Blumenstein and Stereomour

[thdewitt]

OK, First, thank you to Clark and Molly at Blumenstein Audio.  They have been fantastic.  From advice on the type of amp, to speaker placement, to just talking me through their offerings.  Also, the craftsmanship and service are second to none.  I absolutely love my new Orca Deluxe's and Dungeness sub.  For me they are a piece or art that will live in my house as long as I do.  My only concern now is what am I going to buy from them next.  I see some great new products on the horizon.  Probably will pick up a second Sub ASAP.  Clark is currently working on my amp bases for my Crack, Stereomour, and Submissive in Chocolate Bamboo to match.  They system will look sweet when they arrive and I will post some pictures.

BACK to MY QUESTIONS about hum on my Stereomour.  I am a big dummy.  I figured out that the probes on my Oscilloscope where set to 10X but my scope was set to 1X.  After testing on both my scope and my Fluke Meter with the proper settings, i am getting readings of about 1.5 mV after adjusting the Hum pots. 

Grainger and all.  Is there something to look for that would cause this?
Answers to your questions:
I am sure I am testing AC mV on all the right settings.
I am shorting with RCA Plugs as recommended in one our your posts. (I cut up an old RCA twisted together and soldered.
I do have the hum when using shorting plugs.
Also, I do not get any hum in the sub when it is not connected to the Stereomor.  When I connect one speaker side the hum starts, gets louder when second side is connected.
If I adjust the pots with the speakers connected I definitely get to a clear minimum as asked by Paul.
I have looked closely at all solder joints.  I have reflowed any suspect joints.  I have tested the continuity on all the grounds in the circuit and they seem to be fine. 
Could there be a problem with the tubes?
Not sure if I should do anything else or just leave it alone and enjoy the amp/speakers with a slight hum.

Tom

 

[Paul Birkeland]

  After testing on both my scope and my Fluke Meter with the proper settings, i am getting readings of about 1.5 mV after adjusting the Hum pots. 

That sounds about right.

Have you set the levels on your sub amps?  If they are up all the way, then the level of hum will appear to be artificially high.

-PB

 

[Doc B]

Another potential issue is that the subs may be sitting in a spot in the room that is accentuating the hum. You might try moving them around a little to see if you might be setting off a room mode where they are now. Usually moving them about a foot at a time is a reasonable.

 

[thdewitt]

Have you set the levels on your sub amps?  If they are up all the way, then the level of hum will appear to be artificially high.

-PB

Yes, When I adjust the sub gain to the 10 O'Clock position recommended by Clark the hum is minimized but still slightly audible. 

When the system is first turned on, the hum starts very loud and then reduces for a few seconds to barely audible.

Tom

 

[Natural Sound]

Remember, the Stereomour has AC heaters. It will never be perfectly quiet. I have a pair of the discontinued Paramour II amps. The circuitry is similar and I even upgraded the iron to use the Stereomour/S.E.X. iron. I had 2A3's installed originally and later modified the amp for 45's. I always had a bit of hum that you could hear if you were right next to the speaker. Sitting in my listening position it was much less noticeable. And when music was playing you don’t hear the hum at all. I noticed that when I went from 2A3 to 45 the hum was lessened quite a bit. To me that would indicate too much gain. Additional padding in my pre-amp helped even more. In your case you are controlling the volume with the submissive. You could try dumping some of that gain with the pot on the Stereomour. Have tried hooking your source directly into the Stereomour? You might be introducing hum with your interconnects.

 

[thdewitt]

Well, I hooked up the Orcas and Dungenus to two other amps and got zero hum even at 100% gain on the sub.

 

[Doc B]

Is the 1.5mV you measured on the scope peak to peak or rms? If it is peak to peak (Vpp) then you are well below the hum spec for the amp. If it is rms then the hum is slightly higher than average, but low enough that you would probably only get it lower by swapping out tubes until you find a particularly quiet set. The place to start might be the 12AT7.

You could also reduce the hum slightly by wiring the transformers for 4 ohms output rather than 8 ohms. However this will limit your headroom a bit.

 

[thdewitt]

Thanks Doc, I am measuring RMS.  I will take a look at the tube.  Maybe wire the transformers for 4 ohms as well.  I am in a small space.

 

[Doc B]

The 4 ohm thing would only be a liability if you run the system loud enough that it seems to run out of steam on loud passages. If you are not running that loud it should work fine. Also the hum may reduce a little as the tubes burn in. It's usually worth it to touch up the hum balance after a few hours play when you have new tubes.

 

[thdewitt]

I am lucking for a replacement tube on ebay right now.  Any suggestions.  The stock one I got was pretty beat up.  Pens a little bent so it may be suspect.  Do you have a recommendation for a generally accepted high quality replacement.  Cost is not a big issue.

