6922 vs. 6N1P Bass Response

[Sherman]

Recently, as suggested by Simpleton, I removed the 6N1P's from my SE KT88 monoblocks and plugged in a pair of 6922's I had on the shelf. My first impression was good, it seem the 6922 sounded much like the 6N1P but I didn't listen to a wide range of music at the time.

This morning while listening I seemed to notice a lack of bass response. I tried a couple different CDs that I knew had substantial bass and they seemed lacking also. So I switched back to the 6N1P and voila, the bass was there.

I put a 6922 in one channel and a 6N1P in the other and there was a substantial difference between the two. I then swapped the sides the tubes were on and the bass response followed the 6N1P.

The 6N1P's are Svetlana with 'Winged C' logo, the 6922's are Sovteks. Both sets are new.

I have a bunch of questions that perhaps the experts here can answer.

1- Am I hearing a difference between tube types?

2- Between manufacturers?

3- Since I didn't re-bias for the 6922 is it running at a crummy operating point? (Simpleton, I think you told me that you didn't change the schematic for the 6922? What brand are you using?)

4- Could it be something to do with the Millar effect creating a sort of high-pass filter? (I'm still pretty much a newbie and need to get a better grasp of some of these things.)

5- Some other thing I haven't thought of?

Thanks for any feedback. Not a big emergency or anything but an interesting effect I might be able to learn from. In the meantime the 6N1P's are back in.

[cerrem]

Here are a few thoughts to keep in mind...
A tube does not have a frequency response per say...the tube can work all the way down to DC...
The circuit that the tube is built into dictates the overall behavior, one being frequency response...
So swapping tube types will have random results..... You need to examine the transfer function so you can see what the frequency response is and then change parts out to compensate...
For example...If you can swap wives of two "happy" couples, then the results could be devastating or could be awsome
The brain's frequency perception is a bit wacked, unless you have MANY years of training....
In electronic design 1kHz seems to be a reference frequency for audio comparison.... But I believe somewhere around 400 HZ is where the human brain likes to use as reference....
For example, sometimes a RISE in high frequency response can be percieved as loss of low frequency response..because the brain re-references itself ...if it is not well trained...
There are many variables here.....
Also when swapping tubes in voltage amplifying stages....the gm is critical in terms of the "sensitivity" of the music....

Chris

[Simpleton]

Sherman i'm currently using a Philps Miniwatt E88CC (i had a humming problem with a Valvo one).

Well, when i plugged my amp up for the first time, using my mom's living room and speakers, it didn't seem to lack bass, though i find it to have very little bass at the moment in another room with far from ideal acoustics with different speakers (some cheap but decent speakers, claiming 20 to 20KHz response).
I'm gonna borrow my mom's SS amp to see if it's a speaker or amp thing - you got me intrigued.

If you're right with your experimentations, i guess i'll have to buy a 6N1P from Germany

[dsavitsk]

Originally posted by Simpleton
If you're right with your experimentations, i guess i'll have to buy a 6N1P from Germany

They are not necessarilly interchangable in the same circuit. If nothing else, the 6N1P draws considerably more heater current (600mA to the 6DJ8's 365mA), so be sure your transformer is up to the task. here's a data sheet: http://www.mif.pg.gda.pl/homepages/f...112/6/6N1P.pdf

[Simpleton]

Yeah, mine was completely built up to Mikael's specs and a bit more on the PSU side

BTW, after my posting, i went to listen to the amp again, but using my portable CDP as source, since i modified the output stage of the cd player associated to the amp.
I noticed no differences from one CDP to the other.
I played an album from Eros Ramazotti with a bit of punch and sounded good. Probably the speakers themselves, will experiment further tomorrow.

I asked for advise to an enginner of Edonion, that projects tube amps (and also projected my output trannies) before changing the 6N1P for the E88CC for possible stresses on this tube, but he gave me the green light.

Sherman, do you have any other 6DJ8/E88CC from another brand?

[Sherman]

Originally posted by Simpleton
...Sherman, do you have any other 6DJ8/E88CC from another brand?

Unfortunately I don't have any other E88CC. I got the two I have for a project that I decided against. I may have to pick up another pair to try!

I think I'll also have to take some measurements which I didn't do today, voltages and current through the 6922's and compare them to the 6N1P measurements I have. I need to determine the operating point.

This is interesting and it is something I can learn from in a way that I can't from just reading data sheets and books.

[Sherman]

Originally posted by cerrem
Here are a few thoughts to keep in mind...
A tube does not have a frequency response per say...the tube can work all the way down to DC...

The circuit that the tube is built into dictates the overall behavior, one being frequency response...

There are many variables here.....
Also when swapping tubes in voltage amplifying stages....the gm is critical in terms of the "sensitivity" of the music....

Chris

I love the amps with the 6N1P's in them and don't want to tear them apart to experiment with this but... this has caught my attention so at the very least I'll have to measure voltages and currents and probably put the scope on them to compare outputs with each type.

[Original Burnedfingers]

I tried both the Sovtek and some JAN Phillips 6922 tubes in a preamp I have. The Phillips tubes smoked the Sovteks for low end and better midrange. The high frequency was about the same.

[amperex]

I tried a lot of different 6922 & the Siemens 6922 gold pin with A0 code plus grey shield were great. The tubes provided well controlled bass response & accurate mid/high frequencies.

[The Peasant]

When I subbed some 6N1P for the 6922s in my ARC SP9 MKII they didn't work at all, just produced some loud popping sounds!

It could well be the higher heater current, as the ARC has quite a small power transformer.

Take care,
Doug