Confession time
 

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you - promise.

Mike

Confession time
 

Mike Gilmour wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you -
promise.

Mike

Why don't you go first?

Ian

Confession time
 

Mike Gilmour wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you -
promise.

Mike

Why don't you go first?

Ian

Confession time
 

"Ian Bell" wrote in message
...
Mike Gilmour wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you -
promise.

Mike

Why don't you go first?

Ian


Okay. Red face time. Missus is moving the CD player from one room to another
with the remote balanced right on top of the player. The remote slides off &
hits the floor. Next thing I hear 'The remotes not working' Okay lets see
if batteries making connection - okay - opened up remote - nothing obvious.
As I'd got a lot on that day I went to the computer & ordered another remote
on line. The new remote came and didn't work...thats when I saw a little
switch at the back of the CD player that said 'local/remote' ..it had been
flicked over when she carried it. Anyway I've got two identical working
remotes now and a red face.

Next please.......

Confession time
 

"Ian Bell" wrote in message
...
Mike Gilmour wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you -
promise.

Mike

Why don't you go first?

Ian


Okay. Red face time. Missus is moving the CD player from one room to another
with the remote balanced right on top of the player. The remote slides off &
hits the floor. Next thing I hear 'The remotes not working' Okay lets see
if batteries making connection - okay - opened up remote - nothing obvious.
As I'd got a lot on that day I went to the computer & ordered another remote
on line. The new remote came and didn't work...thats when I saw a little
switch at the back of the CD player that said 'local/remote' ..it had been
flicked over when she carried it. Anyway I've got two identical working
remotes now and a red face.

Next please.......

Confession time
 

Not really foolhardiness on my part, but a case of destruction
nevertheless:

I'd just recently got my pair of QUAD II valve power amps. They
were my pride and joy; I'd been drooling, lusting and tossing
over pics of them in the "history" section of the contemporary
Quad brochure for months. I was either a very late 17, or a very
early 18, still living at "home", just before going to university.

I'd left them powered up and connected to the Spendor SP1s overnight.

I was woken in the morning by a loud buzzing from one of the speakers.
And a crackling noise. Which was getting louder and more urgent. On
opening my eyes and peering, contact-lens-less through the blurred
haze, I realised that the valve amps were on fire, and the room was indeed
hazy, filling as it was, rapidly with smoke. Indeed, that smoke was issuing
forth from one of the amps with genuinely impressive urgency and dispatch.

Still half asleep, and confused, I half-fell out of bed, stumbled across the
room, and struggled frantically to unplug them.

It turned out that only one of the amps was dying. The mains xformer,
which, apart from recent use, had lain idle for who knows how many
years, was dying.

Having worked for a year or two on Saturdays and during school
holidays at Chatham branch of Sevenoaks Hi-Fi, I'd heard that Quad
had a good reputation for still stocking parts for their long-
discontinued products, I phoned them, explained that I needed a new
mains xformer for a QUAD II, and was happy to be told that they had
one in stock, and it would set me back 60 quid. I said I'd go and
collect it.

Up I went, got it, brought it back, fitted it, and the amp was fine
after that.

I sold the pair of amps after about 4 or 5 years, in about 1993 or 1994.


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk

Confession time
 

Not really foolhardiness on my part, but a case of destruction
nevertheless:

I'd just recently got my pair of QUAD II valve power amps. They
were my pride and joy; I'd been drooling, lusting and tossing
over pics of them in the "history" section of the contemporary
Quad brochure for months. I was either a very late 17, or a very
early 18, still living at "home", just before going to university.

I'd left them powered up and connected to the Spendor SP1s overnight.

I was woken in the morning by a loud buzzing from one of the speakers.
And a crackling noise. Which was getting louder and more urgent. On
opening my eyes and peering, contact-lens-less through the blurred
haze, I realised that the valve amps were on fire, and the room was indeed
hazy, filling as it was, rapidly with smoke. Indeed, that smoke was issuing
forth from one of the amps with genuinely impressive urgency and dispatch.

