"Dim Dave" wrote in message
news:2008082018130716807-davesworld100scram@hotmailcom...
Thanks very much for your responses. I'm now keeping a look out for some
Tannoy dual concentrics and taken your advice on the PU input. Further
investigation revealed that ther is a plug beneath the "ohms dial" with
sockets for the different ratings - I've left it as it is.

Thanks again, I now feel a bit less clueless.


Your Beam-Echo amp and a pair of Tannoys make an
excellent combination. If you are buying second hand,
a pair of LRMs (Little Red Monitors) will, I feel,
give a very pleasing musical experience.


Good luck.
Iain

The Avantic is a superb toy - a lovely retro machine.

For all that, if I wanted the best sound possible I'd buy some big
full range ribbon speakers - the bigger the better. I happen to know
of a pair of Apogee Caliper Sigs coming up for sale on ebay and you
might just get them before they're listed by phoning Rupert on
07920054344 in the next couple of days.

You'd need at least 15 watts to drive them properly - push pull 300b
should do it.

You could use the Avantics for the treble and bi-amp, but I'd be
tempted to sell them for a good price and get a push pull 300b amp
instead. All that assumes a preference for good sound over tasty retro
amps - a big gimme.

Andy

In article
,
Andy
Evans wrote:


For all that, if I wanted the best sound possible I'd buy some big full
range ribbon speakers - the bigger the better. I happen to know of a
pair of Apogee Caliper Sigs coming up for sale on ebay and you might
just get them before they're listed by phoning Rupert on 07920054344 in
the next couple of days.

You'd need at least 15 watts to drive them properly - push pull 300b
should do it.

You could use the Avantics for the treble and bi-amp, but I'd be tempted
to sell them for a good price and get a push pull 300b amp instead. All
that assumes a preference for good sound over tasty retro amps - a big
gimme.

Makes me wonder about situations where the loudspeaker impedance may be
lower than the output impedance of the power amp... :-)

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article ,
Jim Lesurf wrote:
Makes me wonder about situations where the loudspeaker impedance may be
lower than the output impedance of the power amp... :-)

That's how you get that distinctive 'valve sound' ;-)

--
*Why isn't 11 pronounced onety one? *

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

Jim Lesurf wrote:

In article
,
Andy
Evans wrote:

For all that, if I wanted the best sound possible I'd buy some big full
range ribbon speakers - the bigger the better. I happen to know of a
pair of Apogee Caliper Sigs coming up for sale on ebay and you might
just get them before they're listed by phoning Rupert on 07920054344 in
the next couple of days.

You'd need at least 15 watts to drive them properly - push pull 300b
should do it.

You could use the Avantics for the treble and bi-amp, but I'd be tempted
to sell them for a good price and get a push pull 300b amp instead. All
that assumes a preference for good sound over tasty retro amps - a big
gimme.

Makes me wonder about situations where the loudspeaker impedance may be
lower than the output impedance of the power amp... :-)


What needs to be examined is the speaker sensitivity and ohms when
considering a tube amp.

Most 300B PP amps will have a load on the anode circuit of about 5k. The
300B anode resistance total = 1,600 ohms and if the sec load outlet
match "is for" 6 ohms, then the OPT ratio = 5,000 / 6 = 833 : 1 so the
Ra-a appears as 1,600 / 833 = 1.92 ohms to which we add the OPT winding
resistance of perhaps 0.2 ohms so Rout of the 300B PP amp = 2 ohms.

If 12dB of global NFB is used the Rout will become about 0.5 ohms giving
an DF better than 10 with a 6 ohm load.

Using 300P in SE, or PP or using triode connected KT88, 6550, KT90, the
Rout without NFB is around the 2 ohm mark and will NOT be higher than
the speaker impedance unless some fuctard designed them with Z dipping
to very silly low ohm values.
In that case, if there is a tap on the OPT to give a load match to 3
ohms, the Rout without NFB will be 1 ohm, and loads below 4ohms nominal
will be tolerated OK.

25Watts class AB1 is easy from 300B and if speaker sensitivity is above
88dB/W/M, sound is OK but the higher the sensitivity the better.

What's so great about ribbons though?

Patrick Turner.


Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In that case, if there is a tap on the OPT to give a load match to 3
ohms, the Rout without NFB will be 1 ohm, and loads below 4ohms nominal
will be tolerated OK.

