[J Harris]

Anyone know the input sensitivity of the AKSA 100 N+?

(Mine is converted to balanced inputs - don't know if this affects the question.)

Thanks,
Patrick (J Harris)

P.S. tip: try Auditorium 23 speaker cable with the 100 N+ if you can. It's amazing!

[AKSA]

Hi Patrick,

575mV rms for the single ended version;  for your balanced input version, I would say half this, at each input, 575mV approx fully balanced.

How is it playing?

Cheers,

Hugh

[J Harris]

It's playing absolutely beautifully. The only kit-built/DIY component (well, aside from Garrard turntable plinth) in the system.

I'm experimenting with other cables besides from the Taras and experiencing significant improvement. Auditorium 23s this week, which were wonderful - natural, musical, but neutral - the sound just broadened across the spectrum. Silences becamse more silent. Surface noise on vinyl because slightly more evident but also, oddly, slightly less annoying. It also sounded, subjectively, slightly louder.

Next up: Audience AU-24s. But I have difficulty imagining cables that beat the Auditoriums, at least in this system (synergy being all, in my view).

Note: all these are thin cables. The Audioriums have a handmade cotton shield (that LOOKS handmade - I think these are built to order) that is supposed to act as an excellent dialectric. Who knows, it looks kind of cool and non-audiophile cable-ish.

Edit: I suspect my VMPS hybrid ribbon monitors are tougher to drive than their 90 dB sensitivity rating suggests. The manufacturer recommends a high current amp, whether tube or SS. The AKSA might be pushing it _just slightly_ but it could also be a room-size issue or a cables issue. I can get quite loud, but there is a sense, especially on large-scale orchestral pieces or rock music, that the amp is straining to move air on the VMPS woofers at really ear-splitting volumes. Which one likes to do sometimes.

However it's a tribute to the AKSA that this limitation is making me explore speaker cable and speaker options rather than amp options. I've been through a zillion amps and the AKSA is the most musical and troublefree amp by far. I'm sure a massive tube Conrad-Johnson Premier 4 or other such monster would slay me - also a monster NYAL, or possibly an original Harmon-Kardon Citation II. But I already have the trouble of dealing with 24 tubes in the Io Sig and its power supply, the 8 tubes in the BAT, the maintenance, the replacement parts and tubes, the RF, and finally the heat and electricity bills they all generate! None of this with the nice musical N+.

I prefer to keep my tricky little constant maintenance issues focused where they belong - in the analog (only) front end - and let the rest of the system just do its work, thank you very much.

We'll see if VMPS's new "constant directivity wave guide" mod makes a huge difference (if they ever finally get it into production for my model -- see the VMPS forum for discussion)... and if not, then it's back into the speaker world. I quite like (but haven't heard in my system) Reference 3As. I bet the AKSA would drive 'em like a dream too.

Patrick

[J Harris]

Oh also, dumb question from non-techie, Hugh:

My Io Sig phono stage puts out a mighty 72 dB (from a 3uV MC cartridge), and then my BAT line stage adds up to another 18 dB in gain depending on volume position.

This wouldn't be overloading the 100W N+ with its input sensitivity of 575mV rms at each input, would it?

I don't know the formula here - but I'm trying to figure out the impedance matching and gain matching of each component through the chain - because I have a feeling that these are crucial for obtaining good sound.

The gain matching is above; on the impedance matching I have:

47Kohm output impedance from Io Sig
100K minimum input impedance at BAT (up to 1 meg depending on volume position)

400 ohm per phase output impedance from the BAT
43.5K and 45K input impedance on the 100W N+ (non-inverting and inverting phases respectively)

That all looks pretty smooth and all right, wouldn't you say? (On the impedance front anyway).

Edit: Of course cables could affect all this, couldn't they!

Best
Patrick

[ctviggen]

The formula is gain (in dB) = 10 log (P1/P2), where P is a power.  Because power = the square of voltage divided by resistance, the formula is gain = 20 log (V1/V2).  Thus, 18dB = 20 log (575/v1) or 10^0.9 = 575/V1 or V1 = 575/10^0.9 or 72.4 mV to give you the complete 18dB max output at full throttle (ie, full volume position).  I think what this means is that if your phone stage put out 72.4x2 = 144.8mV, then you'd hit 575mV at only half throttle on the BAT line stage.  So, you'd only have your volume turned up half way but the amp would be maxed out.

[J Harris]

Whoah - lots of information but I think I get it. Thanks ctviggen.

So, all things considered, do I have good gain-matching in place?

Best
Patrick

[AKSA]

Hi Patrick,

Sorry about delay - your rig will work fine, though gains seem a bit high, but if there is too much gain there, you can adjust the volume control circuit with an additional high quality resistor from source to the top of the pot to use only a portion of it.

Generally, the best gauge of whether it's all working correctly and gains are about right is that normal listening levels on the volume pot are approximately 1/3 the way around.   This gives room for really loud settings, yet takes the regular listening point further around than the very tetchy first 90 degrees.

As you can see, terribly technical!!

Thank you, CTViggen, for your generous response!

Cheers,

Hugh

[J Harris]

Hi Hugh!

Heh! My BAT preamp actually has a continuously rotating volume knob (it just keeps going round and round) with a digital display of 0 to 99...

However I think I'm in the right ballpark, gain-wise - it just sounds right.

Best
Patrick