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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
newbee
4,775 posts
 
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.
lowrider57's avatar
lowrider57
5,417 posts
 
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.


sfar's avatar
sfar
1,763 posts
 
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. 
birdfan's avatar
birdfan OP
175 posts
 
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

 
lowrider57's avatar
lowrider57
5,417 posts
 
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.


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