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PostPosted: Wed Mar 07, 2018 8:07 am 
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Uunderhill wrote:
Have you tried a Class A amp biased at low currents,
but with a number of output devices ?
Opinions ?
If the bias is too low, and with number of output you won't enter in the optimal linear region which is a
bit higher than the half, at least for lateral mosfet. I didn't bother to try with any other devices since I don't like them.

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PostPosted: Wed Mar 07, 2018 8:08 am 
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I really hate to agree with Ken on this one... :o
But, I also... Would 'tend to agree' with the following two (2) statements:

Thank-you!

>> The best sounding amplifies with the cleanest clearest sound quality, with no additions and no subtractions and no obscuration of the fine detail we are actually listening for..have one to two output devices per channel. That--and no more. <<

>> That many transistors per rail is a problem. A serious problem that is never spoken of but everyone in the business --who actually listens to the amplifiers-...... knows it is there. <<


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PostPosted: Wed Mar 07, 2018 8:24 am 
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if using only 2 transistor is the best sounding amp, how much maximum power can it produce?


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PostPosted: Wed Mar 07, 2018 8:30 am 
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Well, theoritically Ken is right on this. With only one output there's no matching error.

However, I'm not aware of any single device that can push enough current to render a kickdrum as in real life.
Or the dynamic of a piano or cello or...

Amplifiers with a minimum of output devices are good with bookshelf or little standmount speakers.
But both of them can not render any dynamic as in real life. When we are in the room where someone
is playing piano (as example), we're not just hearing the piano, we also feel it with our body.
How the hell then a bookshelf can transmit that feeling ? Impossible. Simple.

Then, to me, this is not hi-fi. But for some, yes.
To each his own.

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Last edited by Nakamichel on Wed Mar 07, 2018 8:37 am, edited 2 times in total.

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PostPosted: Wed Mar 07, 2018 8:32 am 
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ADCO wrote:
Teo Audio wrote:
ripblade wrote:
A better indicator of whether an amp has good control over a woofer is to look at the number of output devices it has. Higher is better, IMO.



Except for the dirty sound brought about by too many output transistors....this might have been a good idea.

The best sounding amplifies with the cleanest clearest sound quality, with no additions and no subtractions and no obscuration of the fine detail we are actually listening for..have one to two output devices per channel. That--and no more.

I mean, this is going to be one confused sounding grungy mess:

Image

Whether it is $1000 from china or $50,000 from some western country makes no difference.

That many transistors per rail is a problem. A serious problem that is never spoken of but everyone in the business --who actually listens to the amplifiers-...... knows it is there.



I have to agree completely Ken, I have a Gamut amp which uses one giant output device and it is the most transparent to source amplifier I have heard in my system.... and I have had so many now I can't count....

this amp Gamut, how powerfull is it, and is that transistor a integrated circuit ?


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PostPosted: Wed Mar 07, 2018 8:47 am 
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Nakamichel wrote:
I guess you already know that I can't reveal the schematic of my amp.

What I can tell about it is:
I use 8 pair lateral mosfet/ch (one for CCS)
it is full symmetrical, two amp in one, then 2x +/- 14.14v
full dedicated power supply for every output pair (down to windings)
the input stage AND the driver stage is the same and is made with a composite amplifier, for each output pair
all the composite amplifiers work at +/- 18v full dedicated power supply for each composite amp (edit, 18v not 24v)
each composite amplifier is made with an opa inside the loop of another opa.

Why symmetrical ? Because of the capacitors. With that symmetry, power rails are kept at low voltage.
I'm now at 200 000uf all made with 200x 1000uf Nichicon caps/ch.
4 transformers of 4x 10v 800va per channel. (3200 va)

Each amp dissipate all the time just over 200watts of heat. Heatsinks stabilize at 52° after a long half hour...
And you are right about the power, I litterally destroyed 2 woofers voice coil with a stupid error on the volume.
Lateral mosfet are very the best, not as agressive as bipolars are on high dynamics.
But the best part is by far the linearity once the best biasing point is chosen.

DF is over 800 at 120hz. Since symmetrical design halfs the output impedance,
I had to use more output (and current) to deal with my Kappa's woofers (902-4477 instead original smaller magnet 902-3054).
The 2 woofers are in serie in an isobarik design per channel.