Still half asleep, and confused, I half-fell out of bed, stumbled across the
room, and struggled frantically to unplug them.

It turned out that only one of the amps was dying. The mains xformer,
which, apart from recent use, had lain idle for who knows how many
years, was dying.

Having worked for a year or two on Saturdays and during school
holidays at Chatham branch of Sevenoaks Hi-Fi, I'd heard that Quad
had a good reputation for still stocking parts for their long-
discontinued products, I phoned them, explained that I needed a new
mains xformer for a QUAD II, and was happy to be told that they had
one in stock, and it would set me back 60 quid. I said I'd go and
collect it.

Up I went, got it, brought it back, fitted it, and the amp was fine
after that.

I sold the pair of amps after about 4 or 5 years, in about 1993 or 1994.


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk

Confession time
 

"Mike Gilmour" wrote in message
...
Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you -
promise.

Mike



Crossed the speaker wires, Nytech went BANG, and promptly set its self on
fire.

The same amp also destroyed a set of mission 701s and id turned the volume
up to high without noticing. pres play and whack, cones nearly popped out,
and tore all the already rotting foam.

edd

Confession time
 

"Mike Gilmour" wrote in message
...
Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you -
promise.

Mike



Crossed the speaker wires, Nytech went BANG, and promptly set its self on
fire.

The same amp also destroyed a set of mission 701s and id turned the volume
up to high without noticing. pres play and whack, cones nearly popped out,
and tore all the already rotting foam.

edd

Confession time
 

Mike Gilmour wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you -
promise.

Moving into my first flat many moons ago, I was only concerned with the
important stuff - floor cushions, coffee machine and hifi. After getting the
first of two big Kefs up the stairs (a top floor flat, of course), I decided
to take a coffee break before getting on with the rest. As the coffee
brewed, I connected the turntable to the amp and plugged in the speaker. I
get sounds, but realise that only having one speaker means I'm only hearing
one channel. I hit upon a bright idea for hearing both channels - plug both
amp outputs into the single speaker.

No sounds.


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.

Confession time
 

Mike Gilmour wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you -
promise.

Moving into my first flat many moons ago, I was only concerned with the
important stuff - floor cushions, coffee machine and hifi. After getting the
first of two big Kefs up the stairs (a top floor flat, of course), I decided
to take a coffee break before getting on with the rest. As the coffee
brewed, I connected the turntable to the amp and plugged in the speaker. I
get sounds, but realise that only having one speaker means I'm only hearing
one channel. I hit upon a bright idea for hearing both channels - plug both
amp outputs into the single speaker.

No sounds.


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.

Confession time
 

Once i had some new homemade speakers using the Kef T27 tweeters and B200s.

A friend of mine came round for a listen. We were discussing speakers when
he pointed to the T27 with a screw-driver. Yes you guessed it, the magnet
in the T27 pulled the screw-driver right through the dome!

Not very funny, but bloody annoying at the time.

Confession time
 

Once i had some new homemade speakers using the Kef T27 tweeters and B200s.

A friend of mine came round for a listen. We were discussing speakers when
he pointed to the T27 with a screw-driver. Yes you guessed it, the magnet
in the T27 pulled the screw-driver right through the dome!

Not very funny, but bloody annoying at the time.

Confession time
 

On Thu, 20 Nov 2003 18:46:40 -0000
"Mike Gilmour" wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you - promise.

Ok, heres mine...

Just rebuilt Quad405 (40 odd quid in parts,mostly big transistors), and realised that I needed a preamp.

thought 'I know, I'll use this tinypower amp with the gain set low'.

of course, it had a capacitor coupled output, so the first thingit did was runthe Quad405 flat out into its (thankfully connected and working) output protection board.

Anyone got a spare set out output transistors?

Anyhow, this is the event that made me decide to mod the amp. the current limiting on the 405 was too severe, which is what allowed the o/p trannies to blow (before the fuses could save them).

