Would this be suitable for the tweeter amp:
http://sound.westhost.com/project36.htm
It technically specs worse than most class AB designs (distortion figures), but could I expect a smoother sound? Is 10-20W really enough tweeter power (at 92db)?
That design certainly looks achievable with the PCB available too but I would be restricted to the 3055 transistors since the MJL4281 devices arn't really available to me (£15 delivery charge from US). I doubt that makes a lot of difference except mabye limiting the power a bit more (35v might be best). One nice thing about this is that where the output coupling capacitor is usually a large electro, I can use a nice reasonably sized plastic film cap since the frequency is only high; that cap will need to be there regardless of design so its not a problem.
http://sound.westhost.com/project36.htm
It technically specs worse than most class AB designs (distortion figures), but could I expect a smoother sound? Is 10-20W really enough tweeter power (at 92db)?
That design certainly looks achievable with the PCB available too but I would be restricted to the 3055 transistors since the MJL4281 devices arn't really available to me (£15 delivery charge from US). I doubt that makes a lot of difference except mabye limiting the power a bit more (35v might be best). One nice thing about this is that where the output coupling capacitor is usually a large electro, I can use a nice reasonably sized plastic film cap since the frequency is only high; that cap will need to be there regardless of design so its not a problem.
Hi Dr,
92db/W/m and 20W will give about 100db max SPL @ 2.4m listening position.
That is a bit low if you ever turn the wick up. Effectively it limits your system SPL to about 80db average and it's the treble amplifier that starts to clip first. It sounds horrible with clean source.
The idea of ClassA whether single ended or push pull for the treble is certainly worth pursuing.
The ONsemi deal is actually fairly competitive for good transistors here in the UK.
5 off MJ4281/4302 + 5 off BD139 for the cost of US postage is not crippling. Don't go with 3055, even 2sa1943/c5200 which are available in the UK will do much better. Or what about MJ21194 Those power houses are intermediate in speed and when run in single ended will probably sound quite nice. Being 200degC and 250W, they will allow a touch more power if you want it.
What about trying for a 30W and 95db/W/m combination?
92db/W/m and 20W will give about 100db max SPL @ 2.4m listening position.
That is a bit low if you ever turn the wick up. Effectively it limits your system SPL to about 80db average and it's the treble amplifier that starts to clip first. It sounds horrible with clean source.
The idea of ClassA whether single ended or push pull for the treble is certainly worth pursuing.
The ONsemi deal is actually fairly competitive for good transistors here in the UK.
5 off MJ4281/4302 + 5 off BD139 for the cost of US postage is not crippling. Don't go with 3055, even 2sa1943/c5200 which are available in the UK will do much better. Or what about MJ21194 Those power houses are intermediate in speed and when run in single ended will probably sound quite nice. Being 200degC and 250W, they will allow a touch more power if you want it.
What about trying for a 30W and 95db/W/m combination?
Thanks for the advice. I see the 2SC5200 listed here:
http://www.rapidonline.com/producti...er4=High+power+NPN+transistors&moduleno=66252
Thats a perfecty reasonable price to me and should fit straight on the PCB. 35V operation seems most likely for me to use (rectified 25vac).
People seem keen on persuing class A for the tweeter amplification in particular, but what is the actual advantage? Is it simply something you'd have to hear to understand? If it helps alleviate harshness in the sound then its certainly something I want to persue too
I ran some numbers quickly and with my chosen fairly low sensitivity mid I get about the same SPL as the tweeter will produce (ran on 16W) as the mid can at 100W . One thing that I noticed was on Rods own tri-amplified system he noted tweeter power much lower than mid or woofer power with normal (music?) sources. I doubt i'd get much chance to run this up at any real volume so I expect the advantages of the class A outwiegh SPL limitations for me (though its nice to know a system can produce much higher output when called for ).
http://www.rapidonline.com/producti...er4=High+power+NPN+transistors&moduleno=66252
Thats a perfecty reasonable price to me and should fit straight on the PCB. 35V operation seems most likely for me to use (rectified 25vac).