Do you like to hear the real effect of kickdrum not boomy and clear ?
10-15w class A is not enough for that as you said, try a 50w...
104lbs of pure pleasure.


Recall, that in an ideal CCS (constant current source) the input impedance is close to infinite.
So for the CCS, any opinions/advise on using a single switching MOSFET beast like one of these,
rather than paralleling up 8 lateral MOSFET's ?
https://www.mouser.com/ds/2/205/IXFN55N50F-1222358.pdf

.


zon001 wrote:
this amp Gamut, how powerfull is it, and is that transistor a integrated circuit ?

Its a switching MOSFET probably made by IXYS - here is one possible part number for the p type device.
IXYS IXTN170P10P

At reasonable listening levels - its not just about power
IMO the voltage rails on an amp help determine how "loud" an amp can be "turned up" before clipping.
Increasing the voltage rails will allow an amp to be turned up "louder."

But its current that builds up the magnetic field in the voice coil.
So an amp needs to have a low Zout to be able to deliver the current from the power supply
into the speaker load.

Analog amps with the lowest Zout usually have follower output stage.
aka - real class A amps.

.


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PostPosted: Wed Mar 07, 2018 9:16 am 
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No, I really don't know since this beast has an enormous 6700pf Ciss.
My 8 laterals total Ciss is close to half lower than that.
You will need a hell big driver for it. If not, bye bye high freq.
I then can't see any advantage.
It looks like someone has had influence on you, lol.

There are many way to configure a CCS.
The best (to me) is to also drive the CCS mosfet with another mosfet.
But now, you make me talking too much... :D

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PostPosted: Wed Mar 07, 2018 9:51 am 
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many integrated circuit transistors, are here today , gone tomorrow. many japaneese company that where using integrated transistors, where no longer available, just a few years later. and ounce no longer available, it would be very hard to substitute.


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PostPosted: Wed Mar 07, 2018 9:58 am 
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I have really began to learn some things due to especially the last 10 or so posts.
Much appreciated.


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PostPosted: Wed Mar 07, 2018 11:37 am 
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Nakamichel wrote:
No, I really don't know since this beast has an enormous 6700pf Ciss.
My 8 laterals total Ciss is close to half lower than that.
You will need a hell big driver for it. If not, bye bye high freq.
I then can't see any advantage.
It looks like someone has had influence on you, lol.

Well I used this type of switching MOSFET in a 1 hp motor speed controller.
The speed of the motor is changed by changing the ratio of the on and off times.
Then I found out Gamat uses something similar in their analog power amps.
But Ciss is massive so they need a small push - pull amp as a drive stage.

Nakamichel wrote:
There are many way to configure a CCS.
The best (to me) is to also drive the CCS mosfet with another mosfet.
But now, you make me talking too much... :D

I'll need to think about how 2 MOSFET's can be connected, so that the temperature co efficient of one MOSFET
cancels out the temp co efficient of the other one.
Not sure how to do that.

But for a simple CCS, I just use a power MOSFET, a bipolar transistor and a power resistor.
Yes, for this beast Ciss = 6.7nF - but used for a CCS, I don't think it needs much of a drive circuit.

The output section that swings up and down that would need the drive circuit.

So what I'm saying is use the beast for the CCS and the 8 lateral MOSFET's
for the section that swings up and down.

.


zon001 wrote:
many integrated circuit transistors, are here today , gone tomorrow. many japaneese company that where using integrated transistors, where no longer available, just a few years later. and ounce no longer available, it would be very hard to substitute.


Actually, the issue in audio is that Toshiba keeps on discontinuing the jFET's and lateral MOSFET's
they make.
As I said previously - Its a general design rule not to design a product
using components that are made by a "single source."
Make sure 2 or more companies make that part.

What happens if a single source company discontinues that component ?
Or a single source company can jack up the price at will.

.


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PostPosted: Wed Mar 07, 2018 4:29 pm 
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Bumpy wrote:
sthomas1049 wrote:
I don’t think it’s a clear case of no preamp = the best performance, even if one is not required for obvious source selecting etc. There have been many who have gone from no pre or a passive one to active and felt there was an improvement.


An active preamp changes the impedance that the amplifier sees vs a passive, or that of no preamp. So while something like a bare pot might sound fine at certain volumes, it does not at all volumes. An active has a much lower output impedance across the board than such a passive.

