Tube geekery to pass the time.

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Cressy Snr
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#1 Tube geekery to pass the time.

Post by Cressy Snr »

I’ve been doing a bit of geeking about with the vtadiy.com SPICE based load-line calculators, to pass the dark afternoons whilst the missus watches films on the TV. I don’t have the attention span to sit through movies, so I usually end up in my cold and ill-lit garret, staring at my valve boxes, wishing that apart from the 45s, I had some that were any good and dreaming of Tribute, AE Europe and Tango transformers. Sad.

Anyway I produced a little table of some of the valves I have, when they are used in single ended triode mode and using the simulator to look at the distortion they produce at 1W output into their recommended loads.
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685AAC08-4308-4B64-B589-493FDD79B26E.png (201.7 KiB) Viewed 7490 times
However leaving that to one side for a moment. I decided on a whim to look at the 2nd over 3rd ratio and discovered something interesting that backs up what I’ve heard from some of these valves. I’m prepared to be shot down in flames, but I know what I’ve heard.
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Cressy Snr
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#2 Re: Tube geekery to pass the time.

Post by Cressy Snr »

Example:
45 - ratio 2nd to 3rd = 5.9 : 1. Sweet and airy. This has the lowest ratio of 2nd to 3rd harmonic distortion and is a great place to start as a reference.
2A3 has less overall distortion with 2nd @ 1.53% and 3rd @ 0.2% . Not as sweet as the 45 and it is less airy. Ratio of 2nd to 3rd is higher at 7.33 : 1
300B has the least distortion of the lot but is darker sounding than the 2A3 in the amps I’ve heard. Ratio of 2nd to 3rd is roughly 10:1
Overall the DHTs have lower ratios of 2nd to 3rd harmonic distortion at 1W than do the indirect heated triode strapped pentodes and they also sound more musical and airy than the IDH valves.

When you get to the KT120, which I have used extensively in SE mode, they are rich, kick ass and sound loud, even when they are not. They are too much at times. Looking at the 243 : 1 ratio of 2nd to 3rd it’s easy to see why. KT88 not as bad but bad enough. Well it is for me. I can see from the distortion profiles how the tubes might sound. KT150 looks interesting, as does the KT77, which I’ve got. These are the closest to the DHTs in terms of their distortion ratios and the KT77 does indeed sound the best out of the triode strapped pentodes I’ve used in SE mode. It all seems to work.

I reckon if I could afford them, and looking at their distortion profiles, I’d prefer PX4 to the PX25. PX4 detailed and airy, PX25, richer darker and less detailed. It seems to work out for me.

I’ll get me coat.
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Cressy Snr
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#3 Re: Tube geekery to pass the time.

Post by Cressy Snr »

Does beg the question though: is a flea watt SE amp hi-fi or is it just a pleasant distortion machine. The age old debate.

Most of us have abandoned them. Are they yesterday’s news, far too expensive to consider if you don’t have a shed full of old chokes and transformers? Powerful digital amps and DSP seem to be in the ascendancy.

I love my 45 amplifier above anything else I’ve ever used. I’ve come to them too late. Ah well, never mind I got there in the end. Alone in the wreckage, but there you go.
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#4 Re: Tube geekery to pass the time.

Post by Cressy Snr »

It’d be interesting with the DHTs to have a way of pulling down the distortion levels whilst keep the ratios identical to see what would happen.
Conversely with the IDH valves, creating distortion profiles with the same ratios as the DHTs by pulling down the 2nd and upping the 3rd to meet in the middle.
I haven’t a clue how this could be achieved. I’m not that clever and perhaps it is impossible.
And why do it when you can imitate valves digitally as modelling guitar amps do.
Modelling hi-fi amps anyone? Now there’s a thing.

When there are no valves left, their ghosts will still be able to be heard with digital modelling amps.
The best valves need profiling before it’s too late.
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steve s
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#5 Re: Tube geekery to pass the time.

Post by steve s »

It's an interesting topic Steve, my logic is that if it where distortion that made that sweet sound, it would get sweeter with volume?
My sweetest valves are the oldest..
With oversized anodes.
Globe px 25 is much more detailed than straight sided (post ww2) px4

I've not heard real sweetness or from modern made valves.
But I hear a lack of cancellation in se operation
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Nick
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#6 Re: Tube geekery to pass the time.

Post by Nick »

I wasn't going to comment as i think it's far too simplified and there are too many undefined terms being used. But given that, and that a fixed power output seems a odd way of setting the comparison. I don't believe the numbers. A kt88 producing 4% at 1w seems odd if a kt77 produces a lot less. I think all it's doing is comparing the curves and saying very little about reality.
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#7 Re: Tube geekery to pass the time.

