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Pictures of your Tube Amplifiers


henry4841

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  • 4 weeks later...

Here is the schematic. No secrets, just a text book design. Although, the 2A3 filaments are using AC, I can barely hear a trace of hum through my LaScala's. I have to stick my head into the horn mouth to hear the faintest sound of hum.

 

True, the 60Hz hum will modulate your music signal, but I can't hear it and I have a pretty good set of ears (i think). I have amps with both AC & DC filaments, but love them all. 

 

Attached are some measurements as well. 

DIY 2A3 Stereo Schematic_v2.1.0_6SL7GT Paralled_5V4_112818.jpg

2A3 Left 1 Watt_Analyzer Panel.jpg

2A3 Right 1 Watt_Analyzer Panel.jpg

2A3 Left Full Power_Analyzer Panel.jpg

2A3 Frequency Response_Both Channels.jpg

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Here is a "Williamson" Ultra-Linear amp I built about 25 years ago, but recently transferred the circuitry to new chassis'. The output transformers are Edcor 7.6k to 6 ohm. Power transformers are US military surplus. This particular design is super-stable, no motor-boating or other oscillation issues that some people have reported long ago. 

 

I'm also using 1625's since they are less expensive than 807's or KT66's. Originally, these were wired for 807's, but I bought a good stash of 1625's that should last me the rest of my life. 

Top Front View.jpg

Top Right Side View.jpg

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18 hours ago, Curious_George said:

Here is a "Williamson" Ultra-Linear amp I built about 25 years ago, but recently transferred the circuitry to new chassis'. The output transformers are Edcor 7.6k to 6 ohm. Power transformers are US military surplus. This particular design is super-stable, no motor-boating or other oscillation issues that some people have reported long ago. 

 

I'm also using 1625's since they are less expensive than 807's or KT66's. Originally, these were wired for 807's, but I bought a good stash of 1625's that should last me the rest of my life.

 

 

Beautiful amps! I would love to see the "undercarriage" pics if you have any.

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If you built the original version from 1949 or early 50's I do believe the stories of potential instability on some builds. In addition, depending on the output transformers used, the cap & resistor across the first stage anode resistor and the feedback cap & resistor, there was not much room for error. Layout and parts placement should be well thought out. 

 

The Talbot Wright article helps a bit too. IMO, a robust low impedance power supply will help eliminate a lot of the issues. 

 

I really like the Edcor output transformers, especially the 25 watt, 7.6k multi-tap version. I believe this is the closet thing you will get to an original Stancor A-8072. The Edcor is a bit smaller, but it also is using M6, which IMO is a better core material. 

Edited by Curious_George
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  • 2 weeks later...

Here is a 211 based amp I built about 20 years ago, but recently modified it with a interstage transformer.

 

Class A SE, 25 Watts, no feedback (but have been thinking about adding some feedback lately just to mess around with it).   

211 Mono Amp_Rack_3_compress.jpg

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9 hours ago, Curious_George said:

Here is a 211 based amp I built about 20 years ago, but recently modified it with a interstage transformer.

 

Class A SE, 25 Watts, no feedback (but have been thinking about adding some feedback lately just to mess around with it).   

211 Mono Amp_Rack_3_compress.jpg

 

Would love to see a schematic for this one.... Coool!!!!

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