NASA space launch used tube in audio

[tony ky ma]

5876 is a space age tube in used at MERCURY launch, today NOS price is about $30, quality over the price so much, I try to post this to the tube forum here, but I found out most of the readers reply just replacing tubes to their gear for difference and there no market amp using this tube before, so still in DIY is better, may be not too many DIY amp builders in this site and I did post this to diy.com and got some positive reply.there are two type of DIYERS , one is beside with fun in build but mainly for pay less, they use same value numbers of components to the market made amp design and that is the main in that .com, sometime they can have good result by lucky, but sound quality is count on component's quality, so the other type of DIYERS doesn't mind to pay more for better level, sometime just one out put transformer cost more than the whole system in the market, still amp is only one part of the system if looking for the best need others to support otherwise you don't know how good it can be so I try to post in here. Not all old NOS component must be better than today's make, today's cap and transformer has much better quality than the old time made with new material but tube is different story, especially those made for military industrial and high tech use, and now no more jobs for them in their field but it is over quality for audio, so if you can convert it to use in audio, you will have a super quality parts with small cost, here the circuit in using this tube to drive a 809(NOS$30) transmitting tube to have 8 watts in SE out put, the most simple and less parts amp design but you can challenge any high price 300B amp in the market made but with good quality transformers

[JackD201]

First I've ever heard about much less seen a "Pencil" tube. Thanks Tony.

[tony ky ma]

First I've ever heard about much less seen a "Pencil" tube. Thanks Tony.

Hi Jack
You are right they call pencil type, because it is very high gain and less noise I put it to my PHONO stage as well, even you can build a less 1 watt amp just by it alone , the only problem is there are no sockets for sale I use a big fuse holder for socket, it works, expensive NOS 12AX7 or E88CC can compare to this one after you try you will have the answer
tony ma

[JackD201]

What is the connection on top of the 807 for? I see it on some transmitter tubes like the 805 pentode. I noticed the 5876 connects directly to them. Also I noticed only 2 pins?

[tony ky ma]

What is the connection on top of the 807 for? I see it on some transmitter tubes like the 805 pentode. I noticed the 5876 connects directly to them. Also I noticed only 2 pins?

That is 809 is a triode 805 also is a triode too, 807 is pentode, and real triode always sound better than pentode but less power or efficiency. the top connector is the plate connection connect to the out put transformer, two pins you saw is the heater pin of 5876, the fuse holder hold one side of the plate the other side hold the cathode, in the middle round plate is the grid, got interest to build one of this ?

[JackD201]

I have no build talent but for fun I have my friend build stuff for me. Currently he is making me a Single Ended Parallel amps using 2a3 power tubes and AudioNote OPTs. Can this work in place of 6SN7 for driver applications? You said they are strong enough as power tubes. Possible?

[tony ky ma]

I have no build talent but for fun I have my friend build stuff for me. Currently he is making me a Single Ended Parallel amps using 2a3 power tubes and AudioNote OPTs. Can this work in place of 6SN7 for driver applications? You said they are strong enough as power tubes. Possible?

2a3 is a negative bias tube can very easy to drive, 6SN7 with gain of 8 but 5876's gain is over 30, so it can drive a positive bias transmitting tube like 809 826 808 812A to have more than 8 watts out in single single end, parallel 2a3 will have same size out put power but single 809 much cheaper than 2 NOS 2a3 and after you have tasted the positive bias transmitting tube's sound, I am sure you will not go back again ask your friend build one for you, the inter stage transformer can use Audio note's line stage out-put 5K to 600 ohm just make sure current is opposite between pri and sec.

[JackD201]

Interesting! Is the schematic above complete?

[tony ky ma]

Interesting! Is the schematic above complete?

need power supply design, easy job, separate it to other case with tube rectifier( 5V4G or 5U4, 5R4, 5AR4) and choke(10H) in put to get best result, two LM317 adjustable regulator IC for bias voltage supply to adjust 809's current, 6.3V DC voltage supplies for 809 and 5876. you can make one High Voltage power supply for the whole amp, or two for stereo, the best is two for pair 809 and two for pair 5876 too, in doing this way and with all silver audio transformers it will become top of the world in this out put class

[JackD201]

Can you share power supply schematics?