6922 vs 6SN7

[Dworin]

You're no doubt right and I'm not trying to be argumentative, but I don't understand. At 10 mA I read:

1 V - 70 V
2 V - 98 V
3 V - 126 V

Doesn't that mean it's pretty linear?

Henk

[SY]

It actually helps to set one up and measure it, but let's go with the curves. We'll pick a slightly smaller swing but at the same points.

At 10mA:

-1V 70V
-1.5V 86V
-2V 98V

Variable mu in action.

[Dworin]

Ok, thanks for clearing that up for me.

[Bob Richards]

Originally Posted by Positron

Hi Sy,

I think another test I performed years ago might shed some more light on the importance of high frequency response.

I was testing a phono stage and decided to see the relative sonic difference between -1db at 200khz and +-1db at 150khz. (I know, well above the cutter head response, f6 point.) Anyway it was relative.

The added capacitance was just a few pf. There was an immediate sonic change all the way down through the bass. Clear as a bell difference.

I am guessing here, but -1db at 150khz would be about -6db at 500khz. Correct me if I am wrong, or not accurate enough.

200khz -1db, about 670khz at -6db.

Anyway, I thought this might help to demonstrate the importance of high frequency response.

I see some ****, so I guess that is where I said hogwash? I see 45 is also next to 6H30.

I can't imagine hearing a difference between 150kHZ and 200kHZ -1dB BW period. But, what might be going on here (that I just read about in the Morgan Jones book) is that the self inductance of MM cartridges is often designed to work with the loading capacitance to create a slight extension of the otherwise drooping high end response. It forms a resonant circuit, much like a bass reflex speaker does at the low end. But if the capacitance is off at all, the result can be pretty damaging, and possibly cause psyco-acoustic effects all across the spectrum.

[Positron]

Originally Posted by Humdinger

I can't imagine hearing a difference between 150kHZ and 200kHZ -1dB BW period. But, what might be going on here (that I just read about in the Morgan Jones book) is that the self inductance of MM cartridges is often designed to work with the loading capacitance to create a slight extension of the otherwise drooping high end response. It forms a resonant circuit, much like a bass reflex speaker does at the low end. But if the capacitance is off at all, the result can be pretty damaging, and possibly cause psyco-acoustic effects all across the spectrum.

A couple of areas could cause this. First, though, the equalization is not located such that cartridge loading was affected.

Second, a change in overall system risetime occurs which the ear is sensitive too. Jneutron (FermiLab, Brookhaven National Laboratory) has posted information concerning this subject on AVS forum some time ago, and Dr. Kunkur published his research a couple of years ago. Third, Japanese research, using PET and EEG scans has also measured (through ear/brain's activity and not bone conduction) ultra sonic musical stimuli between 22khz and approx. 50khz, the high frequency limit of the test.

Cheers.

[Thatch_Ear]

I found this doing a search as I am using a 6J5 as the amplifier in a SE 6V6 amp. The 6J5 6SN7 are directly descended from the 27 triode that was used in thousands of radios just by itself. The 6SN7 itself has been made since the late 30s and some of the best are the ones made in WWII, probably by the hands of women, using chemicals that can only be used in China who is trading their environment in a bid to own the agriculture lands of the world, since theirs is already ruined. Sorry, I shouldn't say a thing, but the fact is that this tube has been in production for longer than most people with good health care live. It is a rugged tube and has a thousand flavors. With the Hickock Cardomatic tester there are 2 tests, one per side.
6DJ8s on the other hand use 4 cards and have 8 tests and most fail, and most of the ones that don't sound like electric turds. The fact is that they are easy to design around and a good pair of NOS Amperex 7308s will cost as much as an exellent pair of power triodes and probably won't last near as long.
I pulled a bunch out of some old TeK O'scopes and even the ruggedized GE Mil Specs had about a 75% fail rate, the Amperex BB had about a 5% pass rate and those were replacement tubes put in during an overhaul of the scope. They have a place but I will never buy anything that has one in it, I will never build anything that has one in it. They have too many things that WILL go wrong with them, a good sounding pair will run a good $250 for NOS JAN Amperex 7308s and VT-231s are some of the best dual triodes ever built and you can run them for years and they will still sound great, test strong and the fail rate is way down there.
I have the slightly higher gain 6SL7s driving 300Bs and the RCA VT-229s have been in there 8 years and still out perform any other 6SL7s I have tried. They probably had thousands of hours on them when I got them. The stuff made in WWII for the Boys was and is the best of the dual triodes you can use to amplify a CDP directly to the power tubes.
Then you have the 100s of other very good ones made all over the world, and are still being made today.
Dollar for dollar the money spent on a 6SN7, 6J5, 6C5, 70 , 27 will get you more for less than the 6DJ8 family of high failure rate, mostly not very good sounding, easy to use in designs, tubes.
You want to find out about tubes talk to anybody who tests a lot of them as well as listens to them.
There are always going to be some of any kind of audio tube that is great, but if you put down $250 for a pair of dual triodes, don't you want them to last for as long as you want to listen to them?
Having to scrounge and get old gear for pulls a failure rate of 75% vs 5% says more about build quality of a type than almost anything else.
Most of my 6V6s are RCAGTs with the graphite inside that came out of Hammond organs built in the 40s and I think that the average test on those was 75 out of 100, failure rate about 3%. That is better than fair.

Thatch

[Bob Richards]

Thatch, I've heard that a lot of 6DJ8's are noisy as well. In my present preamp design I'm using one 6922 and one 6SN7 for voltage gains (so have different ring frequencies if that's an issue), and 6922 for follower output buffers (the high transconductance makes them better), all with current sources. The voltage gain stages will have Gary Pimm I sources with their "mu" outputs, so the stage becomes a mu follower if I'm not mistaken. I've looked at the distortion spectrum shape to see if putting the Gary Pimm FETs in the circuit do any damage. They did no damage at all. A self biased follower with a IXYS constant current sink also has the very best of distortion spectrum shape (output buffers). You can Google Gary Pimm to learn more about his self powered CCS if interested. Using the low-Z "mu" output reduces noise in the following passive tone control circuit (James). This seems like the best route to go for a line level preamp with tone controls. Minimalist, but not lacking anything desirable.

[v4lve lover]

its common knowledge . that a mini can NEVER be that good as a octal
course in miniaturization the linearity is sacrificed .
plus WHY would you put anything in a amp that does not glow as pretty as a 6sn7 ?

course really 6dj8 is no audio tube .

[SY]

Originally Posted by v4lve lover

its common knowledge . that a mini can NEVER be that good as a octal
course in miniaturization the linearity is sacrificed .
plus WHY would you put anything in a amp that does not glow as pretty as a 6sn7 ?

course really 6dj8 is no audio tube .

Wrong on all counts.

[v4lve lover]

i just like the 6sn7 and dislike the mini hero 6dj8

QUOTE .
The age of tube developments has ended around 1936. it was just further refinement and miniaturization. Even miniaturization was often done at the costs of good tube curves. Of course many famous tubes were made after 1935, but the real kings and queens are from before that date.

no offense but i think its pretty bad people are spending small fortunes on scope pull 6dj8
while there is so much choice .

edit please . if im wrong educate me .
you learn from being embarrassed .