Thanks,

 

[Doc B]

It's very subjective. I like the Mullard CV4024.

 

[Paul Birkeland]

Yes, When I adjust the sub gain to the 10 O'Clock position recommended by Clark the hum is minimized but still slightly audible. 

How is that sub level when you listen?  I would wonder if the level might be a little high for your space. 

 

[thdewitt]

How is that sub level when you listen?  I would wonder if the level might be a little high for your space. 

I think I have the sub level now in a good place.  Slightly less than 10 O'clock.  Sounds just right to me.  Like I said, the hum is now only slightly audible and seems to be getting better.  I have ordered a new pair of JJ 2a3-40 tubes and a mullard nos CV4024.  I am hoping this may also help a little. 

 

[thdewitt]

OK, for those who are interested, my Blumenstein Dungeness Subwoofer is now absolutely quiet.  I took DocB's advice and I changed my setup by modifying the submissive to have two RCA outputs.  I hooked one up to the Sub and absolutely quiet even if I turn the gain up as fair as it will go on the sub.  So now the Stereomour, Submissive, and  Blemenstien Orca Deluxe/Dungeness are awesome.

I am not sure why, but the whole system sounds way better this way.  The Orcas seem to sound better this way.  Not sure what is going one but using the line level input seems to solve all my issues.

I am in Heaven.

Thanks everyone.

 

[Doc B]

You are no longer amplifying the residual noise floor of the Stereomour with the Dungeness amp.

 

[thdewitt]

Yes, Doc, that is it!!!!!  Also, today I received my new JJ 2a3's and my Mullard CV 4024.  Man are these JJ's huge.  The sound with everything is great.  Looking forward to buying my next few items.  Paramounts and a Beepree hopefully.

Thanks again,
Tom

 

[Grainger49]

I'd give this a try with my setup but I might just lose my mind trying to dial in the Dungeness subs again.

 

[Clark B.]

I'd give this a try with my setup but I might just lose my mind trying to dial in the Dungeness subs again.

Grainger, YMMV.  I am not sure if everyone needs to hop off the bandwagon of the way we recommend hooking up the sub amps via speaker wire by switching their whole systems around to RCA hookups.  Doc, Paul and I might differ on this one.  While the RCA signal splitting solution helped out Tom's situation with his noisy stereomour, I've heard RCA splitting practices distort the sound in mine and others' systems, whenever the pre amp section is not up to the task. 

For instance, the sound of the Fix kit inserted into my systems did not work for me and the Orcas, but other folks with other rooms and systems seemed to find more of an improvement.  YMMV.  So, similarly, RCA splitting should be chosen in accordance with personal priorities in performance.

I usually do not try to get my tube amps noise free, personally, I focus most system changes on trying to get better dynamics and natural tonality out of the speaker drivers and source as a raw, unadulturated ingredients.  My Paramounts into Orcas on the desktop do have a little noise in them, for instance, but this is ok as soon as the music is playing.  The SEX amp on the other hand, is truly hum/noise free btw, but uses a different kind of power triode thats less susceptible to all sorts of noise.  I personally (perhaps esoterically) prefer the dynamics of the Paramounts into the Orcas even on the desktop so I put up with the truly miniscule hiss/hum and the potential risk of gently bottoming out the cone with the extra power.  A very small trade off that's easy to deal with for me personally.  But other folks might think differently and that's ok.

-Clark

 

[thdewitt]

Clark, cool post.  I can tell you for me, the difference is amazing. 

If you are ever in San Diego and have a few minutes, you should come buy and take a listen.  I would love to have you listen to this set up.  You are right that these speakers in my 11x9 room is amazing.  It seems to be getting better every day. 

I dont understand your post though.  If you output the signal directly to the subwoofer with the great volume control in the submissive, you basically have the signal going clean to the amplifier in the sub.  Then you don't amplify the noise (if any) from the the Tube Amplifier for the bass signals.

How could it get any better through the Tube amplifier to be further amplified by the solid state amplifier in the Subwoofer??

Not trying to act like I know anything, because i don't, just wondering what your response is.

BTW, I keep you picture over the speakers in my office so I can tell everyone about your speakers when they ask

 

[Grainger49]

Clark,

I might have been unclear about my comment.  It was mainly tongue in cheek.

I am the weak link here.  The Orcas and Dungeness are great products.  I am compulsive and went wild dialing back and fourth on the level and crossover. 

I ended up at your suggested settings after putting the Dungeness on the floor next to the Orca stands.

The flaw is in the user not the speakers.