GM70
- Paul Barker
- Social Sevices have been notified
- Posts: 8998
- Joined: Mon May 21, 2007 9:42 pm
#1 GM70
Something became out of sync when I traced the GM70 first in A1 and then in A2. This seems to happen with any A2 valve. The transition in the way we cross from measuring A1 to A2 is flawed. So we have some data which we must apply reason to.
I have conglomerated the two different traces. Either one half or the other half or both half's to a degree are out of line.
Two pictures merged with Paint, but not manipulated.
Here I have incorporated the +10v line from the A1 curves and manipulated A2 curve position.
Is it simply the inaccuracy of the screen voltage at low voltages?
I have conglomerated the two different traces. Either one half or the other half or both half's to a degree are out of line.
Two pictures merged with Paint, but not manipulated.
Here I have incorporated the +10v line from the A1 curves and manipulated A2 curve position.
Is it simply the inaccuracy of the screen voltage at low voltages?
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
- Paul Barker
- Social Sevices have been notified
- Posts: 8998
- Joined: Mon May 21, 2007 9:42 pm
#3
Shows that the miniscule portion we can observe is a non linear part of the whole picture, and only proves how the present uTracer is outclassed by such a valve as the GM70. It seems the top picture of mine is probably closer to the truth than I realised, as the positive lines only linearise at the higher currents. I am not satisfied that the transition from A1 measurments to A2 measurments is accurate though.
But the uTracer blog shows good progress in development of the uTracer 4 despight Ronald having had a holliday.
We are on holliday this week at home having day trips.
I'd sooner be in the manshed Shhhh, don't tell anyone.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
- Paul Barker
- Social Sevices have been notified
- Posts: 8998
- Joined: Mon May 21, 2007 9:42 pm
#4
Actually the official curves demonstrate a considerable amount of 2nd harmonic at the operating points we use, probably more appropriate for PP operation. I have never been entirely happy with the GM70 SE sound, though we have had loads of fun with it, such valves as the 211 destroy it in my book.
Quite possible the GK71 will kill it once and for all.
We'll see.
Quite possible the GK71 will kill it once and for all.
We'll see.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
- IslandPink
- Amstrad Tower of Power
- Posts: 10041
- Joined: Tue May 29, 2007 7:01 pm
- Location: Denbigh, N.Wales
#5
I think those 'official' curves have been shown to be rubbish recently .
These are more widely accepted nowadays :
http://www.audiocircle.com/index.php?topic=80977.0
or these :
http://www.audiofaidate.org/forum/viewtopic.php?t=4305
although they don't show the A2 section very much .
There's a job for you, Paul !
These are more widely accepted nowadays :
http://www.audiocircle.com/index.php?topic=80977.0
or these :
http://www.audiofaidate.org/forum/viewtopic.php?t=4305
although they don't show the A2 section very much .
There's a job for you, Paul !
"Once you find out ... the Circumstances ; then you can go out"
- andrew Ivimey
- Social Sevices have been notified
- Posts: 8318
- Joined: Mon Jun 11, 2007 8:33 am
- Location: Bedford
#6
Actually the official curves demonstrate a considerable amount of 2nd harmonic at the operating points we use, probably more appropriate for PP operation. I have never been entirely happy with the GM70 SE sound, though we have had loads of fun with it, such valves as the 211 destroy it in my book.
Quite possible the GK71 will kill it once and for all.
We'll see.
_____________
Quoting Paul above ... but they are so cheap! And I enjoy them. VT4cs are very expensive - they are better of course and I'm using audionote iron. GM70s are fun and capable. GK71s, I've doen adn await with baited breath for someone to demonstrate their magic - but at that price, does it matter! I don't see that a GK will 'destroy' a GM actually but dare I also hint ....
Curves are curves and measurements are only measurements but using the valves are something else (Is this being a flat earther?). I'll be advocating homeopathy and talking to trees soon
I am eager to hear this latest generation of GKs and GMs - roll on Owston.
Quite possible the GK71 will kill it once and for all.
We'll see.
_____________
Quoting Paul above ... but they are so cheap! And I enjoy them. VT4cs are very expensive - they are better of course and I'm using audionote iron. GM70s are fun and capable. GK71s, I've doen adn await with baited breath for someone to demonstrate their magic - but at that price, does it matter! I don't see that a GK will 'destroy' a GM actually but dare I also hint ....
Curves are curves and measurements are only measurements but using the valves are something else (Is this being a flat earther?). I'll be advocating homeopathy and talking to trees soon
I am eager to hear this latest generation of GKs and GMs - roll on Owston.
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
#7
Thats why I linked the curves I did.IslandPink wrote:although they don't show the A2 section very much
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
- Paul Barker
- Social Sevices have been notified
- Posts: 8998
- Joined: Mon May 21, 2007 9:42 pm
#8
Again it just demonstrates the limited range we have to work with. But my curves overlay it quite well under the circumstances.
[/URL]
[/URL]
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
- IslandPink
- Amstrad Tower of Power
- Posts: 10041
- Joined: Tue May 29, 2007 7:01 pm
- Location: Denbigh, N.Wales
#9
I know Paul assumed the rest of the A1 curves were representative.Nick wrote:Thats why I linked the curves I did.
"Once you find out ... the Circumstances ; then you can go out"
- Paul Barker
- Social Sevices have been notified
- Posts: 8998
- Joined: Mon May 21, 2007 9:42 pm
#10
I grant you Mark that the bigger picture traces shows very nice A1 curves. No real need to show A2 when there are such good A1 operating criteria available. There also remains a question mark over the transition to A2, which even the official curves show is strange compared to other valves designed for A2.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
- Paul Barker
- Social Sevices have been notified
- Posts: 8998
- Joined: Mon May 21, 2007 9:42 pm
#12
Which makes the curves wrong.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
- IslandPink
- Amstrad Tower of Power
- Posts: 10041
- Joined: Tue May 29, 2007 7:01 pm
- Location: Denbigh, N.Wales
#13
Sent some money to Bud . Ouch !
With a bit of luck I will have them in October.
( 7K>8R/4R , M3, 'level 2' , 90ma , ~40-45H ) .
With a bit of luck I will have them in October.
( 7K>8R/4R , M3, 'level 2' , 90ma , ~40-45H ) .
"Once you find out ... the Circumstances ; then you can go out"