A word to the wise on EH 6CA7 tubes!

[Alabama Thunderpussy]

Your first post and it's to resurrect a 3 year old thread, and not only resurrecting a 3 year old thread, but doing it with anecdotal evidence.

 

[johnfv]

Your first post and it's to resurrect a 3 year old thread, and not only resurrecting a 3 year old thread, but doing it with anecdotal evidence.

I say we give the new guy the benefit of the doubt. Let's not go all Wilder on his ass just yet...

 

[pittbull]

I just switched to the EH6CA7 after using EL34's and I wont go back to any EL34 brand thats for sure.The EH 6CA7 sound fantastic and the quality is very good,I hammer these tubes and they take the abuse.

 

[tazzboy]

Has anyone gotten a hold the new JJ 6CA7 to try out it mention on their web site that it is A.F. OUTPUT PENTODE?

JJ-Electronic - Vacuum tubes, Capacitors, Amplifiers - Power tubes

 

[mickeydg5]

Hello Kenm

No one should worry about substituting an EL34 with a 6CA7 or vice versa.
They both have an 8ET base which means that their pin connections are the same.

Philips/Sylvania 6CA7 (big bottle) and others modeled after its design like EH6CA7 and JJ6CA7 are Beam Pentodes or Beam Tetrodes. Most older data sheets call them Beam Tetrodes but later all refer to them as Beam Pentodes technically because they all have five electrodes. Their G3 (grid #3) are beam forming plates.

Also to add is that a KT77 is a beam type as well with a 7AC base which is the same base/pinout as the KT66 or 6L6 types.

The only difference between a 8ET and 7AC base is this:
8ET has pin#1 connecting to G3 and pin#8 connecting to cathode
7AC has no connection at pin#1 and pin#8 connects to both the cathode and G3

Other Pentodes have a suppressor grid for G3 instead of the beam focusing plates.

 

[charveldan]

I only use the best ^^^^^^

 

[mickeydg5]

If that were true then wouldn't your picture look more like this

Just kidding!

 

[pittbull]

6CA7's sound more open and bright then any EL34.They also sound more aggressive.EL34's have this compressed less open sound.

 

[solarburn]

I've found it depends on the circuit these tubes are in. Yeah they have an individual audio footprint no matter what amp they are in but can sound better or worse in different amps not to mention we don't all use the same speakers, pick ups, guitars etc...which all matter when stating a certain tube sound awesome. It may sound not so good in my set up cause of other variables.

I prefer the EH6CA7's in my JMP or my DSL50 over the Winged =C='s. I use to subscribe to them being the best CP EL34 out there. After rolling a few myself and not buying into Internet lore I found other power tubes pleased my ears more focused on what zone I play in and characteristics I prefer.

The EH 6CA7's are beastly and raw. I've never had a power tube make my amp meaner in a primal way like they do. It's weird but fun as hell. My other faves now are the GT34M's and JJ EL34L's. These are the 3 go too's for my amps and it was expensive to find out what turns me on.LOL

 

[solarburn]

6CA7's sound more open and bright then any EL34.They also sound more aggressive.EL34's have this compressed less open sound.

Yes. I found the openness to equate to that raw beastly characteristic I hear when saturation is added. It's awesome. The top end isn't harsh either in my amps.

 

[MartyStrat54]

The best? Mullard xF1's or xF2's with dual getters. That's the best.

An RFT is better than a Winged C and costs about the same.

 

[pittbull]

The quality of Mullard tubes in the 70s were horrible.Alot of players including Eddie Van halen switched to 6CA7's because of that also they would go with 6550's.Marshall switched to 6550(amps coming to the USA)because of the quality of EL34's.

 

[mickeydg5]

Yes, there were problems with shipping EL34s in the 70s. I do not know why but there could have been a reason.

A big differences between a 6CA7 and an EL34 is that the 6CA7 is the American version which had/has a harder vacuum. This tends to give a different sound, same in character to that of the American 6L6 and a 6550.

 

[MKB]

Now IIRC the USA made 6CA7's back in the glory days were all beam tetrodes. About the only way you could get a true big power pentode was to get a Mullard EL34 or a 7591A. Also many tube substitution guides (anyone still have one of those??) listed the 6CA7 as a direct replacement to a EL34. So this tetrode/pentode issue has been around for quite a while.

If you want to see tubes ran far outside their published specs, just check out almost any EL84 application. It appears you can run the plates fairly high as long as you keep the screens at 300V max. Mesa Engineering has been doing this successfully for years. BTW, if you use a largish RC on the screen grids, don't sell the amp as Randall has this patented and will come and git you.

I always wondered why amp designers just didn't add a big zener to ground on the screens to keep the voltages under 300V. I once made a pair of homemade EL84 to EL34 adapters (like a THD Yellowjacket) and used zeners in the screen grid circuit to get the voltages down to 300V max, along with AC coupling on the signal grids to remove the amp bias and local cathode bias. I ran the plates of the EL84's at full amp voltage, around 495V IIRC. Those things worked perfectly in my 1987 clone, I never had a single problem with them.

 

[Alabama Thunderpussy]

Dan, can you PLEASE refrain from bandwagoning for longer than five minutes?

 

[mickeydg5]

Actually Tung-Sol 6CA7 tubes were power pentodes like the EL34s.

 

[Tüßermensch]

They are different tubes, what will make them somewhat similar (interchangeable) is their electrical happenings, which is the only of the concerns of the producers and of the engineers. the same thing happens in the transistor worlds to an extent.

You have to ask your self this one:

What is what is?

If it has a similar transconductance, a similar internal resistance, and A similar va to vg2 curves, hast that make it an el34 in terms to the sound? How close are those numbers to any real one you buy?

It's pretty much the picture abstract

-Heinrich

 

[RickyLee]

Hello Kenm

No one should worry about substituting an EL34 with a 6CA7 or vice versa.
They both have an 8ET base which means that their pin connections are the same.

Philips/Sylvania 6CA7 (big bottle) and others modeled after its design like EH6CA7 and JJ6CA7 are Beam Pentodes or Beam Tetrodes. Most older data sheets call them Beam Tetrodes but later all refer to them as Beam Pentodes technically because they all have five electrodes. Their G3 (grid #3) are beam forming plates.

Also to add is that a KT77 is a beam type as well with a 7AC base which is the same base/pinout as the KT66 or 6L6 types.

The only difference between a 8ET and 7AC base is this:
8ET has pin#1 connecting to G3 and pin#8 connecting to cathode
7AC has no connection at pin#1 and pin#8 connects to both the cathode and G3

Other Pentodes have a suppressor grid for G3 instead of the beam focusing plates.

Hey Mickey!

I just picked up a '73 Traynor YGL-3A head a few days ago. It has two TAD EL34B (Chinese made) and two old Sylvania 6CA7's in it. This Traynor has the negative bias voltage on pins 1, or the suppressor grid pin. I will not be trying the EH6CA7's in this amp after reading this thread of course.



I am wondering besides the basic EL34 types, what would be a good valve to try in this type circuit? And a very important question, what other valves do I need to avoid in this circuit? Is the JJ 6CA7 safe to run in it?

 

[mickeydg5]

I will have to check out the YGL-3A. Get back to you later.

 

[thrawn86]

Side note to the thread: It's coming up on almost the 1 year anniversary since we last heard from the Major. Hope we get to hear from him again someday.