EL34 Nostalgia

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Cressy Snr
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#31 Re: EL34 Nostalgia

Post by Cressy Snr »

Hmm...that's fast and stable. Not seen anything like that with the ones I've done previously. I can see now why the things I've built, apart from the 6B4G mono-blocks, which had series regulated supplies, have sounded a bit soft and lacking in jump factor. At least I understand now. Thanks Nick/Mark for your patience and persistence.
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#32 Re: EL34 Nostalgia

Post by IslandPink »

I was just about to say "You can checkout, but you can never leave" before you removed the last line !
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#33 Re: EL34 Nostalgia

Post by Cressy Snr »

IslandPink wrote: Mon May 23, 2022 9:14 pm I was just about to say "You can checkout, but you can never leave" before you removed the last line !
Well I decided that it would have been just a teensy bit immature to go off and sulk like some spoilt brat. I mean it’s me that’s the fecking idiot for not understanding something that should be bleed’n obvious to anyone who has been in this game as long as I have. The ego doesn’t like being told it’s wrong, especially when it actually is wrong. But one has to take this sort of thing on the chin and move on.

Of course, I’ll take the resistors out of the power section of the supply tomorrow and report back.
Will expectation bias lead to confirmation bias? I don’t think so as this is proper competent engineering we are dealing with here rather than snake oil BS.
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#34 Re: EL34 Nostalgia

Post by Cressy Snr »

So I've taken the resistors out and it looks like this. But now I'm having trouble with my spatial awareness.
I'm not sure now whether the EL34 on the 'other channel' is getting double the filtering that the the lower EL34 is getting.
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My brain is now in a seriously anxious state, because I simply can't process the diagram now. As Paul said in another thread:

"this is a serious issue. Not all disability is visible."

This is one of the reasons why I wanted a rest from this for a while.

Can the panel put me out of my misery one way or the other please?
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#35 Re: EL34 Nostalgia

Post by IslandPink »

No, you just got a 200u cap after the choke, that's all. The piece of wire going up to the other cap ( & channel ) on your diagram is still a direct connection so the two caps are in parallel.
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#36 Re: EL34 Nostalgia

Post by Cressy Snr »

Thanks Mark. Now you’ve cleared that up, I can see it.
Time for a bit of calm I think. I don’t want that level of anxiety to get re-established, or I’ll be back to square one. I’ve come too far over the past three years or so, to suffer a bloody relapse now. My own well-being is more important than a valve amp.
To borrow a phrase from the gambling adverts:
“When the fun stops - STOP.”
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#37 Re: EL34 Nostalgia

Post by steve s »

I read somewhere that electricity will take the shortest easiest route
If that's the case there's a difference between channels, but I would guess in practice marks right

Even a short length of wire has some resistance
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#38 Re: EL34 Nostalgia

Post by Cressy Snr »

OK. Thanks chaps. :)

As an aside, below is a short passage from one of my stories, that illustrates at least one aspect of poor mental health - specifically anxiety/depression type issues.

In this exerpt, the main character, William, has been dumped in the past, and is observing himself as a child at the dinner table as his mother prepares the evening meal, one Friday after school, some time in the mid 1960s. His illness is a character, “The Tormentor.”

…‘Wash your hands Willie your tea’s out!’ shouted mother. ‘Polly, put that doll in her pram and wash your hands as well!...Your grandad’ll be ‘ere soon!’

For the hundredth time, William wondered why the boy sitting at the table had not followed in his father’s footsteps. Life would have been so much simpler and incomparably happier for the lad, but he had been far too much the people pleaser: self-worth, completely dependant on the validation and approval of others. These traits had been catastrophic for his mental well-being.

He stared at the history before him and wondered how the lad had gone from successful, much loved Head Teacher, to someone who had shaken so hard in the supermarket aisle that it had felt as if his body was falling apart.
Over the years, the Tormentor had gradually convinced him that he didn’t deserve to be head of anything, let alone an ‘outstanding’ school and that he was nothing more than third-rate fraud who had sneaked in through the tradesman’s entrance.

There he sat. The innocent child - unaware of the horrors the Tormentor had in store for him. The boy adored his father, wanted to be like him. The Tormentor began again:

….You could have been a joiner like your dad. But oh no! Couldn’t be satisfied could you! Had to start getting ideas above your station. Don’t like to be the one to say I told you so, but that world was never meant for the likes of you. Couldn’t handle it in the end then? So predictable. Dear oh dear!….

