5687 v.s. 6922 preamp/xover

[mashaffer]

For hifi preamp and crossover service with emphasis on low Zout, noise and microphonics which of these tubes (or similarly priced tubes) do you fancy and why. Assume 12.6v filiment xformer so 6922 tubes will have to be series heaters.

mike

 

[Shoog]

My small experience is that the 5687 is superior in sound to the ECC88. However the 5687 is slightly more demanding of setup with regard to hum. I have seen a few people tearing their hair out trying to solve hum problems with the 5687.

Hope that helps.

Shoog

 

[dsavitsk]

For hifi preamp and crossover service with emphasis on low Zout, noise and microphonics which of these tubes (or similarly priced tubes) do you fancy and why. Assume 12.6v filiment xformer so 6922 tubes will have to be series heaters.

I have become less and less enamored with the sound of the 5687 of late. They are generally better than a cheap 6dj8, but maybe not as good as a good one? Maybe I've only tried cheap ones.

Anyhow, another tube to look into is the 8416. It is a 6922 with a 12V heater. As far as I can tell, the only available model is an Amperex which is the bomb. T think they compare to Amperex tubes that can cost upward of $150 per. I just bought 3 for $10.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=97503&highlight=

Other benefit is that the pinout is more generic, so you can experiment a bit more.

Oh, another one to try might be the 12AT7 -- see Tubelab's SimpleSE for more.

 

[DougL]

For hifi preamp and crossover service with emphasis on low Zout, noise and microphonics which of these tubes (or similarly priced tubes) do you fancy and why.

I believe that this is circuit dependant. For CF or White CF service, the 6922 is excellent. For common cathode operation, the 5687 may be a better choice. Can you give us a better idea of the circuit?

Doug

 

[Shoog]

I have become less and less enamored with the sound of the 5687 of late. They are generally better than a cheap 6dj8, but maybe not as good as a good one? Maybe I've only tried cheap ones.

What are you starting to dislike? I'am just about to use a 5687 as an interstage transformer driver - i'am curious on your thoughts.

Shoog

 

[dsavitsk]

What are you starting to dislike? I'am just about to use a 5687 as an interstage transformer driver - i'am curious on your thoughts.

Shoog

The ones I have, and I am comparing them against a pair of WE 417A's which is probably totally unfair, seem to lack the liquid/detailed midrange of some other tubes. But, as I say, the ones I have are cheapies (1986 manufacture JAN's) which may account for this. I also have some 1950's CSF's (http://thetubestore.com/nos-5687.html) which are better, but I have not spent enough time with them to see how much better they are. They still aren't as nice as the 417A's.

 

[Shoog]

I've heard them described as "dark" sounding, which would probably equate to lack of midrange sparkle. I found them very punchy, which is just what I need for my application.

Shoog

 

[cotdt]

for such an application, wouldn't it be better to use opamps?

 

[dsavitsk]

for such an application, wouldn't it be better to use opamps?

Are you trying to get yourself banned?

 

[cotdt]

Are you trying to get yourself banned?

what kind of question is that? i'm just posting my honest opinion, which is that opamps are quieter and better for this application.

 

[Zen Mod]

for such an application, wouldn't it be better to use opamps?

741 fer sure ;

 

[dsavitsk]

what kind of question is that?

Jeez ... it was a joke which you can tell by a) the wink and b) the humor.

 

[Wavebourn]

I don't understand guys when you speak of frequency responses of tubes, especially in such narrow band like "bass response", "midrange"... All I know, it depends on the application only. However, tubes have different inter-electrode capacitances, but they affect highest frequencies only, depending on source and load resistances.

 

[mashaffer]

I believe that this is circuit dependant. For CF or White CF service, the 6922 is excellent. For common cathode operation, the 5687 may be a better choice. Can you give us a better idea of the circuit?

Doug

The circuits will be quite simple CC circuits. Initially RC coupled. This is dual purpose excercise. 1. to get tube experience and 2. initial work on HT preamp project. Thus one reason for not using opamps. If I can't get the Zout that I need with CC I may end up with some CF outputs but would rather not. That is why I want low Rp.

Now that I have this project I may go ahead and use discreet sand for the expression pedal for my keyboard since I have all those parts lying around.

have become less and less enamored with the sound of the 5687 of late. They are generally better than a cheap 6dj8, but maybe not as good as a good one? Maybe I've only tried cheap ones.

Anyhow, another tube to look into is the 8416. It is a 6922 with a 12V heater. As far as I can tell, the only available model is an Amperex which is the bomb. T think they compare to Amperex tubes that can cost upward of $150 per. I just bought 3 for $10.

http://www.diyaudio.com/forums/show...7503&highlight=

Other benefit is that the pinout is more generic, so you can experiment a bit more.

Oh, another one to try might be the 12AT7 -- see Tubelab's SimpleSE for more.

Thanks I will check those out as well. 8416 is interesting.

mike

 

[Shoog]

Heres a personal observation about the 5687. Previously I have always had real problems with my 5687 and hum so I always went DC on the heaters. Today I used a 5687 in my PP amp and used AC with no particular precautions except I added a 100R anode stopper. Absolutely no hum or noise.

So I think the 5687 may be prone to instability and needs an anode stopper. I say this in light of an experience I had with driving a Gainclone with a 5687 preamp. It got significantly hotter than normal, I never really paid it much attention as I never used the combination for long. It does however suggest that there may have been high frequency instability.

By the way - the PP amp has a fantastic clean sound !!

Shoog

 

[Tweeker]

What was the grid stopper on the 5687? Was the 100ohm anode stopper paralleled by a coil?

 

[Shoog]

1K on the grid. No coil in parallel on the anode.

Shoog

 

[mashaffer]

Not sure that I understand the anode stopper. Was the 5687 used for voltage amplification or phase splitter duty? Was there a plate load resistor also or was this a topology with no anode load? Or are you saying you took the output to the next stage between the stopper and the plate load?

mike

 

[Shoog]

The 5687 is driving an interstage transformer in a in a parafeed setup. The 5687 is load with a CCS, though I do not think that it would matter if this was a plate resistor. There is a flying lead between the anode pin of the 5687 and the CCS/resistor. The plate stopper is added directly to the anode pin and is their to stop the flying lead from turning into a transmitting of recieving antenna. The anode stopper could be anything from 10R to 100R and could have 10 turns of enamelled wire around it.

Hope that helps.

Shoog

 

[mashaffer]

8416 data

Having a devil of a time finding a data sheet for 8416. Can anyone help me find one?

mike