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Old 13th September 2012, 06:52 PM   #371
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Thanks Jacco, very delightful answer!
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Old 13th September 2012, 06:57 PM   #372
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Originally Posted by buzzforb View Post
Its not sarcasm and I am typing on a phone, sorry. I am not the one claiming to know anything, but you continue to argue with ANYONE who does not just accept anything and everything you say. Why not just get the parts and start building. You act as if all the variables you speak of cannot be modified or changed in circuit. You can easily get the parts. You can easily get the heat sinks. You can easily get a custom Piltron toroid. What is stopping you. Drop $1500 and get to work. I am sincerely interested in the results. Don't know what else to say so I'll stop bothering you.

Jacco, you ever heard the phrase " beating a dead horse". Here ya go.
oh my gosh!!!! it is sarcasm from the phone. Just get and build? Are you an engineer or you sell horses?
Before building anything you study and model and analyze and count cost!!!
I am not starting now like I said I am finishing up other projects and I have just limited time available like anybody else in the world.
Tjhe project will start in the next few months.
In the meantime I take advantage to do the upfront work and to locate the right parts needed for the project.
Don't you see your contribute is extremely useless?????
Just go back and re-read your posts in this thread (I hope your contribute to other thread is better)!!!
You only make sarcastc comments that have no point!
So if that is your style of partecipating, then thanks but don't bother!

In other words...bye bye!
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Old 13th September 2012, 06:59 PM   #373
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Janitor.
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Old 13th September 2012, 07:17 PM   #374
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Jacco,

you brought up a good point about the SE.
Using a resitors makes it a variable SE bias with output level.
Have you ever implemented an active SE bias vs passive?
If so would you mind sharing your opinion on this?
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Old 13th September 2012, 08:49 PM   #375
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Originally Posted by Stefanoo View Post
The basic thing you learn from output Mosfet is that their BIAS DEEPLY AFFECTS THE SOUND.

Same goes for amplifier!
Yes except that you've missed one very important point, it's the bias PER DEVICE, that matters for the sound quality, not the total bias of the amplifier (unless you're leaving class A and then you're on a hiding to nothing).

With a low power class A you will say use 1 amp worth of bias and 20 volt rails with a single pair of output transistors. Each device dissipates 20 watts at idle. With a bigger amp you would use two pairs of output transistors biased to 1.5 amps on 30 volt rails, with each device seeing 0.75amps of bias total and dissipating 22.5 watts at idle. Maybe we want to go one step further and use 2 amps idle, 35 volt rails and 6 pairs of output transistors. Now each transistor is has 0.66 amps of current flowing and each one will dissipate 23.31 watts at idle.

Notice something? As the power rails increase in voltage, the bias PER DEVICE drops, to keep the dissipation for each device in check. If you're after an amplifier with the highest bias current, for supposedly the highest sound quality, then going for a lower power design is the only thing you can do!

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Originally Posted by Stefanoo View Post
Now what you don't understand
Stafanoo, you need to be very careful when you make comments like that when your understanding of simple amplifier basics appears to be almost non existent.

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Originally Posted by Stefanoo View Post
is that having deeps doesn't mean lower quality, in the other hand means that they choose a simpler crossover which yealds to better sound in their and my opinion but needs to be matched to a monster amp like a Krell or big Pass.
It does mean lower quality, it is very simple, the output stage of the power amplifier will produce more distortion when driving a difficult load. A simpler crossover also does NOT give you better sound if the design is poor because of its simplicity - which the B&Ws are most certainly a consequence of. Ignoring that though, applying impedance compensation to the loudspeaker, so that it's easier to drive, does not impact on the frequency response or filter transfer functions one bit. All it does is reduce the stress put on the output stage, giving the amplifier an easier time and reducing the distortion that it will produce. Given a class A setting, if you've got a loudspeaker which is a bitch to drive, you might find you're leaving class A most of the time anyway. Compensate the loudspeaker design and now you're always in class A = better sound quality.

It is in my opinion that some loudspeaker manufactures like producing speakers that are difficult to drive because it helps encourage the whole 'I need a Krell' philosophy, that lots of audiophiles would be very happy to adopt.

As an example though KEF and Dynaudio have both used impedance compensation in some of their flagship designs to make them easier to drive. Why most don't do this is beyond me.

