The Newton 300B

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Ant
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#76 Re: The Newton 300B

Post by Ant »

What odds are you giving? :mrgreen:
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Thermionic Idler
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#77 Re: The Newton 300B

Post by Thermionic Idler »

Heh, right now I reckon there's a 60% chance of it lasting, 40% that I have to break into the new reel.

Quite relieved that I was still able to get hold of it as it's not 'green'. I settled on it years ago as it gave consistently better joints over everything else I'd tried (including the Cardas solder), by some way. Being eutectic makes it pretty much idiot-proof.
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'
Speakers: FF225WK Big Mets
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IslandPink
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#78 Re: The Newton 300B

Post by IslandPink »

Hey ... maybe that's what eutectic means !
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Thermionic Idler
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#79 Re: The Newton 300B

Post by Thermionic Idler »

Amplifier B is now complete! At 17:35 today, appropriately whilst David Bowie's "Sound and Vision" was playing, I made the final solder joint connecting the second 22k plate resistor to 12SN7 pin 5 and coupling cap.

I've been working solidly on this pretty much all day to get it done, so I'm going to leave the power-up testing until tomorrow morning as I'm a bit burned out now. Best not to muck about with 500V of B+ when feeling bleary. I also want to have one more look over the circuit when I'm fresh, to make sure nothing's been missed.

So, coming up:

1) Heater test only (all B+ fuses removed)
2) Input stage voltage test
3) Output stage voltage test
4) Signal tests with Analog Discovery - frequency response, square wave and gain test etc.

With regard to whether the solder lasted - yes, it did. Just...

Image

And herewith the obligatory interior shot. The wiring is always neater on the second one...

Image
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'
Speakers: FF225WK Big Mets
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Nick
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#80 Re: The Newton 300B

Post by Nick »

The wiring is always neater on the second one
Make three next time and throw the first away :-)
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IslandPink
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#81 Re: The Newton 300B

Post by IslandPink »

Thermionic Idler wrote: Fri Jan 29, 2021 6:10 pm With regard to whether the solder lasted - yes, it did. Just...
That was a damned close-run thing !
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#82 Re: The Newton 300B

Post by Thermionic Idler »

Nick wrote: Fri Jan 29, 2021 6:36 pm
The wiring is always neater on the second one
Make three next time and throw the first away :-)
:lol:
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'
Speakers: FF225WK Big Mets
Ant
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#83 Re: The Newton 300B

Post by Ant »

Those werent bad odds then!
Shouldve put a tenner down
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Thermionic Idler
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#84 Re: The Newton 300B

Post by Thermionic Idler »

All tests on channel B completed perfectly. We now have stereo, although it seems I do have a dodgy 12SN7 and 6V6. Despite that, it's sublime. I'll write up more later when it's not twenty past one in the morning.
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'
Speakers: FF225WK Big Mets
RhythMick
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#85 Re: The Newton 300B

Post by RhythMick »

Well done that man
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#86 Re: The Newton 300B

Post by Cressy Snr »

:sunny: :thumbright: :salute:
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Irene Idler
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#87 Re: The Newton 300B

Post by Irene Idler »

I must second it: these amps are sublime. They're not quite as good all-rounders as the Beasts, but the clarity and tone are amazing and there's a transparency that's not quite there with the others. As they continue to bed in we'll see whether their reproduction of the trickier recordings improves. To some extent I think it's probably sheer wattage; the Beasts have extra oomph, especially in the low range, so you can get some really satisfying thuds. (But occasionally a little too much thud for our space -- it sometimes echoes off the back wall.)

That said, the bass in the Newtons isn't in any way disappointing -- we can feel it through the floor and the furniture thanks to the bottom-ported Mets. Ironically, I'm always aware of that sort of thing because of a Deaf friend who enjoys music with a good beat that she can feel through her feet! And some of the faster-paced stuff we played last night seemed to get the kitten all amped up. Since she's not a musical cat like Leadbelly was, I think it must have been the vibrations that set her off.

