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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?
128x128birdfan
lowrider57's avatar
lowrider57
5,417 posts
 
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?


bluorion
477 posts
 
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! 
curiousjim's avatar
curiousjim
4,790 posts
 
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
curiousjim's avatar
curiousjim
4,790 posts
 
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
elliottbnewcombjr
5,505 posts
 
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.


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