Recommendations for 5 channel power amp

Archived from groups: rec.audio.high-end (More info?)

Hi Guys,

Looks like it's time for a new amp for the soundroom. I'll probably need to
go 5 channels and will have to be under 3000 euro's. I'm on the east side of
the pond nowadays. Any recommendations?

Possibilities:
NAD Silverline S250
Rotel RMB-1095

Thanks,

Wessel

Archived from groups: rec.audio.high-end (More info?)

Check out this Primare
http://www.primare.net/swwwing/app [...] ARENT=1055

"Wessel Dirksen" <wdirksen@p-we.com> wrote in message
news:cgbau7012vb@news2.newsguy.com...
> Hi Guys,
>
> Looks like it's time for a new amp for the soundroom. I'll probably need
> to
> go 5 channels and will have to be under 3000 euro's. I'm on the east side
> of
> the pond nowadays. Any recommendations?
>
> Possibilities:
> NAD Silverline S250
> Rotel RMB-1095
>
> Thanks,
>
> Wessel
>

Archived from groups: rec.audio.high-end (More info?)

B&D wrote:

> On 8/22/04 7:40 PM, in article cgbau7012vb@news2.newsguy.com, "Wessel
> Dirksen" <wdirksen@p-we.com> wrote:
>
>
>>Hi Guys,
>>
>>Looks like it's time for a new amp for the soundroom. I'll probably need to
>>go 5 channels and will have to be under 3000 euro's. I'm on the east side of
>>the pond nowadays. Any recommendations?

Simple - Bryston makes a superb 5 channel amplifier.

Archived from groups: rec.audio.high-end (More info?)

"Lars Olsson" <lasseolsson@myrealbox.com> wrote in message
news:cgdtdi02uik@news1.newsguy.com...
> Check out this Primare
> http://www.primare.net/swwwing/app [...] ARENT=1055

Anybody familiar with this Primare amp? Reputation?

>
> "Wessel Dirksen" <wdirksen@p-we.com> wrote in message
> news:cgbau7012vb@news2.newsguy.com...
> > Hi Guys,
> >
> > Looks like it's time for a new amp for the soundroom. I'll probably need
> > to
> > go 5 channels and will have to be under 3000 euro's. I'm on the east
side
> > of
> > the pond nowadays. Any recommendations?
> >
> > Possibilities:
> > NAD Silverline S250
> > Rotel RMB-1095
> >
> > Thanks,
> >
> > Wessel
> >

Archived from groups: rec.audio.high-end (More info?)

>The whole NAD silverline is zero negative feedback.

I doubt that... at least, not as it's written there.

They may very well have no _global_ negative feedback.

They almost certainly have _local_ negative feedback, in each
individual stage. You need at least some local feedback in order to
make each stage (e.g. input, driver, output) linear enough to deliver
acceptable performance. Local feedback may be something as simple as
an emitter or source resistor.

Yup... I just checked their brochure, and they state that (e.g.)
"[T]he S300's amplifier circuits avoid overall ('global') negative
feedback altogether."

>Question: Is negative feedback a big deal or not?

Depends on what kind, how you use it, and other details of the circuit.

In general, in order to get either a tube or transistor (bipolar or
MOSFET) to amplify without distortion, you need at least _some_
feedback in order to linearize the device's behavior. The feedback
may be local (e.g. the output of the device is somehow fed back to the
device's input, with appropriate phase inversion), or it may "reach
back" to the beginning of an earlier stage in the amplifier (this is
often referred to as "global" negative feedback).

If you have no negative feedback at all, you're going to be very
limited in both the distortion level you can achieve, and the amount
of power you can deliver.

Some designers prefer to use only local (single-stage) feedback - in
effect, making each stage of the amplifier acceptably linear
(low-enough distortion), and accepting that the remaining distortions
are going to add up. This appears to be what NAD has done in the
Silver series.

Some designers prefer to use both local feedback, and some amount of
global feedback. Done well, this can lower the total distortion
level. Done badly, it can cause problems... in particular, "ringing"
or other forms of instability. [The cause of these stability problems
has been known for decades, and designers really shouldn't be making
this sort of mistake today, but it's always possible...]

Some designers prefer to use only local feedback to reduce distortion
in the audio spectrum, but to include a low-speed global feedback loop
to "null out" any DC offset created by any of the stages in the amp.

I believe it's possible to produce excellent, audibly-transparent
amplifiers with any of these approaches. It's also possible to yngvi
up a design which uses any of these, and generate various sorts of
distortion (some of which may be euphonic, and some of which may sound
downright nasty).

