended somewhere on the F5 thread.
About six weeks ago I reverted back to the dual mono configuration. Well,
sonically there was more detail overall in the sonic picture. The loss just wasn't apparent for me when I went balanced. I venture a guess, that because of mismatches between the two amps in balanced mode, a veiling resulted.
with my CD player I can choose between RCA "single ended" and balanced XLR
I decided a long time ago to let it stay in RCA single ended, and to forget about the balanced option
balanced may have some technical advantage
but it sounds too much of "hifi" to me
single ended sounds more natural to me
to me its common basics, and will always be like that
but balanced has to many become the ultimate
to me its way too overrated, and a myth
but Im sure its also about personal preference
a bit like tube amps vs solid state
horns vs dipole
ribbons vs dome tweeters
alu cone vs paper cone
and so on
but if your speakers are a way too heavy load for a 25watt, ofcourse a balanced with twice the power will sound better
but it doesnt mean its a better amp
or it could be just be a simple matter of SPL preferences
its similar with tube flea amps
every(almost) tube amp builder knows that the smaller the better
but speakers become another issue
or you could just say no free lunch
I decided a long time ago to let it stay in RCA single ended, and to forget about the balanced option
balanced may have some technical advantage
but it sounds too much of "hifi" to me
single ended sounds more natural to me
to me its common basics, and will always be like that
but balanced has to many become the ultimate
to me its way too overrated, and a myth
but Im sure its also about personal preference
a bit like tube amps vs solid state
horns vs dipole
ribbons vs dome tweeters
alu cone vs paper cone
and so on
but if your speakers are a way too heavy load for a 25watt, ofcourse a balanced with twice the power will sound better
but it doesnt mean its a better amp
or it could be just be a simple matter of SPL preferences
its similar with tube flea amps
every(almost) tube amp builder knows that the smaller the better
but speakers become another issue
or you could just say no free lunch
> Which precision for the feedback resistors?
Closed loop gain should be matched to better than 1% (0.1dB).
The 55R (50R in NP F5) is made up of 4x 220R 1W PRP in parallel.
The 11R (10R in NP F5) is made up of 3x 33R 0.25W PRP in parallel.
Standard PRPs are 1% I believe.
So by paralleling you are automatically getting 0.5% for 55R and 0.6% for 11R.
But since you will need 16x 220R and 12x 33R for 2 channels, you can of course measure and then pair them to get 4 identical sets.
And I bet you will have little problem getting below 0.1% match.
Absolute values are not important.
Patrick
Closed loop gain should be matched to better than 1% (0.1dB).
The 55R (50R in NP F5) is made up of 4x 220R 1W PRP in parallel.
The 11R (10R in NP F5) is made up of 3x 33R 0.25W PRP in parallel.
Standard PRPs are 1% I believe.
So by paralleling you are automatically getting 0.5% for 55R and 0.6% for 11R.
But since you will need 16x 220R and 12x 33R for 2 channels, you can of course measure and then pair them to get 4 identical sets.
And I bet you will have little problem getting below 0.1% match.
Absolute values are not important.
Patrick
> I decided a long time ago to let it stay in RCA single ended, and to forget about the balanced option
That discussion we had a long time ago with Aleph and Aleph-X.
It is always a personal choice with audio.
Suffice to say that almost all top of the line Hi-End equipment are balanced from Source to Power amp these days.
Of course it also raise the price & the profit, as a side effect.
Patrick
That discussion we had a long time ago with Aleph and Aleph-X.
It is always a personal choice with audio.
Suffice to say that almost all top of the line Hi-End equipment are balanced from Source to Power amp these days.
Of course it also raise the price & the profit, as a side effect.
Patrick
http://www.passdiy.com/pdf/zenamp.pdf
http://www.passdiy.com/pdf/powersupply.pdf
http://www.passdiy.com/pdf/zen-ver3.pdf
Audio Power Amplifier Design Handbook - Google Books
ESP Projects Pages - DIY Audio and Electronics - Power Supplies
DIY Audio Articles
The Class-A Amplifier Site
Power Supplies - diyAudio
http://www.passdiy.com/pdf/powersupply.pdf
http://www.passdiy.com/pdf/zen-ver3.pdf
Audio Power Amplifier Design Handbook - Google Books
ESP Projects Pages - DIY Audio and Electronics - Power Supplies
DIY Audio Articles
The Class-A Amplifier Site
Power Supplies - diyAudio
you'll have up to 1,22 xVac
look here :
Duncan's Amp Pages
download PSUD2
and play ; help is pretty informative , so don't skip it
I did some simulation and extrapolation from previous builds and come to a heat sink temperature rise of 45~55°C above ambient for dissipation of 145W, which is indeed a bit high. So the concern was well justified.
The MOSFET itself has a thermal resistance of 0.83°C/W, or 27°C rise at 32W. Give another 5°C for Kerafoil insulation. For ambient temperature of 25°C, the junction temperature would be 112°C. So too high for my own taste.
Need experimental verification. Not easy to solve without increasing cost (larger heatsinks and case) or reducing wife acceptance factor (fans on the outside).
Back to the drawing board.
Patrick
The MOSFET itself has a thermal resistance of 0.83°C/W, or 27°C rise at 32W. Give another 5°C for Kerafoil insulation. For ambient temperature of 25°C, the junction temperature would be 112°C. So too high for my own taste.
Need experimental verification. Not easy to solve without increasing cost (larger heatsinks and case) or reducing wife acceptance factor (fans on the outside).
Back to the drawing board.
Patrick
OK, possibly a simple solution.
Add 2 more smaller heatsinks on the inside surfaces of the front and rear plate, something like 250 x 150 x 25mm.
E.g. Fischer SK49-150. Costs 40 Euros extra, but gets the temperature down to 35°C above ambient.
Small price to pay than to go to 400mm sinks (and hence larger housing in all dimensions)
Test on Conrad still useful.
Patrick
PS
Any of the previous mentioned commercial housings from Schuro & Hifi200 has essentially the same heatsink as Conrad MF35-151.
So none of them will do in any case.
Add 2 more smaller heatsinks on the inside surfaces of the front and rear plate, something like 250 x 150 x 25mm.
E.g. Fischer SK49-150. Costs 40 Euros extra, but gets the temperature down to 35°C above ambient.
Small price to pay than to go to 400mm sinks (and hence larger housing in all dimensions)
Test on Conrad still useful.
Patrick
PS
Any of the previous mentioned commercial housings from Schuro & Hifi200 has essentially the same heatsink as Conrad MF35-151.
So none of them will do in any case.
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> and pretty much toasted inside of the amp ;
Not if you have enough ventilation slots.
> quality just doesn't go without proper investment , and even GB project can't avoid that. better go for bigger heatsinks ,
That I totally agree, but variac is already concerned the price is too high that will scare people off.
And I am only doing this on the forum's request.
> with proper ventilation holes on top and bottom plate .
That goes without saying.
Patrick
Not if you have enough ventilation slots.
> quality just doesn't go without proper investment , and even GB project can't avoid that. better go for bigger heatsinks ,
That I totally agree, but variac is already concerned the price is too high that will scare people off.
And I am only doing this on the forum's request.
> with proper ventilation holes on top and bottom plate .
That goes without saying.
Patrick
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