New SE With Triode Mode KT120/150

What people are working on at the moment
steve s
Shed dweller
Posts: 2829
Joined: Wed May 30, 2007 6:19 pm
Location: east yorks

#271 Re: New SE With Triode Mode KT120/150

Post by steve s »

Nick wrote: Wed Aug 12, 2020 12:52 pm

With respect Steve, you seem to be tilting at windmills, reality is what it is, and its just lucky that we can model it with maths at all else we would still be in the dark ages. Its not as it is there to frustrate you, but you can chose to be happy with what works or worry over what you probably don't need to know. Most of us just try to find the level of interpretation that works for us and does what we need.
I'm definitely in that 'what works for me' camp
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
simon
Thermionic Monk Status
Posts: 5600
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

#272 Re: New SE With Triode Mode KT120/150

Post by simon »

Tilting at Windmills - sounds like a Shed 7 song that never made in on to an album
JamesD
Old Hand
Posts: 997
Joined: Tue Oct 09, 2007 4:26 pm
Location: North Yorkshire

#273 Re: New SE With Triode Mode KT120/150

Post by JamesD »

Just a nit-pick on what Nick said - ESR for a capacitor does vary with frequency as it is dependent on the dissipation factor and that is frequency dependent - this is separate from the ESL.

A good discussion of capacitors and audio is on the Rod Elliot site https://sound-au.com/articles/capacitors.htm.

ciao

James
User avatar
Nick
Site Admin
Posts: 15708
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#274 Re: New SE With Triode Mode KT120/150

Post by Nick »

JamesD wrote: Wed Aug 12, 2020 4:21 pm Just a nit-pick on what Nick said - ESR for a capacitor does vary with frequency as it is dependent on the dissipation factor and that is frequency dependent - this is separate from the ESL.

A good discussion of capacitors and audio is on the Rod Elliot site https://sound-au.com/articles/capacitors.htm.

ciao

James
Yep, I was wondering if I should mention the extra perfect LCR components across the perfect cap and decided that that way lay madness, but you are of course correct.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
JamesD
Old Hand
Posts: 997
Joined: Tue Oct 09, 2007 4:26 pm
Location: North Yorkshire

#275 Re: New SE With Triode Mode KT120/150

Post by JamesD »

I think any discussion of capacitors and audio promotes madness...

:D
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#276 Re: New SE With Triode Mode KT120/150

Post by Cressy Snr »

JamesD wrote: Wed Aug 12, 2020 5:09 pm I think any discussion of capacitors and audio promotes madness...

:D
And I don’t know much about algebra, or what a slide rule is for, so I’ve no chance. :lol:
As Nick has advised. I’ll keep to doing what works for me.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8872
Joined: Mon May 21, 2007 9:42 pm

#277 Re: New SE With Triode Mode KT120/150

Post by Paul Barker »

Yer but no but yer but the frequency is 100hz
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8872
Joined: Mon May 21, 2007 9:42 pm

#278 Re: New SE With Triode Mode KT120/150

Post by Paul Barker »

Paul Barker wrote: Wed Aug 12, 2020 7:12 pm Yer but no but yer but the frequency is 100hz
Or isn’t it that simple?
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
User avatar
Ray P
No idea why I do this anymore
Posts: 6294
Joined: Thu Nov 22, 2007 5:18 pm
Location: Somerset

#279 Re: New SE With Triode Mode KT120/150

Post by Ray P »

Cressy Snr wrote: Wed Aug 12, 2020 5:27 pm As Nick has advised. I’ll keep to doing what works for me.
and maybe change your user name to Don Quixote :lol:
Sorry, I couldn't resist!
User avatar
Nick
Site Admin
Posts: 15708
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#280 Re: New SE With Triode Mode KT120/150

Post by Nick »

Paul Barker wrote: Wed Aug 12, 2020 7:13 pm
Paul Barker wrote: Wed Aug 12, 2020 7:12 pm Yer but no but yer but the frequency is 100hz
Or isn’t it that simple?
Don't forget the harmonics.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
JamesD
Old Hand
Posts: 997
Joined: Tue Oct 09, 2007 4:26 pm
Location: North Yorkshire

#281 Re: New SE With Triode Mode KT120/150

Post by JamesD »

And the noise/signalling on the mains that gets through the trannie and rectifiers....

And the signal that finds it way back into the psu...

And the ground/earth noise...

and

and

and....

:D
User avatar
IslandPink
Amstrad Tower of Power
Posts: 10041
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#282 Re: New SE With Triode Mode KT120/150

Post by IslandPink »

" and and and and and and and and and and and and end.. "
As Arthur Lee sang.
"Once you find out ... the Circumstances ; then you can go out"
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8872
Joined: Mon May 21, 2007 9:42 pm

#283 Re: New SE With Triode Mode KT120/150

Post by Paul Barker »

JamesD wrote: Wed Aug 12, 2020 9:45 pm And the noise/signalling on the mains that gets through the trannie and rectifiers....

And the signal that finds it way back into the psu...

And the ground/earth noise...

and

and

and....

:D
Sorry it’s late was woken by a friend whose little girl getting taken to Jimmy’s and then you’re lying awake. It’s certainly true you can hear the microphonics in the Power supply capacitors playing the music in standard SE.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#284 Re: New SE With Triode Mode KT120/150

Post by Cressy Snr »

steve s wrote: Fri Aug 07, 2020 12:19 pm ... my only suggestion to 'improve' it would be a pair of VT75s (KT66).
I brought a pair of grey-glass KT66s out of hibernation to tryout, and the results were encouraging.
At the bias settings I had, they were being over dissipated slightly, but I only had them in for a short time; just long enough to figure that correctly configured, in terms of dissipation and OPT impedance, they would be good.

One change of cathode resistor value to bring the dissipation under 25W, one change of rectifier valve to drop the HT a bit, to make doubly sure, and one rewire of the OPTs for 5K later, we have quite a little performer on our hands. :)
BE989A3B-86D0-4C87-8AAB-F69A550912DA.jpeg
OK, so these KT66 are not the earlier VT75s (I could have wept when I heard those) but they come in at a highly respectable second place. MH4 driving KT66 is a good combination.
steve s
Shed dweller
Posts: 2829
Joined: Wed May 30, 2007 6:19 pm
Location: east yorks

#285 Re: New SE With Triode Mode KT120/150

Post by steve s »

If you didn't mind a top cap /change of base there are a few other valves that may come close to the vt75, early vt75a to start. I'd need to look at my books, but I dont have with me at the moment.
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
Post Reply