Is there such a thing??-- Tube Preamp Question


Hello All,

I have recently acquired my first tube preamp. Its a Blue Circle 21.1 with the stepped attenuator. From the start its been a journey. When I received it there was a distinct buzz/hum. I sent it out for repair and they found it was the power transformer. They made me a spiffy new external power supply which solved the problem. I truly love what it does for tonality, richness of voices and my sound stage appears deeper to me with good placement of instruments within it. However, and maybe my expectations are just to high, the hiss and tube replacements (needed to replace tubes after 6 months) along with a generally fussy nature in terms of the need to pop the top and clean to get the fuzzy sounds out occasionally just seems a bit much. Are all tube pres susceptible to this level of need an "fussy" temperament? Another issue, is when I am watching TV and/or using TV as a source, between songs there are strange sounds(bleeps and squeaks) and moments of scratchy sounds noted in quiet passages and seem triggered by moving from one song to the next. It seems very sensitive to picking up TV noise which I have never noted using solid state gear.  While it isn't evident at medium to high volume it just bothers me and I know that its there. 

Can I have all that this does for me in terms of tonality and sound stage along with a less fussy nature? Does such a thing exist for a reasonable price($1000-$2000). I would like a more silent background with less need for constant attention. 

Does such a thing exist?
Previewbirdfan
Tube preamps which are properly set up AND matched to associated equipment do not have to be a problem, but the potential for problems do exist when the amps and preamps output gain it too much for the speakers you utilized. High sensitivity speaker, i.e. those higher than 92dba, preamps with high output gain, and or amps with high sensitivity, can magnify, unnecessarily, residual noise floor of tube preamps, and/or tubes used. A commmon cure to this noise problem, apart from using less sensitive speakers, is to reduce preamp gain using an inline attenuator between your amp and preamp.

I.m not familiar with your stuff but consider these thing as you do your research.
Agree with everything @newbee stated. I couldn’t find the output gain spec of your preamp, but a reviewer wrote the gain is "quite high." This would support newbee’s comments.

This preamp requires low-noise tubes. This would at least reduce any tube hiss and provide a lower noise floor for your sources. You can use
6922, 6DJ8, or possibly 7308 (slightly higher voltage) tubes.

You need to tell us about your setup; type of amp, sources, your power situation, eg, is your TV on the same circuit as your audio.
It’s possible the noises you hear may be from the TV and other devices contaminating the AC line.


To answer your basic question, no, the problems and fussiness you're experiencing are not something you should expect from tube gear, either preamps, amps or integrateds. Well designed, built and matched tube gear is, in my experience, no more trouble than solid state gear. 
Thanks Newbee and All. 

The preamp has a handy dandy gain switch which can be accessed from inside the cover. I have played with this and swapped in a range of speakers. My OB Spatial holograms certainly do magnify the problem as they are higher efficiency. when those are in the mix I set the gain switch to its lower settings. When using my Anthony Gallo 3.1's I use the lower setting. The associated equipment as follows:

Amps: Red Dragon M1000 (mkI) Mono Blocks-- I'm not sure the input sensitivity
Cabling: All interconnects are Anti Cable entry Level. Cullen pwoer cables, 
Tubes: Currently Running Electro harmonix 6922
Speakers: Green Mountain Audio Continuum 1's, GMA Chroma HD, Gallo 3.1, Magnepan 1.7i, Magnepan MMG, Spatial Hologram M3 Turbo S
Power conditioning:  Furman Power Conditioner (PST-8)
Sources: TV, JA Michel Gyrodec, Thorens TD166, Bluesound Node 2, 
Phono Stage: Lounge Audio LCR mkIII

 
I couldn’t find the output gain spec of your preamp, but a reviewer wrote the gain is "quite high."

I think you should stop using the gain switch. Since your pre has high gain, use the low setting for both sets of speakers. Your monoblocks don’t need the increased gain to drive your speakers.

Very nice system, btw.


Wow, you have a lot of speakers! From the spec’s on the speakers and the Amp I would guess that the greatest noise issue would develope when you are using the Spatials. Very high sensitivity amp (2.9v) coupled with high speaker efficiency (95db) would probably operate best with minimal to no pre-amp gain. (Contingent on a lot of other issues of course). The other speakers should be less problematic, but never the less still need less fixed gain. All depends on your pre-amps minimum fixed gain as well as the input from your sources and how much attenuation you apply to this signal via you use of the VC on the pre-amp. At a minimum I would set the pre-amp to its minimum setting as suggested by Lowrider.

BTW, while I doubt that you would be guilty of this, do not judge your pre-amps ’quietness’ by just rotating the VC to max and putting your ear in front of the tweeter. That will always result in a worst case scenario and create unnecessary angst. Just select an input and set your VC to produce the maximum volume you would use. Then mute your source and the residual noise you hear is really all that matters. I think an ear about 3ft from the speaker would be a good distance to judge noise, although some even go so far as judging from the listening position.

BTW, tube life - if you are using low noise tubes appropriate for the pre-amp (Some pre-s are very hard on less than ’rugged’ tubes but other than that you should expect at least 3000 hours or much much more).

