There are some rumblings in the big thread about folks trying a lower voltage, lower dissipation F5. There is a dedicated thread using 16V rails for F5X designs. But, I haven't seen much about folks actually trying a Mini F5.
I've got a Halfer chassis I'd like to use. But, I think the mini makes sense for quite a few folks in general. 10ish watts will do fine for many of us. You can save space, money on heatsinks, and quite a bit of carbon footprint (for those of us that care about such things).
12V transformers abound, so it seems like 16V rails should be the standard. It sounds like 2SK1530/2SJ201 (or 2SK1529/2SJ200 at a higher cost) might be the way to go. But, thoughts about bias? Resistor changes?
And more importantly, have folks actually built them?
Paul
I've got a Halfer chassis I'd like to use. But, I think the mini makes sense for quite a few folks in general. 10ish watts will do fine for many of us. You can save space, money on heatsinks, and quite a bit of carbon footprint (for those of us that care about such things).
12V transformers abound, so it seems like 16V rails should be the standard. It sounds like 2SK1530/2SJ201 (or 2SK1529/2SJ200 at a higher cost) might be the way to go. But, thoughts about bias? Resistor changes?
And more importantly, have folks actually built them?
Paul
from what i understand about it, with the standard F5 mosfets you will probably have more distortion with lower voltage
but maybe it would work better if driving smaller TO-220 mosfets hard
I have been looking at a lot of them, and thought of using them in multiples
in the end I realised it would not make sense
but i never thought of using them for a 'mini-F5'
but maybe it would work better if driving smaller TO-220 mosfets hard
I have been looking at a lot of them, and thought of using them in multiples
in the end I realised it would not make sense
but i never thought of using them for a 'mini-F5'
If we are looking at 16V rails and about 1A total bias per channel, 3 pairs of 2sk2013/2sj313 are better solution than 1 pair of 2SK1530/2SJ201 from standpoint of transconductance vs. parasitic capacitances. Also, IME it sounds better.
It's more probable that you'll get 16V DC from 12V AC with 2A constant load (1A per channel) if you use schottky rectifiers (much lower voltage drop across them) like MBR745 or similar. Good filter caps (low ESR) help too.
It's more probable that you'll get 16V DC from 12V AC with 2A constant load (1A per channel) if you use schottky rectifiers (much lower voltage drop across them) like MBR745 or similar. Good filter caps (low ESR) help too.
Juma,
Thanks! I had seen that recommendation, but like other 'mini' talk, it is sort of scattered through threads and it isn't clear to me whether someone has actually tried it.
Silly question, but any worries about lead length or the way you hook the pairs up?
I know 16V may be a bit high, and I'm not terribly concerned about hitting that number. 1V doesn't seem like a big deal to those of us coming from the tube world, but I suppose it affects these operating points.
My goal here is in part to make an inexpensive F5. Schottkys are not that!
Paul
Thanks! I had seen that recommendation, but like other 'mini' talk, it is sort of scattered through threads and it isn't clear to me whether someone has actually tried it.
Silly question, but any worries about lead length or the way you hook the pairs up?
I know 16V may be a bit high, and I'm not terribly concerned about hitting that number. 1V doesn't seem like a big deal to those of us coming from the tube world, but I suppose it affects these operating points.
My goal here is in part to make an inexpensive F5. Schottkys are not that!
Paul
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Not at all - I used 20cm (8") wire lengths without problem (just solder gate resistors directly to the pin of the MOSFET). Look at the actual build pictures in the link provided by flg in post #4:
Novi amp sa 2SK2013/2SJ313 - Stranica 2 - Solid State - diyAudio.rs
http://www.diyaudio.com/forums/pass-labs/168040-f5-2sk2013-2sj313-6.html#post2665979
Not really. 15 or 16V rails don't make a difference - I just thought that it's important to you.
33 cents a piece makes them dirt cheap in anybody's book:
MBR745G - ON SEMICONDUCTOR MBR745G - SCHOTTKY RECTIFIER, 7.5A, 45V, TO-220AC | Newark element14 US
Besides, they'll run cooler (because of lower voltage drop).
EDIT:
MBR1040 are even better choice. Cheaper too:
MBR1040 - MULTICOMP MBR1040 - SCHOTTKY DIODE, 10A, 40V, TO-220A | Newark element14 US
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diodes are not expencive, but the 2013/313 might be
how about trying smaller 'automotive' output devices designed for lower voltage ?
Juma, nice photo with hardwired output
Hi Gareth,
Interesting but rather difficult to execute. Maintaining F5 basic concept of two stage amplification with bipolar outputs usually hit a brick wall of choice of available parts. Those with high enough beta are usually low current. Perhaps you have a suggestion on parts we have overlooked?
How big is your nice case? Perhaps my low power F5 mod may fit. Still on testing stage as posted in Recommendation 5-10W amp thread. As drawn, dissipation is about 25W total both channels. Should be stable with 1K/W heatsink, but bias can be reduced on smaller case.
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Hi All,
Just offering another possibility here: would an F5 with 24V rails but biased low, say 0.8-1.0A also give less heat dissipation + smaller transformer requirement and hence fit into a chassis with less heat sinking and space, but at the same time have the extra headroom in AB mode work better for driving speakers (not really a good idea for headphones though)?
Just offering another possibility here: would an F5 with 24V rails but biased low, say 0.8-1.0A also give less heat dissipation + smaller transformer requirement and hence fit into a chassis with less heat sinking and space, but at the same time have the extra headroom in AB mode work better for driving speakers (not really a good idea for headphones though)?
I agree, with 0.8A bias, a 200VA 18-0-18 Transformer would be about right (correct me if I am wrong), and from Antec website, the weight and dimensions of 300VA and 200VA transformers are as follows:
200VA
Weight: 6.0lb
Dimensions: 4.9" d x 2.5" h
300VA
Weight: 7.0lb
Dimensions: 5.0" d x 3.1" h
So the savings in space for transformer is quite minimal for this approach. It would just have less heat dissipation.
200VA
Weight: 6.0lb
Dimensions: 4.9" d x 2.5" h
300VA
Weight: 7.0lb
Dimensions: 5.0" d x 3.1" h
So the savings in space for transformer is quite minimal for this approach. It would just have less heat dissipation.
Correct, that would not be a good idea for headphones as it would have enough power to easily damage your hearing and destroy your headphones with just a slip of the volume control.
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