GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Melquiades Amplifier
In the Thread: A different breed of 6C33C amplifier.

Post Subject: Further thoughtsPosted by KOTriode on: 3/16/2012

Romy, in the contrary, it is very unfair to compare my 845 amp with the 6C33C. The main reason is the 845 amp used the best output/interstage transformer available, while the 6C33C's output xformer is pretty good but far from being best for the 6C33C. I can see sine wave distortion on the 6C33C at full power (15W) below 30Hz, while the 845 has no problem down to 20Hz (limit of my audio analyzer). Since there are not much 6C33C transformer availability out there, I just have to settle with what I have, but that's in the amplifier department.
Now, the main reason that I built the 6C33C preamp is to experience the pure sound of 6C33C, with one cathode bias resistor/cap and a transformer load , it is as pure as it can be. It even have double output, one is through the output transformer, the second output using the transformer primary as choke load and output through a capacitor. It's output is pretty flat from 20Hz-20Khz with low distortion, sine wave looked pretty good at 20Hz, this is what I compared with a 845 preamp (even though with different output transformer), both do not have any other inoput/driver tube to inject their own sound. And it was these two preamp that lead me to compare the bass of the two tubes.
When I described the 6C33C sound in the bass, I think you might have misunderstood that I criticized in a bad way. " On dynamic, the 6C33C tube showed its ability to go deep in the bass on Ray Brown trio recording of Soular Energy which is excellent for a 15W SE , the 845 amp can do better, but not by much, but probably because of its 25W output give it more headroom than the 6C33C"
After living with 845 tubes over 20 years, with no less than 7 845 amplifier built, including 2 pair of push pull class a 50W and 100W(to satisfy my curiosity, I made a Parallel push pull with 4 845 tube per side to get 100w), I can say thay 845 is king in the bass area that no other tube can approach, now if the 6C33C being second best in the bass department at my first shot at it, I would say this tube is a miracle, I was so ecstatic adding this tubes to my stable and racing toward implementing it in a mono block version. I wish there are more output transformer available for the 6C33C, the Tango is too small to be serious, that leave Sowter and Lundahl, I might have left some others but if anybody know something I dont then I am all ears.
Regarding the Milq, it's not easy to modify my amp to the Milq cricuit, my amp was designed with DC coupled, therefore the B+ is pretty high, at about 500V it has twice the voltage of the Milq, the regulator cant regulate down to 220V without problem (too much voltage and current for the pass tube). To duplicate the Milq, it would require different power transformer, but that can be done and I will put some thought into it.

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