The Latest Push-Pull Build
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#886 Re: The Latest Push-Pull Build
Bought half a dozen of these cute little Brimar top-cap grid pentodes.
These are cheap and plentiful and are the grid top-cap version of the Brimar 6BR7
which was the equivalent of the Mullard/Phillips EF86.
I'll be replacing the 12SJ7s with these, when I rebuild the audio cct sometime this week.
There will be four on the Barbarik front end and the other two will be the front end of the mono amp
to be housed in the radiogram chassis.
These are cheap and plentiful and are the grid top-cap version of the Brimar 6BR7
which was the equivalent of the Mullard/Phillips EF86.
I'll be replacing the 12SJ7s with these, when I rebuild the audio cct sometime this week.
There will be four on the Barbarik front end and the other two will be the front end of the mono amp
to be housed in the radiogram chassis.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- IslandPink
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#887 Re: The Latest Push-Pull Build
Cool !
"Once you find out ... the Circumstances ; then you can go out"
- Thermionic Idler
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#888 Re: The Latest Push-Pull Build
Good lord I didn't know Noval base valves with top caps even existed.
How did you achieve this with the existing transformer - did you use the 75V secondary to make 525VAC into the bridge rectifier?HT to the output stage has also been increased to 475V
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
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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#889 Re: The Latest Push-Pull Build
I cheated with a small 3.3uF cap off the 450V winding, before the choke, so I suppose the HT supply is now, strictly speaking, cap input.
The 6BS7 is an unusual little valve isn't it.
There are plenty about. It wasn't a great success as an audio valve, though that was its original purpose (it was directly up against the EF86) but it eventually found a niche as an industrial valve in electrometer applications, such as pH meters and valve voltmeters.
More info: http://www.r-type.org/exhib/aab0164.htm
The 6BS7 is an unusual little valve isn't it.
There are plenty about. It wasn't a great success as an audio valve, though that was its original purpose (it was directly up against the EF86) but it eventually found a niche as an industrial valve in electrometer applications, such as pH meters and valve voltmeters.
More info: http://www.r-type.org/exhib/aab0164.htm
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- Mike H
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#890 Re: The Latest Push-Pull Build
http://www.r-type.org/exhib/aab0164.htmThermionic Idler wrote:Good lord I didn't know Noval base valves with top caps even existed.
Interesting blurb about the reason for the top cap!
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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#891 Re: The Latest Push-Pull Build
Indeed; it was designed for incompetent DIY'ers.Mike H wrote:http://www.r-type.org/exhib/aab0164.htmThermionic Idler wrote:Good lord I didn't know Noval base valves with top caps even existed.
Interesting blurb about the reason for the top cap!
That's why I decided to use it. Right up my street!
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- Paul Barker
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#892 Re: The Latest Push-Pull Build
Well spotted as a valve find Steve. HAve you got it playing? IS it a good sound?
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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#893 Re: The Latest Push-Pull Build
Have not got it playing yet Paul. That'll be a job for Fri, Sat and Sun.
I'll have to make some adaptor plates out of perforated steel to take the noval sockets, as the holes at the front of the chassis are octal sized and therefore too big. After that the adaptor plates and sockets can be fitted and the font end reconstructed.
The valves themselves look to be of extremely high quality. The anodes are bright nickel and the insides are built like the proverbial brick outhouse. I'm quietly confident.
I'll have to make some adaptor plates out of perforated steel to take the noval sockets, as the holes at the front of the chassis are octal sized and therefore too big. After that the adaptor plates and sockets can be fitted and the font end reconstructed.
The valves themselves look to be of extremely high quality. The anodes are bright nickel and the insides are built like the proverbial brick outhouse. I'm quietly confident.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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#894 Re: The Latest Push-Pull Build
Had a bit of a job on with the adapter plates for converting octal holes to take Noval sockets. It certainly took some thinking about as I do not want to ruin the looks of the chassis.
After much head-scratching and rejecting about half a dozen less than satisfactory solutions. I found four grotty old octal sockets that had seen better days and carefully hacksawed out the middles, freeing up their fixing flanges. The result is below:
A satisfactory solution I think. Omce I get inside the amplifier, it is simply out with the old sockets and in with the new, using the same fixing holes. Nice little gap around the circumferences for airflow too.
After much head-scratching and rejecting about half a dozen less than satisfactory solutions. I found four grotty old octal sockets that had seen better days and carefully hacksawed out the middles, freeing up their fixing flanges. The result is below:
A satisfactory solution I think. Omce I get inside the amplifier, it is simply out with the old sockets and in with the new, using the same fixing holes. Nice little gap around the circumferences for airflow too.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- Mike H
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#895 Re: The Latest Push-Pull Build
That is bluddy brilliant.
Me likes.
Me likes.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- IslandPink
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#896 Re: The Latest Push-Pull Build
Top notch !
"Once you find out ... the Circumstances ; then you can go out"
- Dave the bass
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#898 Re: The Latest Push-Pull Build
Impressive as ever Steve.
#899 Re: The Latest Push-Pull Build
+1! Very impressived!Mike H wrote:That is bluddy brilliant.
Me likes.
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#900 Re: The Latest Push-Pull Build
Aye....It was one of those light bulb moments.
At the moment I'm on with rebuilding the front-end. I'll try to report on the results this evening, unless I fook something up.
At the moment I'm on with rebuilding the front-end. I'll try to report on the results this evening, unless I fook something up.
Sgt. Baker started talkin’ with a Bullhorn in his hand.