[AKSA]

However, Steve, by the time you reach this point, you've forgotten half of what you know......

Reminds me of a bumper sticker I saw on a grey nomad's four wheel drive:  'Adventure before Dementia'.

Long may our blood flow down one leg and up the other......

Cheers,

Hugh

[painkiller]

Absolutely!!  We need to put in a low pass filter so it doesn't pick up radio stations!!

So, what's your take on the low pass Fc in this day and age? 

Been hovering these new amp threads for a while. I'm confident that your latest creations will be absolutely brilliant! Still enjoying my LF55 monoblocks. They've been with me for two or three years now, and I've never looked back. Epic gear.

[AKSA]

Hi PK,

Great to see you here, and thanks for the comments about your LF55, very nice of you.

At the moment I'm using 1K/220pF, but I'm sure open to suggestion.  You feel you can hear them, don't you?  Problem is, when you have very good HF performance, you have to guard against the entry of RF and other EMI.  It's also necessary on the output with a choke, of course.

Cheers,

Hugh

[stvnharr]

However, Steve, by the time you reach this point, you've forgotten half of what you know......

I think most people that know everything have it all down by 25, 30 at the limit. 

Therefore, you are too old to know everything, so you have to keep learning.
And the problem is, you don't know which half you know and which half you don't.

Just an aside.

Steve

[VYnuhl.Addict]

Hugh,


    Your right in all regards about the LPF!, except this filter is largely depndant on the amount of feedback used, in a "Lower" feedback amp we can get away with a very high -3db point as the amp is much less likely to ever get peturbed by RF signals. I still feel the audibility factor is there, and perhaps this may be related to phase anomalies with a lower cutoff FR. Strangely enough I do too notice improvements in sound with a higher cutoff frequency, provided the amplifier is stable initially without a LPF...



Colin

[painkiller]

At the moment I'm using 1K/220pF, but I'm sure open to suggestion.

That's a great choice. I landed on the same values for my LF's. The cap is pretty light, so it's an easy load for any preamp. It's not dark sounding, but it won't be bright or harsh sounding either. Perfect. 

[AKSA]

Thanks Colin,

Agree about the fb issue;  less means less filtering.  I guess it's important we realise that a speaker is actually an active load, and feeds back into the amp almost as much program material as it receives!

PK,

I'm delighted we hit the sweet spot!  I suspect that the phase shift of this cap is important somehow at high audio frequencies, smaller is better.  The highish R is an issue, I feel, but if the bias in the first stage is kept very low the series drop is still around 5mV, which is still acceptable for good input control.

Cheers,

Hugh

[Afterimage]

Simple little question on the Aspen Amps.  Can we leave them on 24/7 or do you recommend we turn them on and off according to use?

[AKSA]

Absolutely, Kieran,

You can leave on the Maya, it consumes 32 watts at idle, while the NAKSA70 does about 8W at idle.  The Lifeforce series are a little less than this - a tad more efficient - but as a general rule, all Aspen products are designed to offer this choice, either off, or on 24/7.

Years ago, I did a Class A amp called the Glass Harmony.  Each channel, and it was built as a monobloc, consumed 155W of power, so it made a very good room heater, suitable for lattitude higher than about 40 degrees, but NOT good in subtropical areas, let alone tropical.  This taught me the useful lesson that in a future, green world we would all have to consider energy use, and since then I have strived to avoid excessive waste of energy.

Hope this answers the question, now and again I miss the point!

Hugh

[chlorofille]

Hi Hugh,

Does the Soraya CB105 come as a module or only as an assembled stereo amplifier ?

Regards,
Dinesh

[AKSA]

Hi Dinesh,

The Soraya is a full on retail product, so comes only fully assembled.

Hope this helps,

Hugh

[chlorofille]

thanks Hugh!

Doing a little research atm. Kind of impressive considering Carlos,
who has built over 3300 amplifiers still praises your original 55 watt Aksa !! 

So if this Soraya is an improvement...

[AKSA]

Dinesh,

Sorry for late reply.

Carlos is an institution at DIYaudio, but all too often now is caught up in technical debates he cannot win because his knowledge is chiefly empirical and subjective, original sin in the eyes of a credentialled EE!

He has always been very enthusiastic about my amps, it is true, and this has been reassuring because his ear is VERY good.  I tire of the mutual mistrust between the EEs and the golden ears;  the truth is, both are needed, it's a lawyer/police standoff and it isn't improving with time.  In fact the whole adversarial 'stand and deliver' approach of the west makes me shake my head these days.

My thoughts are this:  no one escapes the basic engineering, it's perennial as the grass, and a thorough, working knowledge of Ohms and Kirchoffs laws is mandatory to design a power amp.  However, I challenge the notion that if you can't measure it, it is not there, as I have heard many subtle changes by simply changing operating points and component choices.  Neither do I accept the largely defeatist argument that the subjective is just that, and can't be trusted, and should therefore be ignored.  I think it is true that tastes vary, just as they do with food, art and sport, and they even change according to mood - especially with music.  But if subjectivity is so unreliable for the individual, then we must look to the group, and assess en masse, looking for preferences and consensus.  When you do this, you can pick out certain immutable observations, which are very useful for someone designing for mass appeal.  As a business, you must sell in numbers, so this approach is extremely useful anyway.

I try not to trust my own ears too much - I'm only one guy, and I'm clearly biased as the designer.  I get lots of friends, acquaintances and committed audiophiles to listen, and I can very quickly now find consensus.  Furthermore, I find that getting the engineering dead right is merely first base.  Then begins the tuning for best sound, with operating point and component choices.  This is the difference between competence and excellence.  This makes audio design something like art, because you find that different designers tend to have a 'house' sound.  Within limits, I think this is true of people like Nelson Pass, Andy Grove (Audio Note UK), Tim de Paravicini (EAR) and D'Agostino (Krell).  People buy on name, and for very good reasons.

Hugh