New SE With Triode Mode KT120/150

[Cressy Snr]

Moving the cap from the input stage to the driver stage seems to have done the trick.
It's picked up the gain, but not to a ridiculous degree. The sound doesn't seem to have suffered.
Cap value is on the circuit diagram now too:

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[Ray P]

Good to see you having fun Steve.

How was Steph's Packed Lunch?

[Cressy Snr]

Good to see you having fun Steve.

How was Steph's Packed Lunch?

Lightweight inoffensive viewing.

[Cressy Snr]

Got the crappy components replaced with some that are summat like.

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Also, I replaced the earth busbar in the signal side of the amp, with copper.
I polished it with Brasso, and rinsed with isopropanol and did the same to all the new component leads, prior to soldering them in.
Everything in the resistor department apart from the input stage grid resistors are Kiwame, Mills, or Takman. You can just about see the green Russian PIO coupling caps, right at the bottom.
The sound has not been fooked up.

[IslandPink]

Result !

[Mike H]

Moving the [cathode bypass] cap from the input stage to the driver stage seems to have done the trick.

This is what I was trying to suggest earlier, but seems may have got lost in 'translation' ...

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[Mike H]

Good to see you having fun Steve.

How was Steph's Packed Lunch?

Lightweight inoffensive viewing.

Ha! ..

[Mike H]

I thought everyone else was using posh resistors and caps.

Nope! Well ClarityCaps is as far as I'll normally go.

[pre65]

I like to use Kiwame or Takman resistors for up to 5W, and I prefer not to use very small (ie 1/4W or 1/2W) resistors.


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[Cressy Snr]

This is what I was trying to suggest earlier, but seems may have got lost in 'translation' ...

I get what you were trying to say Mike, but the resulting gain was simply way too high.
Taking the cathode bypass off the input stage and having the bypass on the driver stage, is better, and is a reasonable compromise between the extreme gain of everything bypassed, and almost not having enough, ie, the gain of 14 into a gain of just above unity, then into the output valve, with the driver cathode un-bypassed. I only got away with that scenario because of the 100dB speakers.

For the efficiency of the speakers, the present gain remains slightly high, but short of removing the cathode feedback and replacing it with global feedback to the input stage cathode there’s not much I can do about that. Anyhow, I don’t want to invite instability, or end up with possible high order odd harmonics causing a shriekfest.

I could also down shift the signal level between input and driver, as it’s a direct-coupled setup. Merlin Blencowe talks about level shifting, somewhere in his preamp book. MJ doesn’t seem to be that keen on the practice for hi-fi amps.

However, it’s not, of course, simply a question of putting a potential divider between the two stages. Any change in the voltage coming from the input stage would upset the whole input/driver relationship. And as I’ve just this minute, bought good components and installed them, paying careful attention to the making of clean soldered joints, I’m not prepared to mess about further in that department.

I suppose I could simply level shift the input signal itself using a fixed potential divider, as a few people did with the old WAD power amps, before someone came up with the cathode follower mod to the Pre II

However....I think it’s time now to just enjoy the music. We’ve gone far enough. Messing any further with the gain is pursuing the nth degree for the sake of it, and really, in the wider scheme of things, it’s unnecessary.

[Cressy Snr]

DOH!

The Beresford DAC, has a variable output, so I can just set the input level from there. The solution was hiding in plain sight. Problem solved.

The phono stage and CD player are fine. It was just the streamer that was too loud. Not any more.

[Cressy Snr]

Nah...
I’m not at all happy with the bypassed driver cathode, so back to the drawing board. A re-evaluation is needed, as I’m getting further and further away from the sound I want. Some serious use of the ears is needed along with some back-to-basics thinking about the fundamentals of the circuit and what has/has not worked in the past.
I’ve rolled back the circuit to where it was a few days ago, still keeping the new components in, and it’s as it was, ie. sounding nice...ish. Unfortunately of course, now I’ve got back to where I was, a hangover from the ‘forward’ movement I made, has hitched a lift back on the coat tails of the rollback and has become noticeable, where it wasn’t before.

But that’s OK. Rather than get frustrated, why not use your experience to look into what you think might be going on? IOW what exactly is it that your ears telling you and can you translate that into a working engineering hypothesis, then test it and see what your ears have to tell you about the results. Short of a battery of test equipment, that is all the kitchen table bodger has at their disposal - their ears. Now let’s see. Think man!

[Nick]

Instead of focusing on what it is one likes about a circuit and trying to move toward that, which I find can lead us down the different is better sound that will wear off when its not different any more path. I find it better to focus on what it is is wrong and try and progress away from that, that way we can reduce the different is better trap. Finding what we don't like takes longer so requires further listening.

[Cressy Snr]

Instead of focusing on what it is one likes about a circuit and trying to move toward that, which I find can lead us down the different is better sound that will wear off when its not different any more path. I find it better to focus on what it is is wrong and try and progress away from that, that way we can reduce the different is better trap. Finding what we don't like takes longer so requires further listening.

OK, Here’s the gist of it. I don’t like coloration on black female vocals, or black tenor male vocals, such as those of Levi Stubbs of the Four Tops. I absolutely cannot abide it, and for someone heavily into soul and 50s/60s R&B, that is an absolute deal breaker. Unfortunately as the years have passed and my hearing at high frequencies has got worse, exacerbated by the Bell’s Palsy I had a few years ago, this problem has only increased in its severity, due to upper mids becoming more dominant in the spectrum that I can hear. As a consequence, singers such as Diana Ross, Randy Crawford, Beverley Knight or N’Dea Davenport, late of the Brand New Heavies, become unlistenable: piercing on vowel sounds. They only have to hit a loud ‘eeee’ and it is wince inducing, both for me and the missus, who also has exacerbated, age-related HF loss. You can 95% sort out Cilla, Dusty and Petula, but Diana, Randy, Beverley and N’Deah are on another level entirely. And it wasn’t always like this on my hi-fi back in the late 90s. They don’t sound like that in the car either.

Now one could reasonably ask a simple question such as, “Then why in the name of bloody hell are you using a single-driver speaker with whizzers then? WTF’ing hell do you expect? Build some different speakers, you know...with crossovers like...three way even. You’re looking in the wrong place for a solution. Just sayin’ an’ all that”

Indeed a change of speakers may be the long-term solution, but amps are perfectly capable of adding their own two penn ‘orth to the situation, and this one at the moment, is doing just that, and I’ve got an idea why. Having played around with pentodes quite a bit in the past, I know high order, odd harmonic distortion when I hear it. Combine that with the aforementioned female singers, HF hearing loss and single drivers with whizzers and you have a recipe for aural misery. Getting that high order odd harmonic distortion out of the equation has to be the first step. After that, I’ll have a look at the speaker question this year.

[steve s]

I've seen it so many times that what people think is making a difference is not always correct.
I.E.improving one thing can reveal other issues with the circuit.

Me i would not use an ecc82 at those signal voltages with a power supply arranged like that, as I feel there will be some cancellation of the signal
I'm not saying it won't sound good
But its not how I would build a driver stage now, to me there not enough smoothing between the anodes...
I'll run for cover now !