The Newton 300B

What people are working on at the moment
izzy wizzy
Old Hand
Posts: 1218
Joined: Fri Nov 02, 2007 7:02 pm
Location: Folkestone
Contact:

Re: The Newton 300B

Post by izzy wizzy » Wed Jan 06, 2021 9:00 am

Thermionic Idler wrote:
Wed Jan 06, 2021 1:22 am
More listening into the early hours tonight, so I'm going to be like a dead duck in the morning - again. I really need to get this thing back onto a space near the bench with the base off so that I can use it as a visual reference to quickly get the second one finished, but I can't stop listening to it. Maybe mono is where it's at...

One of the things I'm noticing is that you don't have to listen to reference recordings to hear its benefits. Everything sounds right - we had some old Kay Kyser recordings playing earlier - these were either 70's or 80's transfers onto LP which pre-dated all the awful intrusive digital "clean-up" efforts - and they somehow just sounded right. Maybe it was the signal chain consisting entirely of 30's era valves - who knows.

Tomorrow - tomorrow I'll get it back on the bench.
I feel your pain. Good PP amps are rather fine :wink:

User avatar
Thermionic Idler
Old Hand
Posts: 610
Joined: Sun Apr 22, 2012 8:22 pm
Location: Surrey

Re: The Newton 300B

Post by Thermionic Idler » Wed Jan 06, 2021 5:43 pm

Here's a full interior build pic, actually in focus this time. There is one item outstanding and that is to wire in the power relay at top right, so that it can be remotely powered up / down from the preamp.

Image
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Scratch built Transcendent "three quarter" Beast OTL monoblocks
Speakers - FF225WK Metronomes

User avatar
Ray P
Eternally single
Posts: 4425
Joined: Thu Nov 22, 2007 5:18 pm
Location: Somerset

Re: The Newton 300B

Post by Ray P » Wed Jan 06, 2021 6:26 pm

Cracking build Dave

User avatar
Thermionic Idler
Old Hand
Posts: 610
Joined: Sun Apr 22, 2012 8:22 pm
Location: Surrey

Re: The Newton 300B

Post by Thermionic Idler » Wed Jan 06, 2021 7:04 pm

Ray P wrote:
Wed Jan 06, 2021 6:26 pm
Cracking build Dave
Thanks Ray. I think I succeeded more or less in optimising the signal path lengths and layout, being able to plan it all out beforehand in CAD helped, although I did end up making a few tweaks at build time. It helped that Lynn laid out the ground paths in his schematic, and I followed them to the letter as he knows a lot more about good grounding than I do! It paid off, these things are quieter than the Beasts - at least the first one is.

With a heavy heart, it's now back on the bench. I want to document the measured voltages - I do remember all the voltages on the output stage were within a volt or two of the Spice model. On the driver stage, Spice predicted 517V or so HT whereas it was about 504V measured, with values down the chain reflecting the slightly reduced value. The HT was supposed to sit around 500V anyway, so I think that's all good.

So I just need to progress the other one and then we'll see how the stereo performance is. I think these actually could replace the OTL's, Meredith was swooning in front of the Ella Fitzgerald LP I dug out, and I found the sound utterly addictive. One bonus is that re-valving costs are about half that of the OTL's (unless I upgrade the 300B's to Shuguang Treasures or something), and I don't have to rely on one manufacturer - it uses valves that are still being made except for the 12SN7 - and if the world runs out of those all I have to do is tweak the heater wiring a bit to convert it for 6SN7. The other bonus is that the electricity usage, even with the valves deep in class A, is still about half that of the OTL's (I think).
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Scratch built Transcendent "three quarter" Beast OTL monoblocks
Speakers - FF225WK Metronomes

izzy wizzy
Old Hand
Posts: 1218
Joined: Fri Nov 02, 2007 7:02 pm
Location: Folkestone
Contact:

Re: The Newton 300B

Post by izzy wizzy » Wed Jan 06, 2021 8:08 pm

I'm sure Lynn would love to see your build and hear your thoughts on it.

User avatar
Thermionic Idler
Old Hand
Posts: 610
Joined: Sun Apr 22, 2012 8:22 pm
Location: Surrey

Re: The Newton 300B

Post by Thermionic Idler » Wed Jan 06, 2021 11:31 pm

I have posted a reply on the diyaudio thread where he originally shared the Symmetric Reichert circuit, in the hope he may spot it.
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Scratch built Transcendent "three quarter" Beast OTL monoblocks
Speakers - FF225WK Metronomes

User avatar
Dave the bass
Amstrad Tower of Power
Posts: 11548
Joined: Tue May 22, 2007 4:36 pm
Location: NW Kent, Darn Sarf innit.