The impedence of the speakers is around 3 ohms. So as you say you
figure for a low ohm tap on the secondary. I'm getting good sound with
a PPP 6S4A amp with a nominal 8k a-a into 4 ohms, which works out just
about OK. Sounds fine. My brother uses a Nagra VPA 845 PP valve amp,
which sounds great. A friend uses a KT88 amp with feedback. That works
too. All of us have Caliper Sigs, though my friend just upgraded to
Duettas. Drool.


25Watts class AB1 is easy from 300B and if speaker sensitivity is above
88dB/W/M, sound is OK but the higher the sensitivity the better.

Apogees are what, about 85db - something like that.

What's so great about ribbons though?

Have you heard the big Apogees? They're now built down under.
http://www.apogeeacoustics.com/index.html

Are you anywhere near Queensland's "sunshine coast"?

Andy

Andy Evans wrote:

In that case, if there is a tap on the OPT to give a load match to 3
ohms, the Rout without NFB will be 1 ohm, and loads below 4ohms nominal
will be tolerated OK.

The impedence of the speakers is around 3 ohms. So as you say you
figure for a low ohm tap on the secondary. I'm getting good sound with
a PPP 6S4A amp with a nominal 8k a-a into 4 ohms, which works out just
about OK. Sounds fine. My brother uses a Nagra VPA 845 PP valve amp,
which sounds great. A friend uses a KT88 amp with feedback. That works
too. All of us have Caliper Sigs, though my friend just upgraded to
Duettas. Drool.


25Watts class AB1 is easy from 300B and if speaker sensitivity is above
88dB/W/M, sound is OK but the higher the sensitivity the better.

Apogees are what, about 85db - something like that.


With 85dB its getting a bit hard to drive and I'd like to have 50W
available....

What's so great about ribbons though?

Have you heard the big Apogees? They're now built down under.
http://www.apogeeacoustics.com/index.html

I wasn't aware of that.

There is another ribbon company, Ambience on the sth coast NSW.

Are you anywhere near Queensland's "sunshine coast"?

No, I'm in Canberra, 300km sthwest of Sydney.

I prefer really well done dynamic cones and domes.

Patrick Turner.

Andy

In article
,
Andy
Evans wrote:

In that case, if there is a tap on the OPT to give a load match to 3
ohms, the Rout without NFB will be 1 ohm, and loads below 4ohms
nominal will be tolerated OK.

The impedence of the speakers is around 3 ohms. So as you say you figure
for a low ohm tap on the secondary. I'm getting good sound with a PPP
6S4A amp with a nominal 8k a-a into 4 ohms, which works out just about
OK. Sounds fine. My brother uses a Nagra VPA 845 PP valve amp, which
sounds great. A friend uses a KT88 amp with feedback. That works too.
All of us have Caliper Sigs, though my friend just upgraded to Duettas.
Drool.


25Watts class AB1 is easy from 300B and if speaker sensitivity is
above 88dB/W/M, sound is OK but the higher the sensitivity the better.

Apogees are what, about 85db - something like that.

I suspect that may be rather 'optimistic'. :-) If you look at something
like MCs review of the Apogee Caliper in HFN (1986) he reported a 2.86V
sensitivity of just 80dB. Very different to needing 88dB or more! If my
memory isn't playing me false, some other Apogees had even lower
efficiencies and/or impedances.

If you then factor in what Patrick went over (although that wasn't the
actual point of my previous comment which actually took what he
described for granted) you may find an even lower effective sensitivity
for reasons I assume are now obvious! :-)

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

On 2008-09-29 23:35:18 +0100, Andy Evans said:

The Avantic is a superb toy - a lovely retro machine.

For all that, if I wanted the best sound possible I'd buy some big
full range ribbon speakers - the bigger the better. I happen to know
of a pair of Apogee Caliper Sigs coming up for sale on ebay and you
might just get them before they're listed by phoning Rupert on
07920054344 in the next couple of days.

You'd need at least 15 watts to drive them properly - push pull 300b
should do it.

You could use the Avantics for the treble and bi-amp, but I'd be
tempted to sell them for a good price and get a push pull 300b amp
instead. All that assumes a preference for good sound over tasty retro
amps - a big gimme.

Andy

Andy
Thanks for the tip on the speakers. I know that if I want the best
sound possible I'll need to spend a lot more money than I currently
want to. Also sadly those speakers just wouldn't fit well into my
little pad and I'd rarely get the chance to play them at a suitable
volume anyway. So...I'm very happy for now with the lovely Avantic
(dunno if it's retro, it's younger than me) and would hate to see it up
on ebay just yet. Thanks anyway...

Dave