The MC-60 uses a 12AX7 input tube as a cascode. The MC-30 and MC-40 also use a 12AX7 but only use one section, leaving the other section with nothing to do.
While a cascode is better than a resistance loaded gain stage (more gain with less distortion) the upper triode does not have its heater voltage elevated. The only tube I'm aware of that is designed to be used as a cascode is the 6DJ8.
The 12AX7 has about 3 times the mu of the 6DJ8, but I suspect the 6DJ8 will have plenty of gain for the amp.
Does anyone see a sonic reason not to redesign the input circuit to use a 6DJ8?
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Topic - McIntosh MC-60 Cascode - Lee of Omaha 10:14:18 09/23/17 (14)
- RE: McIntosh MC-60 Cascode - Tre' 12:50:30 09/23/17 (4)
- The lower section is a voltage regulator - Triode_Kingdom 13:01:55 09/23/17 (3)
- RE: The lower section is a voltage regulator - Lee of Omaha 17:50:21 09/23/17 (1)
- Are you experiencing failures?.... - Steve O 18:35:06 09/23/17 (0)
- There are at least 3 versions of the 60... - Steve O 13:42:24 09/23/17 (0)
- RE: McIntosh MC-60 Cascode - Caucasian Blackplate 10:38:37 09/23/17 (8)
- That's not a "cascode" and the cathode follower drivers are there for good reason... - Steve O 11:03:19 09/23/17 (7)
- Tim de Paravicini stated the unity coupled circuit was the only electrical innovation - Cleantimestream 12:32:45 09/24/17 (0)
- RE: That's not a "cascode" and the cathode follower drivers are there for good reason... - Caucasian Blackplate 16:20:52 09/23/17 (3)
- LOL 12AX7 may not be optimum but pointless it most certainly is not! (nt) - Steve O 18:14:51 09/23/17 (2)
- RE: LOL 12AX7 may not be optimum but pointless it most certainly is not! (nt) - Caucasian Blackplate 18:20:25 09/23/17 (1)
- Mac "upgraded" to 12AT7/12AZ7 in CF position but only in MC75/MC275 ... - Steve O 18:27:59 09/23/17 (0)
- RE: That's not a "cascode" and the cathode follower drivers are there for good reason... - Lee of Omaha 11:36:19 09/23/17 (1)
- I'm talking about both portions of the circuit in order of discussion (nt) - Steve O 12:15:28 09/23/17 (0)