Going Big class A?

[PeterA]

Here is a bit more info class is slow but delicate so good on soft low volume passages in classical but all genre
Now of your amp is too far into class A when faster music starts it’s slow less dynamic
Class AB has jump it’s why am amps class change needs to suite the needs of the setup and what we play.
My no 33 idle at 9 amps each that’s a lot of class A watts
But since my speakers are nom 4 but really below 2 at times they move mine out of class A sooner
Take my amps ona very high eff setup that’s 8 ohms they are slow not as dynamic
I do play loud so I need plenty of reserve power
My amps can deliver 60 amps into 1 ohm continues and have there own regen inside. A truly working marvel that pounds the caps inside. But yields dynamics that you feel in your chest 16 feet back. Yet play soft passages with immense details and suppleness
While there are better amps made now they are legacy amps playing legacy speakers
Into my legacy old ears lol.

I found that my Pass XA160.5 (160 Class A watts into 8 ohm load, 320 Class A watts into 4 ohm load) was more dynamic than my former XA100.5. So in this case, the more Class A watts, the more dynamic in my 4 ohm load Magico Mini II speakers. And my 90dB Magico Q3 is even more dynamic with all of those Class A watts. It is also delicate with softer low volume passages in classical.

Are you suggesting that my system would be more dynamic with an amp that moves out of Class A sooner?

 

[microstrip]

(...) To say an amp is pure class A is an error and is used to mislead all of us from the makers
It’s a advertisement word made up. Now given an amp that has a higher class reting needs a much larger psu but still all are class AB and all amps clip at some point even if on a test bench.

Again, sorry, it is not. It is a technically valid specification that can be properly used or misleading, depending on manufacturers.

Anyone with some technical knowledge knows that pure class A means class A into a certain load. The problem is that usually manufacturers admit an 8 ohm load for this specification, and most speakers have impedance much lower than that.

You were correct in pointing Lamm - their way of showing specifications in excellent for knowledgeable consumers.

 

[Alrainbow]

Yes
but allow me to ask this what is the idle in amps ? I don’t know the amps but class A goes down not up typically
Lamm correctly states this.
In fact Lamm quotes what I have been shown to be 1/4 watts at halving of the amps imp. If the pass amp sounded more dynamic I tnink you are making my point it’s going into AB. Again I don’t know the amp and NELson pass is a very good designer

 

[Alrainbow]

Kudos micro we agree on something.
The whole class thing is a big complex debate and many sides leading to stances
I agree with some of yours too

 

[microstrip]

I found that my Pass XA160.5 (160 Class A watts into 8 ohm load, 320 Class A watts into 4 ohm load) was more dynamic than my former XA100.5. So in this case, the more Class A watts, the more dynamic in my 4 ohm load Magico Mini II speakers. And my 90dB Magico Q3 is even more dynamic with all of those Class A watts. It is also delicate with softer low volume passages in classical.

Are you suggesting that my system would be more dynamic with an amp that moves out of Class A sooner?

Peter,

You are quoting class AB values, not class A. Usually class A power decreases linearly when the impedance decreases.

 

[Alrainbow]

Thanks micro

 

[microstrip]

Yes
but allow me to ask this what is the idle in amps ? I don’t know the amps but class A goes down not up typically
Lamm correctly states this.
In fact Lamm quotes what I have been shown to be 1/4 watts at halving of the amps imp. If the pass amp sounded more dynamic I tnink you are making my point it’s going into AB. Again I don’t know the amp and NELson pass is a very good designer

In SS push pull amplifiers we can easily get the approximate value of the bias current using idle power and maximum output voltage - just admit that in class A amplifiers most power is dissipated in the output stage and P idle = 2 x Vout max RMS x 1.4 x I bias .

Lamm M1.2r class A specs are very accurate 110 W 8 ohm,55W 4ohm and 27.5W - 2ohm.

Pass high power amplifiers are class AB.

 

[Alrainbow]

Ty micro for your posts. So how many watts are my no 33 in class the spec says at 125
Volts 8.5 amps per amp

 

[morricab]

Kudos micro we agree on something.
The whole class thing is a big complex debate and many sides leading to stances
I agree with some of yours too

If your amps are single ended then the debate is rather simple...it is Class A all the time and into all loads...

 

[microstrip]

Ty micro for your posts. So how many watts are my no 33 in class the spec says at 125
Volts 8.5 amps per amp

As far as I remember the 33 is a fully balanced amplifier using two bridged amplifiers - it needs some extra thought ...

