I'm thinking of separating the preamp from the rest of the system. (I want
to keep the preamp in front of the listening position, but I'd rather get
the amps and processor boxes out of the way.) The preamp is line level with
unbalanced outputs, and the receiver is an active crossover which has
balanced inputs. Would an unbalanced interconnect, say 10m long, be likely
to have a problem?

I mention the balanced input of the active crossover because, somewhere in
my system's future, are mods to the preamp to add remote control volume and
source selection. If there is a possibility of some sort of degradation that
a balanced line would fix, then it would make sense to include a balanced
output in my plans for the preamp.


--
Wally
www.wally.myby.co.uk

In article ,
Wally wrote:
I mention the balanced input of the active crossover because, somewhere
in my system's future, are mods to the preamp to add remote control
volume and source selection. If there is a possibility of some sort of
degradation that a balanced line would fix, then it would make sense to
include a balanced output in my plans for the preamp.

All that balancing really does is to cancel out any interference picked up
on the line - and to allow the use of cheap cable over long distances.
There's nothing intrinsically better with it - indeed it could be said to
degrade things *slightly* since by nature it needs extra circuitry.

Try your longer leads - if the pre-amp has a low output impedance you'll
probably be ok - but keep the leads clear of power cables etc or at least
make sure they cross at as near right angles as possible.

--
*A person who smiles in the face of adversity probably has a scapegoat *

Dave Plowman London SW
To e-mail, change noise into sound.

What sort of long term plans do you have for a balanced preamp? I've
been using balanced line stages for a while, and while it is heavier on
parts (double everything) it is easier on the volume control in the
sense you can use a simple shunt stepped attenuator on the output - I
personally don't mind a 12 step one for domestic listening, though
others are more demanding. I happen to use directly heated triodes, but
you can build it or buy it any way you want. One use of a balanced tube
line stage is that it can function as a tube output stage for a
differential DAC board, which is how I use it. The signal from the DAC,
with DC on it, goes direct into the grids of the line stage, which is a
differential pair with a constant current sink under it. This
arrangement works very well and can be made to sound excellent - after
the tube stage choice is cap coupling, transformer Push Pull or
parafeed. All can give you good results. Something to ponder on. Andy

Andy Evans wrote:

What sort of long term plans do you have for a balanced preamp? I've
been using balanced line stages for a while, and while it is heavier
on parts (double everything) it is easier on the volume control in the
sense you can use a simple shunt stepped attenuator on the output - I
personally don't mind a 12 step one for domestic listening, though
others are more demanding.

Motorised Alps volume pot with IR control. Volume indication by means of one
LED in the middle of the knob, and a different one for the 'pointer' - can
thus tell at a glance what the setting is by the angle from the centre LED
to the pointer.

IR-selectable sources with complementary front panel momentary switches. Row
of indicator LEDs for sources: all LEDs are lit dimly, except selected
source, which is brighter - can tell from a glance at the row of LEDs which
source is active.

Sources are CD, cable TV box, computer, DVD player, ANOther random device.
No RIAA, no tape loop. Reusing existing black box Cambridge C75 preamp's
case (with a new front panel) and PSU, probably the volume knob and
circuitry.

Possible circuit tweaks (aside from balanced o/p) include trimmers on the
inputs to match levels (DAC is louder than everything else), and probably
some sort of mute or attenuator function.



I happen to use directly heated triodes,
but you can build it or buy it any way you want. One use of a
balanced tube line stage is that it can function as a tube output
stage for a differential DAC board, which is how I use it. The signal
from the DAC, with DC on it, goes direct into the grids of the line
stage, which is a differential pair with a constant current sink
under it. This arrangement works very well and can be made to sound
excellent - after the tube stage choice is cap coupling, transformer
Push Pull or parafeed. All can give you good results. Something to
ponder on. Andy

What sort of HT should I use on NE5532s?


--
Wally
www.wally.myby.co.uk

Bob Latham wrote:

I had pre to power leads around 10 metres at one time. I measured
their capacitance at 1.3nF. Once you know the capacitance and the
output impedance of the pre-amp you can work out the hf loss in the
cable. For leads of that length you need a pre with some drive, well
less than 100 ohms imho.

Do you mean outout impedance?


Wouldn't have thought this would make much difference to the effect
lead length has unless you are picking up noise/interference.

I was sort of asking if that length was likely to be susceptible to
interference in a domestic environment.


Of course, if cables do sound different, you'll really hear it with
that length.

Okay.


--
Wally
www.wally.myby.co.uk

Dave Plowman (News) wrote:

All that balancing really does is to cancel out any interference
picked up on the line - and to allow the use of cheap cable over long
distances. There's nothing intrinsically better with it - indeed it
could be said to degrade things *slightly* since by nature it needs
extra circuitry.

Yup. I was wondering both about noise pick up and whatever effects the
length might have.


Try your longer leads - if the pre-amp has a low output impedance
you'll probably be ok - but keep the leads clear of power cables etc
or at least make sure they cross at as near right angles as possible.

For a parallel run, say for 2 or 3 metres, how far apart would you say they
have to be for the signal to be unaffected?


--
Wally
www.wally.myby.co.uk

What sort of HT should I use on NE5532s?

Hi Wally - we're at different ends of the spectrum here! I have no
convenience features - just hair shirt circuits with best parts. Good
luck! Andy

In article ,
Wally wrote:
What sort of HT should I use on NE5532s?

Absolute max is +/-22v. But in practice for domestic use +/-15v will be
fine.

--


Dave Plowman London SW
To e-mail, change noise into sound.

Andy Evans wrote:

What sort of HT should I use on NE5532s?

Hi Wally - we're at different ends of the spectrum here!

Ever so slightly. :-)


I have no
convenience features - just hair shirt circuits with best parts. Good
luck!

Thanks. I have taken an interest in valve circuits, though more from a
guitar amp perspective. I used to build my mess-about preamp circuits on
bits of wooden plank - bang in panel pins at strategic locations, run tinned
copper wire between the pins to 'draw' a schematic, and then solder sockets,
valve bases and pots on top of the pins as needed. Had some good fun playing
with biassing to bring out the 2nd harmonic distortion, but found that that
particular sound wasn't what I was after in a valve guitar amp (no 'rip' - I
like a distorted amp to lie somewhere between chainsaw and endless sustain).


--
Wally
www.wally.myby.co.uk

On Fri, 14 Jul 2006 20:47:18 +0100, "Wally" wrote:

I'm thinking of separating the preamp from the rest of the system. (I want
to keep the preamp in front of the listening position, but I'd rather get
the amps and processor boxes out of the way.) The preamp is line level with
unbalanced outputs, and the receiver is an active crossover which has
balanced inputs. Would an unbalanced interconnect, say 10m long, be likely
to have a problem?

The main amp may have a potentially balanced input, but you're
unbalancing it :-)

A professional audio setup wouldn't dream of using an unbalanced
connection, especially of this length. They have to KNOW the
connection won't get noisy, even if a new piece of equipment is added.
But the audiophile world is only loosely connected to the pro-audio
world :-) I imagine once set up, your setup will stay as it is? Try.
If it hums get a box to balance the preamp output.