Im modding the amp (rebuilding the PCBs) such that:

the gain is halved (1Vp-t-p inputs, less noise)
use better quality parts in the input,particularly one resistor that sets the performance of the whole amp
double the input cap values
use a more modern op-amp and adjust the supply to it to avoid hiss
dc couple some transistors now that higher voltage parts exist - like the 606 design. eliminates a couple of passive components.
apply the 405-mkII current limiter (better performance, less blown outputs.

I'll make full parts lists and layouts available once Im ready.

Jim... did you ever look at the schematic I sent you ?

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with ketchup.

Confession time
 

On Thu, 20 Nov 2003 18:46:40 -0000
"Mike Gilmour" wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you - promise.

Ok, heres mine...

Just rebuilt Quad405 (40 odd quid in parts,mostly big transistors), and realised that I needed a preamp.

thought 'I know, I'll use this tinypower amp with the gain set low'.

of course, it had a capacitor coupled output, so the first thingit did was runthe Quad405 flat out into its (thankfully connected and working) output protection board.

Anyone got a spare set out output transistors?

Anyhow, this is the event that made me decide to mod the amp. the current limiting on the 405 was too severe, which is what allowed the o/p trannies to blow (before the fuses could save them).

Im modding the amp (rebuilding the PCBs) such that:

the gain is halved (1Vp-t-p inputs, less noise)
use better quality parts in the input,particularly one resistor that sets the performance of the whole amp
double the input cap values
use a more modern op-amp and adjust the supply to it to avoid hiss
dc couple some transistors now that higher voltage parts exist - like the 606 design. eliminates a couple of passive components.
apply the 405-mkII current limiter (better performance, less blown outputs.

I'll make full parts lists and layouts available once Im ready.

Jim... did you ever look at the schematic I sent you ?

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with ketchup.

Confession time
 

Ian Molton wrote:

On Thu, 20 Nov 2003 18:46:40 -0000
"Mike Gilmour" wrote:


Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you - promise.


Ok, heres mine...

Just rebuilt Quad405 (40 odd quid in parts,mostly big transistors), and realised that I needed a preamp.

thought 'I know, I'll use this tinypower amp with the gain set low'.

of course, it had a capacitor coupled output, so the first thingit did was runthe Quad405 flat out into its (thankfully connected and working) output protection board.

Anyone got a spare set out output transistors?

Anyhow, this is the event that made me decide to mod the amp. the current limiting on the 405 was too severe, which is what allowed the o/p trannies to blow (before the fuses could save them).

Im modding the amp (rebuilding the PCBs) such that:

the gain is halved (1Vp-t-p inputs, less noise)
use better quality parts in the input,particularly one resistor that sets the performance of the whole amp
double the input cap values
use a more modern op-amp and adjust the supply to it to avoid hiss
dc couple some transistors now that higher voltage parts exist - like the 606 design. eliminates a couple of passive components.
apply the 405-mkII current limiter (better performance, less blown outputs.

I'll make full parts lists and layouts available once Im ready.


As the priest said to the sinner,
"My son, you aren't confessing, you're boasting."

--
Roger.

Confession time
 

Ian Molton wrote:

On Thu, 20 Nov 2003 18:46:40 -0000
"Mike Gilmour" wrote:


Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you - promise.


Ok, heres mine...

Just rebuilt Quad405 (40 odd quid in parts,mostly big transistors), and realised that I needed a preamp.

thought 'I know, I'll use this tinypower amp with the gain set low'.

of course, it had a capacitor coupled output, so the first thingit did was runthe Quad405 flat out into its (thankfully connected and working) output protection board.

Anyone got a spare set out output transistors?

Anyhow, this is the event that made me decide to mod the amp. the current limiting on the 405 was too severe, which is what allowed the o/p trannies to blow (before the fuses could save them).

