Caution Light?

[Zlofengir]

I just switched over to some EH 6CA7 tubes, and noticed the red light over the bias switch was on... Kinda hard to tell if this light is a warning, or if it's just to say that the amp is in EL-34 mode.

It did seem that the amp was running a bit hotter... Gonna try the old tubes, and see what happens.

 

[jb's 52]

That's the case when it's on EL34.

 

[Zlofengir]

That's the case when it's on EL34.

Good to know... The manual doesn't say anything about that. Thanks!!

 

[masterMarkV]

Manual say:

"The adjacent LED indicator alerts you that the bias has been set to accommodate the EL34’s."

This is just a warn to tell you that you put the switch to EL34 mode. This is not an abnormal situation if you have EL34, this switch must be in EL34 position and the warn light will glow

 

[Zlofengir]

Manual say:

"The adjacent LED indicator alerts you that the bias has been set to accommodate the EL34’s."

This is just a warn to tell you that you put the switch to EL34 mode. This is not an abnormal situation if you have EL34, this switch must be in EL34 position and the warn light will glow

I looked many times, didn't see that...

 

[Zlofengir]

Having "Caution" over the light doesn't help either... Confusing. We're guitar players, not rocket scientists.

 

[bandit2013]

Yes, it can be misleading, if the light is on, assuming you moved the amp, or changed tubes, the light is on to indicate el34. Caution statement is to verify tubes match type selected by switch. Running the wrong bias for the tubes will result in damage to the amp. EL34 will run very hot compared to 6L6 types. Not quite sure what runs hotter, 6CA7, KT77 or EL34's. EL34 have the smallest diameter bottles so they win, KT77 (depends on make, Gold Lions are a bit wider than EL34 but smaller than 6CA7.) My guess is the KT77 will be hotter due to the higher wattage compared to the others. That reminds me that I have not tried the EH6CA7 yet, guess I should order some before those get overpriced like everything else.

 

[Zlofengir]

Yes, it can be misleading, if the light is on, assuming you moved the amp, or changed tubes, the light is on to indicate el34. Caution statement is to verify tubes match type selected by switch. Running the wrong bias for the tubes will result in damage to the amp. EL34 will run very hot compared to 6L6 types. Not quite sure what runs hotter, 6CA7, KT77 or EL34's. EL34 have the smallest diameter bottles so they win, KT77 (depends on make, Gold Lions are a bit wider than EL34 but smaller than 6CA7.) My guess is the KT77 will be hotter due to the higher wattage compared to the others. That reminds me that I have not tried the EH6CA7 yet, guess I should order some before those get overpriced like everything else.

I'm quite happy with the EH6CA7's; they definitely have a different vibe from the 6L6's. I've found that the highest gain mode on each channel is much louder than before; and the gain structure is somewhat different. I went all out, and replaced all the tubes with EH's from Tube Depot; I would have loved to have gone with some Gold Lions, but at $50 a pop... I'd have to have some well paying gigs lined up!

 

[bandit2013]

I gave the JJ6CA7 a try. I was blown away by the tone and character of the tubes in the Mark V. Unfortunately one of the tubes would shut down intermittently. So I pulled it and marked it as bad. After that, I installed two of them in the Mark IV (I had them in there before hoping to get a similar tone that I had with a Mark III that came with RCA 6CA7/EL34 and 6L6GC. That did not happen. However the second use in the Mark IV turned them into arc welders and sudden toast.

I have not yet tried the EH version. Plate design looks nearly identical to the RCA tubes I had long ago.

Gold Lion KT77, not as deep as the 6CA7 but definitely more than an EL34. Still have not been better than the SED 6L6GC. Ch2 crunch mode is kick-ass with the SED's, but the KT77 are killer with CH3. What best describes the tone and character of the 6CA7: tone of a SED 6L6GC blended with character of a TAD6L6GC-STR and packed with the complex harmonics of the KT77 running parallel to EL34. Note: Current production 6CA7 are not like those used back in the previous decades. The RCA 6CA7 was more or less similar to combining SED 6L6GC and TAD6L6GC-STR as an integrated quad. Still unique in character. I should definitely get a set of the EH6CA7.

I found the EH12AX7 to be great tubes, but prefer the Tung Sols. Right now I have:
v1 TS gold pin
V2, V3 vintage Mesa Chinese 12AX7A (bought these back in the 90's)
V4-V6 standard Tung Sol
V7 Mullard Reissue. (unmatched triodes). Normally use Sovtek LPS but tubes sound the same.
V8-V11: SED 6L6GC.

When I run the KT77, I found the JAN/GE 5751 to work the best in V7. I am reserving the KT77 for the RA100 so when the SED EL34 give out I have replacements. I actually prefer the SED EL34 in the RA100 than any other tube I tried.