Post by Cressy Snr »

Nick wrote: Wed Dec 29, 2021 3:40 pm I wasn't going to comment as i think it's far too simplified and there are too many undefined terms being used. But given that, and that a fixed power output seems a odd way of setting the comparison. I don't believe the numbers. A kt88 producing 4% at 1w seems odd if a kt77 produces a lot less. I think all it's doing is comparing the curves and saying very little about reality.
Just shows you that science is best left to those with the nous to use it properly.
When you get fecking idiots like me making up figures off the internet you end up with anti-vaxxers and 5G conspiracists.
It's the thin end of the wedge.
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Greg
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#8 Re: Tube geekery to pass the time.

Post by Greg »

‘Willie Parker’?

You can get a knitted warmer for that :wink:
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#9 Re: Tube geekery to pass the time.

Post by steve s »

Cressy Snr wrote: Wed Dec 29, 2021 3:53 pm

Just shows you that science is best left to those with the nous to use it properly.
When you get fecking idiots like me making up figures off the internet you end up with anti-vaxxers and 5G conspiracists.
It's the thin end of the wedge.
I'll get back to writing my book. Pete Shaw's just told Willie Parker that Brian Crookshank's wife has died. :D
Don't underestimate yourself Steve, I think it'd very a miss understood aspect of hifi ( and me included in that)

Your conclusion is the same as much the hifi press and many manufacturers and experts would have us believe.

To me, it doesn't stack up though

I'm not saying that added harmonics can't improve some systems, I've heard it do that. But in my experience those distortions cause the music not to sound quite as natural.


My view is actually contrary to the mainstream view, in that single ended feedback less operation can be closer to the truth.
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
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ed
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#10 Re: Tube geekery to pass the time.

Post by ed »

The discussion around H2 and H3 has been going on in fet circles for ages. I can't lay my hands on it but there is a paper discussing the various merits of each distortion, I think by Nelson Pass.

anyways, I think this is a relevant discussion:

https://www.diyaudio.com/community/thre ... on.330451/

There is also the H2 generator which Nelson released which goes some way to scratching the itch which some have:

https://www.firstwatt.com/pdf/art_h2_v1.pdf

edit...found it:
https://www.passdiy.com/project/article ... d-feedback
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Cressy Snr
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#11 Re: Tube geekery to pass the time.

Post by Cressy Snr »

Greg wrote: Wed Dec 29, 2021 4:39 pm ‘Willie Parker’?

You can get a knitted warmer for that :wink:
Indeed!
I wouldn’t be without one. :lol:
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Paul Barker
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#12 Re: Tube geekery to pass the time.

Post by Paul Barker »

steve s wrote: Wed Dec 29, 2021 5:18 pm
Cressy Snr wrote: Wed Dec 29, 2021 3:53 pm

Just shows you that science is best left to those with the nous to use it properly.
When you get fecking idiots like me making up figures off the internet you end up with anti-vaxxers and 5G conspiracists.
It's the thin end of the wedge.
I'll get back to writing my book. Pete Shaw's just told Willie Parker that Brian Crookshank's wife has died. :D
Don't underestimate yourself Steve, I think it'd very a miss understood aspect of hifi ( and me included in that)

Your conclusion is the same as much the hifi press and many manufacturers and experts would have us believe.

To me, it doesn't stack up though

I'm not saying that added harmonics can't improve some systems, I've heard it do that. But in my experience those distortions cause the music not to sound quite as natural.


My view is actually contrary to the mainstream view, in that single ended feedback less operation can be closer to the truth.
i read somewhere, its the odd order distortions that give SE topology the perceived louder sound.

I certainly find I want to turn up PP amps.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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#13 Re: Tube geekery to pass the time.

Post by Nick »

The transfer function can bend from linear such that gain increases with level (expanding) or decrease (compressing) both are measured as distortion but will sound different. Typical se triodes have decreasing gain with level so increasing level will reduce dynamic range.
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#14 Re: Tube geekery to pass the time.

Post by steve s »

Paul Barker wrote: Wed Dec 29, 2021 7:44 pm


i read somewhere, its the odd order distortions that give SE topology the perceived louder sound.

I certainly find I want to turn up PP amps.
Thats the issue for me Paul, all the good things about se operation are blamed on distortion. And I'm pretty sure that not true unless they are used near their limit. As nick has just described

I'd put it to you that the reason you want to turn your push pull amp up is that most push pull amps cancel a small part of the signal.
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
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#15 Re: Tube geekery to pass the time.

Post by Paul Barker »

steve s wrote: Wed Dec 29, 2021 8:13 pm I'd put it to you that the reason you want to turn your push pull amp up is that most push pull amps cancel a small part of the signal.
Id buy that.

I didnt feel I needed something more from the Pp amp I transformer phase split into the opts, the only pp part of the amp.

Stephie did some circuits the other way round, PP first then SE output valve. Not tried that myself.

Sukuma San had quite a few of all ways, he wasnt averse to PP at least somewhere.

I just wish Id have found those phase splitting transformers again. I could always wind a phase splitting choke, or use primary only of PPopt as a choke.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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