Symmetric Reichert 300B push-pull

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IslandPink
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#31 Re: Symmetric Reichert 300B push-pull

Post by IslandPink »

I think most of those 530v caps can safely be replaced with 500 or 600, apart from the main PS cap, but there, 600V should be OK.
One thing I don't like about the values here, is why have 2x coupling with 0.1u/100k ? You've immediately got 2-off 16Hz roll-offs there, that's 2dB down at 32Hz, so you've got phase rotations coming in from 50Hz downwards. Seems a shame to spoil the bass advantages of a PP output transformer by cutting off the bass high, with coupling caps. Maybe it was something to do with replicating the Flesh and Blood, but that's a SE amp, shouldn't have to read across to a PP amp. So, if you want to build it as-is, keep some other values in hand for when you've tested it. First place to start would be to raise the grid-leaks on the first stage from 100k to 220k or more.
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#32 Re: Symmetric Reichert 300B push-pull

Post by Nick »

I would look for motor run for the frrst caps in the power supply, and I would stick with the voltage rating of those parts. Also, I would not use 10uf for 5uf, will increase the stress on the rectifiers and maybe increase the output voltage. I would also try simulating the supplies and check what the off load voltage is and spec the caps wit that in mind.
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#33 Re: Symmetric Reichert 300B push-pull

Post by Thermionic Idler »

Thanks - I think I need to dust off Spice and model this thing (last used it in 2015). I thought those coupling cap values looked a little on the low side, and I'm not sure anyone's actually built it - looking through the DIYaudio thread now.
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#34 Re: Symmetric Reichert 300B push-pull

Post by izzy wizzy »

Thermionic Idler wrote: Sat Jul 25, 2020 3:55 pm Thanks - I think I need to dust off Spice and model this thing (last used it in 2015). I thought those coupling cap values looked a little on the low side, and I'm not sure anyone's actually built it - looking through the DIYaudio thread now.
Lynn has posted a number of variations to his Karna amplifier and ideas coming from it; this one on this thread, Karna Kay and 3 variations to Karna. I've never seen a build of one and I'm pretty sure he hasn't built any of them. If he has, I haven't seen the results. His amp theory is the basis of mine so I'm always super keen to see any further thoughts/thinking he comes up with.

There is a SN7 46 300B amp that is interesting https://www.diyaudio.com/forums/tubes-v ... build.html but 46s are virtually unobtanium.
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#35 Re: Symmetric Reichert 300B push-pull

Post by Paul Barker »

1/ 50 uF 10hz 100 uF 5hz
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#36 Re: Symmetric Reichert 300B push-pull

Post by Thermionic Idler »

Nick wrote: Sat Jul 25, 2020 3:24 pm I would look for motor run for the frrst caps in the power supply, and I would stick with the voltage rating of those parts. Also, I would not use 10uf for 5uf, will increase the stress on the rectifiers and maybe increase the output voltage. I would also try simulating the supplies and check what the off load voltage is and spec the caps wit that in mind.
Thanks Nick, I'll follow that advice. Sanity check: most of the data sheets for these motor run caps have the rating in VAC, and the most common value seems to be 440 VAC. Multiplying this out by 1.44 for RMS gives 633.6, so by my reckoning these are the ones to get - have I got that right?
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#37 Re: Symmetric Reichert 300B push-pull

Post by steve s »

That's what I nearly always use( motor run), I double up with with an electrolitic if I want higher values.
440 ac 630 dc, .. funny that dc voltage seems a standard rating for many makes of film caps
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#38 Re: Symmetric Reichert 300B push-pull

Post by Nick »

funny that dc voltage seems a standard rating for many makes of film caps
It depends on the expected use.
Multiplying this out by 1.44 for RMS gives 633.6, so by my reckoning these are the ones to get - have I got that right?
Yes, though many will give a DC and AC rating.
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#39 Re: Symmetric Reichert 300B push-pull

Post by Paul Barker »

Phil posted a link to good value 50uF 1k5 dcv polypropylene
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#40 Re: Symmetric Reichert 300B push-pull

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Height of a baked bean tin smaller diameter.
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#41 Re: Symmetric Reichert 300B push-pull

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Paul Barker wrote: Mon Jul 27, 2020 3:19 pm Height of a baked bean tin smaller diameter approximately 5cn
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#42 Re: Symmetric Reichert 300B push-pull

Post by pre65 »

Paul Barker wrote: Mon Jul 27, 2020 3:18 pm Phil posted a link to good value 50uF 1k5 dcv polypropylene
He's got some 80uf 1.5Kv MKP on offer at the moment. Check his other items for sale.

https://www.ebay.co.uk/itm/2-x-Digitex- ... Sw10FeNyB0

Or these, from a different vendor.

https://www.ebay.co.uk/itm/LOT-OF-3pcs- ... SwFwNeNCMB
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Thermionic Idler
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#43 Re: Symmetric Reichert 300B push-pull

Post by Thermionic Idler »

Thanks everyone. Much food for thought.

Sit rep, just getting my Spice environment up and running (I've switched over to the Windows version as I now have a Windows virtual machine on the Mac). Also, I think I"m going to use 6AH4 for the driver valves, as they are more in keeping with the dissipation requirements. Two per chassis means I can connect the 6V heaters in series for the 12V heater supply.
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#44 Re: Symmetric Reichert 300B push-pull

Post by Paul Barker »

pre65 wrote: Mon Jul 27, 2020 3:28 pm
Paul Barker wrote: Mon Jul 27, 2020 3:18 pm Phil posted a link to good value 50uF 1k5 dcv polypropylene
He's got some 80uf 1.5Kv MKP on offer at the moment. Check his other items for sale.

https://www.ebay.co.uk/itm/2-x-Digitex- ... Sw10FeNyB0

Or these, from a different vendor.

https://www.ebay.co.uk/itm/LOT-OF-3pcs- ... SwFwNeNCMB
I’m confused by the data of the 80 uF. What does the term KVAR mean? “Max 415v AC” on another line. That voltage would demonstrate purposes for phase balancing 3 phases in engineering with a lot of three phase motors which unbalance the demand from grid as a powerful motor starts up. This phase alignment is monitored and caps are used to correct any imbalance in the 3 phases. This is a duty, but there is financial remuneration from the supplier for keeping the demand even to what extent possible. No single caps but banks of these caps switched in or out as required.

But where do you see 1k5 DC?
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#45 Re: Symmetric Reichert 300B push-pull

Post by Nick »

But where do you see 1k5 DC
Its on the sticker on the cap in the picture.
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