Im modding the amp (rebuilding the PCBs) such that:

the gain is halved (1Vp-t-p inputs, less noise)
use better quality parts in the input,particularly one resistor that sets the performance of the whole amp
double the input cap values
use a more modern op-amp and adjust the supply to it to avoid hiss
dc couple some transistors now that higher voltage parts exist - like the 606 design. eliminates a couple of passive components.
apply the 405-mkII current limiter (better performance, less blown outputs.

I'll make full parts lists and layouts available once Im ready.


As the priest said to the sinner,
"My son, you aren't confessing, you're boasting."

--
Roger.

Confession time
 

On Fri, 21 Nov 2003 08:21:10 +0000
Old Fart at Play wrote:

As the priest said to the sinner,
"My son, you aren't confessing, you're boasting."

LOL ;-)

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with ketchup.

Confession time
 

On Fri, 21 Nov 2003 08:21:10 +0000
Old Fart at Play wrote:

As the priest said to the sinner,
"My son, you aren't confessing, you're boasting."

LOL ;-)

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with ketchup.

Confession time
 

In article , Ian Molton
wrote:
On Thu, 20 Nov 2003 18:46:40 -0000 "Mike Gilmour"
wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you -
promise.

Ok, heres mine...

Just rebuilt Quad405 (40 odd quid in parts,mostly big transistors), and
realised that I needed a preamp.

thought 'I know, I'll use this tinypower amp with the gain set low'.

of course, it had a capacitor coupled output, so the first thingit did
was runthe Quad405 flat out into its (thankfully connected and working)
output protection board.

Anyone got a spare set out output transistors?

Not clear what you are describing above. Are you saying that the *Quad 405*
blew its output devices due to your injecting an input spike when your
'preamp' sic was switched on? Or are you saying the preamp output
devoices blew?

Anyhow, this is the event that made me decide to mod the amp. the
current limiting on the 405 was too severe, which is what allowed the
o/p trannies to blow (before the fuses could save them).

Puzzled. The point of the current limiting is to ensure the output devices
*never* blow up. The severe limiting on early 405's gets in the way of the
music sometimes, but should avoid failures. Hence I am puzzled by your last
sentence above.

Im modding the amp (rebuilding the PCBs) such that:

the gain is halved (1Vp-t-p inputs, less noise) use better quality parts
in the input,particularly one resistor that sets the performance of the
whole amp double the input cap values use a more modern op-amp and
adjust the supply to it to avoid hiss dc couple some transistors now
that higher voltage parts exist - like the 606 design. eliminates a
couple of passive components. apply the 405-mkII current limiter (better
performance, less blown outputs.

I'll make full parts lists and layouts available once Im ready.

Have you checked the stability margin? Reducing the overall gain and
changing various devices to different types may affect this.

Jim... did you ever look at the schematic I sent you ?

I am afraid I haven't. :-/ Too many other things have been distracting me
over the summer - many of them unfortunate. Sorry about this, but I had
completely forgotten. Can you remind me of the details by email?

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Confession time
 

In article , Ian Molton
wrote:
On Thu, 20 Nov 2003 18:46:40 -0000 "Mike Gilmour"
wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you -
promise.

Ok, heres mine...

Just rebuilt Quad405 (40 odd quid in parts,mostly big transistors), and
realised that I needed a preamp.

thought 'I know, I'll use this tinypower amp with the gain set low'.

of course, it had a capacitor coupled output, so the first thingit did
was runthe Quad405 flat out into its (thankfully connected and working)
output protection board.

Anyone got a spare set out output transistors?

Not clear what you are describing above. Are you saying that the *Quad 405*
blew its output devices due to your injecting an input spike when your
'preamp' sic was switched on? Or are you saying the preamp output
devoices blew?

Anyhow, this is the event that made me decide to mod the amp. the
current limiting on the 405 was too severe, which is what allowed the
o/p trannies to blow (before the fuses could save them).

Puzzled. The point of the current limiting is to ensure the output devices
*never* blow up. The severe limiting on early 405's gets in the way of the
music sometimes, but should avoid failures. Hence I am puzzled by your last
sentence above.