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Originally Posted by Stefanoo View Post
Which also makes sense since you spent so much on speaker you are not going to buy a cheap amp to match with.
Price has nothing to do with it. If you've got a difficult loudspeaker to drive, then not even the XA200.5 is going to cut it. You need a monster Krell or a Kilowatt from MF. This is the point, difficult to drive loudspeakers and class A amps do not make for happy bed fellows. The loudspeaker has put a limit on your system which says, do not even consider class A as it's ill advised. The class A amp might cost $1,000,000 so surely you're not skimping, but it will sound terrible. This is one of the reasons why it would make lots of sense for you to measure what you need, even if you were going to buy something from the XA series measuring would make sense then too, because you might find you don't even need the XA200.5 and can easily do with the model below it, saving you some pennies and the planet from the reduced energy consumption.

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They claim that final result will be batter than having a speaker with more complicated crossover and simpler power amp and if you think through this makes total sense.
None of that makes any sense. Even a monster Krell will sound better if the loudspeakers are easier to drive.

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Originally Posted by Stefanoo View Post
I don't need to audition the XA200.5 to know that it is a wonderful amplifier.
No, it seems that anything with a large price tag, in your opinion, is going to sound wonderful.

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Originally Posted by Stefanoo View Post
In the meantime I take the opportunity to build something fun and hopefully very sound rewarding to not feel the need to spend this amount next year and instead use it for something else or save it.
Building something like an XA200.5 as a first DIY amplifier project has the potential to turn into something the opposite of fun. This is one of the reasons why I recommend you build something lower power with less invested and a lot less to go wrong. At the very least measure how much voltage swing you need to reproduce music at a normal listening level, so you actually know how big you need to go, for it to work appropriately.
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Old 13th September 2012, 09:17 PM   #376
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oh thanks for your insight 5th.
I didn't notice that current drops down as voltage goes up to check the fixed 19W Power dissipation's target!
Thank you so much!!!!

Ok now seriously, there are trade offs on both worlds and if you read NP's comment on Aleph X thread, he states that a good low power amp can sound just as good as a well designed high power's and vice-versa.
You might decide that dynamic and realm are not your cup of tea and decide that you don't need the extra power and you might go for a very high-efficiency low power approach which can be very neat too.
Myself, I go for the high power and wouldn't like to debate this since it is my personal choice I am the one who is gonna make it and listen to it.

This is not my first project, maybe you don't understand my background which is ok, it doesn't matter!

About speaker manufacturer desing's choice I don't criticize them as behind those there is a team of very experienced and skilled engineers who have worked on speakers for a long time.
If you don't like B&Ws don't get them and move on, but I wouldn't say they haven't forgotten something that you see because obviously they have noted the same thing long before you and that there is a reason as to why they have done that and you have to be willing to accept that they might be right as well.
Ultimetly the sound of the speaker is wonderful and the simple X250 can drive them very well with no problem, so I don't agree with you AT ALL that 800 are hard speakers to drive.
I see that needle moves a little out of the Class A zone which means that the speaker requires more than what the X250 can offer in terms of pure Class A.

Once more, I don't need to audition the XA200.5 to know it is a wonderful amp.
Obviously when I will bring my self to buy one I will audition that against 600.5 just because they are significantly different and I might prefer one over the other but no question they are both state of the art amplifications.

So bottom line I don't want to argue or I will stop posting, because it seems that people here are in the mood for argument and attacking and sarcasm.
I ask honest questions, if you don't feel like answering then don't, if you do, just asnwer polite that is my policy!!
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Last edited by Stefanoo; 13th September 2012 at 09:24 PM.
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Old 13th September 2012, 09:28 PM   #377
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Quote:
Originally Posted by buzzforb View Post
ever heard the phrase
Me been spanking Stefanoo for the last 6 years : Krell KSA 50 pcb

So, why give up now ?
Who knows, maybe some other folks like to read my dribble on mixed SE-PP trivia.
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Old 13th September 2012, 09:31 PM   #378
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ahahahaha....that was fun old time!!!

I was back in Italy back then...ohhhh...nice...miss that!!!


I think that the insight you are giving on the SE-PP are really usefull for everybody! but hey don't forget I like to learn new things and that is why I don't give up either and you are definitely more expert than I am in audio design.
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Last edited by Stefanoo; 13th September 2012 at 09:33 PM.
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Old 13th September 2012, 09:42 PM   #379
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better and better

recently I discovered that isn't Stefanoo one - who is idiot and/or dyslexic .

I am idiot ......... having so short memory , forgetting how many times I read , or even was sucked in burlesque
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Old 13th September 2012, 09:49 PM   #380
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Zen really I want to be in peace, so I am sorry if I was offensive to you or if I mis-uinderstood and I don't hold gradges if you mis-uinderstood me and called me names.
Let's just move on as I appreciate you comments....

are we good?
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