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On this page I will publish my DIY projects concerning Tube Amplification, and discuss the topic. I shall also make a page with tube amplifier theory (not finished). The designs are made using graphical methods and the GlassWare SE Amp CAD and Tube CAD programs.

The tube amplifier section has unfortunately suffered from lack of time and nothing much is happening at the moment. I get most feedback on the Quad ESL section and have focused on the topics there, this does NOT mean that I am not interested in this section anymore. I will get back to the projects here as soon as I get the necessary time.

JJ Electronics have launched a new(?) very interesting tube, suitable for driving for instance 300B's, the ECC99. Take a look at the
JJ Electronics site.


My Present Tube Amplifier Projects

MT Audio Design 'Quadimodo': A push-pull design built around the transformers from two Quad II amplifiers, using triode coupled KT-88 as output tubes. The input/driver stage is a totem pole design with parafeed to an SE-PP interstage transformer. It is designed as an integrated amplifier with SRPP-coupled 6BL7 in the pre-amplifier section. The estimated output power is around 15W Class A1, and the distortion shall be below 1% at full power without global feedback. I bought a couple of Quad II amplifiers at a low cost, because I was interested in the split load used in these (10% cathode and 90% anode). Press the 'Quadimodo' button to get the whole story. The status of this project is 'building phase'. Just for fun I calculated the characteristics and results of a typical Class AB KT-88 amplifier for comparison with my 'Quadimodo' design. The status of this project is 'building phase'.

MT Audio Design 'Sep Yep': A parallel SE design using JJ 300B as output tubes with split load (25% cathode and 75% anode). This configuration looks promising on the design stage, but the driver stage is tricky. The driver stage must be able to deliver +/- 200V at low distortion, and I found the solution in the 6BX7 tube. This driver stage uses a split load (25% cathode and 75% anode) interstage transformer, and the results are amazingly good on paper. Hopefully the sounding result will be the same. The amplification in the driver and output stages are low, which means that a three stage design is necessary, and as input stage I use transformer coupled (1:2.25 step-up) 6BL7. More information is found if you press the 'Sep Yep' button. The status of this project is 'planning phase' (I have bought all the tubes, but the iron is expensive and will have to wait for some time).


Abandoned Projects

'Cathode loaded 6C33C-B' SE':

This was first attempt to solve the problems associated with SE amplifiers. The choice of 6C33C-B as output tube was because of its low voltage requirements, which makes the driver stage much easier to design. After some feedback from Thorsten Loesch on this design I decided to use split load 300B instead. The 300B is much more linear and with a split load OPT the driver stage is possible to make, and the distortion is lower than with a cathode loaded 6C33C-B. At the time Thorsten was busy designing the super mu stage used in his 'Fuge' design, which can be found at the 'Triode Guild'. This super mu stage is an interesting design. Many thanks to Thorsten Loesch for his very useful feedback.

'VV52B SE':

Basically the same design as the 'Sep Yep', but with a single KR VV52B as output tube. I decided to use two JJ 300B in parallel instead, which gives me the opportunity to try it as a push-pull amplifier (only some transformer connections needs to be altered) and examine the pros and cons of this. The VV52B is also expensive and has been unreliable in the past. The JJ 300B is quite cheap (check my 'Losconi' link), and the reviews have been very favorable on this tube.



Interesting Designs

In this section I will publish links to tube amplifier designs that I like.

 

 

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