If we had the space, I'd propose we build shelves and create a Wall o' Monoblocks with a patch bay so we could swap between amps based on what we're playing, but I suppose the electric bill might get a bit steep.
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Thermionic Idler
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#88 Re: The Newton 300B

Post by Thermionic Idler »

Been a bit tardy writing up my own post as I've been too busy listening to music! :D

So yesterday afternoon I completed all the measurements and checking. All the voltages checked out more or less identically to the first one, which was a good sign, and the gain and 10kHz square wave checked out the same as well. That said, the heater voltages seemed to measure a little high - 5.49V on the 300Bs, similar on the GZ34s and 14.06V across the 12SN7. I didn't measure them on Channel A but would guess they are similar. It doesn't seem to be adversely affecting the sound (see below) but I have seen discussion that suggests it can make a difference, so I may need to look at putting some in-line resistors in the heater runs to drop the voltages a bit on the signal valves at least.

I also ran a frequency response and phase shift analysis from 10Hz to 100kHz. I haven't checked it out against the Spice prediction yet but the results are below, these things are pretty wide bandwidth:

Image

I then got Channel B up and running in the living room, playing music to run it in whilst I checked the current source settings and activated the relay remote start on the first amp, which required moving a wire from one terminal to another and soldering in a couple of links from the XLR4 socket. There was a scary moment when I walked back into the living room and - no sound! To cut a long story short, I'd shifted the position of the co-ax SPDIF cable that runs into the DAC from the server via a USB-to-SPDIF converter that allows me to play 96kHz files (the DACMagic only goes up to 48kHz via USB). This cable seems to be a bit of a diva, moving things around sometimes causes the DAC to lose sync. This issue will go away once I make up that DAC from the stuff Ray just sold me.

Channel A was then hauled into the living room, populated with valves, and powered up. Slowly, glorious stereo faded into view, along with some not-so-glorious crackling and popping. This turned out to be the 12SN7, one of the two I'd bought, and of course I didn't have any spares. Moving the valve bulb a little does stop it for a bit, it seems like a dicey connection in the base. One of the 6V6's also seems to have the same problem and is also microphonic, although the crackling is somewhat quieter because it's further down the gain chain. This morning I ordered some spares, so hopefully this issue will go away soon too.

So, on to how they sound when the valves aren't playing up. The Beasts do project a wider soundstage - real widescreen, however to my ears the Newtons compensate for that with more depth. The other element the Newtons give way to the Beasts on is in the bass - the Beasts have tremendously tight, well controlled bass that reaches really deep. I get the sense that the bass from the Newtons is just that little bit looser and not as well controlled. However, in the upper registers, the level of detail retrieval and transparancy is leagues better. I believe audiophiles use the term 'air' around the musicians. Another interesting side-effect is that surface noise from LPs seems less intrusive.

But... but...

All of this would mean nothing if these amps just reproduced audio instead of playing music. Not true with these, they slam the meaning of what you're listening to straight to your cerebral cortex in a manner that takes your breath away. The fact it's taken me until today to post about them speaks volumes about how addictive they are. We were listening to records into the early hours and I was up early this morning as well checking out the Wagner whilst Meredith was still asleep.

Might they not be as good all-rounders as the Beasts? Depends, my take is that the slightly looser bass may not do film soundtracks and some rock any favours, but my priority is on how well they play the music we mostly listen to. So far, I absolutely love listening to these amps, they put a big smile on your face and send shivers down the spine, which pretty much nails it for me. It should be noted that there is some further bedding in to do, and we also need to take into account the fact that a couple of the valves are a bit sick.

Herewith the obligatory picture, last night's setup:

Image
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'
Speakers: FF225WK Big Mets
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Greg
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#89 Re: The Newton 300B

Post by Greg »

Nice write up and photo. Great news that you are really happy with them.

Ah, the open hearth fire on the TV screen. I’ve got that, complete with authentic crackle in my car :lol:
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pre65
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#90 Re: The Newton 300B

Post by pre65 »

Well done. :)

I like the fire. :lol:
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