Re: The Newton 300B

Post by Dave the bass » Thu Jan 07, 2021 9:34 am

Ray P wrote:
Wed Jan 06, 2021 6:26 pm
Cracking build Dave
It might just be a dry joint.
"The fat bourgeois and his doppelganger"

User avatar
Thermionic Idler
Old Hand
Posts: 610
Joined: Sun Apr 22, 2012 8:22 pm
Location: Surrey

Re: The Newton 300B

Post by Thermionic Idler » Sat Jan 09, 2021 3:37 pm

Quickly powered it back up on the bench as I wanted to actually record the voltages and also re-run the scope tests to measure the gain.

Here are the voltages, the first figure is that predicted by Spice and PSUD, the second is the actual:

Output stage B+ 467V / 471V
300B Plate Phase + 460V / 467V
300B Plate Phase - 460V / 467V
300B Cathode (between hum bucker and 500R cathode resistor) 78V / 77V

Input stage B+ 517V / 510V
between CCS and 820R: 293V / 312V +phase / 313V -phase
6V6 plates: 269V / 286V +phase / 289V -phase
6V6 cathose: 17V / 18V

12SN7 plate resistors: 494V / 485V
12SN7 plate + phase: 220V / 212V
12SN7 plate - phase: 220V / 213V
12SN7 cathode: 5V / 5V

Whilst measurements only tell part of the story, here's what a 10kHz square wave looks like, as captured by the Analog Discovery device:

Image
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Scratch built Transcendent "three quarter" Beast OTL monoblocks
Speakers - FF225WK Metronomes

User avatar
Thermionic Idler
Old Hand
Posts: 610
Joined: Sun Apr 22, 2012 8:22 pm
Location: Surrey

Re: The Newton 300B

Post by Thermionic Idler » Mon Jan 11, 2021 7:22 pm

Some more pics of Channel A final build after setting up on a shelf behind my desk / bench under some strip lights, to refer to when building the second. The signal section:

Image

and the power supply section:

Image

Here's where I'm at on Channel B, transformers all fitted, and this time around I'm going to tie off (insulate and secure) the unused wires BEFORE installing anything else - one of the most awkward final jobs on Channel A was trying to do that after the PTFE boards and filament transformers were mounted in place. There are a lot of unused wires (the 6.3V secondary, the 5V centre tap, plus several primary taps to allow a whole range of input voltages to be set). The build of Channel B will still go left to right, so with the mirror imaging this means the power supply gets done before the signal section.

Image
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Scratch built Transcendent "three quarter" Beast OTL monoblocks
Speakers - FF225WK Metronomes

User avatar
Thermionic Idler
Old Hand
Posts: 610
Joined: Sun Apr 22, 2012 8:22 pm
Location: Surrey

Re: The Newton 300B

Post by Thermionic Idler » Tue Jan 12, 2021 11:34 am

Also, if anyone is having issues viewing the images can you please PM me, as it seems some configurations might be blocking them. Ta!
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Scratch built Transcendent "three quarter" Beast OTL monoblocks
Speakers - FF225WK Metronomes

User avatar
Ray P
Eternally single
Posts: 4425
Joined: Thu Nov 22, 2007 5:18 pm
Location: Somerset

Re: The Newton 300B

Post by Ray P » Tue Jan 12, 2021 7:27 pm

Your images work fine for me Dave.

User avatar
pre65
Amstrad Tower of Power
Posts: 19085
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex

Re: The Newton 300B

Post by pre65 » Tue Jan 12, 2021 7:35 pm

Ray P wrote:
Tue Jan 12, 2021 7:27 pm
Your images work fine for me Dave.
And me. :)
Life is what happens to you while you're busy making other plans. John Lennon

G-Popz THE easy listening connoisseur. (Philip)

Cressy Snr
Loony Bin!
Posts: 9130
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: The Newton 300B

Post by Cressy Snr » Tue Jan 12, 2021 8:03 pm

And me
Who IS The Phantom Flan Flinger?

User avatar
Thermionic Idler
Old Hand
Posts: 610
Joined: Sun Apr 22, 2012 8:22 pm
Location: Surrey

Re: The Newton 300B

Post by Thermionic Idler » Thu Jan 14, 2021 5:43 pm

Heater wiring - probably my least favourite part of any build, now done. Also the transformers are all connected up except for the HT secondaries (red and red/yellow wiring). The unconnected black wires are from the two chokes.

Image
Deck: Garrard 301
Audio Origami PU7
Van Den Hul Black Beauty
Phono: Whest PS30RDT
Pre-amp - Scratch built AMB α24/LCDuino
Amp - Scratch built Transcendent "three quarter" Beast OTL monoblocks
Speakers - FF225WK Metronomes

Post Reply