Prologue 1626/5842 Tube Amp prototype

This project refers to Jim de Kort's 1626 project called Prologue.

Im planning to use a mixer to drive the amp so I just need one stereo input. A parts list is available. I've decided to use standard 6 and 12V regulators, but ordered 3 LM350 variable voltage regulators, too. Jim de Kort does have some very useful tips on regulating power for filaments on his site.

Update [2010-12-03]

I'm moving this prototype into a new housing since the board has been getting more and more dry. Have a look at the Prologue 1626/5842 Tube Amplifier page.

Update [2004-05-18]

I finished the breadboard version of the 1626 prologue amp about two months ago and I was very pleased with the outcome of my first HiFi tubeamp endeavors. The amp sounds great and no - I repeat: no - hum at all is hearable. I added a standby-switch to turn on the filament power and heat up the tubes before high voltage reaches the plates. That was necassary since I switched from voltage source to current source on the output tubes' filaments which improves the sound somewhat. They heat up much slower now because they can't draw more current than provided and having the tubes preheated is generally a desireable thing, so I decided to care for their tube life ;-) Concerning listening experince: The amp sounds great! The sound is warm and clear, no harshness, or muddled highs. It doesn't drive my speakers to earache levels because they're crappy, cheap and old but this will be another project yet to begin with.

Update [2004-02-04]

I decided to (and actually did) spend some money today on a power transformer, chokes and an output transformer. The OT is a universal one for single ended designs where you can easily adjust the input impedance for testing different tubes and circuits. There is a major drawback though, it's range goes only from roughly 150Hz up to 15000Hz. That's kind of thin for a HiFi tubeamp but the expensive ones (two for stereo) will follow as soon as the circuit has proven on the breadboard. seems to be a great resource for Hammond transformers and chokes here in Germany.

Update [2004-01-17]

I bought another 5Y3G rectifier by accident from a seller I know now quite well. It turned out that I will receive another type #80 globe shaped rectifier along with a type #83 mercury vapor filled rectifier tube. Those 83s have a blue glow when they heat up (due to the mercury vapor) and should fit in easily without changing much of the circuit.

Update [2004-01-03]

80.jpg5y3g.jpgJust for fun I added a type #80 rectifier tube to my collection of tubes. This one matches those nice two Sylvania 5Y3G rectifiers I acquired from the same seller but it has a 4 pin socket instead of an octal one.

Update [2003-12-22]

Got three more of those Raytheon 5842 preamp tubes. I think it's better to keep some in stock.

Update [2003-12-20]

5y3gt.jpg1626_2.jpgGot two 5Y3GT rectifier tubes and three additional 1626 power triodes.

Update [2003-12-17]

Bought Tubesockets.

Update [2003-12-09]

Went to buy some capacitors, pots, resistors, diodes and wire. Just tube sockets, iron and high voltage electrolytics for the power supply are still missing.

Update [2003-11-25]

raytheon5842.jpgThose Raytheon 5842 arrived today.

Update [2003-11-17]

The two Raytheon 5842 stated above have been shipped today. Hopefully they will arrive next week. They tested 36 and 40 on a TV-7 tube tester where 35 equals 100%.

Update [2003-11-08]

1626.jpgI have been able to obtain two NOS RCA 1626 VT 137 tubes from the mid-40's for the beginning. Hopefully two Raytheon 5842 will be sent to me, too.