Dunno about 20 kW audio there. maybe a 500W PA with decent bins would blow that lot into the weeds. That guy is not quite the efficiency expert, for sure.Both !!Oh , here's them inefficient speakers..
OS
Mikelm,
This is very, very good news, better than the JLH indeed, huh? Thank you for building. Your choice of the word 'classic' seems like it could be right on the money....
Palmito,
Power for an audio amp into 8R is simply peak to peak unclipped output squared divided by 64. For 4R double this. So, if our power supply is 36V, and sags to say 33V at full power into 4R, we lose about 8V from each rail using lateral fets with 4R loads (5V with 8R loads) because of losses in the output devices, so deduct 16V from our peak to peak voltage which might be 66Vpp, giving us 50Vpp.
Now, square 50 to get 2500, divide by 64 to get 39, and double it for four ohm loads. This is 78 watts, quite a lot of power.
However, on this amp with its smaller output stage (only two devices), there would be plenty of compressive distortion at full power. Using 8R, you would probably get around 34V rail sag, with only 5V lost from each rail, giving you (68 - 10)Vpp, or 58. That corresponds to 58 squared divided by 64, or 52.5 watts.
For most, that is plenty of power, particularly with 88dB/watt/metre speaks or higher.
Cheers,
Hugh
This is very, very good news, better than the JLH indeed, huh? Thank you for building. Your choice of the word 'classic' seems like it could be right on the money....
Palmito,
Power for an audio amp into 8R is simply peak to peak unclipped output squared divided by 64. For 4R double this. So, if our power supply is 36V, and sags to say 33V at full power into 4R, we lose about 8V from each rail using lateral fets with 4R loads (5V with 8R loads) because of losses in the output devices, so deduct 16V from our peak to peak voltage which might be 66Vpp, giving us 50Vpp.
Now, square 50 to get 2500, divide by 64 to get 39, and double it for four ohm loads. This is 78 watts, quite a lot of power.
However, on this amp with its smaller output stage (only two devices), there would be plenty of compressive distortion at full power. Using 8R, you would probably get around 34V rail sag, with only 5V lost from each rail, giving you (68 - 10)Vpp, or 58. That corresponds to 58 squared divided by 64, or 52.5 watts.
For most, that is plenty of power, particularly with 88dB/watt/metre speaks or higher.
Cheers,
Hugh
Ah so that's how you work out power - hehe
well Hugh, I know taste in audio is a very personal thing so I will have to wait to see if others agree but for me this amp is a bit special.
The dynamics are like I rarely, perhaps never, heard before. It's so life like but it also seems very smooth as well. I can hear, in my current set up, that the sound isn't perfect but there's something about it that draws me into the music and I'm just really enjoying listening to it - it's slowing down my development of the my DC linked design
I'll begin that work in earnest when my boards arrive in about 10 days. At present it's drifting up to around zero from about -200mV but I'm pretty sure I can reduce that significantly. I'll keep my current amp as an unmodified reference and hopefully my mods to reduce the drift will not impact the sound.
Great, all good posts.
Mikelm, can you please remind me which schematic you are using, and possibly a link? I only have my phone and searching is very painful and slow. Your drift sounds quite high compared to mine (remember my plots from a few weeks ago)? I agree about the power, 25w is more than enough for me. I have scoped my speakers and I am absolutely sure there is no way it clips, with only a few volts ever across the speakers.
Stan, regarding the silky treble you want. I would suggest experimenting with different bias currents in the vas and output stage. The more current the silkier it gets IMO. If you can deal with the heat 1A is quite good.
I would also experiment with the bias spreader bypass cap. You could try various values from zero to 50uF. JLH used to like 22uf or so.
Many thanks for the listening impressions Stan and mikelm, it is great news that others agree on how this thing sounds. It is most certainly engaging and gives the music a certain oomph and liveliness I haven't heard before.
Can't wait to get home from my holiday and resume experimenting!
Mikelm, can you please remind me which schematic you are using, and possibly a link? I only have my phone and searching is very painful and slow. Your drift sounds quite high compared to mine (remember my plots from a few weeks ago)? I agree about the power, 25w is more than enough for me. I have scoped my speakers and I am absolutely sure there is no way it clips, with only a few volts ever across the speakers.
Stan, regarding the silky treble you want. I would suggest experimenting with different bias currents in the vas and output stage. The more current the silkier it gets IMO. If you can deal with the heat 1A is quite good.
I would also experiment with the bias spreader bypass cap. You could try various values from zero to 50uF. JLH used to like 22uf or so.
Many thanks for the listening impressions Stan and mikelm, it is great news that others agree on how this thing sounds. It is most certainly engaging and gives the music a certain oomph and liveliness I haven't heard before.
Can't wait to get home from my holiday and resume experimenting!
Stan and mikelm,
As I just posted above, I would really try fiddling with the bias spreader bypass cap. I have a gut feeling making it larger will increase the smoothness somewhat and take off any harsh edges. Don't ask me why, it's just a feeling. You can use a good quality electro if necessary.
You could also try removing it completely but I think that will have the opposite effect.
As I just posted above, I would really try fiddling with the bias spreader bypass cap. I have a gut feeling making it larger will increase the smoothness somewhat and take off any harsh edges. Don't ask me why, it's just a feeling. You can use a good quality electro if necessary.
You could also try removing it completely but I think that will have the opposite effect.