Im modding the amp (rebuilding the PCBs) such that:

the gain is halved (1Vp-t-p inputs, less noise) use better quality parts
in the input,particularly one resistor that sets the performance of the
whole amp double the input cap values use a more modern op-amp and
adjust the supply to it to avoid hiss dc couple some transistors now
that higher voltage parts exist - like the 606 design. eliminates a
couple of passive components. apply the 405-mkII current limiter (better
performance, less blown outputs.

I'll make full parts lists and layouts available once Im ready.

Have you checked the stability margin? Reducing the overall gain and
changing various devices to different types may affect this.

Jim... did you ever look at the schematic I sent you ?

I am afraid I haven't. :-/ Too many other things have been distracting me
over the summer - many of them unfortunate. Sorry about this, but I had
completely forgotten. Can you remind me of the details by email?

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Confession time
 

On Thu, 20 Nov 2003 18:46:40 -0000, "Mike Gilmour"
wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you - promise.

Many years ago I acquired a HiFi News Test CD. I decided to use the
spot frequencies to see how high I could hear. I was pleasantly
surprised to be able to hear 18kHz (not too bad, being in my late 30s
at the time). But I couldn't hear 20kHz.
Thinks: "I wonder if I would hear it if it was louder?". So I slowly
raised the volume control until I did hear something: the distinctive
popping sound of both tweeters burning out.

Confession time
 

On Thu, 20 Nov 2003 18:46:40 -0000, "Mike Gilmour"
wrote:

Any audio tales of stoopid actions .i.e. like plugging in when mains
selector set to 110V...come on, we'll laugh with you not at you - promise.

Many years ago I acquired a HiFi News Test CD. I decided to use the
spot frequencies to see how high I could hear. I was pleasantly
surprised to be able to hear 18kHz (not too bad, being in my late 30s
at the time). But I couldn't hear 20kHz.
Thinks: "I wonder if I would hear it if it was louder?". So I slowly
raised the volume control until I did hear something: the distinctive
popping sound of both tweeters burning out.

Confession time
 

On Fri, 21 Nov 2003 08:55:19 +0000 (GMT)
Jim Lesurf wrote:

Not clear what you are describing above. Are you saying that the *Quad
405* blew its output devices due to your injecting an input spike when
your'preamp' sic was switched on? Or are you saying the preamp
output devoices blew?

the 405.

Anyhow, this is the event that made me decide to mod the amp. the
current limiting on the 405 was too severe, which is what allowed
the o/p trannies to blow (before the fuses could save them).

Puzzled. The point of the current limiting is to ensure the output
devices*never* blow up. The severe limiting on early 405's gets in the
way of the music sometimes, but should avoid failures. Hence I am
puzzled by your last sentence above.

It appears to limit current just enough to prevent the fuses blowing but
not quite enough to save the transistors.

Im modding the amp (rebuilding the PCBs) such that:

Have you checked the stability margin? Reducing the overall gain and
changing various devices to different types may affect this.

No, not yet. I havent really had time for the project lately...

Jim... did you ever look at the schematic I sent you ?

I am afraid I haven't. :-/ Too many other things have been
distracting me over the summer - many of them unfortunate. Sorry about
this, but I had completely forgotten. Can you remind me of the details
by email?

Sure.

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with
ketchup.

Confession time
 

On Fri, 21 Nov 2003 08:55:19 +0000 (GMT)
Jim Lesurf wrote:

Not clear what you are describing above. Are you saying that the *Quad
405* blew its output devices due to your injecting an input spike when
your'preamp' sic was switched on? Or are you saying the preamp
output devoices blew?

the 405.

Anyhow, this is the event that made me decide to mod the amp. the
current limiting on the 405 was too severe, which is what allowed
the o/p trannies to blow (before the fuses could save them).

Puzzled. The point of the current limiting is to ensure the output
devices*never* blow up. The severe limiting on early 405's gets in the
way of the music sometimes, but should avoid failures. Hence I am
puzzled by your last sentence above.

