E80CC

[SoundCity85]

Scored a nice batch of tubes a couple of weeks ago, and today discovered a few more gems. Three pieces of E80CC with gold pins, one of them with pinched waist. It seems to be more or less a direct replacement of ECC82, with two major things to consider, it pulls 0.6 A instead of 0.3, and max voltage is 250V. But besides that, it seems to have the characteristics of a good tube. I'm considering a two channel SLO-100 build, but haven't decided on the schematic yet. I'm using Partridge transformers that I know can pull 6 ECC83s without a problem, moreover it can handle 6x EL34, while I'll convert it to 4x EL34. So I guess when I make sure voltage is not more than 250V, it's harmless to use them for this situation. So the question is, where can I make it shine in this concept? The SLO seems to be using a lot of attenuator resistors to drop the signal level, so I was guessing why not go for a lower Mu tube and skip the attenuator  ?

Cheers

[DummyLoad]

AV = 27 ; ra = 10KΩ ; gm 1.7mA/V

seems like they'd do nicely in long tail pair duty.

--pete

[HotBluePlates]

... The SLO seems to be using a lot of attenuator resistors to drop the signal level, so I was guessing why not go for a lower Mu tube and skip the attenuator  ...

High-gain master volume amps have had a lengthy period of evolution.  It seems one of the core lessons was "a bunch of dirt in one place doesn't sound as smooth as a little dirt in a lot of places."

There are voltage dividers (those "attenuator resistors") between each gain stage. The drive signal is made large enough to get one stage to "add a little distortion" but the amplification of that stage delivers too much signal to the next stage (i.e., the next stage distorts too much, and harshly).  So the voltage divider knocks the signal level down to an appropriate level to get "just a little more" added distortion in the subsequent gain stage.

Rinse & Repeat, until the distortion is thickened up.

Tone is in the ear of the beholder, but I think you'll find the SLO is more about exploiting a 12AX7's tendency to distort when operated in a certain portion of its characteristics & with a certain amount of applied signal, and less about the interstage voltage dividers.  12AU7 or E80CC will probably require a complete re-think of the approach.

[SoundCity85]

Thanks both of you. Don't mess around with the ECC83 in the concept, but possibly consider it for the PI then. Need to dig into the Chapter 9 of Merlins book again

[HotBluePlates]

... Need to dig into the Chapter 9 of Merlins book again

It's worthwhile to try it out and hear for yourself whether you get the results you hoped for.

Dummyload has "tried stuff out" a lot more than I have.  But I've also tried some of my "bright ideas" and found the fell flat.  Practical experience goes hand-in-hand with the theory that explains the experience.

[SoundCity85]

As a chemical engineer, working in R&D, I've learned that understanding the theory is also needed to obtain good experimental results, because surely not all experiments give good results, and you need to understand where the tweaking needs to happen to make things work the way it should :-)

But yeah I see your point, there is no harm in just trying it (only gotta make sure I'm under 250V on the PI)

[PRR]

> gotta make sure I'm under 250V on the PI

250V on the tube is not 250V from the power supply. Tube typically takes half. So a 500V rail is not obscene, though inconvenient in other ways.

I also don't think 250V is an instant-BANG spec. The ratings are for small-signal (radio) and HIGH reliability. If you need large signals, treat it like 12AU7/12AT7... it's probably the same stuff inside.

[DummyLoad]

> gotta make sure I'm under 250V on the PI

250V on the tube is not 250V from the power supply. Tube typically takes half. So a 500V rail is not obscene, though inconvenient in other ways.

I also don't think 250V is an instant-BANG spec. The ratings are for small-signal (radio) and HIGH reliability. If you need large signals, treat it like 12AU7/12AT7... it's probably the same stuff inside.

Va max is stated to be 300V, Vao is 600V. (absolute max. rating system).   


--pete

[SoundCity85]

> gotta make sure I'm under 250V on the PI

250V on the tube is not 250V from the power supply. Tube typically takes half. So a 500V rail is not obscene, though inconvenient in other ways.

I also don't think 250V is an instant-BANG spec. The ratings are for small-signal (radio) and HIGH reliability. If you need large signals, treat it like 12AU7/12AT7... it's probably the same stuff inside.

Indeed I forgot the plate resistor. Thanks for pointing that out to me

[HotBluePlates]

> gotta make sure I'm under 250V on the PI

250V on the tube is not 250V from the power supply. Tube typically takes half. ...

Va max is stated to be 300V, Vao is 600V. (absolute max. rating system).

I forget the wording, but I thought "Vao" is "max supply voltage" or "max plate voltage at zero plate current."

Either way, the data sheet is telling you the tube won't arc at 301v.