This lowered output impedance is beneficial if the amplifier has a low input impedance.

The rule of thumb I've heard is input impedance = 100 x output impedance. Some will say 60x is enough.

-- 06 Mar 2018 19:18 --

Teo Audio wrote:
analogluvr wrote:

I heard one and was not overly impressed. Sounded like a typical passive to me. Which is all it is. There were three of us at the listening session and two of us preferred a tricked out Bottlehead to the TEO. The third individual said he preferred the lows and mids of the Bottlehead but the highs of the TEO. Definitely not the grand slam it's purported to be, but that's Audio for you… :roll:



I was waiting for that. You see, yours is the only negative comment the preamp has ever garnered in any print or conversation, anywhere that I am aware of..

Any time the Teo passive pre is mentioned on this forum, you always go out of your way to get in there and deliver your commentary.

Isn't that interesting.

It's like you want it to fail and not be available to anyone. Bizarre.

This is all small scale audio manufacturing done by people pouring their lives into it ... to serve the music you so desperately want to hear - as best you can.

Yet you seem to have a need to get in their and make sure your personal result is taken as a gospel of high weighting, when the overall results in a far larger group...say otherwise. From my point of view, there is just no understanding of your logic, here.

For example, the two reviewers, overall (especially Doug) tried it out in multitudes of configurations and systems. Dozens of configurations, if not more. We've even had distributors of 35 years experiences in the highest of the high end (Hong Kong extreme market) say it is the best device they've ever heard, or not heard. Yet it sells poorly as it can't compete with the profit margin on a $20k-40k preamp, or the remote control convenience of other devices (it is necessarily hard core, as those volume pots are all compromises).

A Manufacturer of $5k-10k-15k tube preamps told their own customers/dealers once, right to their face, in our presence, that the Teo Passive is better than the best they've ever built or designed. Even in that extreme condition, still..no sale. It's downright weird. Passive preamps seem to fall in a hardcore disbelief hole of expectations.


We were not there to witness the event.

As far as we know, and quite possibly how the prospective buyer felt, this manufacturer may have been attempting to help the sale along for other reasons.

It's not enough to say something like "Nelson Pass says this is the best piece of gear he's ever heard" and cause a stampede to the gear makers door. People want to hear for themselves. Then they want to hear in their systems. Then it is quite possible that if the unit is totally transparent, they don't like what they hear because they finally hear how their other components sound; they prefer the coloration of the other piece.

There is no "one size fits all" solution here. And I am sure you've been around long enough to know that.

All your babbling about liquid wire operating under different laws of physics is just complete nonsense. But that's your usual MO. You talk people's ear off trying to use as many big words as you can and sound Uber intelligent, but ultimately you end up saying nothing at all meaningful.
And all that notwithstanding I am simply reporting exactly what we heard. Our source was a phono stage so perhaps that was a bit of a handicap as it may have slightly less drive then a digital source. I think Anatech has hit the nail on the head. A simple passive will do less damage than a bad preamp. And that's all you have there, a simple passive. Definitely not worth 5000 bucks or whatever it is you're trying to charge for it. One reason I jump in there is because I'm one of the few that is actually heard it. I would've loved it if people would've steered me away from some of my bad choices in Audio.
I was on a passive kick myself for a while. Ultimately the lack of dynamics and drive turned me away. I myself believe the reason an active preamp sounds better is because of the impedance matching.

Edited By Mod


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PostPosted: Wed Mar 07, 2018 4:30 pm 
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Sorry for the late reply, it's the international Wowen's Day. I had to do something for my beloved wife.
Hope you all guys did something for her. If not yet, it still time... you got few hrs left. C'mon guys !
:D

