Hello,
I am a new member ,located in Germany 49 years old and since the age of 14 I have been fascinated by some glowing parts in a radio.
After some years of being occupied with other things, I would like to build another tube amp.
I have been attracted by a design called "unity coupled" formerly used by McIntosh.It seems that it might be possible to design a tube amp with all the advantages of such a unit combined with a higher damping factor than in conventional tube amp designs.
I own some Telefunken V69's and like them much but would prefer a better speaker control the low frequency range.
Has anyone made some experiences with a unity coupled design,perhaps with the Van der Veen toroidal output transformers?
Greetings from Germany Ralph
I am a new member ,located in Germany 49 years old and since the age of 14 I have been fascinated by some glowing parts in a radio.
After some years of being occupied with other things, I would like to build another tube amp.
I have been attracted by a design called "unity coupled" formerly used by McIntosh.It seems that it might be possible to design a tube amp with all the advantages of such a unit combined with a higher damping factor than in conventional tube amp designs.
I own some Telefunken V69's and like them much but would prefer a better speaker control the low frequency range.
Has anyone made some experiences with a unity coupled design,perhaps with the Van der Veen toroidal output transformers?
Greetings from Germany Ralph
If you are going to get involved with unity coupled design, study Frank McIntosh's designs, like the MC240.
Completely different in topology is the Harman/Kardon Citation II, but it too controls woofer voice coils very well. Plitron offers toroidal O/P "iron" with the bandwidth needed to "replicate" Stu Hegeman's design.
Completely different in topology is the Harman/Kardon Citation II, but it too controls woofer voice coils very well. Plitron offers toroidal O/P "iron" with the bandwidth needed to "replicate" Stu Hegeman's design.
Jan V. did a Mac project:
BigMac, Unity coupled output amplifier
Likely some threads here on diyAudio too. Seach for McIntosh or CFB or unity gain.
BigMac, Unity coupled output amplifier
Likely some threads here on diyAudio too. Seach for McIntosh or CFB or unity gain.
search also for 'LW6-180' an design using TV sweeps.
The unity coupled design requires large drive voltage swing; it is moderately troublesome. There are a few ways to solve it. Examine the 12BH7 part of the McIntosh circuits( on the 75/275 for example ). There is positive FB there to deliver the headroom required. One can deliver the headroom without positive feedback by substituting a CCS for the 12kOhm resistors( the 12BH7 plate loads ).
cheers,
Douglas
The unity coupled design requires large drive voltage swing; it is moderately troublesome. There are a few ways to solve it. Examine the 12BH7 part of the McIntosh circuits( on the 75/275 for example ). There is positive FB there to deliver the headroom required. One can deliver the headroom without positive feedback by substituting a CCS for the 12kOhm resistors( the 12BH7 plate loads ).
cheers,
Douglas
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Hi,
thank you for all the answers.I knew that the unity coupled design is a bit tricky because of the recommended high voltage swing for driving the output tubes.I considered a common cathode phase splitter as first stage followed by a mu stage driver in combination with a white cathode follower.(comments welcome...)When I find the time needed I will mount these stages for doing some measurements before buying the "iron".
Ralph
thank you for all the answers.I knew that the unity coupled design is a bit tricky because of the recommended high voltage swing for driving the output tubes.I considered a common cathode phase splitter as first stage followed by a mu stage driver in combination with a white cathode follower.(comments welcome...)When I find the time needed I will mount these stages for doing some measurements before buying the "iron".
Ralph
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