[tourmaline]

Quote:

Originally Posted by geoges.ravel /img/forum/go_quote.gif Hi guys, sorry for not responding for a long time. I was busy chasing the tubes. I don't know why the thread alert doesn't work. Now I've gotten some Tungsol 6SL7GTs and see why people said what they said about the Cary. It does sound beautyful! And I would like to thank all you guys helped me figure out the problem. (A special thank goes to Sergei who helped a lot!) Now let's start another round of quest. But before that I need to mention that my Cary is a 1994 version so quite old. No that it sounds great, but there is very annoying hum problem. headphone is usable only at a very high level. With speakers, I have to raise the volume to cover the hum but that's OK. The volume of the hum is unrelated to the change of volume or sources. I tried swapping the tubes: with the 6SN7EH, hum is much less severe but I prefer the Tungsol with hum than the ElectroHarmonix without hum. I have no idea where the hum comes from, is it related to the tubes or it is amp? Would it be possible to fix it by replacing parts or something? If it is basically caused by the tubes, what tube do you think has the most effect on that? The driver (6SL7), input(6SL7), or output(300B) tubes? If it is the output tubes I'll not be able to experiment since I have only one pair of them. Please help guys.

That's because you swapped the tubes and they might have different specs, so other tubes then originals might have some hum from the powersupply.

 

[Skylab]

Quote:

Originally Posted by geoges.ravel /img/forum/go_quote.gif No that it sounds great, but there is very annoying hum problem. headphone is usable only at a very high level. With speakers, I have to raise the volume to cover the hum but that's OK. The volume of the hum is unrelated to the change of volume or sources. I tried swapping the tubes: with the 6SN7EH, hum is much less severe but I prefer the Tungsol with hum than the ElectroHarmonix without hum. I have no idea where the hum comes from, is it related to the tubes or it is amp? Would it be possible to fix it by replacing parts or something? If it is basically caused by the tubes, what tube do you think has the most effect on that? The driver (6SL7), input(6SL7), or output(300B) tubes? If it is the output tubes I'll not be able to experiment since I have only one pair of them. Please help guys.

This could well be an issue with the specific tubes you got. It would be best to get one more pair of 6SL7GT's and try those. I can sell you a decent set of NOS Sylvanias cheap if you want, PM me.

Quote:

Originally Posted by tourmaline /img/forum/go_quote.gif Voltage might difffer, there is also the ecc82 as so called known substitute for the 6sn7 but it draws considerably more current and you could fry your amp!!!

First of all you meant ECC32, not ECC82

And second, his amp needs 6SL7's, not 6SN7's

 

[nikongod]

Quote:

Originally Posted by geoges.ravel /img/forum/go_quote.gif (snip) Now let's start another round of quest. But before that I need to mention that my Cary is a 1994 version so quite old. (snip)

Good to hear the amp is working better. When that amp gets going full speed, it is very very nice.

As a somewhat educated wild guess, the hum COULD be heater hum if you have AC heaters. I would personally try different tubes (although just switching the positions may help) and/or tube dampers. IME tube dampers are a SMALL help against tube microphonics, and heater noise but if you go cheap (hi-temp silicon o-rings) worth the experiment.

 

[daleda@sbcglobal]

Sorry to tell you that the "hum" is a fact of life with the older 300 SEI's - mine went back to Cary and it returned with the hum intact. No amount of tube rolling ever cured it! It is one of the main reasons I sold mine - best of luck with a cure. For an amp of this caliber a less than black noise floor is unacceptable IMO.

 

[geoges.ravel]

I tried to let the amp have its own wall socket and the hum reduce considerably. (And the outlet does not have a ground!) I'll try to find an outlet with ground to see if it gets any better.

Now the hum is tolerable through the headphone and is completely covered by the music through the speakers. I'll have my RCA 5691 tubes arrived this evening so I can have test to see if it is the tube.

nikongod: I'm very interested in what you are saying but I con't figure out what you mean

.

"if you have AC heaters" : how can I know that?
Also I currently using tungsol 6SL7TG with heater current of 0.3mA
the 5691 have 0.6mA heaters current. So can I use the 5691 safely or should I ask cary for confirmation (I feel it is painful even for them to find out the information related to my version)

 

[geoges.ravel]

Ok, I tried the 5691 on the Cary and now I'm pretty satisfied with the sound. Hum is further reduced, bass is tight and high is smoother. Now I'll give it a pause to my quest and reward my self with some good music.

Cary told me that the amp can handle any of the heater current, so it cool. Now I feel confident to try some AKG K1000 and bidget high efficiency speakers (Zu Druid for example).

Thanks again to everybody!

 

[mikeymad]

Very cool geoges.. I am glad you stuck with it... and you were rewarded with good sound for doing so...

Now we can really say Welcome to the 300SEI club...

Cheers,

 

[jamato8]

The Sylvania 1952 to 53 are very, very good. I was lucky and picked up 16 nos a few years a ago along with the same number of 1952 Sylvania 6SN7's. The 6SL7's 1952 have good detail, fast bass that is deep and natural mids. I find little to fault with it.

 

[MIREKFR]

Plese advice speakers(monitors also)-Cary 300SEI(300B),only holders or former holders CAD- 300SEI.

 

[herbie12389]

Haters gonna hate, ballers gonna ball. The 300 sei is a great headphone amp... god knows what else you have going on your system to give you such a poor review... shame sir

 

[jdmeyers77]

To my ears, my Cary 300SEI with NOS tubes is the finest head amp I have ever heard with Senn 800s and the T1.  And I've owned quite a few high end tube head amps.  As well, it drives my big Spendor loudspeakers with sublime elegance.  YMMV!

 

[MIREKFR]

help, I need an amplifier diagram CARY CAD-300-SEI