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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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5th Oct 2022, 6:09 pm | #21 | |
Heptode
Join Date: Dec 2020
Location: Swaffham, Norfolk, UK.
Posts: 582
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Re: GZ37 rectifier and the Wadar amp
Quote:
As for the capacitors around the S/S diodes, I'd still prefer to put a fast rectifier in there rather than the 1N400* series. Greg. |
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5th Oct 2022, 8:59 pm | #22 |
Octode
Join Date: Jun 2004
Location: Reading/Fakenham, UK.
Posts: 1,320
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Re: GZ37 rectifier and the Wadar amp
Thanks G. Castle. There's some interesting info in that thread that I missed.
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6th Oct 2022, 2:47 pm | #23 | |
Heptode
Join Date: Oct 2009
Location: Melbourne Australia
Posts: 898
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Re: GZ37 rectifier and the Wadar amp
Quote:
Power supplies for low voltage high current ss amplifiers cause a much more onerous turn-off transition with the rectifier diodes, making the ss diode reverse recovery characteristic become noticeable. |
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6th Oct 2022, 5:02 pm | #24 | |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
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Re: GZ37 rectifier and the Wadar amp
Quote:
Agree about leakage current - the dopants which give fast recovery, work by creating recombination centres to neutralise stored charge. And unfortunately they also act to give more leakage current. |
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7th Oct 2022, 12:00 am | #25 |
Heptode
Join Date: Oct 2009
Location: Melbourne Australia
Posts: 898
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Re: GZ37 rectifier and the Wadar amp
There are many who have measured the actual PIV of their 1N4007, and even 1N4004 have been measured as the same. The topic of modern day manufacture was one reason for peoples interest, as it made no commercial sense to batch manufacture specifically for the 1N400x variants, especially from 1N4004 upwards.
My batch of 1N4004 achieve better than circa 1.4kV. Sure, not all manufacturers are the same given the generic part, but if you have a batch from a reputed manufacturer and can do a quick test (as a few have done), then for 'back-up' applications like using them in series with a valve diode it can be a benefit, with the caveat that if the valve is operating in an application needed a PIV above 1kV (eg. above circa 300-0-300V secondary given tolerances) then at least 2x 1N4007 in series are preferred. |
7th Oct 2022, 9:06 am | #26 |
Octode
Join Date: Aug 2008
Location: Rayleigh near Southend-On-Sea, Essex, UK.
Posts: 1,852
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Re: GZ37 rectifier and the Wadar amp
Hello Ian,
Am I right in assuming you wrote ‘At Last I built a Wadar amplifier’ in the Autumn 2019 edition of the BVWS Bulletin? If so, it was a nice article and I made reference to that article in my Article on the Haverson amplifier in the Spring 2022 Bulletin. Gerrys amplifier is not dissimilar to the basic design used in the Rogers Cadet and the GEC 9-10 making as near a hi-fi amplifier as Gerry would have been comfortable with. Anyway, a bit of tangential rambling… A good while back I briefly experimented with putting BY133 in series with PY33 to ‘make’ a high voltage hybrid silicon/valve rectifier with a mains transformer secondary voltage of 350-0-350V using a cheaper valve rectifier. I abandoned this quite quickly as I felt it generated too many problems for my own liking especially with PY33 heater voltage. I was concerned about the balance of the voltage across the valve and diode seeing the PY33 has a Va (RMS) max voltage of 250V and the transformer voltage and because of this I considered the two balancing resistors. Pic attached. Regards Terry Last edited by Valvepower; 7th Oct 2022 at 9:18 am. |
7th Oct 2022, 9:25 am | #27 | |
Octode
Join Date: Jun 2004
Location: Reading/Fakenham, UK.
Posts: 1,320
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Re: GZ37 rectifier and the Wadar amp
Quote:
Unfortunately I did make an error on the circuit. I labelled V1 6J7 when is should have been labelled 6SJ7! Regards, Ian |
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7th Oct 2022, 9:31 am | #28 |
Hexode
Join Date: Jul 2009
Location: Wokingham, Berkshire, UK.
