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Old 27th September 2012, 07:45 PM   #31
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Hi Andrew.
Doable at 8 ohms . I guess not so doable into 4 Ohms. Well doable but with dramatically increasing cost. I was looking for a low cost introduction to class A . Do i want class A i dont know . the closest i have come to listening to class A amplification is a big old Pa amplifier at approx approx 1 Watt . Not a good introduction To class A i Know btu there it is . I have bee listening to A 80 watt onkyo from the 90,s . Wide bandwidth , Low distortion . Highish slew rate 150 V ms. It gives a cold impression . Loads of feed back maybe to get good mesurement .. The Tangent sounds more neutral and all about the music . In fact very nice
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Old 27th September 2012, 08:11 PM   #32
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Hi Madtecchy,

I am stating my own subjective experience only and not general to DIY, but in my opinion there is a bigger difference in sound character between single ended class A and push-pull class A than between push-pull class A and class AB.

Also your question regarding 4 and 8 ohms. No there need not be an increase in power dissipation if you set the power into 4 ohms the same as 8 ohms.

In other words, although you would increase the bias current to accommodate 4 ohm load, you would decrease the supply voltage accordingly and the heat caused by dissipation would remain basically unchanged. In other words a 10 watt into 8 ohms class A amp would get just as hot as a 10 watt into 4 ohm class A amp.
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Last edited by Nico Ras; 27th September 2012 at 08:14 PM.
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Old 27th September 2012, 08:59 PM   #33
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Hi Nico .
I Understood it was your subjective expirience. yours and jays and andrews advice became a good aid while i was thinking about what to do next. for now i have decided to Mono block the amp so i can place an amp directly behind each loud speaker. I have read a few krell ksa50 reviews and cant help wonder how much the topology of the amplifier has in the krells sound character . From what i am hearing at the moment on the tangent i would say quite a bit .
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Old 27th September 2012, 11:23 PM   #34
Jay is offline Jay  Indonesia
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Madtecchy, your amp has different topology than the Krell, or what Nico has posted.

(1) Your amp has a CFP driver, or the output takes the input from collector of the driver.
(2) Your amp has its driver's NOT connected to the output.

The Krell has emitter follower driver with emitter tied to the output.

Both of the 2 points above make a big different in character. And I favor your amp!
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Old 28th September 2012, 09:07 AM   #35
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by Jay View Post
Take for example a 30W class-A amp. ...................even if we listen below 5W,.............
30W amplifier.
I hope you do most of your listening with average levels below 300mW, not 5W !!!!!
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Old 28th September 2012, 09:14 AM   #36
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Quote:
Originally Posted by Jay View Post
Madtecchy, your amp has different topology than the Krell, or what Nico has posted.

(1) Your amp has a CFP driver, or the output takes the input from collector of the driver.
(2) Your amp has its driver's NOT connected to the output.

The Krell has emitter follower driver with emitter tied to the output.

Both of the 2 points above make a big different in character. And I favor your amp!
Madtecchy, there you have it in a nutshell. Krell sounds good but it would seem that your amp sounds more favorable.

I learned to use the word "better" very selectively here on DIY as it can get you into a ton of trouble. It appears that Jay has learned this lesson too.
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Old 28th September 2012, 10:25 AM   #37
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Nico Ras View Post
I learned to use the word "better" very selectively here on DIY as it can get you into a ton of trouble. It appears that Jay has learned this lesson too.
Hehehe I understand what you mean. But I think I have never learnt that one

I used "favor" because I'm 100% sure that the Krell will be favored by at least 75% listeners, may be even including Madtecchy (no surprises for me, and I'm firmed with my opinions). So it was not because I didn't want to get into trouble, but I tried not to mislead people.

I'm aware that the more experience people have, their preference may change. For me, speaker is the most important. From amps (and from audio system), what I need is musical enjoyment, and that means no fatigue. Fatigue may come from IMD or whatever, I don't care. I just know it when it is there, and I don't want it. It is for me the most important criteria of an audio system, period.
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Old 28th September 2012, 10:36 AM   #38
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by AndrewT View Post
30W amplifier.
I hope you do most of your listening with average levels below 300mW, not 5W !!!!!
I mean 30W class-A (full power), but listened at 5W output.

Take for example, a case where we listen to music at 300mW, and assume we get 300mW at class-A with 400mA bias. Now, isn't it obvious that THD and listening tests show differences with changing bias from 600mA to 1.5mA? So listening in class-A region (no crossover distortion) is not really the point.

Quote:
Originally Posted by AndrewT View Post
I hope you do most of your listening with average levels below 300mW, not 5W !!!!!
Theoretically we don't listen to watts or power but SPL
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Old 29th September 2012, 11:39 AM   #39
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by Jay View Post
I mean 30W class-A (full power), but listened at 5W output.
You seem to be missing my point.
If your average listening level is really of the order of 5W and you are using a 30W amplifier then you have an overhead of ~ 8dB to allow for peaks in the audio signal of just 8dB above the average level.
That means that even for highly compressed music the audio signal will be frequenctly and repeatedly clipped.

If the overhead is increased to say 16dB then the clipping events will be less frequent.

If you choose to listen to less compressed audio signals then your are more likely to need an overhead (from average level to peak level) of 20dB and some music can require upto 30dB of overhead to avoid clipping of the Audio Signal.

You can't listen at average levels of 5W from a 30W amplifier without risking very frequent clipping of the audio signal.
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Old 29th September 2012, 12:12 PM   #40
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by AndrewT View Post
You can't listen at average levels of 5W from a 30W amplifier without risking very frequent clipping of the audio signal.
I don't fully understand your point. May be I don't understand at all

I like to shoot for the lowest THD at 5W, instead of 0.3 volt input (the 5W number came from my experience listening to small chip amplifiers). It is supposed to be a class-A amp with clipping above 30W. Of course some music have dynamic short term power. But what is the context that I cannot listen at average level of 5W from a 30W amp? That I will experience clipping? What happen then if I experience clipping? Why did you hope I do most of my listening with average level below 300mW, not 5W?

Quote:
Originally Posted by AndrewT View Post
30W amplifier.
I hope you do most of your listening with average levels below 300mW, not 5W !!!!!
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