ecc88 arcing at shutdown problem...

[kavermei]

Originally Posted by aardvarkash10

Electronic components (including cables) don't "break in". Some may undergo some rapid changes in the first few (milli)seconds of operation (caps and the like...) but other than that the only thing breaking in is your hearing. This process takes as long as it takes to talk your brain into liking the new sounds it thinks it is hearing.

+1

[pauldune]

Originally Posted by Gordy

Example of protection diode: More cathode follower stuff

Credit: J Broskie / TubeCad

The same can be used in your amp.

Thanks! I'm gonna look into that. But there's only a 3v difference between the cathode and the plate. Doesn't that mean that al ac signals larger than 2.3v (3-0.7) get their tops shaven off?

Does it make any sense at all to place a resistor before the ccs, so that drops already some voltage? (and functions as a limiter in power off)

[ErikdeBest]

Hi Pauldune

there is 'always' about 3V between the cathode and plate: it is about the polarization of the second valve whose cathode plate will always be at a higher value than its grid (which is at the same potential than the plate of the first valve).

Erik

[pointy]

sorry i just thought you many have had some new caps in the amp which were in need of a bit of veriac treatment.
this would have given the running-in like sound.

[pauldune]

Originally Posted by ErikdeBest

Hi Pauldune

there is 'always' about 3V between the cathode and plate: it is about the polarization of the second valve whose cathode plate will always be at a higher value than its grid (which is at the same potential than the plate of the first valve).

Erik

I really dont understand the fine workings of the dc coupled concertina with gain stage. Especially the bias-setting of the actual phase splitter eludes me. With ecc81 or ecc88 and the same resistors, still the same 7 mA, and same voltage.

Ive searched, but never found any good reads about it. Any tips?

[pauldune]

Originally Posted by pointy

sorry i just thought you many have had some new caps in the amp which were in need of a bit of veriac treatment.
this would have given the running-in like sound.

Strange thing is, i'm really shure the amp started sounding better... with the ecc81, i just had bought new supermatched 6201 (sq) And they sounded really good.
Then I put in the ccs and the ecc88's. Now about the "color" of the sound, i find that very difficult, and mostly my own mood is involved in how good it sounds. But the sound field, (focus/ depth/ imaging) thats another thing. With the ecc81 it was pretty good, but right after the change, it sounded just like my pioneer receiver; bad soundfield. Almost difficult to hear the "voice in the middle", and very clouded. instruments were not "loose" and not easy to differentiate.
And that, you can imagine, was a great dissapointment. especially because the THD in the concertina dropped 90%. (from about 0.5 to 0.05) Still have some spectrum analyzer shots of that.

I was already looking into changing the splitter to a LTP with CCS in the tail, when the sound cleared up. And now after 4 days, im going to order some Dale resistors, to replace the temp cheap metal film R's I put in, because the sound is now better than ever.

[aardvarkash10]

lol - you just described a move from relatively high distortion to relatively low. Your ears LIKE the high distortion spectrum they were hearing. Thats so common its a truism. We like distortion in moderate quantities. So it sounds "worse" because of the drop in distortion, not in spite of it. The effect is not helped by your expectation that things would sound "better" instead of "different".

In the interim, you have retrained your ears to like what you now hear.

Welcome to a brief and personal introduction to psycho-acoustics.

[pauldune]

Originally Posted by aardvarkash10

lol - you just described a move from relatively high distortion to relatively low. Your ears LIKE the high distortion spectrum they were hearing. Thats so common its a truism. We like distortion in moderate quantities. So it sounds "worse" because of the drop in distortion, not in spite of it. The effect is not helped by your expectation that things would sound "better" instead of "different".

In the interim, you have retrained your ears to like what you now hear.

Welcome to a brief and personal introduction to psycho-acoustics.

I really value your opinion, and maybe your right.

But I like to keep an open mind to things which are a bit mysterious, and dont want to prentend we know everything about sound/ amplifiers and related stuff.

And I like to think that the truth is somewere in the middle... I changed tubes, resistors and put some molten sand in the circuit. Maybe I had too high hopes. But the change is too much to just say "your ears got used to it"

Whatever... As long as i'm happy with the amplifiers, i guess it doesnt really matter.

[aardvarkash10]

Originally Posted by pauldune

whatever... As long as i'm happy with the amplifiers, i guess it doesnt really matter.

exactly!!!!

[Gordy]

Originally Posted by pauldune

Thanks! I'm gonna look into that. But there's only a 3v difference between the cathode and the plate. Doesn't that mean that al ac signals larger than 2.3v (3-0.7) get their tops shaven off?

Does it make any sense at all to place a resistor before the ccs, so that drops already some voltage? (and functions as a limiter in power off)

1.
Surely cathode 'follows' the grid. Grid rises with AC input signal and so cathode rises (approximately) the same amount also.

2.
The resistor may be a good idea. I think I have seen that done, but do not remember where.