A basic power amplifier delivering more than 16 Watt.
An amplifier that could be before D.Self published his Blameless.
The THD distortion is moderate, but the harmonics are interesting. Mostly 2nd harmonic.
Enjoy this simple amp!
An amplifier that could be before D.Self published his Blameless.
The THD distortion is moderate, but the harmonics are interesting. Mostly 2nd harmonic.
Enjoy this simple amp!
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Any questions or comments?
I see The One and Only has LIKED my amp ...
So it can not be so bad then.
I see The One and Only has LIKED my amp ...
So it can not be so bad then.
This is not very good.
People looks at my amplifier but there is not any post.
What is wrong?
I have done some good work to create this but noone post anything.
Come on!
People looks at my amplifier but there is not any post.
What is wrong?
I have done some good work to create this but noone post anything.
Come on!
Pretty straight forward and fun, Fast little guys for the outputs.
I posted a amp using them and was a " horrible person" lol.
.0006 distortion almost to crest power with 5534/32 driver.
C6 seems very high. Just needs constant current source for diff and a little degen.
Then C6 value would go way way down.
KSC2690 and KSC3503 are both lifetime status only PNP is hard to get.
So might wake up a little trying those for U4
Add typical 100n cap to U3
Amplifier is non inverting so DC offset should be positive on output.
Value is nice and low though.
I posted a amp using them and was a " horrible person" lol.
.0006 distortion almost to crest power with 5534/32 driver.
C6 seems very high. Just needs constant current source for diff and a little degen.
Then C6 value would go way way down.
KSC2690 and KSC3503 are both lifetime status only PNP is hard to get.
So might wake up a little trying those for U4
Add typical 100n cap to U3
Amplifier is non inverting so DC offset should be positive on output.
Value is nice and low though.
I understand you are keeping its simplicity but any plans on inserting current mirrors? I've read that these bootstrap types are known for turn on and off thump. I built one but included the current mirrors to somehow mitigate turn on and off thump.
Keep the cap small then, bootstrap cause a phase shift at low frequency. Easily avoided if the cap is large enough.
Just a simple RC filter calculation. Technically it doesn't need to be larger than 47u with the 1.8k resistors.
Most will double the values to feels better to 100u. anything bigger is just silly at these voltages
They are fun and easy at low voltages the resistor values are high enough so the cap can be pretty small actually and have
not much negative effect on low frequency.
Startup thump can be caused by many things at startup when the power supply stabilize.
Though it was more a differential thing, as the power supply comes up.
Didnt know a bootstrap caused thump. Because non bootstrapped amps can thump too.
Mirror/Current source is fast enough to have no offset at switch on?
Be cool if it does , never thought about it.
Guess a commercial product should have no thump.
I cant stand high DC offset on the output, aside from the usual THD improvements.
I just liked mirrors for low offset over a wide temperature range
Almost all my solid state 100 to 150 watts Musical Instrument amps thump on start up, I just stopped caring after years.
maybe 200 watt or up amps had a output relay. So they didnt thump.
Just a simple RC filter calculation. Technically it doesn't need to be larger than 47u with the 1.8k resistors.
Most will double the values to feels better to 100u. anything bigger is just silly at these voltages
They are fun and easy at low voltages the resistor values are high enough so the cap can be pretty small actually and have
not much negative effect on low frequency.
Startup thump can be caused by many things at startup when the power supply stabilize.
Though it was more a differential thing, as the power supply comes up.
Didnt know a bootstrap caused thump. Because non bootstrapped amps can thump too.
Mirror/Current source is fast enough to have no offset at switch on?
Be cool if it does , never thought about it.
Guess a commercial product should have no thump.
I cant stand high DC offset on the output, aside from the usual THD improvements.
I just liked mirrors for low offset over a wide temperature range
Almost all my solid state 100 to 150 watts Musical Instrument amps thump on start up, I just stopped caring after years.
maybe 200 watt or up amps had a output relay. So they didnt thump.
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I will add a 100nF cap across U3.
Other then that I wont change anything.
KSC3503 is a very good VAS transistor. But BD139 is easier to get.
C6 value was chosen because of AC Sweep without overshot.
There will be no current mirrors.
That is the intended to keep this simplicity. I don't want to post another Blameless.
Hi Lineup,
Indeed there are many amps like this. Rod Elliot is in particular tuning this configuration (his is slightly different but same in principle) into perfection since 1999
https://sound-au.com/project3a.htm
Indeed there are many amps like this. Rod Elliot is in particular tuning this configuration (his is slightly different but same in principle) into perfection since 1999
https://sound-au.com/project3a.htm
Either is fine.
Usually with unregulated supply, current source is my only pet peeve.
Diff input always would have a current source in my book.
Mirrors of course start leading to typical blameless at that point.
But current source slightly improves distortion even simplified, but DC offset on output
will hold better at different power levels and temperature.
Simplified amps like this typically can do pretty good H2 profile.
"Upside Down" version using NPN inputs, basically usually guarantee a strong H2
People often say the " bootstrap" for the second gain stage gets the H2.
Usually just a simplified 2nd gain stage will get it, Using a " good enough"
but not magical transistor will get it.
As mentioned NPN input with PNP second gain stage simplified amp like this typically guarantees it as well.
Least at low frequency it does. The " magic trick" to get it above 10k where H3 will typically always then rise.
Is the trick I will not reveal lol.
Holding H2 above 10k is the tricky one
Usually with unregulated supply, current source is my only pet peeve.
Diff input always would have a current source in my book.
Mirrors of course start leading to typical blameless at that point.
But current source slightly improves distortion even simplified, but DC offset on output
will hold better at different power levels and temperature.
Simplified amps like this typically can do pretty good H2 profile.
"Upside Down" version using NPN inputs, basically usually guarantee a strong H2
People often say the " bootstrap" for the second gain stage gets the H2.
Usually just a simplified 2nd gain stage will get it, Using a " good enough"
but not magical transistor will get it.
As mentioned NPN input with PNP second gain stage simplified amp like this typically guarantees it as well.
Least at low frequency it does. The " magic trick" to get it above 10k where H3 will typically always then rise.
Is the trick I will not reveal lol.
Holding H2 above 10k is the tricky one
Member LKA had this addl' components in one of his bootstraped amp designs, he called it VAS starter. If I read it correctly its duty is to prevent turn on and off thump. I adapted it and run it in sim but I did not verify it in a real world build but perhaps from a lower rail voltage like lineup's it may not be necessary.
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Hi to all
it is a simple design like mine I tried and get help by Whitedragon and others too.
JAT EZ amp. i use daringtons - they are slow.
the Toshiba TTC004B_Q and TTA004B_Q are fine and available. for the VBe multiplier i would choos a isolated version because you should mount it at one of your output transistors. i have no idea to do that with two hands if you use a non isolated TO126..and the mounting set😆
33pF should b enough or you us a 68p...330pF is a way to conservative. also John audio tech did a correction at his JAT501 hot rodded version. he explain that 100pF is rock stable but he will use 68pF.
kr
chris