Cavalli EHHA

Quick update:

Replaced the output devices with the MJE234/243. In this application, the BJTs seem to be less bassy but a bit cleaner and less grainy. To my taste, an overall improvement.

I sent all my 6922's type toobz on tour with the Reduction, but between the 6GM8 (NOS ECC86 type) and the 6H30pi (production Sovteks), the 6GM8 is the obvious winner. More clear and articulate with a hint of that tube wetness. Only real positive of the 6H30pi is a bassier sound for those looking to compensate for something else, otherwise it's more compressed and "euphonic" sounding. 6H30 is closer to the euphonic and muddy sound that noobs and minions think toobz sound like, while the 6GM8 is closer to the clarity, plankton, and articulation we get with the best NOS tubes.

 

Have you tried the Toshiba BJTs, they were a significant improvement to my ears.

 

OJ , your findings make perfect sense.

I am sure you know this but for the benefit of those who don't and are reading this thread

The 6GM8 tubes were designed as field tubes for portable ham radios and optimized for use with batteries that ran at 25V. The earlier space charge tubes were early automotive and ran at 12V , they were nowhere near as linear but people managed to put them to good audio use (Millet Headphone amp = Millet Max)

These tubes worked on something called the "space charge" principle, which basically used the first grid after the cathode to accelerate electrons toward the weakly-charged plate which was working at lower plate voltage ( 12-25 vs 100 - 300)

The 6GM8 is thus running a tad hot in the EHHA but within it's spec and really optimal for this circuit. When you run a tube at significantly reduced B+ , the effect is to increase tube compression and this is exactly as you describe the 6H30 in this circuit. Alex designed this amp with the 6GM8 in mind and it's evolution (the Liquid Fire) increased the supply rails to +- 100V so that the 6922/6DJ8 tubes were optimized ( the reason for this is that the 6GM8's are not that easily available and as the LF was a commercial product, it needed current production tubes )

It brings to mind a thread I read earlier on SBAF regarding random tube rolling, it really helps to understand the operating characteristics of the circuit and know then be able to interpret why the various tubes sound the way they do and that sometimes, the tube being rolled has no place being forced into the socket pins ( Marv does an eloquent job of detailing why this is not a good idea )

I have heard about the Toshibas, iirc Saachi ran his with Toshiba output devices but in all honesty , I cannot recall the sound. The Mosfet vs BJT differences are just as OJ describes.

.dB

 

I do have a pair of these 2SA1943 and 2SC5200 but they don't fit the board footprint

 

I meant the Toshiba 2sc2238 and 2sa968. They come in a similar to-220 package although the pin out is reversed.
Not sure of their current availability though.

 

Magic! Who needs LISST!

 

epic !

 

Next level shit yo

 

man i wanna hear that it looks epiiiqqqqq

 

LISST sales go through the roof!

 

@OJneg : how does it compare to the tubes?

 

Another DIY LISST solid state rectifier in house:




vs Tube later.

 

Is that a half-wave rectifier?

 

@gurubhai - Your turn.

 

Its just a couple of diodes I wired up on a octal base in full wave configuration to be used in place of the tube rectifier.

 

So... Erm, why calling it a diy LISST?

 

I thought LISST was similar, or is it not ?

 

It's pretty trivial to replace a valve rectifier with a solid state one (and should absolutely be done!). Amplification valves (like the Schiit LISST) are whole different ballgame.

 

Post rectified.