And that, for a lot of sufferers is basically the sort of negative thinking that goes on 24/7. The situations and the thoughts about them will of course be different for each person, but absolutely all of them will be negative in nature, and sadly, the outcomes are often all too predictable.
“Idiots make it into every company. They tend to interview well.”

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Nick
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#39 Re: EL34 Nostalgia

Post by Nick »

steve s wrote: Tue May 24, 2022 11:34 am I read somewhere that electricity will take the shortest easiest route
If that's the case there's a difference between channels, but I would guess in practice marks right

Even a short length of wire has some resistance
1. Ohms law, that tells you all you need to know in this case. What you read is sort of true, but makes it seem like it only takes the one route. It doesn't.
2. Its a drawing, the actual implementation is where the length of wires may matter (but are unlikely to in this case). The map is not the territory.
3. And the short length of wire also has capacitance and inductance, but none are likely to matter enough to worry about in everyday amp design. Though I do remember measuring the increasing level of induced noise as I moved a scope probe along a length of silver wire when working on a regulator design. Once you start having high current, high speed transients in the signal, then the inductance gets involved far faster than you may imagine.

One place where the position may matter. The point you take the feedback from on a push pull solid state amp. If the feedback point is not at or after exactly where the push and pull signals combine, distortion goes (relatively) through the roof. That's one of Self's sources of distortion.
Little known fact, coherent thought can destructively interfere with itself leaving no thought at all, that’s why I prefer incoherent thought.
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#40 Re: EL34 Nostalgia

Post by steve s »

I thanks nick that's good clarification

I base my practical knowledge on, but very different conditions, doubling up batteries,
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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Nick
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#41 Re: EL34 Nostalgia

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steve s wrote: Tue May 24, 2022 12:22 pm I thanks nick that's good clarification

I base my practical knowledge on, but very different conditions, doubling up batteries,
That's actually a complex situation, as the voltage on each battery is unlikely to be exactly the same, so if you apply a load to the pair in parallel, the battery with the lower voltage will only start providing current when the load pulls the voltage on the higher voltage batter down to the lower voltage battery state. Though in practice, the higher voltage battery when they are sitting there will discharge into the lower voltage battery until they are the same voltage.
Little known fact, coherent thought can destructively interfere with itself leaving no thought at all, that’s why I prefer incoherent thought.
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#42 Re: EL34 Nostalgia

Post by steve s »

Nick wrote: Tue May 24, 2022 12:44 pm
steve s wrote: Tue May 24, 2022 12:22 pm I thanks nick that's good clarification

I base my practical knowledge on, but very different conditions, doubling up batteries,
That's actually a complex situation, as the voltage on each battery is unlikely to be exactly the same, so if you apply a load to the pair in parallel, the battery with the lower voltage will only start providing current when the load pulls the voltage on the higher voltage batter down to the lower voltage battery state. Though in practice, the higher voltage battery when they are sitting there will discharge into the lower voltage battery until they are the same voltage.
Exactly, a few inches of wire can effect charge and load/discharge by a fair percent, and as we only have at most a volt between full charge and nearly flat, it matters

Thinking out loud, Steve's power supply is doing 2 jobs, smoothing the dc, which we are are relating to in terms of resistance.
But Steve is also thinking of suppressing or putting a barrier between channels, so the ac modulation is 'contained' for want of a better description
We are then talking low voltages so the layout 'may' be more critical looking from the anode ?

I'm still not sure the correct term is for the modulation I'm describing, but you get my drift
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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#43 Re: EL34 Nostalgia

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The phase your are looking for (maybe) is coupling between the channels. That's controlled by a combination of the isolation between the channels, and the power supply rejection ratio (the sensitivity of the circuit output to changes on its power supply). The change that has been made will certainly reduce the isolation between the channels, and that may or may not be an issue, as I said, YMMV. Then the voltage amplifier will have a lower PSRR but that still has the isolation provided by its individual RC stages.

Its why its always a compromise between all the various aspects of the circuit, and there is no single correct answer.
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#44 Re: EL34 Nostalgia

Post by IslandPink »

Ideally you'd have two LC legs to the channels, but if it's a choice between RC final stage with L&R split, vs. LC final stage, shared, I'd go with the latter , from experience.
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#45 Re: EL34 Nostalgia

Post by steve s »

Me too mark, thats logical, I've tried a few combinations since I built that 4 powersupply px25 amp, all to see where the tipping point was.

To be honest my thoughts are that containing the signal to a reasonable level gives overall more advantages than a slightly more agile dc supply..

But that's only my opinion, that will always change if I hear better !

But may be... from the holding back the modulation aspect, the resisters look better than nothing.
As ever always a comprimise
Listening is the deciding factor for me
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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