45 SET

[simon]

18 months ago I built this amp - time flies. I haven't done anything to it in that time except enjoy it. Marvellous.

I keep meaning to box it up but then have nagging thoughts that I could make improvements. Improvements might just be differences though...

The old article from Sound Practices including circuit was available on Gordon Rankin's Wavelength Audio website for years but it's not there now so I don't think I should post the circuit. But it's a 5751 SRPP driver with a small 47nF coupling cap to the 45. I actually use 10nF as I use the amp above 300Hz.

The 45 filaments are AC heated, and the PS has a GZ33 rectifier to 2x LC, one per channel, a 30H small Hammond choke and 200uF WKZ. A further 10uF Solen PP for the driver.

So some thoughts on possible changes:

An obvious one is to try a shunt reg. Would this be better though? Maybe if I was using the amp full range I might get some benefit in the bass? And might I lose some if the mellifluous single ended 45 magic I love so much?

Try some PP reservoir caps instead of the WKZs?

DC heat the 45s?

A "nicer" 10uF cap instead of the cooking Solens?

A different driver? A trioded D3a would perhaps give me enough gain.

Try the ECL82-45 amp discussed earlier in this thread, the one that uses the pentode section as CCS. I can't find my Sound Practices CD and don't have the circuit though.

Just box the Bugle up and stop making things complicated for myself?

Any thoughts from the panel?

[Nick]

May sound factious but describe what better is. Listen to all your music and decide what it can't do and why. Then fix that. If you can't answer that. Enjoy what you have.

[simon]

Yeah yeah, I know.

But sometimes things just sound better. I'd quite like to try a 26 driving the 45, but that gets a lot more complicated. I'm driven by detail and openness - yeah real hi fi words. Dont ask me to explain that! But this helps me make more sense of the melody, and pretty much everything else.

[Nick]

Take psychoactive drugs:-)

[simon]

Not awfully compatible with random drugs and alcohol testing at work sadly

[Paul Barker]

We get that in Gas work as well Simon. Ive enjoyed music u der the influence when I was a nurse where we weren’t random tested. You do stupid things like buy speKers that in the cold light of day are horrible .

But addiction in nursing isn’t uncommon often its their way of facing the job.

I recall taking just one df118. for pain. I had to sit in the rest room with two sisters both very bossy and couldnt talk as if i did i sounded drunk.

My dad a GP coped with its stresses drinking half a bottle of Whisky every evening. His wife , not my mother, was a Heroin addict. You’d be surprised.

Ive been to hifi houses to buy a cartrige for example and they smoked weed freely in their listening. For sure they hear things you don’t.

[Paul Barker]

Here is an interesting thing Simon. Normal high 2nd of loved dht’s single ended. Zero 3rd. Is that the magic? So in theory you could build it push pull, wipe out the 2nd and not suffer 3rd. That ought to sound better, only in the case of the 45. Which means I need to build a push pull 45 amp.




So if I built a 45 amp with the tributes it would be 10k load 1.4 watts and that would be very interesting too. I dont recall what peak to peak Dr John’s Sowters are, maybe 8k. So maybe 1.6 watt x2 for class a pp. similar reduced distortion, cancelled anyway. 1% 3rd because not cancelled. Interesting.

I suppose the really interesting thing is the 7% 2nd . Maybe people who love 45 SE are on 2nd harmonic drugs and if you put it into a 10k load you would no longer be satiated. LOL

[Paul Barker]

Who can hear the difference between 2 watt and 1.44 watt, but maybe reducing 2nd from 7% to half is the biggest improvement you could make. Forget boutique components, this is measurable science. This is what the different loadlines look like. Getting better all the time. Biggest improvement you could make. Then put it into a Mofo and youve cracked it.
LOL


Does actually make me consider building a 10k load SE45 and a tiny little Mofo on the output. Ermmmm, trouble is it makes more sense than building a 30 watt valve output stage for same result.
Damn I’m flirting with the Dark side. But anyway look at those loadlines, a picture tells a thousand words.

[Paul Barker]

How brave are you ? Would you take a stereo pair of ST 45’s and get this power into 10kohm

You stay at 10 watts dissipation but you risk the voltage tolerance 380v 25mA -90 bias quiescent

I have enough ST 45’s to give that a go. Bet it squashes any boitique component you could buy.

9.5 watts dissipation 38% ratio to power output.

Or stay in 275v limit and get some 10k peak to peak push pull transformers

[Paul Barker]

I can suure you operating my EL34 SE where its second is better than any dht has prevented me leaving the room, its addictive. The biggest improvement fixing the 2nd harmonic elephant in the room. Thats why Im not wasting time on the EL36. Sorry to report. Its a dead loss not using the valves the beautiful designers in days of yore ran with sweat trying to achieve these special valves. 71a 45 dare I say EL34? Yes I dare, its a glorious happenstance. But I doubt found by accident. No someone sweated to creat it. Do you think, that in a sweat shop in China anyone gives that much of a fook, as these Mullard designers who came up with the EL34. Yes they can copy, and are getting better at that. But you arent going to see a new valve entirely new that blows the audio world away. No Sir.

[Nick]

Who can hear the difference between 2 watt and 1.44 watt, but maybe reducing 2nd from 7% to half is the biggest improvement you could make. Forget boutique components, this is measurable science. This is what the different loadlines look like. Getting better all the time. Biggest improvement you could make. Then put it into a Mofo and youve cracked it.
LOL

Not sure if this is irony or just clever marketing, but I clicked on the load line image by mistake and it took me to the photo hosting page where it inserted an advert for hearing aids

[Paul Barker]

Well its free hosting

[simon]

Interesting stuff Paul. I woke up this morning thinking about a low voltage 26 direct coupled to 45, but this is a very different direction. I need to study reread your posts when I have a bit more time, but I don't have any 10k OPTs, only 5k, so might not be a goer anyway.

[Ant]

Reminds me of the mr I pp 45 i built a long long time ago, i think that was 10k pp transformers, used a 7f8w for the driver. Although it was abit crap until i put some proper interstage transformers in it, the hammonds i used initially were rubbish, the llundahls i put in it later were not. Then it was lively and lovely.
Must be 15 years ago now. I think i sold it in parts when i got made redundant. Think i modded it to have 2a3s in it at some point too

[simon]

I had a bit of a play with vtadiy.com's loadline calculator as it's easier than building spreadsheets like you Paul.

https://www.vtadiy.com/loadline-calcula ... calculator

The results are a little different from Paul's - it's based on Koren spice models.

This is the 45 with 4k6 OPTs
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45SE - 4-6kZ.png (96.55 KiB) Viewed 5254 times

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This is with 10k OPTs
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45SE - 10kZ.png (172.11 KiB) Viewed 5254 times

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Out of interest I looked at my GM70 amp too
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GM70 - 5kZ.png (188.41 KiB) Viewed 5254 times

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Remarkably low. I preferred the 45 when I switched though.