Sansui B-55 as a monitor amp ?

Archived from groups: rec.audio.pro (More info?)

In article <SeZqe.146450$IN.2531684@twister2.libero.it> daniele@nonstaqui.com writes:

> does anyone know if it would be possible to feed a pair of passive ADAM
> NF-10 with a Sansui B-55 hi-fi amp? The problem is that the NF-10 are 4 ohm
> and the B-55 accepts 8 or 16 ohm loads. Is there a way I could do this?

Those are just rough guidelines. Just don't push the volume and it'll
probably work OK. But start saving your pennies for a more suitable
amplifier.

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Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1118607791k@trad...

> Those are just rough guidelines. Just don't push the volume and it'll
> probably work OK. But start saving your pennies for a more suitable
> amplifier.

Thanks Mike, I think I'll do that until I have the money for something like
the Hafler "P" series which I noticed gets recommended a lot here.

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> Daniele <daniele@nonstaqui.com> wrote:

>> does anyone know if it would be possible to feed a pair
>> of passive ADAM NF-10 with a Sansui B-55 hi-fi amp?

Yes.

>> The problem is that the NF-10 are 4 ohm and the B-55
>> accepts 8 or 16 ohm loads. Is there a way I could do this?

Standard loudspeaker cable.

> You _could_ do it with an autotransformer.

Scott, the B-55 is a strange amp, as I recall its powerspec it has no
more power in 4 ohms than in 8 ohms, quite possibly less. I have two,
they were on sale in the mid 1980'ties. I bought one, tested on the
KEF's and found it good and went and got another and I have been
regretting ever since that I didn't get a third too. Like the current
Cambridge dual ""60 watt"" amp it is a lot better at not having to
bother with bass, for the very same reason: there is not much and
possibly less capacitance in the psu than in some preamp designs.

A simple mod to the B-55 is to remove the frequency analysis display,
the sound gets remarkably cleaner. I use mine with compression drivers
and hardly ever reach the one watt indication. The power metering LED's
remain functional with the analyser pcb physically removed. I also
replaced the input coupling cap with a smaller polypropylene cap and
replaced the DC servo opamp with a 275, since the guy who helped me said
that he had heard it mentioned that such servo opamps could matter. The
logic of that defies my understanding but it was easy and fast to do
with the critters in surgery anyway.

The total mod took them from good to very very good and they are so
wonderfully clean when not at all delivering power - midrange amp output
0.65 volts at 1 volt in at the attenuator box. Yep - the midrange amp
overall is functionally an attenuator, but one with a very low output
impedance.

> EV makes one that costs around $120/channel. Frankly it would
> be cheaper and sound better just to get an amp that is up to the job.

I agree in this context, this amp will get loose and sloppy in the bass
if having to work hard in a 4 Ohm load. What this amp excels uniquely at
is to do near nothing, not very many amps are good at that discipline.

> --scott


Kind regards

Peter Larsen

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Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> Peter Larsen <SPAMSHIELD_plarsen@mail.tele.dk> wrote:

>> Scott, the B-55 is a strange amp, as I recall its powerspec
>> it has no more power in 4 ohms than in 8 ohms, quite possibly
>> less.

> This is the sign of an undersized power supply.

I agree, and it is why it is not an optimum choice for the intended use,
even though well sounding ex works.

>> A simple mod to the B-55 is to remove the frequency analysis
>> display, the sound gets remarkably cleaner.

> That is even scarier.

It is a fluorescent display. Some DAT's and CD players have the option
to turn off similar displays with a similar gain in quality. No
soldering is required to remove that display, a couple of screws and
pulling a connection. Not scary.

>> I agree in this context, this amp will get loose and sloppy
>> in the bass if having to work hard in a 4 Ohm load. What
>> this amp excels uniquely at is to do near nothing, not very
>> many amps are good at that discipline.

> That's what Class A amplification is for!

And being the last burp from the quality wars, but badly afflicted from
cost saving, the Sansui B55 happens to be a "New class A" amp with
variable power supply voltage. It is not good at playing disco-dance in
4 ohms, but it is very good at providing signal to a compression driver,
which is what I use them for and it is also potentially useful in other
multi-amp contexts. Space, clarity and silence are all OK.

> --scott


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
* The Vienna Copyright convention applies *
*******************************************