Uunderhill wrote:
Nakamichel wrote:
There are many way to configure a CCS.
The best (to me) is to also drive the CCS mosfet with another mosfet.
But now, you make me talking too much... :D
I'll need to think about how 2 MOSFET's can be connected, so that the temperature co efficient of one MOSFET
cancels out the temp co efficient of the other one.
Not sure how to do that.
Well, I can tell you that you seem to have a really good level in audio electronic.
It's actually because of the tempco that I use another mosfet. But they are not identical, of course. But well seen, man.
Uunderhill wrote:
But for a simple CCS, I just use a power MOSFET, a bipolar transistor and a power resistor.
Here you have to experiment.
In fact it is not that simple. A mosfet as CCS doesn't require current but voltage. In fact, that's the trick. I use ultra low current to drive them.
We need to stabilize that voltage with more that a simple bipolar. Not an easy task at all.
Uunderhill wrote:
The output section that swings up and down that would need the drive circuit.
So what I'm saying is use the beast for the CCS and the 8 lateral MOSFET's
for the section that swings up and down.
One of the main idea of my design is ultra short signal path. To achieve that,
all my circuit is just under the heatsinks. Note that I use point to point shielded wiring. No PCB at all.
Also, all the mosfets are in sandwich between both heatsinks for maximum cooling. I had then to use identical devices physically.

zon001 wrote:
many integrated circuit transistors, are here today , gone tomorrow. many japaneese company that where using integrated transistors, where no longer available, just a few years later. and ounce no longer available, it would be very hard to substitute.
Sadly, it happened to me.
The mosfet I use (Alfet) are no longer available. They have the linearity of the amazing real Hitachi 2sk1058...
The only good laterals remaining are the Exicon. But they are not even close as the Alfet for linearity... according to my experiments.

I still have around 1200 mosfets left. But after close matching, only enough to build only around 25 pair.
I have only two pair built. Still in their R&D's casing (very ugly computer casing). They at least sound close to what I like. And need for my Kappa's.

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PostPosted: Wed Mar 07, 2018 5:55 pm 
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zon001 wrote:
many integrated circuit transistors, are here today , gone tomorrow. many japaneese company that where using integrated transistors, where no longer available, just a few years later. and ounce no longer available, it would be very hard to substitute.


The Gamut is 200 watts , doubles up at 4 ohms and to the best of my knowledge can confidently push against 2 ohms

As for who said something about a single mosfet not rendering a kickbdrum realistic
Flat out and completely wrong. The Gamut amps are utterly transparent , I have yet to hear it clip ever and is as dynamic as anything I have ever heard.

What the Gamut product won't do is add anything... at all . It's the only amp I have had through here that is so transparent that every change I make is audible for better or worse.

I have no idea if it "integrated".... apparently it's a military spec unit , what ever that means


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PostPosted: Wed Mar 07, 2018 6:20 pm 
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ADCO wrote:
... As for who said something about a single mosfet not rendering a kickbdrum realistic
Flat out and completely wrong. The Gamut amps are utterly transparent , I have yet to hear it clip ever and is as dynamic as anything I have ever heard.

What the Gamut product won't do is add anything... at all . It's the only amp I have had through here that is so transparent that every change I make is audible for better or worse...

+1.

A good friend of mine uses TOTL 'Gamut Audio' Power Amplifiers in his Audio System (*And he can 'truly' afford anything).
He 'absolutely' swears by them.


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PostPosted: Wed Mar 07, 2018 6:42 pm 
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Nakamichel wrote:
Well, theoritically Ken is right on this. With only one output there's no matching error.

However, I'm not aware of any single device that can push enough current to render a kickdrum as in real life.
Or the dynamic of a piano or cello or...

Amplifiers with a minimum of output devices are good with bookshelf or little standmount speakers.
But both of them can not render any dynamic as in real life. When we are in the room where someone
is playing piano (as example), we're not just hearing the piano, we also feel it with our body.
How the hell then a bookshelf can transmit that feeling ? Impossible. Simple.

Then, to me, this is not hi-fi. But for some, yes.
To each his own.



Just to reiterate , and I am no tech here but your just wrong...sorry , not looking for a fight and/or argument but it's clear you have never spent time with a Gamut product.
While I don't know of any other product using their build tech ( or similar ) I can say with absolute confidence you are making a generalization that simply doesn't cover all .
In fact , using your piano example I can say that is also wrong with the Gamut products I have had . Further, my significate other was a young piano prodigy in England and still plays stunningly well... however her developement of Tourette's has all but halted her playing... anyway my current rig ( with Gamut) presents piano so well that she can normally tell you what piano brand is being played. Which blows me away on so many different levels.

Anyway, on these highly technical subjects I rarely chime in unless I no for certain the facts are just plain incorrect

Again, not trying to offend but that's just how it goes sometimes


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