Magfan posted


Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17722
Registered: May-04

"Magfan posted on Wednesday, February 13, 2013 - 20:21 GMT

Pass is experimenting w/ V-FETs.

'd' amps have indeed come a LONG way. The DIY crowd, however, while likeing the 'chip' amps have also gone heavy for HYPEX the peak of which is the NEW N-core stuff.....NOT available to OEM or commercial builders."

Your link to the HYPEX article doesn't seem to work, leo.

You know I appreciate NP's position in audio, but this, " ... triode performance is limited partly by the need to transform the high voltage / low current operation of the triode down to the low voltage / high current domain of loudspeakers. This means a transformer and all the distortion comes with it" ...

seems a bit gratuitous. Suddenly Pass has problems with electro-magnetic induction?! I would think that should come as a bit of a surprise to most folks who follow Pass and First Watt.

"Of course it would be nice if Triodes drove speakers without transformers."

It would, but as Pass says, "It has been a goal of some designers to get transistors to sound like Triodes, with very limited success. Fets can sound like Pentodes, but it takes a particular set of gyrations to make a Fet do the 'Triode trick'."

Why ask a triode to not act as a triode? Triodes have been driving sensble loudspeakers for nearly one hundred years. They just don't like what today's "modern" speaker designers tend to put out.

"Second, we want a low Drain resistance, equivalent to the Plate impedance of the Triode. This is where gain device can be regarded as a variable resistor instead of a variable current source.

Why do we want this characteristic? Three reasons:

First, it allows a single gain stage with both voltage and current gain, and having a high input impedance and low output impedance without a feedback loop or degeneration.

Second, this character allows "working the load-line", the particular description of the path of the gain device through the voltage/current region in the course of amplifying into the loudspeaker. By choosing this line wisely, you can achieve intrinsically lower distortion. Pentodes and Mosfets aren't very good at this."

Gosh! Do you really think Pass has never heard of a "beam power" tube? Surely, he must know triodes tend to have only second order distortions? What am I missing here?

"Of course the audience for such an amplifier will only want to know about the sound. How does it compare with SETs from a subjective point of view? Having made a variety of these amplifiers at this point I can say that first off, they can be made to sound exquisitely in many of the systems that would enjoy the performance of a SET amplifier.

These would be your high sensitivity loudspeakers featuring compression drivers or �€ï¿½wide band�€ï¿½ drivers with big magnets and light paper cones.

Here is a comment made by a listener who lived with a simple prototype SIT amplifier driving Lowthers:

The amp sounds "big". There is a large, open sound stage that fills the room, that is the first thing that you notice when the amp is plugged in. The effect is a little intoxicating. ...the SIT seems to bring a lot more control & detail to the speaker. The tube sweetness is present, yet the presentation is very clean. This is like a very nice low distortion SET. The SIT presents details, but with proper dynamic contrast. Details do not poke you in the eye, they just naturally unfold as part of the music.

Do simple SIT amplifiers sound the same as single-ended Triodes (SETs)? That would be a matter of opinion. Without an output transformer with its significant limitations, the SIT has a bandwidth and distortion edge. On the other hand, some people like the sound of their transformers."}

No matter what Pass has already accomplished,this seems to be re-inventing the wheel when simply refining the wheel is what is being called for.

"There is an incremental, yet noticeable shift in the character of the Millenia amplifier when it is used in battery mode. For this evaluation I used an automotive jump pack for its battery and recharging capabilities. A cable had to be fabricated to fit the power port of the jump pack, but that was an easy task to accomplish. When being fed 12-volt power, the Millenia amplifier has increased micro detail, lower noise floor, and improved spatial presentation. The tonal balance of the amplifier undergoes a subtle shift, moving from a slightly warm and full character to one that is delicate and lighter in tone.

In many respects the Millenia amplifier in battery mode is closer in sonics to my Electra Print 300B SET amplifier than it is any conventional solid-state piece. When revisiting the Lucia Hwong piece I found that high frequency notes had a longer decay pattern and had a greater degree of shimmer. The distinctive tone of the wood flute in the opening passage had gained a higher degree of realism. The vocal passages moved farther back in the sound stage and now floated in a space above the instruments, expressing the surrealistic feel of this composition. These gains in musical reproduction move the Millenia amplifier closer to what the Electra Print amplifier achieves, which happens to be a $4000 amp and preamp package. While the Millenia does not have the harmonic density, or the complete transparency of the SET amplifier, it comes shockingly close.

Which is quite an accomplishment for a $500 integrated amplifier.



Gold Member
Username: Superjazzyjames

Post Number: 2110
Registered: Oct-10

Gold Member
Username: Magfan


Post Number: 3009
Registered: Oct-07
Jan, I suggest you take up your objections with Pass his-own-self.

Is Pass reaching the 'end of the rope'? I don't know. He has certainly had a prolific career with many meaningful and good sounding inventions. Is there an end? Will he feel the need to prove 'I've still got it'? I don't know......But DO lust after some of the XA series....maybe a pair of the biamp my panels!

One day I'd love to have the time....and more importantly, the $$$ to experiment with high sensitivity speakers. To that end, the amp you linked would certainly be a nice addition. Good power, minimalist design.

The N-Core Hypex is also attractive...having also garnered some decent reviews. I'd love to biamp my panels with a pair per side. That'd do it, don't you think?

Gold Member
Username: Superjazzyjames

Post Number: 2159
Registered: Oct-10
Wow! That was weird! Jan when I first saw your op, all that showed up was a bracket...that's it. Now, I look back and there is post. Any idea what happened?

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