> I once had a chance
>to compare 2 similar tube amps built by a local tube tweek in Holland,
>One was with some kind of config with a bit of negative feedback, and
>the other with absolutely none. The result: I really felt the one with
>no negative feedback was more detailed. (I was blinded later when I
>really wanted to know) The amps were identical outside and in. I could
>discern the difference reliably not only because of the detail, but
>also the bass sounded tighter with the neg feedback. But the clarity
>was noticable.

This might indicate more accuracy in the amp without global feedback,
or it might indicate that the amp without global feedback was actually
introducing a slight high-frequency boost for some reason. Impossible
to tell from your description, I'm afraid.

Archived from groups: rec.audio.high-end (More info?)

On 8/24/04 11:13 PM, in article cgh0540283p@news2.newsguy.com, "Dave Platt"
<dplatt@radagast.org> wrote:

>> The whole NAD silverline is zero negative feedback.
>
> I doubt that... at least, not as it's written there.
>
> They may very well have no _global_ negative feedback.
>
> They almost certainly have _local_ negative feedback, in each
> individual stage. You need at least some local feedback in order to
> make each stage (e.g. input, driver, output) linear enough to deliver
> acceptable performance.

Not to mention to maintain stability into all kinds of loads!!

>Local feedback may be something as simple as
> an emitter or source resistor.

Yes - but I think they were talking about loop feedback, not ballasting
resistors.

>
> Yup... I just checked their brochure, and they state that (e.g.)
> "[T]he S300's amplifier circuits avoid overall ('global') negative
> feedback altogether."

Archived from groups: rec.audio.high-end (More info?)

"Jay1Bala" <jay1bala@aol.com> wrote in message
news:cgj7br01h2u@news4.newsguy.com...
> << Looks like it's time for a new amp for the soundroom. I'll probably
need to
> go 5 channels and will have to be under 3000 euro's. I'm on the east side
of
> the pond nowadays. Any recommendations? >>

>
>
> 5 ch? What is your application? If its home theater, its 7 channel these
days,
> even Dolby has adapted 7 channel with IIx.
>
> Regards,
> Jay Bala.

Sorry, only en extremis. Most home theatre is still 5.1. 7.1 "capability"
is now featured, but usually only practiced in the most expensive systems.

Archived from groups: rec.audio.high-end (More info?)

B&D wrote:
> On 8/26/04 7:17 PM, in article cglr37013g3@news1.newsguy.com, "chung"
> <chunglau@covad.net> wrote:
>
>> B&D wrote:
>>> On 8/24/04 11:13 PM, in article cgh0540283p@news2.newsguy.com, "Dave Platt"
>>> <dplatt@radagast.org> wrote:
>>>
>>>>> The whole NAD silverline is zero negative feedback.
>>>>
>>>> I doubt that... at least, not as it's written there.
>>>>
>>>> They may very well have no _global_ negative feedback.
>>>>
>>>> They almost certainly have _local_ negative feedback, in each
>>>> individual stage. You need at least some local feedback in order to
>>>> make each stage (e.g. input, driver, output) linear enough to deliver
>>>> acceptable performance.
>>>
>>> Not to mention to maintain stability into all kinds of loads!!
>>
>> Uhh, a circuit with no feedback will be stable. Feedback is not used to
>> provide stability. Instability is the result of incorrectly applying
>> feedback.
>
> Negative Feedback can and is used to stabilize amplifiers - if you apply it
> in some ways, it certainly can make an amplifier unstable (such as use of
> positive feedback in regenerative circuitry) - negative feedback properly
> applied does make amplifiers more stable.
>

You failed to understand that an amplifier with no feedback cannot be
unstable. You were saying feedback was used to maintain stability.


>
>>
>>>> Local feedback may be something as simple as
>>>> an emitter or source resistor.
>>>
>>> Yes - but I think they were talking about loop feedback, not ballasting
>>> resistors.
>>
>> Uhh, using emitter resistor or source resistor *is* applying feedback.
>> You should be able to clearly visualize the feedback loop.
>
> Chung - you misunderstood what I was saying - the folks claiming "Zero
> feedback" most certainly mean they are not feeding back signal from the
> output to the input, but applying things like what we were talking about
> (ballasting resistors - on the source, or emitter to provide localized
> negative feedback is not taking the output signal and applying it to the
> input of an amplifier)
>

But then why were you arguing with Mr. Platt? Please re-read what he
wrote. He already said that some of these amps may very well have no
global feedback, but instead have local feedback.