People seem keen on persuing class A for the tweeter amplification in particular, but what is the actual advantage? Is it simply something you'd have to hear to understand? If it helps alleviate harshness in the sound then its certainly something I want to persue too
I ran some numbers quickly and with my chosen fairly low sensitivity mid I get about the same SPL as the tweeter will produce (ran on 16W) as the mid can at 100W
. One thing that I noticed was on Rods own tri-amplified system he noted tweeter power much lower than mid or woofer power with normal (music?) sources. I doubt i'd get much chance to run this up at any real volume so I expect the advantages of the class A outwiegh SPL limitations for me (though its nice to know a system can produce much higher output when called for ).The averaged power delivered to each of the frequency bands gives little clue to the peak SPL from each of the frequency bands.
No matter how much science one puts into gathering averaged voltage or averaged power to display as data tables or coloured graphs, the information gets no where near predicting the peak levels.
It's that sort of averaged data that has been misinterpreted by many in selecting power for the various channels. This averaged information is very useful for designing the PSU to supply each amplifier for each frequency band.
The voltage drive for each frequency band is what should determine the amplifier capability.
Don't copy "Disco" style amplifier set ups or you'll end up with "disco sound". All bass (great for dancing) and searing, clipped treble that never resembles real treble information.
No matter how much science one puts into gathering averaged voltage or averaged power to display as data tables or coloured graphs, the information gets no where near predicting the peak levels.
It's that sort of averaged data that has been misinterpreted by many in selecting power for the various channels. This averaged information is very useful for designing the PSU to supply each amplifier for each frequency band.
The voltage drive for each frequency band is what should determine the amplifier capability.
Don't copy "Disco" style amplifier set ups or you'll end up with "disco sound". All bass (great for dancing) and searing, clipped treble that never resembles real treble information.
I suppose bridging is a potential option. Using a lower than 30V supply to achive around 60wpc might be possible in cooling terms.
Fanless cooling gets difficult with so much dissipation though. This sink:
http://uk.farnell.com/jsp/search/productdetail.jsp?sku=4105990
With 2 of these fans:
http://www.noctua.at/main.php?show=productview&products_id=9&lng=en
gets enough cooling in a reasonable space for the 4 amps when bridged at about 20-25v I reckon (can always play with fan speed). Run at lower speeds those fans just about qualify as silent. I have the 120mm in my case and before installing it I tried it out and at the lower speed I really couldn't hear it much over a metre away. So although I don't find fans attractive for cooling amps I guess it would be acceptable. The "bearing" on those also last about 20 years without degredation which is nice.
However, as a whole it seems all I would be doing is ensuring the mid clips before the treble since the mid produces the same output from its 100W amp as the tweeter will from its 16W due to sensitivity. I could up the mid power a little however its already over the specified limit (I figured I could go a little over it since it will only be handling over 250hz band).
Fanless cooling gets difficult with so much dissipation though. This sink:
http://uk.farnell.com/jsp/search/productdetail.jsp?sku=4105990
With 2 of these fans:
http://www.noctua.at/main.php?show=productview&products_id=9&lng=en
gets enough cooling in a reasonable space for the 4 amps when bridged at about 20-25v I reckon (can always play with fan speed). Run at lower speeds those fans just about qualify as silent. I have the 120mm in my case and before installing it I tried it out and at the lower speed I really couldn't hear it much over a metre away. So although I don't find fans attractive for cooling amps I guess it would be acceptable. The "bearing" on those also last about 20 years without degredation which is nice.
However, as a whole it seems all I would be doing is ensuring the mid clips before the treble since the mid produces the same output from its 100W amp as the tweeter will from its 16W due to sensitivity. I could up the mid power a little however its already over the specified limit (I figured I could go a little over it since it will only be handling over 250hz band).
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.