Subminiature Tubes (6111, 6021) on 9-Pin socket (6DJ8, ECC88, 6922 etc)

January 4, 2011 - filed under: Tube

Since I have solder the subminiture tube on the SE mu-stage preamp, it do not allow easy swapping of tubes and thus lack lots of fun.  Thus I have found some 9-pin extention sockets and find a way to put a submini tube onto it.   I solder the leads of submini tube onto a pin head with 1mm diameter size.  The pin head can be inserted into the 9-pin socket.  Thus now I can swap tubes easily again!

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In picture, the tube is 6021 to replace the 6DJ8 tube on my SE mu-stage preamp.  I put the two triodes in parallel and thus there will be only 5 connections from submini tube onto socket.

Hybrid Balance Mu-Stage preamp with subminiature tube

December 31, 2010 - filed under: Tube

This is a new made preamp – Hybrid Balance Mu-Stage.  Dual triode medium gain subminiature tube like 6N16B-V, 6N18B-V, 6N28B-V, 6111, & 6021 etc… can be used.  The choice of submini tube is due to its low noise and good microphonic effect. 

Features: 

1. Hybrid (Mosfet + Tube) mu-stage design with full balance at input and output
2. Supply voltages: +128V, +59V, -69V and two 6.3V DC – all regulated supply
3. Tube biased at about 1.5mA at about 60V plate voltage
4. Mosfet IRF710 as Source Follower biased at about 7.5mA
5. Gain about mu of the tube, about 20 to 40 times
6. Non feedback design and thus tube may need to match for gain.
7. Tube can be replacable using IC sockets, the submini tube is first soldered on 8-pins leads and then inserted into IC socket.

FFT measurment:

FFT Balance Mu Preamp

Update new photo on Jan 3rd, 2011 …..

Mu-Stage with subminiature tubes – 6111, 6021 etc…

December 20, 2010 - filed under: Tube

For 9 pin tubes, I think Amperex 6DJ8 is very good performer in mu-stage pre-amp.  Thus many other triodes are evaluated in Tube post.  Now here is some photos of the mu-stage with subminiature tubes.  The way is to solder the small tube on the bottom of the tube socket and the two triodes in one tube is put in parallel.  Insulation shrink tubes is used to prevent short circuit of leads.

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I have purchased one pair Sylvania 6021 and 4 pcs Raytheon 6111 tubes (non marking type).  The pair of 6021 give very good matching for the gain but only 2 out of 6111 tube are with good gain match.  The worst 6111 tube is about 1 db lower gain than the other 3 pcs. 

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Note that the mu-stage is also upgraded with KBG and Telfon capacitors!