Can anyone recommend real power pentode for audio other than EL84 and EL34? Ones that are not scarce like European's EL60 or 4699.
There are some threads that suggest beam power pentode but I'm looking for real pentode in affordable price. Thanks in advance for your help 🙂
There are some threads that suggest beam power pentode but I'm looking for real pentode in affordable price. Thanks in advance for your help 🙂
I bought JJ 6CA7's in 2011. Matched quad. They were fine, produce the >17 Vac into 8 ohms I expect out of my stock ST70. A little more glass, a little different spec sheet than an EL34. Mine were made in Slovakia.
GU50. Its built like a tank. and very conservatively rated. their plate structure and the thick high temperature glass suggest these tubes could be used at higher power then their 46 watt rating (40 anode 5 screen grid 1 watt G1) suggests.
kind regards.
V4lve
kind regards.
V4lve
@Ketje
Thanks for EL506. It looks interesting.
@indianajo
I thought 6CA7 is a beam pentode but it's actually real pentode. Thanks for the reminder!
Other suggestions are welcome 😀
Thanks for EL506. It looks interesting.
@indianajo
I thought 6CA7 is a beam pentode but it's actually real pentode. Thanks for the reminder!
Other suggestions are welcome 😀
They sell it like a replacement of the EL34, IT'S NOT !
For the data you can use those from the 7591 tube (very close).
The base is like this,
Attachments
@v4lve lover
Thanks for your suggestion, however GU50 seems to have low screen grid rating. I'm looking for pentode that can be used in Ultra-Linear mode. Have you tried it before?
Thanks for your suggestion, however GU50 seems to have low screen grid rating. I'm looking for pentode that can be used in Ultra-Linear mode. Have you tried it before?
An old favorite of mine is the EL41. I tried it once in SE triode. Close to 1W output and I loved it 😎. It is a smaller ancestor of the EL84, rated at 9W and just about every European factory made it. Rimlock base.
Haven't tried it yet, but the EL90 Is a 12W pentode in a 7pin miniature base. Often listed as equivalent to the 6AQ5, but that one is smaller and a beam tetrode.
Go big: EL156. 50W pentode made only by Telefunken. There is a Chinese copy with an octal base.
Haven't tried it yet, but the EL90 Is a 12W pentode in a 7pin miniature base. Often listed as equivalent to the 6AQ5, but that one is smaller and a beam tetrode.
Go big: EL156. 50W pentode made only by Telefunken. There is a Chinese copy with an octal base.
Almost forgot the EL38: 25W pentode for sweep duty. Top connection for the anode, meaning a very high voltage rating. I used it in PP screen drive with good sounding results.
A real power pentode? Are there unreal ones? 🙂 Or do you mean a power pentode that's not a beam power pentode?
4P1L is a directly heated power pentode. Supposed to be pretty good - especially in triode mode.
~Tom
4P1L is a directly heated power pentode. Supposed to be pretty good - especially in triode mode.
~Tom
@tomchr
Thanks for your suggestion. The real pentode I'm looking for is pentode with suppressor grid wire rather than beam (which I think it's called beam pentode... or beam tetrode?😕). Also, my goal is to use it in ultralinear mode.
Thanks for your suggestion. The real pentode I'm looking for is pentode with suppressor grid wire rather than beam (which I think it's called beam pentode... or beam tetrode?😕). Also, my goal is to use it in ultralinear mode.
It's hard to beat the EL34 and EL84, when selecting true, 3 grid, power O/P tubes, for use in combination with ultralinear mode. They have tough screen grids. Another nice "12" W. true pentode is the 6CH6/EL821. Here, g2 is not especially tough. So, put 1 KOhm resistors in the lines leading to the UL taps on the O/P trafos, to ensure the g2 dissipation limit is not exceeded.
If you have the requisite "deep pockets", custom O/P "iron" with tertiary separate screen grid windings is THE way to go. You get the local NFB of UL mode and the benefit of regulated g2 B+.
If you have the requisite "deep pockets", custom O/P "iron" with tertiary separate screen grid windings is THE way to go. You get the local NFB of UL mode and the benefit of regulated g2 B+.
In UL, G2 is wired to the UL tap from the OPT. So you can use beam power pentodes/tetrodes for ultra-linear operation as well.
~Tom
~Tom
Do you mean suppressor grid (G3)? An UL OPT already has a wire for G2. G3 is normally connected to the cathode. Or am I missing something really fundamental here?
Which turns ratios do you recommend for the G2 and G3 taps?
~Tom
Tom,
With separate screen grid windings, regulating g2 B+ is feasible. It's still UL, as the tertiary g2 winding is a % of the plate winding. It's well known that max. open loop linearity in pentodes occurs, when g2 B+ is regulated at a fraction of anode B+. Having a separate tertiary g2 winding allows the cake to be eaten and retained, simultaneously. In "standard" UL "iron", g2 B+ can't be regulated. "Money talks and bull$hit walks."
The handling of the suppressor grids is unchanged.
With separate screen grid windings, regulating g2 B+ is feasible. It's still UL, as the tertiary g2 winding is a % of the plate winding. It's well known that max. open loop linearity in pentodes occurs, when g2 B+ is regulated at a fraction of anode B+. Having a separate tertiary g2 winding allows the cake to be eaten and retained, simultaneously. In "standard" UL "iron", g2 B+ can't be regulated. "Money talks and bull$hit walks."
The handling of the suppressor grids is unchanged.
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