Tube amps = too expensive, draw loads of power, prone to overheating and dangerous to service. The FET Sansui amp I've got sounds brill compared to the MOSFET Skytronic amp. Infact if memory serves me well, the original Skytronic amp which blew at the beginnning of this thread sounded better than my current one and was much less harsh on the highs... and I'm pretty sure it's not cos of the piezo tweeters cos they sound fine on the Sansui amp.
Skytronic is equal to this price point http://www.diyaudio.com/forums/solid-state/167693-inside-no-brand-pa-amp.html
Turns out no MOSFET and other misleading specs.
Sight unseen proly the best indicator of quality/durability or lack there of, can be gauged by weight rather than $/watt.
Turns out no MOSFET and other misleading specs.
Sight unseen proly the best indicator of quality/durability or lack there of, can be gauged by weight rather than $/watt.
I'm not sure of your pre-conceptions...
My new Sweet Peach was £185 delivered, + £25 import tax from TNT. My old transistor amp was £1500.
The Sweet Peach uses 160 Watts at idle. My transistor amp used 495 Watts.
Correctly designed amps do not overheat - overheating is a symptom of poor design or excessive cost cutting.
As for danger to service, after about 20 seconds the highest remaining voltage is 12V and falling. My Pioneer SX838 on the other hand used to hold 40+40 = 80V for a number of days across the main power caps. I have not opened my old transistor power amp.
I like the sound of Sansui solid state amps (I own a few), but sonically they cannot compete with tube - in my system anyway, maybe you heard a bad tube amp?
Also - your MOSFET amp has no mosfets - therefore it's not a MOSFET amp? Piezo tweeters sound nice IMO.
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Then how the hell does it work? I would open it but the warrenty is still intact. And seeing as Skytronic are 'bad' I think I'll need the warrenty.
Aparrently, piezo tweeters sound horrible according to many internet sources. They don't handle much either - only 150W! But they are affordable 😀
Maybe next time I'll try compression drivers.
If it's the same as the 'inside a no-name PA amp' then it uses bipolar transistors.
When you have a chance listen with your own ears to some Motorola or JBL piezo tweeters, you'll notice the low distortion. Remember something that can render music at 120dB will just be coasting at hi-fi levels, and they have low IM distortion as the natural roll-off is better than most cheap crossovers that over-stretch soft dome tweeters. In fact you don't even need a crossover for them..
Also no soft dome will handle 150W - about 10W is the usual max power. Think about how hot a 150W light bulb gets before you assume too much - also piezo is _far_ more efficient: less heat, far more volume.
Most hi-fi listening is done below 1 Watt.
Not me, I push it up depending on my mood and I'm pretty sure it's more than 1 watt.
A piezo tweeter doesn't have a soft dome, it has some rigid paper cone thingy attatched to some metal gold thingy with wires flying off to solder tags.
Also I noticed that my Skytronic amp sometimes makes a MASSIVE 'turn off' THUMP or CLICK. Should I be worried about this or is it normal?
Try measuring the AC volts going to your speakers with a multimeter or 'scope. If your speaker is over 90dB/watt you will only need one.
Piezo tweeters are made from piezo ceramic.
Turn your amp volume down before switching on or off!
proper amp design
Properly designed amps suppress the output thump, a problem that developed with the invention of the transistor amp. If your speaker cone rubber is a little aged or heat stressed, the thump can rip it. My ST120 had a power off click until I installed Metal Oxide Suppressors across the power switch; these weren't invented until two decades after the amp was sold and built. Actually, these MOS suppressors may be how a non-MOSFET amp calls itself a MOS amp, as they are required on all new design electronics that meet the radio emmisions specs. (in the US, FCC certifications). These devices are blue and have a capacitor symbol with a "Z" through it on them, also a rating like "UL" "CSA" or "VDO".
My favorite speaker at the moment has has piezo tweeters (piezo driven horns), the SP2, also my previous ones the T-300. The horns spread the good sound spot all over the top half of the room, the T--300 had no horns and had a very narrow sweet spot. JBL, Mackie, others also sell woofer+piezo horn 2 way speakers, they are very popular in bar bands with keyboards. Piezo tweeters are only as good as the people specifying them and quality assuring them to provide a smooth wide angle response.
Training yourself to work on tube equipment (checking that energy is dissipated with a known working meter before touching any metal) is similar to the lockout training that electricians learn to work on factory mains circuits. It is also similar to the training physicists require to work on particle accelerators. Actually, transistor amps over 50 watts per channel into 8 ohms have lethal voltages in the output stage, over 28 VDC. Any circuit having caps rated over 28 VDC should be checked for energy dissipation before touching the metal parts.
Properly designed amps suppress the output thump, a problem that developed with the invention of the transistor amp. If your speaker cone rubber is a little aged or heat stressed, the thump can rip it. My ST120 had a power off click until I installed Metal Oxide Suppressors across the power switch; these weren't invented until two decades after the amp was sold and built. Actually, these MOS suppressors may be how a non-MOSFET amp calls itself a MOS amp, as they are required on all new design electronics that meet the radio emmisions specs. (in the US, FCC certifications). These devices are blue and have a capacitor symbol with a "Z" through it on them, also a rating like "UL" "CSA" or "VDO".
My favorite speaker at the moment has has piezo tweeters (piezo driven horns), the SP2, also my previous ones the T-300. The horns spread the good sound spot all over the top half of the room, the T--300 had no horns and had a very narrow sweet spot. JBL, Mackie, others also sell woofer+piezo horn 2 way speakers, they are very popular in bar bands with keyboards. Piezo tweeters are only as good as the people specifying them and quality assuring them to provide a smooth wide angle response.
Training yourself to work on tube equipment (checking that energy is dissipated with a known working meter before touching any metal) is similar to the lockout training that electricians learn to work on factory mains circuits. It is also similar to the training physicists require to work on particle accelerators. Actually, transistor amps over 50 watts per channel into 8 ohms have lethal voltages in the output stage, over 28 VDC. Any circuit having caps rated over 28 VDC should be checked for energy dissipation before touching the metal parts.
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Yeah I turn it all the way down and I still get a HUGE turn off THUMP (all VU meter LEDs flash)
Infact, sometimes when I leave the gains up and switch it off, there's no thump.
There's no switch on thump, infact I don't get any signal through the speakers until about 0.5 seconds after power up and the amp makes some CLICK noise loudly (from INSIDE amp, not speakers). It's just when powering down.
Well the piezo tweeter's diaphragm is definately some stiff paper having opened it.
Sounds like there is a either a soft start or a protection circuit - perhaps if a protection circuit it is not working.
I'd try a suppressor across the switch (as described above IIRC) before something goes pop - sounds like a nasty transient. I still reckon you ought to gut the box and build a tube amp inside instead though 😉
As for Piezo tweeters - like any tweeter they are not all created equally - go for a big name like Motorola or JBL, the cheap ones will have frequency responses and distortion all over the place. I have very old Motorola Bullets that sound lovely - but I've heard a few cheap shockers too...
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