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Old 27th November 2005, 10:19 AM   #21
djk is offline djk
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"In my opinion , Class-G does the commutation more linearly than Class-H ......But it uses More Devices whereas in Class-H the Switching element may be a high power Mosfet with lower RDS , and is much cheaper to implement then Class-G...what do you think....."

Yes, that is why I mentioned the cost difference between the two.

"The Spikes originating from the switching phenomena might have their impact on the sonics what are your views....."

The noise is largely a function of the switch (diode) used. Existing designs do not use the best available diodes, they consider them un-needed for PA.

Carver used an ordinary fast diode with a snubber, and sounded quite good.

Crest made a special version of one of their 4000 series amps just for HF use. It was class AB rather than class G, which indicates some users must have objected to the sound of the class G amps on the HF drivers. I have about eight various Crest CA series amps. The smallest of which (CA4) is class AB. The end users (this is for rental use) prefer the AB International 600 for sonics. A similar class AB amp, it does sound better for HF use.

The design of the AB 600 is virtually identical to the v4.0 Leach. Since both the AB and the Crest are class AB amplifers with very similar EF type output stages, it must be the front end and the overall execution of details. I've been meaning to try a v4.5 Leach with an added class G output stage just to hear for myself what can be done with class G.

A newer design commercial class G stage:

http://patft.uspto.gov/netacgi/nph-P...S=PN/5,387,876
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Old 27th November 2005, 04:02 PM   #22
anatech is offline anatech  Canada
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Hi Kanwar,
The switching in class H is visible on an oscilloscope when looking at the output waveform. You can hear it as well.

Carver changed to class G for some later amps for that reason. They later developed the "down converter" as an efficient type of power control that emulates class G. I am impressed with the performance of the original Lightstar for that reason.

The Lightstar is a real animal (for North America). It's rated at 300 W 8 R, 600 W 4R and 1200 W 2R. That's per mono channel. It has a dual mono design, two power cords.

I think the technology has proved itself. We even had failures due to the feedback resistor burning out (someone should be slapped).

-Chris
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Old 28th November 2005, 04:29 AM   #23
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Quote:
Originally posted by djk
"In my opinion , Class-G does the commutation more linearly than Class-H ......But it uses More Devices whereas in Class-H the Switching element may be a high power Mosfet with lower RDS , and is much cheaper to implement then Class-G...what do you think....."

Yes, that is why I mentioned the cost difference between the two.

"The Spikes originating from the switching phenomena might have their impact on the sonics what are your views....."

The noise is largely a function of the switch (diode) used. Existing designs do not use the best available diodes, they consider them un-needed for PA.

Carver used an ordinary fast diode with a snubber, and sounded quite good.

Crest made a special version of one of their 4000 series amps just for HF use. It was class AB rather than class G, which indicates some users must have objected to the sound of the class G amps on the HF drivers. I have about eight various Crest CA series amps. The smallest of which (CA4) is class AB. The end users (this is for rental use) prefer the AB International 600 for sonics. A similar class AB amp, it does sound better for HF use.

The design of the AB 600 is virtually identical to the v4.0 Leach. Since both the AB and the Crest are class AB amplifers with very similar EF type output stages, it must be the front end and the overall execution of details. I've been meaning to try a v4.5 Leach with an added class G output stage just to hear for myself what can be done with class G.

A newer design commercial class G stage:

http://patft.uspto.gov/netacgi/nph-P...S=PN/5,387,876

Hi DJK,

That's the Peavey patent, its very similar to the Yorkville amps of Canada http://www.yorkville.com/downloads/servman/smap6020.pdf
...So Class-G wins over Class-H interms of Sonics in HF region.....

Quote:
Originally posted by anatech
Hi Kanwar,
The switching in class H is visible on an oscilloscope when looking at the output waveform. You can hear it as well.

Carver changed to class G for some later amps for that reason. They later developed the "down converter" as an efficient type of power control that emulates class G. I am impressed with the performance of the original Lightstar for that reason.

The Lightstar is a real animal (for North America). It's rated at 300 W 8 R, 600 W 4R and 1200 W 2R. That's per mono channel. It has a dual mono design, two power cords.

