Been thinking about a while regarding these few doubts on passlabs and Firstwatt.
Passlabs amps had many Mosfets in the output and little bias per mosfet.
As in order to overcome the gate capacitances the bias is increased and when you add many mosfets on the output the bias is being split and these days its more than 10 per rail ( if its super symmetry ) so consider if the bias is about 2.2Amp for a 100W class A then since its super symmetry there are two amplifiers in fully balanced config. so consider using about 10 per rail and total 40 per channel so the bias per mosfet is about 50ma which is quite low even if this value being 200ma per mosfet is quite low. Why does Nelson choose this route in passlabs.
In Firstwatt amp you have exactly using as much required with few mosfets in the output stage.
Why does passlabs chooses the huge number of mosfets in the output stages? where Firstwatt doesnt.
when the review was made in the comparision with F3 , XA30.5 and 30.8 the review was better for the 30.8 as substantial difference in sonic qualities.
http://www.avsforum.com/forum/90-re...series-vs-xa30-5-vs-first-watt-f3-review.html
why not nelson using the large number of output stages in the Firstwatt amplifiers?
Passlabs amps had many Mosfets in the output and little bias per mosfet.
As in order to overcome the gate capacitances the bias is increased and when you add many mosfets on the output the bias is being split and these days its more than 10 per rail ( if its super symmetry ) so consider if the bias is about 2.2Amp for a 100W class A then since its super symmetry there are two amplifiers in fully balanced config. so consider using about 10 per rail and total 40 per channel so the bias per mosfet is about 50ma which is quite low even if this value being 200ma per mosfet is quite low. Why does Nelson choose this route in passlabs.
In Firstwatt amp you have exactly using as much required with few mosfets in the output stage.
Why does passlabs chooses the huge number of mosfets in the output stages? where Firstwatt doesnt.
when the review was made in the comparision with F3 , XA30.5 and 30.8 the review was better for the 30.8 as substantial difference in sonic qualities.
http://www.avsforum.com/forum/90-re...series-vs-xa30-5-vs-first-watt-f3-review.html
why not nelson using the large number of output stages in the Firstwatt amplifiers?
Comparing low powered Single ended circuit (F3) vs Push Pull circuit is not a fair comparison without considering speakers.
why cant we add 10x output mosfets with reduced bias per fet with Firstwatt series.
So you mean to say that using many mosfets will control the driver well than 1 mosfet?
If you have a speaker that hits 2 Ohms in places and is 83dB, then certainly more mosfets is better.
You can build these amps anyway you want. If you are building for yourself then it makes sense to consider the speaker you are building the amp for and build accordingly.
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also - driving one (or just maybe two) pair(s) of output mosfets is putting vastly different challlenge to front end , than driving 10 pairs (per side)
say that one typical PL (side) OS is presenting ~5K of load to preceding stage ....... not counting amount of capacitive burden , included in that
say that one typical PL (side) OS is presenting ~5K of load to preceding stage ....... not counting amount of capacitive burden , included in that
I don't mean to sound rude but I have to speak the truth here,
if this guy has 108dB speakers and with F3 at max volume he says it's not loud enough, then the guy honestly must have serious inadequacies with his ears and therefore everything he has to say is not worth a cent unless of course someone else had the same hearing inadequacies.
"The amp has no/minimal added gain and therefore could not drive the Duo Omegas to the desired volume level with my pre-amp."
I don't believe a word he has to say.
if this guy has 108dB speakers and with F3 at max volume he says it's not loud enough, then the guy honestly must have serious inadequacies with his ears and therefore everything he has to say is not worth a cent unless of course someone else had the same hearing inadequacies.
"The amp has no/minimal added gain and therefore could not drive the Duo Omegas to the desired volume level with my pre-amp."
I don't believe a word he has to say.
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Yeah unfortunately. I thought I better at least look at the link if I am going to comment about his question.
What a load of crap.
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If you keep an eye on updates for the 6moons F7 review it is highly relevant to your concerns.
"From speakers like the 85dB EnigmAcoustics Mythology M1 super monitors to the 87dB German Physiks HRS120 full-bandwidth omnis; from the 85dB transmission-line Albedo Audio Aptica to the 92dB impedance-compensated Sounddeco Sigma 2 and 93dB augmented widebander of the soundkaos Wave 40 - was our XA30.8 actually overkill? Would/could the F7 do just as fine a job? If not, where and how did it fall short? At $6'500 and given its specs, one naturally expects the smallest Pass Labs stereo amp to fly the taller flag. But did my loads and listening SPL exploit its advantage? Or was the XA30.8's true potential sitting there sadly untapped like a V12 taken out for a grocery run on sunny smooth roads?"
I think the difference is primarily in bias levels. More devices (and bigger sinks) let you spread out the heat and utilize more of the heatsink. The Pass Labs stuff is (usually) higher wattage and able to deliver more current into low-Z loads (which means more bias). Also, running more devices at lower currents may be more durable.
The firstwatt stuff is also geared to (eventually) be D.I.Y-ed. It's not really easy for an individual to match dozens of output devices. Also, I am not sure the front end of an amp like the F5 will drive dozens of outputs. The firstwatt amps are generally designed with simplicity in mind...
But, it's entirely possible to build a a BA output stage or F4 with many, many devices.
I've wondered if there is a difference between say 2 output devices with 2 amps total bias and 4 output devices with the same overall bias. I tried it with my F5. It wasn't a totally fair fight as the single pair f5 had IRF outputs and the 2 pair F5 had Toshiba mosfets. The 2 pair F5 sounded better to me than the single pair f5 at the same bias.
The moral of the story: Bias is king and big heatsinks are the best money you can spend.
The firstwatt stuff is also geared to (eventually) be D.I.Y-ed. It's not really easy for an individual to match dozens of output devices. Also, I am not sure the front end of an amp like the F5 will drive dozens of outputs. The firstwatt amps are generally designed with simplicity in mind...
But, it's entirely possible to build a a BA output stage or F4 with many, many devices.
I've wondered if there is a difference between say 2 output devices with 2 amps total bias and 4 output devices with the same overall bias. I tried it with my F5. It wasn't a totally fair fight as the single pair f5 had IRF outputs and the 2 pair F5 had Toshiba mosfets. The 2 pair F5 sounded better to me than the single pair f5 at the same bias.
The moral of the story: Bias is king and big heatsinks are the best money you can spend.
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