For years, I have been thinking about building, more accurately, getting myself 300B push pull amp build by Alan Hobkirk. I have done so much reading on it and pulling designs from the web, but life was always getting in the way to pull the trigger. Now I have been decided it is time. You might have read my comments about the Ongaku replica in past months, and my own ideas to build a 300B push pull go back to the time when Alan build this great amp for a friend. Experiencing the magic of such an amp and the reading about the Sun Audio 300B pp I thought that one must try and see how close one can get to SET virtues, with a bit more usable qualities such as more usable output impedance that help with the use of speakers and on a practical level lower voltages etc. It won't be a quick build, as the Air speakers are priorities but I did think it might be an interesting project for some of the valve enthusiast and I might just get some good input along the way.
Since I had an EAR 834 as one of my 1st amps, and did some upgrades to it, I always thought that it could be a good test bed to build a 300B PP. The transformers of De Pavaracini is wideband, does bass quite well and in my view must be good. I knew of an EAR amp that was butchered by someone and it so happened that I now have the OTP and power transformers. That will save me some costs and will be the start of the amp.
In terms of the design, Alan will do all the final decisions, but he is such a nice guy that he entertains all my crazy ideas and questions etc. I don't have the stomach for excess of the Olson design, how good they might be but will try to take note of all the good principles that he tested. On the other hand, I do like the WAD 300B design for it simplicity. However, I have done a U-Turn on a phase splitter interstage when a transformer designer who highlighted the technical challenges with designing such units.
So for the moment, the idea is as follows:
-Siemens d3a input valve in triode
-5867 Long tail phase splitter and driver through an interstage
-300B in push-pull (much like the WAD operating points)
I must come clean, I know little about amplifier design and only know the metaphorical maps not the territory, so I will share what I can but most of the detail I am out of my depth, but I am open to learning and discuss your ideas and experience as well.
So what do you guys think?
Stefan
Since I had an EAR 834 as one of my 1st amps, and did some upgrades to it, I always thought that it could be a good test bed to build a 300B PP. The transformers of De Pavaracini is wideband, does bass quite well and in my view must be good. I knew of an EAR amp that was butchered by someone and it so happened that I now have the OTP and power transformers. That will save me some costs and will be the start of the amp.
In terms of the design, Alan will do all the final decisions, but he is such a nice guy that he entertains all my crazy ideas and questions etc. I don't have the stomach for excess of the Olson design, how good they might be but will try to take note of all the good principles that he tested. On the other hand, I do like the WAD 300B design for it simplicity. However, I have done a U-Turn on a phase splitter interstage when a transformer designer who highlighted the technical challenges with designing such units.
So for the moment, the idea is as follows:
-Siemens d3a input valve in triode
-5867 Long tail phase splitter and driver through an interstage
-300B in push-pull (much like the WAD operating points)
I must come clean, I know little about amplifier design and only know the metaphorical maps not the territory, so I will share what I can but most of the detail I am out of my depth, but I am open to learning and discuss your ideas and experience as well.
So what do you guys think?
Stefan