 

[Alrainbow]

Hahaha where did you get this from. And my ampsmamd preamp are actually fully balanced the real way not half or partially
But that’s not the debate here anyway.
In truth the audio industry’ is filled with half truths ,
Miss Leadig comments and worst is lies in specs. When I went to the Lamm website I was shocked at the level of truth in there specs.
Way back when I had hair and was in school getting my ENG degree they played with watts.rms , peak and peak to peak all the same but numbers get bigger or smaller and this sells products. Then vane slew rate and noise in so many ways it was nuts
Amps to this day play games and sadly the reviews do this to.
What is reality and fiction is blurred and at the prices should not be.
But even if like Lamm they post it correct how many know what it is
Lower is better
More is better
It’s upside down and what does matter is not known and
The vast amount of variables is not even figured into what is needed
On my speakers I was lucky to come across a few good guys who know not just specs like me but why it sounds like it does.

 

[PeterA]

Peter,

You are quoting class AB values, not class A. Usually class A power decreases linearly when the impedance decreases.

Hello Fransisco,

Have I been falsely assuming that my amps are capable of delivered 320 watts of Class A into the 4 ohm load of my Magico speakers? Could you provide some information that the figures I quote are Class AB values and not Class A? It is my understanding that Pass XA model amplifiers are named for their nominal power rating in Class A. I will quote liberally from information found on the Pass Labs website:

https://www.passlabs.com/sites/default/files/Point8_specs_0.pdf

And this from the Stereophile review of the Pass XA60.8, measurement section:

Specified as putting out 60W into 8 ohms and 120W into 4 ohms (both 17.8dBW), the XA60.8 considerably exceeded that power, delivering, at 1% total harmonic distortion (THD), 150W into 8 ohms (21.8dBW, fig.4), 240W into 4 ohms (20.8dBW, fig.5), and 380W into 2 ohms (19.8dBW, fig.6).
Read more at https://www.stereophile.com/content...er-amplifier-measurements#qCdTMSQlDSRJkc47.99

Finally this from the Pass paper titled, "Leaving Class A":

Class B has no bias current, Class AB has a moderate bias current, and Class A has a high bias current. Class AB push-pull amplifiers are hybrids between Class B and Class A. Class AB run Class A at low power levels, and become Class B amplifiers at output currents determined by the bias.

For several years Pass Labs has specified the nominal wattages at which our amplifiers leave push-pull Class A operation into an eight ohm load.



From the Stereophile measurements, I assumed that the 60 watt specification was Class A into 8 ohms and that the measured 150 watts into 8 ohms was total class AB. Could you please explain the distinction?

 

[twitch]

52 feet by 20 ft 88db 4ohm

hire your own musicians, might be cheaper ........

 

[microstrip]

Hello Fransisco,

Have I been falsely assuming that my amps are capable of delivered 320 watts of Class A into the 4 ohm load of my Magico speakers? Could you provide some information that the figures I quote are Class AB values and not Class A? (...)

Yes, it is not true. At 4 ohms class A power should be half of the 8 ohm value. Besides Pass use RMS power for class AB and peak power for class A ... IMHO your amplifier should have around 80W class A at 4 ohms - probably more than enough 99.99% of the time.

Please see these old WBF posts by Charlesp210. http://www.whatsbestforum.com/showthread.php?13781-What-are-the-most-powerful-Pure-Class-A-Amplifiers-ever-made&p=252569&viewfull=1#post252569.

 

[PeterA]

Yes, it is not true. At 4 ohms class A power should be half of the 8 ohm value. Besides Pass use RMS power for class AB and peak power for class A ... IMHO your amplifier should have around 80W class A at 4 ohms - probably more than enough 99.99% of the time.

Please see these old WBF posts by Charlesp210. http://www.whatsbestforum.com/showthread.php?13781-What-are-the-most-powerful-Pure-Class-A-Amplifiers-ever-made&p=252569&viewfull=1#post252569.

Thank you Fransisco. 80W Class A at 4 ohms and 320 watts peak Class AB at 4 ohms. I have seen the needles on my meters move once indicating leaving class A. It was during the Sheffield Drum Track recording playing at a peak volume of 97 dB. I never play louder than that.

