Can I ask an audio question here Re: NAD MosFet & Bipolar stereo amps?

[audionaut99]

Hello all, forgive me if this is wasn't entirely appropriate for this forum but some of you might know precisely what I'm speaking of;

Can anyone tell me (with ABSOLUTE certainty) which of the older generation NAD amplifiers (2200, 3xxx, N2xx, eN3xx, etc.) used bipolar output transistors and which one's used mosfet devices? I already know that the 2400 & 2600 'power envelope' used fast & tight sounding Bipolar devices but I can't find one in Europe that runs on 220v-50Hz. I see many of the other NADs for sale locally but I fear they might be of their Mosfet design which not ideal for the bass amp in bi-amping.

Also, I am eventually seeking an older generation (110v powered) NAD Integrated amp (or similar durable brand) which uses mosfets and not bipolars to modify and give to a friend in America - can anyone please tell me which of the older lower-power (40-75wpc) NAD Integrated amps (or similar sweet-sounding durable Fet integrated amps) that are likely to be found cheaply but used only m-Fets in their output stage?

I'm only seeking advice and model numbers to research at this time. please reply to sam_and_marty1(at) yahoo Thanks!

[Steve Conner]

The MOSFET sound thing is a myth, there's no audible difference between MOSFETs and bipolars in well-designed hi-fi amps.

I imagine they are switchable to run on either 110 or 220V, since NAD sold their stuff worldwide.

[audionaut99]

[Steve Conner wrote] 'The MOSFET sound thing is a myth, there's no audible difference between MOSFETs and bipolars in well-designed hi-fi amps.'

...uh, Steve, thanks for your time but I was asking for facts & advice. Your reply did not answer my question, but allow me to offer a brief summary of fact: For one thing; Fet's and Bipolars have a DRAMATIC difference, and my 20 years of personal experiences with using Fet's on the bottom-end of bi-amping (vs. using them strictly for amplifying the mid & high freq upper-end of a system) easily & perennially backs up this long-known fact.

Bipolars are 'Current amplifiers', actually have a slew rate conducive to bass control, and so control bass signals immediately & noticeably faster & tightly where Mosfets certainly cannot.

MosFets, like vacuum tubes, are on the other hand 'Voltage amplifiers' and reproduce more faithfully at mid & higher frequencies and so are accordingly relied upon in that application.

The well-known fact is (unless one has $50,000+? to invest in a pair of Boulder (Fet) mono blocks, or make a Mark Levinson Bipolar -> Fet compromise) Fets immediately and painfully sound mushy and-or muddy at bass frequencies, but then they surprise-pacify you with their life-like midrange+ presentation. But just because some manufacturers already had 1000's of Fet Amps stored and so builds powered subwoofers with them does not change this fact; if you see a powered subwoofer powered with a Fet amp, no matter how much one pays for it - it still sounds muddy with uncontrolled slushy bass notes (compared to a Bipo amp) no matter how good your room acoustics are. A 'real' powered sub especially below 70Hz should use Bipolar output devices and NOT Fets because of this.

If one is only using a single Amplifier for full-range (not bi-amping) then it is that person's musical preferences for sweet top-end vs. solid bottom end telling him to use a Fet or Bipo design - which can be not as easy in deciding for example in the personal choice of a Fork vs. a Spoon to eat your bowl of rice with.

We should never see in our lifetime the classic Amp Manufacturers like Krell, Threshold, Bryston, etc. ever use fets on their output stages or they would not be regarded as the famous 'rock-solid' Amp building companies we have always referenced for tight bass reproduction & overall solidity. Fets can sound great but you can never go wrong with Bipolars.

[Steve Conner also wrote] 'I imagine they are switcha'ble to run on either 110 or 220V, since NAD sold their stuff worldwide.'
Uh..., Steve, but it might be better that one replies to a forum question when they are only certain of a given thing, but thanks for your guess.

