"EF86" sound from 12AX7 tube?

[klobasa]

In this video (starting from 7:30) they discuss that the 2023 version of Bad Cat Black Cat had one significant chance: the EF86 tube was replaced with 12AX7, but they tweaked the circuit that 12AX7 would still sound like EF86.

Any ideas what did they do to achieve it?

I have no idea if it actually does sound like EF86...if it does, I want similiar changes to my amp. I have a older Cub 2, which has a rotary switch tone (ala Matchless), but it has 12AX7 instead of EF86.

https://youtu.be/w6OveFZ2Kf0?si=cDQbiwJre7Ikts0X

[didit]

Hello --

A cascode maybe? Or maybe not? A TAG thread on the topic.

Best ..

[martin manning]

Seems like they just got tired of dealing with the EF86's shortcomings. If I wanted to get rid of the EF86 while keeping its high gain, I would replace it with a twin triode configured as a cascode.

edit: thinking alike, I guess.

More discussion here: https://ampgarage.com/forum/viewtopic.p ... 14#p378314

[klobasa]

I don't actually need the massive gain of EF86, since I play mostly with clean tones. IME there are just some magical harmonics in the EF86 sound that is often missing with 12A_7 preamps.

[didit]

I don't actually need the massive gain of EF86, since I play mostly with clean tones. IME there are just some magical harmonics in the EF86 sound that is often missing with 12A_7 preamps.

For baffling (un)reason, in the "voodoo of MI amps" bubble, the equation "gain == distortion" and "gain != clean" holds majick powers. Not strictly so, though "hi-gain" designs inevitably rely on several layers of stacked gain. That said, tuning a cascode to twinkle like some small signal pentodes proved somewhat elusive, at least according to reports by those venturing few who've walked that circle looking for a heffalump. Maybe Bad Cat has?

Best ..

[TUBEDUDE]

Seems like they just got tired of dealing with the EF86's shortcomings. If I wanted to get rid of the EF86 while keeping its high gain, I would replace it with a twin triode configured as a cascode.

edit: thinking alike, I guess.

More discussion here: https://ampgarage.com/forum/viewtopic.p ... 14#p378314

The obvious fix is to use a different pentode, say the 5879, which was made for audio. You'll see it in several boutique amps. It is my favorite to use as a distortion generator, but i use it as an input tube also. You'll recognize the sound.

[bepone]

many pentodes are good for audio.. i also like EF86 and there is no any problem there if the tube is made well (using german brands)

[two tone]

Actually the Top Boost Vox installed later, comes pretty close to the tone of an EF86. (set the Treble and Bass Pots to zero or very low)