45 SE

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Cressy Snr
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#1 45 SE

Post by Cressy Snr »

OK, so I’m very late to the party: twenty years probably, but let’s see what happens.

From the other thread:
steve s wrote: Sat May 01, 2021 10:13 am
Cressy Snr wrote: Thu Apr 29, 2021 2:27 pm
It’ll be something new. The EL34 amp is exceptional: way too good and way too quiet to be bodging AC heated 45s onto it.
I’ll wait and do it properly.
Thats a good move steve, you will have both to compare
Unfortunately Steve, as yourself and the rest of the panel, probably suspected, I wouldn’t be able to resist the temptation to see what 45s are all about for long, and as I write this, the EL34 amp is in a state of dismlantlation (is that a real word? If not, it should be.) I do of course have my NVA A60 clone to fall back on if I either fook things up (unlikely) or if I can’t get the job done in a day (a possibility.)

In the first instance, I’ll be going simple and opting for AC filaments and humdinger pots. If the experiment proves to be successful, the ultimate aim is to use what I’ve learned over the last ten years, to recreate and improve on the series regulated 6B4G monoblock concept that was so successful and let’s be honest, gave such phenomenal sound quality into my old Mets, that I’ve spent a fruitless decade trying to get it back.

45s wouldn’t be much good for the Mets at the 94dB/ they are, hence Dave’s use of push-pull 300Bs on them, but with my 100dB Fanes, 45s should, in theory, be a great match.
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Cressy Snr
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#2 Re: 45 SE

Post by Cressy Snr »

I’ll be back at midnight.
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IslandPink
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#3 Re: 45 SE

Post by IslandPink »

You've got a lot of choices, because it only needs about 3ma to drive a 45 cleanly.
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Paul Barker
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#4 Re: 45 SE

Post by Paul Barker »

Image

I’ve selected these two because they are matched. Probably only matched pair.

One Kenrad one Cunningham.
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Paul Barker
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#5 Re: 45 SE

Post by Paul Barker »

I’d keep the front end and reduce b+ these are at least 50 years old. Run them at 80%, they’re irreplaceable.

I’d try ac Thomas Mayer said u can get away with it at 1.5v.
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simon
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#6 Re: 45 SE

Post by simon »

Yes, I used simple AC and it was silent. I didn't bother with humdingers, just a couple of resistors and the cathode resistor from the centre point. Nice and simple.
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#7 Re: 45 SE

Post by Paul Barker »

I have a few globes but not letting those go. I’ve never tried though they’re very old and used. I’ll bring them if/when we’re allowed indoors together to first find out if the globes are reasonable strength still, secondly if they sound better.

You need 5k opt option minimum. Lose the sweetness treating them as 2a3. Don’t know what Jono used but I remember an old story when he purchased very special amorphous core opts long before they hit public knowledge. If he had those in the amp James and I loved. Those might matter very much. But at least strive for the impedance.
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Cressy Snr
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#8 Re: 45 SE

Post by Cressy Snr »

Paul Barker wrote: Sat May 01, 2021 4:45 pm I’d keep the front end and reduce b+ these are at least 50 years old. Run them at 80%, they’re irreplaceable.

I’d try ac Thomas Mayer said u can get away with it at 1.5v.
Thanks Paul. :)
Looking fwd to having them in my care.
I've worked out a plan to run the valves at no more than 260V a-k, around 32mA, which is 8.3-ish Watts dissipation.
I'm very conscious of the age of these things and the fact that they are, as you say, irreplaceable.
I'm about half way through the conversion job ATM.

It'll be nice to see you when this lot is over.
Last edited by Cressy Snr on Sat May 01, 2021 5:17 pm, edited 1 time in total.
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#9 Re: 45 SE

Post by Paul Barker »

Ps I paid much more for the globes. But there may be at least one gem among them, if there are two and they stir our emotions we might have to go to offy for something to enjoy with them! Who knows? I find ballon px25 better than shoulder not subtle. Unlike Steve I don’t have any balloon px4’s.

But both of us are lucky boys not to have missed a few English valves when we started collecting. I bought most from Jim Fish at National fair when it was at NEC. I think I payed £60 each for about 5 and two 4212’s for £200 a piece.

Go find them now? People didn’t know the worth at the time. I don’t know that I’ll ever build another 212 amp, I prefer the 833 in a not subtle way.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
Cressy Snr
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#10 Re: 45 SE

Post by Cressy Snr »

After a marathon 9 hour session, rebuilding everything except the input/driver stage, we have music.

A763D928-4964-46AB-B0E0-16A2D13D7350.jpeg
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Mains toroid has been moved inside the chassis. Which has meant a complete rearrangement and a total rebuild of the power supply.
The filament transformer is underneath the black cover on top of the chassis and is a Hammond 266M5, with the 2.5V 3A windings feeding a 45 each. The other 266M5 next to the blue can cap, provides the rectifier with 5V.
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Cressy Snr
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#11 Re: 45 SE

Post by Cressy Snr »

In terms of the quality of the sound, it’s big tone all the way. Frankly, it’s beautiful 😻
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#12 Re: 45 SE

Post by simon »

Impressive stuff Steve!
Makes me want to dig my 45s out again.
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Nick
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#13 Re: 45 SE

Post by Nick »

Want a long term loan of a Black Gate WKZ to go with it? I think I have a dual 350v one on the shelf.
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Cressy Snr
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#14 Re: 45 SE

Post by Cressy Snr »

simon wrote: Sat May 01, 2021 10:35 pm Impressive stuff Steve!
Makes me want to dig my 45s out again.
Cheers Simon :)
I’ve had to use humdinger pots in the end because I had no suitable matching resistors in my stash.
Nick wrote: Sat May 01, 2021 10:40 pm Want a long term loan of a Black Gate WKZ to go with it? I think I have a dual 350v one on the shelf.
Yes indeedy. :bounce:

Thanks Nick. :D

The whole thing has made me decide definitely to do a recreation/update of my long gone 6B4G amp, but using 45s.
The amplifier as it is now, works really well with the Fane speakers. I’d no idea the speakers were that good.
And I’ve found an amp worthy of my fat-bottle GZ37.
Last edited by Cressy Snr on Sun May 02, 2021 7:35 am, edited 1 time in total.
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Paul Barker
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#15 Re: 45 SE

Post by Paul Barker »

That was quick
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