FWIW finding a good used tubed pre-amp for $2000 should not be at all difficult, but from what I’ve read about your’s I’m not sure how much you would improve your situation. I would look for other cures first.
Once again I'm in total agreement with newbee. That's a well regarded preamp, I would not be looking to ditch it. You've had it serviced and there is no hum present. 
This won't solve your problem, but order some NOS tubes; matched and tested for noise and microphonics. You'll have a lower noise floor and improved sonics over the EH tubes.
It's possible one of your tubes is microphonic. In this state, the preamp can pick up and present all kinds of crazy sounds. It's like having a microphone in your system.

Your TV uses a SMPS, a switched mode power supply, which often adds noise to your AC line and into the audio signal. I suggest unplugging the TV while you do some troubleshooting.  

Are all your components plugged into the Furman? Are you using a shared AC line that also has lights or dimmers on it?


This is an interesting question. I'm a newbie too so please forgive me for this stupid question: but do these issues occur in solid state preamps? The reason I'm asking is because I'm about to get a new preamp (my first tube preamp) and I hope I don't have these issues. I prefer low maintenance equipment so this better not happen. If so, I'm going back to SS! 
Hi birdfan,

While I can’t speak about your specific equipment, I can say a bit about tubes. EH makes at least two models of 6922’s and they both should last you for years. The 7308’s are the  Cadillac of the 6DJ8‘s  tubes  and therefore are priced  accordingly.  They don’t last as long as the 6922’s but will sound the best of all the  6DJ8 line.
 As for possible monophonic problems, have you ever heard of tube dampers? Just a thought.
BTW, what were the stock tubes  that came with your preamp? 

All the best with your journey.

JD
Hi blueorion,

I’ve used mostly tube equipment for decades and have never most of the issues mentioned above. The best part of tubes is you can change them in and out to other brands and types and get different sounds from your equipment. With SS you need to change the equipment to change the sound. There are other things you do to change the sound in both, but that’s for another thread.

All ll the best.

JD
I have 30 wpc tube monoblocks made in 1956. I still have two 35 wpc fisher 500c, 1 35 wpc fisher 800c, have had other tube stuff, and friends with tube stuff. I just bought an old McIntosh tuner/preamp from the 60's. One of these

https://www.ebay.com/itm/McIntosh-MX110z-Vintage-Tube-Preamplifier-FM-Tuner-Very-Good-Condition/264282601872?hash=item3d88787990:g:mAEAAOSwvcBch~My

Plugged it in, play: noiseless. Nice FM antenna, awesome radio. TT, fab sounding phono eq, ...

Just bought a tube amp, 22/45 wpc, NO NOISE.

Tube amps and tube preamps SHOULD NOT MAKE NOISE! If so, something is wrong. I would never mess around like you have. It's not your fault. Tube life is much longer than most people understand, typical power tubes rated for 10,000 hours. Smaller preamp-tuner tubes much longer than that. Military spec tubes have ridiculously long lives, your grandchildren will still be playing them, unless they read too much.


IF you are driving low sensitivity speakers with tubes, probably not enough power, you will get noise, then perhaps no sound!
This sounds like tube issues if you are using old NOS tubes or tubes that are just no measuring good any longer. Also could be the tube sockets. You may want to clean the sockets and tube pins first.

Removing the transformer into a separate chassis was a good idea as it
isolates the transformer noise from the tubes.

If cleaning doe snot work, I can repair the unit or my suggestions would be:

1) Counterpoint SA-2000 or 3000 preamps. Send them to me and I will upgrade them and you will have a preamp that competes with almost anything out there.  The upgrades are volume control, Nichicon capacitors, Amtrans and Caddock resistors, and V-caps - read the review of the new V-Cap that just came out.  I also rewire some of the internal design to improve the sound. 

2) My friend purchase a Prima Luna 6922/6DJ8 tube preamp that I thought sounded very good for the money $2300?

If I can be of any help, send me a message through Agon.

Happy Listening.
Thanks all for your feedback. Removing the tv removed the problem. I also am using the low gain setting on all the speakers except the Maggie’s. Cleaned the tube sockets and tube pins as well as everything in the preamp with deoxit. It’s dead quite now. Thanks for all the guidance!! 

@curiousjim  do you have a recommendation on which brand 7308’s to look into?
The 7308’s are the  Cadillac of the 6DJ8‘s  tubes  and therefore are priced  accordingly.  They don’t last as long as the 6922’s but will sound the best of all the  6DJ8 line.

Where this incorrect information coming from? Brent Jesse??? If you actually listen to the tubes and to people that have, there are very few 7308 tubes that rank highly in the 6DJ8/6922 application. Especially compared to the CCa tubes from Siemens and Telefunken. 

But, I like using the Western Electric 396A/JW 2C51with a 5670 to 6922 adapter. That tube beats every 6922 variety I tried.
Invest in some  super low noise selected NOS pre amp tubes from a serious seller
I got mine from Andy at Vintage Tube services. I can now only hear soft hiss from one foot from tweeter when nothing playing. That’s pretty good, and has zero neg effect.  Other tubes I could hear across the room!

a bit of crackling or tinkling is normal as tubes warm up. I get a little of that for a minute or two. 

also I believe good tubes in a pre amp will last years not 6 months. I have NOS Sylvania 6sn7s , been using for years. Was told to expect easily 10000 hours.

am using a Rogue 99 magnum.