It appears to limit current just enough to prevent the fuses blowing but
not quite enough to save the transistors.

Im modding the amp (rebuilding the PCBs) such that:

Have you checked the stability margin? Reducing the overall gain and
changing various devices to different types may affect this.

No, not yet. I havent really had time for the project lately...

Jim... did you ever look at the schematic I sent you ?

I am afraid I haven't. :-/ Too many other things have been
distracting me over the summer - many of them unfortunate. Sorry about
this, but I had completely forgotten. Can you remind me of the details
by email?

Sure.

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with
ketchup.

Confession time
 

In article , Ian Molton
wrote:
On Fri, 21 Nov 2003 08:55:19 +0000 (GMT) Jim Lesurf
wrote:

Anyhow, this is the event that made me decide to mod the amp. the
current limiting on the 405 was too severe, which is what allowed
the o/p trannies to blow (before the fuses could save them).

Puzzled. The point of the current limiting is to ensure the output
devices*never* blow up. The severe limiting on early 405's gets in the
way of the music sometimes, but should avoid failures. Hence I am
puzzled by your last sentence above.

It appears to limit current just enough to prevent the fuses blowing but
not quite enough to save the transistors.

That is odd. The protection was - particularly in earlier models - too
severe. However it really *should* protect the output devices. Were some
small signal devices earlier in the amp also damaged? If so, it may be that
this lead to a failure that the protection system isn't designed to deal
with.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Confession time
 

In article , Ian Molton
wrote:
On Fri, 21 Nov 2003 08:55:19 +0000 (GMT) Jim Lesurf
wrote:

Anyhow, this is the event that made me decide to mod the amp. the
current limiting on the 405 was too severe, which is what allowed
the o/p trannies to blow (before the fuses could save them).

Puzzled. The point of the current limiting is to ensure the output
devices*never* blow up. The severe limiting on early 405's gets in the
way of the music sometimes, but should avoid failures. Hence I am
puzzled by your last sentence above.

It appears to limit current just enough to prevent the fuses blowing but
not quite enough to save the transistors.

That is odd. The protection was - particularly in earlier models - too
severe. However it really *should* protect the output devices. Were some
small signal devices earlier in the amp also damaged? If so, it may be that
this lead to a failure that the protection system isn't designed to deal
with.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Confession time
 

On Sat, 22 Nov 2003 09:39:53 +0000 (GMT)
Jim Lesurf wrote:

That is odd. The protection was - particularly in earlier models - too
severe. However it really *should* protect the output devices. Were some
small signal devices earlier in the amp also damaged? If so, it may be that
this lead to a failure that the protection system isn't designed to deal
with.

on one board yes - the class A 'pre' driver failed.

on the other, just the output transistors.

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with ketchup.

Confession time
 

On Sat, 22 Nov 2003 09:39:53 +0000 (GMT)
Jim Lesurf wrote:

That is odd. The protection was - particularly in earlier models - too
severe. However it really *should* protect the output devices. Were some
small signal devices earlier in the amp also damaged? If so, it may be that
this lead to a failure that the protection system isn't designed to deal
with.

on one board yes - the class A 'pre' driver failed.

on the other, just the output transistors.

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with ketchup.

Confession time
 

On Thu, 20 Nov 2003 23:39:51 GMT, "Wally" wrote:

Moving into my first flat many moons ago, I was only concerned with the
important stuff - floor cushions, coffee machine and hifi.

I lived in several accommodations where I slept on a mattress, propped
against a wall by day. Then I could fit my piano in.

Confession time
 

On Thu, 20 Nov 2003 23:39:51 GMT, "Wally" wrote:

Moving into my first flat many moons ago, I was only concerned with the
important stuff - floor cushions, coffee machine and hifi.

I lived in several accommodations where I slept on a mattress, propped
against a wall by day. Then I could fit my piano in.

