Finally the amp is tested, some test results are published on top of this topic. Only the main building steps I have published here, building the amplifier took me quite some time and work, as every single part to mount pieces (PCB's, transformators, switches etc.) had to be handmade.

Part 3 shows some additional photographs and schematics of my amp.

 

 

Go to part 3>>>

 

 

 

Tu-be or not Tu-be...?

 

Part 2
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Again the µP controlled attenuator of Jos van Eijndhoven is used in this amplifier, just because it delivers excellent performances in my previous projects. Because this unit is located on top (or under) the output transformers I have made some Mu-metal bins from a scratch plate of Mu-metal. This Mu-metal forms a screen for magnetic- as wel as electrical influences. The edges are soldered with normal soldering wire, meaning 60/40 Tin/Lead, and finally the bin is connected to central ground. The gold contacts are made by removing them from an old high-grade connector, which I found on the shelf...These massive 1.5mm contact pins, just fit the PCB holes on the attenuator, works just great! Sometimes I like to improvise on certain issues:)

Photo beneath:

A impression of the right section of this amplifier, showing the attenuator, and his small 6Vac transformer. The JJ cap's of 50µF+50µF/500V (to the wooden side bar) and the 500µF/500V on the chassis close to each other, together with the 22k/3W and 1k/3W resistors. The black sleeve transportes the wires from the attenuator to the front panel, to activate the input LED's. The left PCB is the Tent Labs heater supply, providing a clean 12,6Vdc voltage to heat the 12SN7 tube. The red capacitors are the 0.47µF Superior-Z coupling cap's from Jantzen Audio.

 

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Left, a close look at the ECC99 sockets, showing the Allen Bradley 2W anode resistors, and the 10k/3W cathode resistor. The smal brown resistors are (heating supply) hum eliminating resistors of 120 Ohm connected via a small cap to ground. I use high quality ceramic solder tags, which I bought at Ebay in the past. As there was non metric wire, I had to re-cut the wire to metric size, so I could mount it on a M3 sized nut.
All ground connections are transported to one central grounding point, as can be seen in the middle of the photo. The ground connection of the High-Voltage JJ capacitors are connected by 2.5mm^2 (AWG13)  massive cupper wires to the central ground point. The two big black resistors in the middle are the cathode resistors of the 12SN7 tube. They are a little over the top with there spec's (500 Ohm 0.1% 7W Non-Inductive) but it won't do no harm, and they where on the shelf. So I think this fellows are quite stable in this application:)

The original brackets from the output transformers are removed, this to make it suitable for horizontal mounting on the chassis plate. I made a new construction on the alu chassis plate with M5 distance spacers, and locked the output trafo's with their M5 screws. Offcoarse the trafo's are turned 90 degrees on the main power trafo, to eliminate magnetic influences on each other.