Hi,
got the inverted version powered up last night (that's the zvn2110a version). Done a little bit of testing using lab supply set to between +-18Vdc to +-24Vdc.
Switch on pulse exceeds 2Vpk. Will check with a scope. Output offset settles to ~20mV in a second or so and falls to <3mV over the next 15 minutes warming up. Seems stable with +-1mV of offset variation over the next hour. I have tried cooling and re-warming twice and get similar results.
Output AC measures 0.0mVac on my non rms DVM.
Running ~ 6mA through the LEDs, ~2.2mA through the j74 (1k0 collector needs to be changed, probably to ~330r), ~8mA through the zvn, ~ 100mA through the Laterals.
Next: to get a low voltage transformer wired up and listen to output noise with headphones.
got the inverted version powered up last night (that's the zvn2110a version). Done a little bit of testing using lab supply set to between +-18Vdc to +-24Vdc.
Switch on pulse exceeds 2Vpk. Will check with a scope. Output offset settles to ~20mV in a second or so and falls to <3mV over the next 15 minutes warming up. Seems stable with +-1mV of offset variation over the next hour. I have tried cooling and re-warming twice and get similar results.
Output AC measures 0.0mVac on my non rms DVM.
Running ~ 6mA through the LEDs, ~2.2mA through the j74 (1k0 collector needs to be changed, probably to ~330r), ~8mA through the zvn, ~ 100mA through the Laterals.
Next: to get a low voltage transformer wired up and listen to output noise with headphones.
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There are other ways to improve the "bias spreader". See this thread:
http://www.diyaudio.com/forums/solid-state/117047-differences-between-various-vbe-multipliers.html
BTW, has anyone ever thought of using Salas' shunt regulator as a bias spreader?
- keantoken
http://www.diyaudio.com/forums/solid-state/117047-differences-between-various-vbe-multipliers.html
BTW, has anyone ever thought of using Salas' shunt regulator as a bias spreader?
- keantoken
BTW - I connected the amp through different speakers - Quad 11L's - and the result sounded as dull as dishwater. So this fast, exciting and engaging sound I've been going on about depends on the whole chain being up to scratch in that regard.
My current version is irf9610 with 20 ohms degen, about 15mA, BD139 & 2 led's, 300R gatestoppers and about 650mA o/p bias. FB = 47 / 500, no miller, 47pF + 100R lead comp.
p.s. my previous listening has been through heavily modded B&W602's - with redesigned X-overs and other good stuff - much more clean & transparent in the midrange than the originals
My current version is irf9610 with 20 ohms degen, about 15mA, BD139 & 2 led's, 300R gatestoppers and about 650mA o/p bias. FB = 47 / 500, no miller, 47pF + 100R lead comp.
p.s. my previous listening has been through heavily modded B&W602's - with redesigned X-overs and other good stuff - much more clean & transparent in the midrange than the originals
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Thanks Andrew,
Very helpful information.
Could I ask what the 'inverted' version is? Put another way, is your amplifier gay? Would you be happy to post your circuit?
Very good offset control. Extremely quiet. Are you using the ZVP2110a as input, or as VAS?
Mike,
Good results. It seems the amp might be sensitive to phase shift/back EMF coming off the speaker, unusual for a FET output stage.
Might be an idea to try removing the phase lead 47pF and putting about 15pF lag compensation across the VAS?
Cheers,
Hugh
Very helpful information.
Could I ask what the 'inverted' version is? Put another way, is your amplifier gay?
Would you be happy to post your circuit?Very good offset control. Extremely quiet. Are you using the ZVP2110a as input, or as VAS?
Mike,
Good results. It seems the amp might be sensitive to phase shift/back EMF coming off the speaker, unusual for a FET output stage.
Might be an idea to try removing the phase lead 47pF and putting about 15pF lag compensation across the VAS?
Cheers,
Hugh
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Hey guys
We're getting off on a false premise here.
Quad 11L's are not electrostatic speakers - they are beautifully finished but rather mundane sounding moving coil mini monitors which I suspect would not sound fast & exciting whatever you connect to them.
Great to smooth & sweeten if you have poor quality source or amp but not really my cup of tea.
see them here . . . mmm, a right click only seems to work here
We're getting off on a false premise here.
Quad 11L's are not electrostatic speakers - they are beautifully finished but rather mundane sounding moving coil mini monitors which I suspect would not sound fast & exciting whatever you connect to them.
Great to smooth & sweeten if you have poor quality source or amp but not really my cup of tea.
see them here . . . mmm, a right click only seems to work here
An externally hosted image should be here but it was not working when we last tested it.
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Ohh... sorry.. did not know that quad..had migrated into "normal" speakers...but I agree that amplifiers can be sensitive to that kind of phaseshift...when simulating I can see a hump on the frequency plot developing at app 120 KHz with 1uf across 8 ohm load...not enough to cause oscillation..but taking it closer...
AndrewT,
Nice results, and similar to mine. My dc offset stability was very good too - rapid settling to within 5mV. Perhaps mikelm's problems arise from the use of a bjt ccs? I also found that larger feedback caps and smaller shunt resistor values improved things.
Look forward to your listening impressions!
Nice results, and similar to mine. My dc offset stability was very good too - rapid settling to within 5mV. Perhaps mikelm's problems arise from the use of a bjt ccs? I also found that larger feedback caps and smaller shunt resistor values improved things.
Look forward to your listening impressions!
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