[modwright]

Interesting about the C.J.'s needing constant repair.  It could have had to do with the solder they used or too thin of traces.

We do use fiberglass boards with good thick traces.  The relationship is largely between current and trace width.  The same is true with wire gauge.  Voltage has more to do with dialectric strength, while current directly relates to power and thus heat generation.  If too hig of a current is forced through a wire of inadequate gauge, heat will be generated.  Likewise, if a PCB trace is two thin, the same will occur. The main high-current portion of a tube preamp is the heaters and these are larger in comparison to everything else.  The actual signal current is pretty minor - on the order of 25mA-80mA, while the heater current in this case is closer to 500mA to 1A.  Compare this to amplifiers (especially SS), where current can range from mA to 15A+ and you can see the diff.

Dan

[guest1632]

I see ;)...sorry.  

I really like the 5687 tube because it is linear, handles high-current and sounds exceptional in my opinion.  Other options included the 6H30 and ECC99.  The ECC99 I couldn't get consistent quality tubes and wasn't crazy about the sound.  The 6H30 is good, but I found it to be a bit darker than the 5687 and also difficult to source.

The 6SN7/6CG7 were also viable alternatives, but I still preferred the 5687.  I was concerned about availability, as they are only NOS,  ...

Hi Dan, Are 6SN7's drop in replacements for the 5687 tubes? Just thinking in case something were to happen and you were not available to supply the tubes? Thanks. Ray

[Bill Baker]

Are 6SN7's drop in replacements for the 5687 tubes?

  No, these are not the same at all. Besides electrical parameters, the 6SN7 uses an 8 pin base (same as the EL34, 6550 type tubes) and the 5687 utilizes a standard 9 pin such as a 12AX, 12AU, etc. And no, these tubes are also not a replacement for the 5687.

 As far as availability, there are still plenty of these tubes around. Another alternative is the JAN Philips 5687 which I also really like. I wouldn't worry too much about running out of these tubes

[guest1632]

Are 6SN7's drop in replacements for the 5687 tubes?

  No, these are not the same at all. Besides electrical parameters, the 6SN7 uses an 8 pin base (same as the EL34, 6550 type tubes) and the 5687 utilizes a standard 9 pin such as a 12AX, 12AU, etc. And no, these tubes are also not a replacement for the 5687.

 As far as availability, there are still plenty of these tubes around. Another alternative is the JAN Philips 5687 which I also really like. I wouldn't worry too much about running out of these tubes

[Bill Baker]

So these have the old octal socket like a 6l6? Don't know that much about tubes. just remember my boyhood days replacing a 6l6 in an old Helicrafters shortwave receiver.

 NO, the 6SN7 has the same octal base as the 6L6. The 5687 is the same as any of the 9 pin input tubes as mentioned. The 5687 looks the same as any 12AX7, 6922, etc.