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Old 13th January 2019, 07:51 PM   #8691
MagicBus is offline MagicBus  Greece
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That's good news! Not that I want more power but it makes me feel relaxed.
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Old 15th January 2019, 10:20 PM   #8692
PampaAudio is offline PampaAudio  Argentina
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Just finished my latest project. A 45 single ended amp with 2 24A triode strapped tubes in the preamp.

All cloth wire and cable laced point to point wiring.
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Old 16th January 2019, 12:09 PM   #8693
gideon1990 is offline gideon1990  Netherlands
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what a beauty! love that nice wiring loom and I didn't know they made those Russian caps in such a pretty colour Do you happen to have more pictures
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Old 16th January 2019, 12:20 PM   #8694
bonzo15011978 is offline bonzo15011978  Italy
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Quote:
Originally Posted by PampaAudio View Post
Just finished my latest project. A 45 single ended amp with 2 24A triode strapped tubes in the preamp.

All cloth wire and cable laced point to point wiring.
Very, very interesting!
Would you mind share the scheme and your sound impressions?
I'd like to build one too, and maybe with an option to use 46 tubes as well (like the old "Ragtop" amp).
Thank you in advance!
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Old 16th January 2019, 01:55 PM   #8695
PampaAudio is offline PampaAudio  Argentina
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Quote:
Originally Posted by gideon1990 View Post
what a beauty! love that nice wiring loom and I didn't know they made those Russian caps in such a pretty colour Do you happen to have more pictures
Thank you! Of course there are more pictures

As far as I know the only russan PIO caps that come in that nice blue colour are the 250nF 630V ones.

Quote:
Originally Posted by bonzo15011978 View Post
Very, very interesting!
Would you mind share the scheme and your sound impressions?
I'd like to build one too, and maybe with an option to use 46 tubes as well (like the old "Ragtop" amp).
Thank you in advance!
The circuit is really very simple. The 24A screen grids are connected to the anode with 100 ohm resistors and biased at 2.5mA and 100V, I have attached the tube curves below so you can see. The 45s are biased at 33mA and 250V with a 6K load giving about 1.3Watts.

The preamp tubes are really nice but nobody ever uses them. They are very linear as you can see in the curves, and plentiful and cheap. The biggest downside is the high heater current.
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File Type: jpg luces_90.JPG (118.5 KB, 187 views)
File Type: png 24A triode curves.png (72.4 KB, 173 views)
File Type: jpg natural_90.JPG (145.1 KB, 199 views)
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Old 16th January 2019, 05:25 PM   #8696
mondogenerator is offline mondogenerator  England
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Default First ever tube circuit!

So I became interested in Valves/Tubes a long time ago, but never got much further than drawing a load line.

I finished a first ever tube circuit this week. A very simple textbook cathode biased voltage amplifier stage.

Using a load line I get fairly close to reality, biasing voltage isn't quite right, and the cathode bypassing capacitor isn't large enough, but it functions fairly well.

Near to centre bias I get a voltage gain of around 41 times, which isn't too far shy of the 2/3rds Mu (mu is 70).

A great little circuit built in 15mins! I'm hooked!
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I must be a child of good times... the scariest thing I've seen done thus far, has been connecting a cathode bypass capacitor reverse polarity...Then rushing to cut the HT!
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Old 17th January 2019, 02:22 PM   #8697
gideon1990 is offline gideon1990  Netherlands
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Quote:
Originally Posted by mondogenerator View Post
So I became interested in Valves/Tubes a long time ago, but never got much further than drawing a load line.

I finished a first ever tube circuit this week. A very simple textbook cathode biased voltage amplifier stage.

Using a load line I get fairly close to reality, biasing voltage isn't quite right, and the cathode bypassing capacitor isn't large enough, but it functions fairly well.

Near to centre bias I get a voltage gain of around 41 times, which isn't too far shy of the 2/3rds Mu (mu is 70).

A great little circuit built in 15mins! I'm hooked!
I have the same powersupply laying around, I believe you can even modify it to give you a negative voltage by just adding a diode and a capacitor
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Old 18th January 2019, 10:20 AM   #8698
mondogenerator is offline mondogenerator  England
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Quote:
Originally Posted by gideon1990 View Post
I have the same powersupply laying around, I believe you can even modify it to give you a negative voltage by just adding a diode and a capacitor
I have a couple, and I believe you are correct, just the fly back diode, output capacitor and a couple of and resistors need soldering.

(However, I blew the diode quite quickly and required a replacement)
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I must be a child of good times... the scariest thing I've seen done thus far, has been connecting a cathode bypass capacitor reverse polarity...Then rushing to cut the HT!
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Old 18th January 2019, 09:44 PM   #8699
kodabmx is offline kodabmx  Canada
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Finished my monoblocs...
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Old 19th January 2019, 08:46 AM   #8700
thuanth43 is offline thuanth43  Viet Nam
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My 845 amp for electrostatic headphones. Double C-Core amorphous output transformers and C-Core power transformer.
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