45 SE

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steve s
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#91 Re: 45 SE

Post by steve s »

11th June.. OK with me any one else ?
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Nick
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#92 Re: 45 SE

Post by Nick »

Might be an excuse for a day out. If there is a space left put my name down.
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steve s
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#93 Re: 45 SE

Post by steve s »

Good stuff..
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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Thermionic Idler
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#94 Re: 45 SE

Post by Thermionic Idler »

Very nice project Steve, I've only just caught up as we moved house a couple of weeks ago, that was quick! DHT's do things that other valve types just don't. The 45 is a really nice valve, it's one of the most linear types out there. Lynn Olson likes it as a driver for the 300B in his designs because of that linearity. If cost/space had been no object I'd have probably done the same, but implementing the 6V6 driver stage was far easier and cheaper.

Would love to take the day off and join you at that little get-together too but I suspect I'd take the numbers beyond the permitted 6 - plus I've only had one jab so far.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
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Power amps: 300B PP 'Symmetric Reichert'
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Toppsy
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#95 Re: 45 SE

Post by Toppsy »

Thermionic Idler wrote: Sat May 22, 2021 1:20 pm Would love to take the day off and join you at that little get-together too but I suspect I'd take the numbers beyond the permitted 6 - plus I've only had one jab so far.
The latest covid relaxed restrictions state quote Indoors , six people (or two households of any size) can meet, with overnight stays allowed . Nearly got caught out with the two household restriction recently when trying to organise a dinner party at my place. Might be worth waiting until after 21st June when hopefully all restrictions for home gatherings may be lifted?

Edit.
Having thought more about the latest indoor gathering restrictions I may have interpreted the rules wrong and am still confused whether you can invite 5 mates around that live in different households so with yourself that would make up the 6. Or if the indoor gathering is just from 2 households the 6 restriction doesn't apply and you can have as many members of those 2 households at the indoor gathering?
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Nick
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#96 Re: 45 SE

Post by Nick »

Yes, it would seem the only way I can read that rule is that the choices are:

1. 6 people of no defined relationship or origin.
2. Any number of people all from at most two households.
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#97 Re: 45 SE

Post by steve s »

That was my interpretation of the law nick. Its simple enough..
Cheers
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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Ray P
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#98 Re: 45 SE

Post by Ray P »

I would love to join in but its a long old trip to do in a day, which is the most time I could hope for as I have leave booked the week before.
Sorry, I couldn't resist!
Cressy Snr
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#99 Re: 45 SE

Post by Cressy Snr »

OK, so with much cursing (God it was fiddly) I’ve changed out the 6V rectifier heater transformer for a 5V one, and fitted an octal socket in place of one of the Magnovals so that 5V rectifiers can be used. I slotted a 5U4G into place and it sounds great.
Best thing is there is zero hum on startup; no waiting for the IDH damper diodes to start to conduct. The rectifier and the 45s come up in perfect synch.

HT is of course down on what it was, but I’m getting 252V across each 45, at 32mA, for 8.064W plate dissipation, which is fine, and good for long valve life. TBH I can hear why some seasoned fans of the 45, like the 5U4G as their rectifier.
36CB7D77-D990-4C96-B8C4-0B8E14B4FF57.jpeg
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Last edited by Cressy Snr on Sat May 29, 2021 7:56 pm, edited 1 time in total.
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Thermionic Idler
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#100 Re: 45 SE

Post by Thermionic Idler »

That's excellent Steve - there's something that seems right about using DH rectification with DH valves isn't there? It'll be interesting to see whether I get similarly positive results on the 300B's.

I pondered whether to use the 5U4 at least twice - once during the design phase and again when I made that power supply cock-up that fried two GZ34's. I could have just subbed a 5U4 and that would have solved the problem on its own (at least on the output stage). Unfortunately, my obsession with maximising the HT voltage won out in the end - I picked the GZ34 on the basis that it looked like the most efficient option.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
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Nick
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#101 Re: 45 SE

Post by Nick »

the most efficient option
That would be a couple of UF4007's
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#102 Re: 45 SE

Post by Cressy Snr »

Nick wrote: Sat May 29, 2021 4:00 pm
the most efficient option
That would be a couple of UF4007's
Yes but they don't light up, unless you connect them backwards. :)
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#103 Re: 45 SE

Post by Cressy Snr »

After reading the discussion on max first cap values over on the 300B thread, I thought I'd do a small alteration to the power supply for my 45 SE job.
The first cap is now an 8uF/450V black/green, Sprague Atom electrolytic.
The power supply now branches out after the first cap:
45ps.png
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Voltages were slightly down so the diagrams have been altered accordingly. 45s are now dissipating 7.8W, which is fine by me.
45acct.png
45acct.png (56.55 KiB) Viewed 3178 times
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Cressy Snr
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#104 Re: 45 SE

Post by Cressy Snr »

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izzy wizzy
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#105 Re: 45 SE

Post by izzy wizzy »

Did that make any audible difference? I've heard how technically a full wave bridge utilises the transformer better; more efficiently as it's always doing something rather than one half being cutoff each half cycle. Of course changing the transformer and the rectifier config is two things at once but I had to ask.
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