I think the technology has proved itself. We even had failures due to the feedback resistor burning out (someone should be slapped).

-Chris
HI CHRIS,
Yeah I had an Access to QSC RMX1850HD , Seen the Waveforms...Glitched during HF reproduction....
So Class-G is more accurate than Class-H but Costlier.....

To DJK & ANATECH,

Why Pro amps [QSC,CREST&others]are rated like this:
500W 8R, 800W 4R , 1200W 2R.....
is there anytype of limitation in term of Supply sagging , or limited power....

meanwhile We rate 500W 8R, 950W 4R , 1800W 2R
Rail sag is just 6Volts Max and output peak voltage Swing is within less 1 V max than VCC
Or there are any other circumstances involved...


Thanks Very Much
regards,

K a n w a r
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Old 28th November 2005, 04:50 AM   #24
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Hi Kanwar,

500W 8R ; 950W 4R ; 1900W 2R

But this does not reflect increased loss in 2R c.f. 4R or , in fact, any loss in your power supply due to lower load Z?

You lose 2.3 more volts going 8R -> 4R, then no more for 4R -> 2R.
I want your transformer manufacturer name.

Cheers,
Greg
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Old 28th November 2005, 05:06 AM   #25
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Quote:
Originally posted by amplifierguru
Hi Kanwar,

500W 8R ; 950W 4R ; 1900W 2R

But this does not reflect increased loss in 2R c.f. 4R or , in fact, any loss in your power supply due to lower load Z?

You lose 2.3 more volts going 8R -> 4R, then no more for 4R -> 2R.
I want your transformer manufacturer name.

Cheers,
Greg
Oh Greg,
Its written by mistake
I corrected the mistake......
It was Actually around measured at 1KHZ
500W 8R, 980W 4R, 1800W 2R

Thanks for the pointing the mistake...

K a n wa r
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Old 28th November 2005, 05:26 AM   #26
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Ah,

you must've known I'd be lurking. Almost had to take out the calculator!

Still, that PS with <0.1 ohm impedance including ripple. Amazing.



Cheers,
Greg
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Old 28th November 2005, 07:12 PM   #27
anatech is offline anatech  Canada
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Hi,
The Lightstar has an active power supply. The specs are published ratings that the amps will exceed. Therefore, the actual power output will show some sag in the supply.

We also have 110 ~ 125 VAC supplies. That will limit the power output to below what you can get on a 220V system depending on the current fusing.

Considering that this is an amplifier aimed at the home market, the output power is excessive anyway. Imagine needing two circuits at 15A, 120V for one amplifier.

-Chris
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Old 28th November 2005, 07:31 PM   #28
K-amps is offline K-amps  United States
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Quote:
Originally posted by anatech

The Lightstar would interest you. They used variable duty cycle to reduce a higher supply voltage to what was required. The frequency was very high, I can't remember off hand. I owned one of these Carvers too. It was the best sounding one they ever put out.

-Chris
Chris,

Since Bob designed the Carver Lightstar and the Original Sunfire around the same time, 94-95-96, I remember a white paper he wrote.... He mentioned 7000Hz ! So above 7kHz, the rails would stick to the higher one. (or max?)
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Old 28th November 2005, 07:58 PM   #29
anatech is offline anatech  Canada
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Hi Arif,
Good question. Never had a problem with this. My guess is the supply control looked at the peak (held) signal amplitude. The output was filtered so there was no residual RF in the output.

If you ran a 10KHz, high amplitude signal in, the supply would probably lock to the required voltage and not follow the waveform anymore. It would track lower frequency waveforms as in real music.

-Chris
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Old 28th November 2005, 08:41 PM   #30
K-amps is offline K-amps  United States
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That is what I gather as well... however, personally I never liked the Sunfire in the treble area... (Actually 2kHz and up). Can't explain it. I sold the Sunfire I had the next day back to the dealer (actually it was a 600wpc Sunfire signature) and got a Krell KAV-250a for the same price... Still have the 250a after 8 years.
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