So if my amps rarely leave class A and Alrainbow writes that class A is not as dynamic as class AB, why does my system sound so dynamic? It seems class A can deliver dynamics. Perhaps I should try an X.5 amp to see if it is more dynamic.

 

[ack]

Yes, it is not true. At 4 ohms class A power should be half of the 8 ohm value. Besides Pass use RMS power for class AB and peak power for class A ... IMHO your amplifier should have around 80W class A at 4 ohms - probably more than enough 99.99% of the time.

Please see these old WBF posts by Charlesp210. http://www.whatsbestforum.com/showt...iers-ever-made&p=252569&viewfull=1#post252569.

You may be over generalizing wrt Class A and impedance. For example, from the link you posted, the ML-2 is said to instead DOUBLE its Class A power as the impedance is halved:

Now you can see the stark tradeoff given a certain amount of transformer iron, or heatsink area. With a given amount of metal, you can have low rail voltage (like Levinson ML-2) and get large class A power into 8,4,2 ohms, but that's it no more, or Class AB which gives you far more max Class AB power, but smaller class A power, sometimes surprisingly small. IIRC the ML-2 stays in Class A until 2 ohms (25W at 8, 50W at 4, and 100W at 2, all class A).

 

[microstrip]

You may be over generalizing wrt Class A and impedance. For example, from the link you posted, the ML-2 is said to instead DOUBLE its Class A power as the impedance is halved:

OK, my comment was made admitting that the limit to class A is the bias current, as any AB design, or in a class A amplifier designed for minimum idle power versus output power at 8 ohm operation. I addressed mainly the Pass amplifier being debated, not all amplifier designs. Thanks for pointing it.

 

[Alrainbow]

Great thread as it gets us all making sure what we post is making sense and correct.
Let’s say am amp is 100 watts at 8 ohms
And 200 at 4 ohms
It’s biased at leaving pure class a at 10 watts at 8 ohms
Same amp leaves class a at 4 ohms at 2.5 watts even though it’s rated at 200 watts
Now when I say jump at a/b it means when an amp leaves class a it’s due to dynamics not continues
So if the dynamic hit leaves the amp in class a the jump is not as much but neither is the dynamic hit.
If we play music that has very poor dynamics an amp rated at 10 watts class a at 8 ohms may stay in class a. But on a more dynamic track this happens many times and can be shown on a scope. But a trained ear can pick it out.
Most of us hear it all the time a word the female sings that is very predictable. Now lowering the volume 3 dB then 6db will get you
To stop this and at this point you now know where you clip

Play these songs
Worlds greatest vocals dsd JAMES tailor is isn’t she lovely
Key word Isent is the word as he sings it the word will jump just that word like a bump. It’s not the
Loudest he sings but it’s sure where it clips for me
Gloria estiphone mia tia album cd track one same word lol really it jumps
Now this was with my Aragon 4004 mkii eve. After doubling caps
On my no 33 it’s just another word no jump or peak
Last weak I had Fred of Lampi over by me he has an Aragon We played my amp and then the Aragon
I pointed as it happened every time
He looked at me lol. A man has shown me Heaven and he’ll clpping is part of hell.

 

[ack]

OK, my comment was made admitting that the limit to class A is the bias current, as any AB design, or in a class A amplifier designed for minimum idle power versus output power at 8 ohm operation. I addressed mainly the Pass amplifier being debated, not all amplifier designs. Thanks for pointing it.

I am not sure I follow you 100%... you seem to be inferring that Pass amps may not be sliding its bias by load impedance, unlike the ML-2? Am I correct? If so, how do you know that? And don't forget Pass invented the sliding bias in his Threshold designs. I actually do not know how Pass amps nowadays work, but I wonder, why would he not be sliding the bias current...

 

[LL21]

I always thought if the MAX 8ohm Class A was, for example, 80 watts...then at 4ohms, it WAS 40 watts. And that the way that it DOUBLED into 4ohms to 160 watts was because the 8ohm rating was super-under spec'd. For example, Vitus Class A also doubles into 4ohms.

Vitus Masterpiece is 25 watts Class A 8ohm and then 50watts Class A into 4 ohms...but it burns like 550 watts out of the wall...so since Class A power useage is often 5x the wattage into 8ohms...I always 'guessed' the Vitus Masterpiece was probably capable of something like 100 watts Class A at 8ohms except that for some reason Vitus may have elected to limit it for technical reasons. Clearly i am no techie!