Regards to the group forum

[imaradiostar]

Hello all, forgive me if this is wasn't entirely appropriate for this forum but some of you might know precisely what I'm speaking of;

Can anyone tell me (with ABSOLUTE certainty) which of the older generation NAD amplifiers (2200, 3xxx, N2xx, eN3xx, etc.) used bipolar output transistors and which one's used mosfet devices? I already know that the 2400 & 2600 'power envelope' used fast & tight sounding Bipolar devices but I can't find one in Europe that runs on 220v-50Hz. I see many of the other NADs for sale locally but I fear they might be of their Mosfet design which not ideal for the bass amp in bi-amping.

Also, I am eventually seeking an older generation (110v powered) NAD Integrated amp (or similar durable brand) which uses mosfets and not bipolars to modify and give to a friend in America - can anyone please tell me which of the older lower-power (40-75wpc) NAD Integrated amps (or similar sweet-sounding durable Fet integrated amps) that are likely to be found cheaply but used only m-Fets in their output stage?

I'm only seeking advice and model numbers to research at this time. please reply to sam_and_marty1(at) yahoo Thanks!

no questions allowed.

Just kidding.

I tend to agree with Steve here- mosfets and bipolars both are pretty linear right up till they run out of voltage to swing. If a mosfet amp sounds different from a bipolar amp it has less to do with the device itself and more to do with how each device has different strengths and weaknesses. Perhaps the differences in sound are the result of the output devices not being equally spec'd- differing output impedance, etc.

I guess I'm saying if the fet amps don't sound as good there should be a measurable difference in output impedance or slew rate or something- an equally (or better) spec'd device would function as the bipolar.

Uh..., Steve, but it might be better that one replies to a forum question when they are only certain of a given thing, but thanks for your guess.

Dude, ice burn!

This is a guitar amp forum where we try to learn from one another, not smack each other around. He was only trying to help and he's a pretty smart and helpful guy. If you didn't like what he had to say just ignore it or say thanks and move on!

jamie

[Steve Conner]

As you noticed, I know nothing about NAD amps and have nothing useful to contribute.

I just think the MOSFET/bipolar thing is complete BS. I've built both MOSFET and bipolar hi-fi amps, and they measure fine in the lab and sound identical. There are some minuscule differences in THD at high frequencies, because MOSFETs can switch faster, but it's nothing that would be audible. If I took one of my amps and swapped the output stage between FETs and BJTs, I guarantee you wouldn't hear a difference in a properly controlled test.

Krell, Bryston et al could make absolutely perfect-sounding MOSFET amps if they wanted to, their use of bipolars is just a personal preference by the designers.

[jmaf]

...uh, Steve, thanks for your time but I was asking for facts & advice.

I stopped reading right there.

[audionaut99]

Oops!

Oops - I'm really sorry guy (& gals?). I am not sure what got into me. I've never been accused of Barking in a forum before so I feel pretty embarassed.

I think I was stressed and tired of responding to different forum which can occasionally become juvenile in user response tact and I took it out on Steve whom offered his valuable time to help.

This is your forum and you have all earned your keep - I am just the guest and especially should have displayed much better behavior. For my punishment I will not play my guitar or records for one week(?), while Steve licks his wounds.

I should have also been more careful asking full-range Amp vs. guitar Amp questions here. Hope you will all at least read my apology.

[Steve Conner]

Well, before this thread sinks to the bottom, does anyone know the answer to the original question?

The only tidbit I know that might be of use: The original poster was looking for a cheap MOSFET integrated amp. Now I once fixed a Mission Cyrus 2 (I think it was 2?!) for a friend and I'm sure I remember that had MOSFETs in it.

Edit: I checked and the interwebs disagrees with me, it says the Cyrus amps were all bipolar, argh, sorry, ignore me.

[Enzo]

Welcome to the forum, 99, and yes, this is a forum, not an information service.

The problem with pronouncements like ALL FET amps thus and so is that very rarely have the two been used side by side in otherwise identical amps.

I find the MOSFET power amps used in Trace Elliot bass guitar amps of old sounded perfectly effortless and clear. And several other FET based bass amps also come to mind. Not the place to put a bad bottom end, one's bass amp.