Tube question

[puddy]

I have the RM50 combo. I want to tube it soon. I just recently sold my Marshall Vintage Modern. The Marshall runs on KT66 power tubes and ECC83 pre amp tubes. Before I sold the Marshall I had bought brand new tubes for it. I am kinda stuck with the tubes now. Would these be able to work in the RM50? How would I bias them? What does anyone think KT66 power tubes would sound in the RM50? and the ECC83 sound in the preamps?

Any help would be great.

Thanks,
Scott

 

[audiomidijace]

You'll have no problem using these tubes. There's some KT tube guys that will chime in I'm sure about bias. I tried KT88s in my RM50 and didn't care for it. However, the guys that love them seem to be playing live and loud. I'm just recording and don't play that loud.

 

[puddy]

I will need the mV setting so I can bias them correctly. Anyone know. The manual doesn't mention a setting for the KT66.

 

[BigBrewtus]

I think the KT66s run the same mV bias ratings as 6550/KT88s.

 

[kc2eeb]

KT66s are more in the 6L6GC family of tubes and you could bias them the same as 6L6s, around 30-35 ma.

 

[JKMV12]

i did a quick search and it looks like 35mV is an acceptable number. I wouldn't go too much above that. The KT66's are usually grouped with the 6L6's so stick around that range to be safe.

ECC83 is just the British name for the 12AX7. You should be fine with them. If you are in the market for new preamp tubes then i have had good experiences with Ruby and Penta tubes. Tungsol also has some nice stuff. Try a JAN 5751 in the phase inverter for clarity and noise control. It is basically a 12AX7 with a lower gain factor (don't let this deter you!).

The phase inverter's main job is to make a copy of the signal that is 180 degrees out of phase so that each group of tubes in the push-pull power amp can each amplify half of the signal. In your case each KT66 will receive half of the signal and be responsible for it. Actually at low volumes they each take the signal somewhat equally...when you turn up the volume each tube starts taking turns in amplifying the signal. Tube amps are pretty cool.

 

[puddy]

Great stuff. great advice. Thanks!
Is the phase inverter the pre-amp tube inside the RM50? I haven't looked yet to see what is in there. How many pre-amp tubes are in the amp - not in the modules but in the amp itself?

Thanks again for the help.
Any more info and personal experiences are welcomed - keep it coming.

And yes, tube amps are very cool - I have a lot learn about the tech stuff.

 

[JKMV12]

Great stuff. great advice. Thanks!
Is the phase inverter the pre-amp tube inside the RM50? I haven't looked yet to see what is in there. How many pre-amp tubes are in the amp - not in the modules but in the amp itself?

Thanks again for the help.
Any more info and personal experiences are welcomed - keep it coming.

And yes, tube amps are very cool - I have a lot learn about the tech stuff.

there are three tubes in the amp: the first gain stage (V1), the phase inverter (PI), and the FX loop buffer. The PI is closest to the power tubes and the V1 is closest to the guitar input.

For more technical info on tube amps i recommend the books by Richard Kuehnel and Merlin Blencowe. Merlin has a website with some of the basic info. There are plenty of great resources on the net. Let me know if you want any recommendations.