Posts: 437
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Re: GZ37 rectifier and the Wadar amp
If there is space on the chassis and you are up to a bit of modification, you could always use a pair of 6D22s colour tv boost diodes - cheap, bomb proof and the 6.3V heaters will run off of the 5V supply very well as their heater current consumption for 2 is less that one GZ37, See Eric Barbour's comments.
I use them in my GEC 88/50 amp as I am not, and never have been, a lover of direct heated rectifiers ie 5U4 types and the GZ32-37 valve range are suffering from "audiophoolery" You will of course need to be careful as 6D22's have a top cap anode so will require suitable protection unless you don't have nosy children. John |
7th Oct 2022, 9:32 am | #29 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
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Re: GZ37 rectifier and the Wadar amp
Gerry employed any rectifiers he had to hand providing they supplied enough current for the amps demand. I am not a great enthusiast for directly heated rectifiers but as I mentioned earlier I have a U52/5U4G in mine with absolutely no problems. On switch on they are subject to a great strain that can be seen when looking downwards through the anodes when a very short duration blue glow can be seen as the reservoir cap charges. Elderly examples usually fail on switch rather than fade away due to lack of emission.
These amps do sound really nice on record reproduction and CDs. John. Last edited by Heatercathodeshort; 7th Oct 2022 at 9:43 am. |
7th Oct 2022, 9:46 am | #30 | ||
Octode
Join Date: Aug 2008
Location: Rayleigh near Southend-On-Sea, Essex, UK.
Posts: 1,852
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Re: GZ37 rectifier and the Wadar amp
Hello Ian,
Thought it was yourself. As regards the error we all do it – its easily done… You can proofread until the cows come home, but there will be that blooper which will wriggle through the net. I made the mistake of mixing up the 6J5 triode and 6J7 pentode in the Sterns 8-10 article. Regards Terry. Quote:
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7th Oct 2022, 10:23 am | #31 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
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Re: GZ37 rectifier and the Wadar amp
Why not make a full-wave rectifier in silicon, then you can have a generous reservoir capacitor, then use a thermionic rectifier (maybe a full wave one with anodes strapped) as a slow-start device and also a source of droop to warm the cockles of a guitarist's heart?
You no longer have the anode-to-anode pyrotechnics risk from dubiously manufactured valves Rate the reservoir for off-load HT with the silicon rectifier. Use fast rectifiers for low noise, and have no worries about leakage. David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
7th Oct 2022, 1:40 pm | #32 |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
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Re: GZ37 rectifier and the Wadar amp
You'll certainly have to be careful, stand back as the HT electrolytics go pop! The top cap is the CATHODE, as it's the electrode which swings around by a couple of kV in the conventional LOP stage!
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7th Oct 2022, 2:14 pm | #33 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: GZ37 rectifier and the Wadar amp
The U54 is given as an equivalent to the GZ37 in Babani's book, it's max. Ia(peak) rating is much higher than normal, it being 1.5 Amps which is 12 x max. diode current:
https://frank.pocnet.net/sheets/126/u/U54.pdf Lawrence. |
7th Oct 2022, 4:50 pm | #34 |
Hexode
Join Date: Jul 2009
Location: Wokingham, Berkshire, UK.
Posts: 437
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Re: GZ37 rectifier and the Wadar amp
kalee wrote
"The top cap is the CATHODE, as it's the electrode which swings around by a couple of kV in the conventional LOP stage!" Oops sorry! put it down to senile decay and the like, sticks head in sand! John |
7th Oct 2022, 9:58 pm | #35 |
Octode
Join Date: Jul 2009
Location: Carmel, Llannerchymedd, Anglesey, UK.
Posts: 1,498
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Re: GZ37 rectifier and the Wadar amp
I read with some interest the points made here & elsewhere regarding silicon diodes being responsible for generating noise - I am not at all decrying the statements made, but I find it odd that I have built very many PSU's for various applications over the years including use of the 1N400x series and have never detected a shred of noise...
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