Tube DIY Asylum

Connecting Diodes on a 6AV6.........?????

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In Reply to: RE: 6SL7 posted by GeorgePope on March 20, 2017 at 09:30:46

A normal E.E. will tie the diodes to ground. LOL, one good EE I trust has already told me to do so. Another tells me, last night, the two diode sections, tied to ground, will lose high end, more-so than when tied to the plate. I don't know who to listen to for sure.

Separate point: you fail to look at the driver requirement in any realistic way George. I hope you realize, I am talking about a two stage amp that is directly coupled, Driver's plate to Finals control grid?? This makes for an ease of driving the Finals, being a direct couple. If it were a cap couple, ( the worst way to couple two stages ) you would be correct. If it were to be a transformer couple, ( far better than a cap couple ), you may still be a correct. But I am talking of NO devices at all to " drive through " between the two stages , except a few inches of high quality wire, silver, silver coated, etc, etc.

Direct coupling greatly eases the burden on the initial driver stage. A huge percentage of DIY amps in the Orient are Loftin White varients, over several decades now, mainly....because it sounds good. Isamu Asano, Nobu Shishido, all used mu of 100, low current triodes.

An EE type will typically look at it from their textbook basis only - in term of maximum swing as it approaches 0 VDC of bias. That is hardly how the circuit operates!!!

You are correct about when "approaching zero" , but you are considering the wrong things !! Its like a MD operating on Cancer, when all the patient really needed is to eat fresh fruits and more vegetables.

In the real world, 99.999 percent of the time, the tube is centered at about 1.5 VDC of self bais, running maybe -1 to -2 VDC of bias, playing music at normal ( even loud ) levels in the home. I design and optimize for that parameter, normal use on a 98 dB ALTEC VOTT or ALTEC 604.

I doubt you have listened to such a circuit as I describe, much at all.

From your comments, and understanding,you certainly wouldn't ever design it, because it would require thinking outside of the box. Most trained E.E.s can not mentally do that, due to their schooling and training. poor fellas !!

It is clearly more fun listening-wise, executed as good as possible, when the mu is 100 and NOT a mu of 70 !! Herb Reichert "got it", when he used the term " presence " of the performers in the room, at normal listening levels - at RMAF 2016 last October. I was there in the room. A mu of 70, or 50 driver, can't do that.

You likely have no experience at this. I have substantial listening experience of this George.

When looking at a 12AX7, 6AV6, or a 7B4, as a DCed 2A3 driver, and also throw in your 6SL7, I would suggest all four are very similarly and nicely linear, in the ranges they will operate in for this circuit, 99 percent of the time. I am excluding " zero bias " conditions, because it is simply backwards to what occurs in the real world use George.

So...get with it, think out of the box, not textbook and formula rigid . The truth will set you free. Results is what counts, not formulas and half-baked theory !!!

As for the question of what to do with the 6AV6 diodes, tie them to plate or ground, I am entirely "open" to see what others, who think they have an answer, have to say about this.

I have not yet used the tube, plan to, driving a Type 46, next month for two friends' DC amps, and I would be open to LEARNING from others. on what to do with the two diodes.

So far, two people I respect, have given me opposite answers. What do I know ??? I was a business major.

Lets see what smarter than I, more experienced people than I, suggest !!

Thanks,

Jeff Medwin

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