Confession time
 

On Thu, 20 Nov 2003 21:49:19 -0000, "edd" zoe.hellen wrote:

Crossed the speaker wires, Nytech went BANG, and promptly set its self on
fire.

Thus neatly illustrating the stupidity of omitting output protection
circuitry in the quest for the last 0.1% of "high fidelity" :-(


The same amp also destroyed a set of mission 701s and id turned the volume
up to high without noticing. pres play and whack, cones nearly popped out,
and tore all the already rotting foam.

Well, if the foam was rotting anyway...:-)

Confession time
 

On Thu, 20 Nov 2003 21:49:19 -0000, "edd" zoe.hellen wrote:

Crossed the speaker wires, Nytech went BANG, and promptly set its self on
fire.

Thus neatly illustrating the stupidity of omitting output protection
circuitry in the quest for the last 0.1% of "high fidelity" :-(


The same amp also destroyed a set of mission 701s and id turned the volume
up to high without noticing. pres play and whack, cones nearly popped out,
and tore all the already rotting foam.

Well, if the foam was rotting anyway...:-)

Confession time
 

On Fri, 21 Nov 2003 00:32:18 +0000, G.Snail
wrote:

Left bird crap on Mazda Xedos 6 and Volvo 480 Turbo (both
fairly new) in the baking sun for a week. Washed the cars - poop had
eaten through the paint - they both needed full resprays.

Once again, an illustration of the stupidity of putting appearance
over durability. Reminds me of plastic covers over the new 3-piece
suite "to keep it looking nice" :-)

Confession time
 

On Fri, 21 Nov 2003 00:32:18 +0000, G.Snail
wrote:

Left bird crap on Mazda Xedos 6 and Volvo 480 Turbo (both
fairly new) in the baking sun for a week. Washed the cars - poop had
eaten through the paint - they both needed full resprays.

Once again, an illustration of the stupidity of putting appearance
over durability. Reminds me of plastic covers over the new 3-piece
suite "to keep it looking nice" :-)

Confession time
 

"Laurence Payne" wrote in message
...
On Fri, 21 Nov 2003 00:32:18 +0000, G.Snail
wrote:

Left bird crap on Mazda Xedos 6 and Volvo 480 Turbo (both
fairly new) in the baking sun for a week. Washed the cars - poop had
eaten through the paint - they both needed full resprays.

Once again, an illustration of the stupidity of putting appearance
over durability. Reminds me of plastic covers over the new 3-piece
suite "to keep it looking nice" :-)



Hmmm, you are discounting the 'placebo effect' here.....!!

Confession time
 

"Laurence Payne" wrote in message
...
On Fri, 21 Nov 2003 00:32:18 +0000, G.Snail
wrote:

Left bird crap on Mazda Xedos 6 and Volvo 480 Turbo (both
fairly new) in the baking sun for a week. Washed the cars - poop had
eaten through the paint - they both needed full resprays.

Once again, an illustration of the stupidity of putting appearance
over durability. Reminds me of plastic covers over the new 3-piece
suite "to keep it looking nice" :-)



Hmmm, you are discounting the 'placebo effect' here.....!!

Confession time
 

"Laurence Payne" wrote in message
...
On Thu, 20 Nov 2003 23:39:51 GMT, "Wally" wrote:

Moving into my first flat many moons ago, I was only concerned with the
important stuff - floor cushions, coffee machine and hifi.

I lived in several accommodations where I slept on a mattress, propped
against a wall by day. Then I could fit my piano in.



Swim's new piano (having displaced half my kit) has bloody near put me in
that situation!

Confession time
 

"Laurence Payne" wrote in message
...
On Thu, 20 Nov 2003 23:39:51 GMT, "Wally" wrote:

Moving into my first flat many moons ago, I was only concerned with the
important stuff - floor cushions, coffee machine and hifi.

I lived in several accommodations where I slept on a mattress, propped
against a wall by day. Then I could fit my piano in.



Swim's new piano (having displaced half my kit) has bloody near put me in
that situation!