Ok, I know this is a newby question - but I just need some straight talk here-

I have a new to me set of Dodd 120's, and I have found that when mated with the BlueBerry X, that the tube hum was pretty loud, as I was having to turn up the gains to maybe one o'clock and the volume to 1 or two oclock, causing some unpleasant hiss, on the 8 ohm taps

So in a stroke, I decided to move to the 4 ohm taps, and of course, I don't have to turn the volume up near as high - but I am hearing some very different things; the bass appears to be stronger, the dynamics louder and faster and the treble sounds a bit rolled off...or am I just out of my mind?

First, can I hurt my speaks doing this?  Am I driving the amps too hard to produce this signal?  What technically am I doing here?  Have any of you tried the 4 ohm tap for any modern speakers, say for the RF7 with the deep impedance drops?  I am experimenting right now with my line arrays thaat while they are not as efficient as Klipsch, they are relatively decent.

I haven't tried the turntable with this setup yet, but with the tube hum, and the needle hum - the noise is palpable and I have yet to figurre out what to do about it -

Anyone care to weigh in?  Is what I am hearing just nuts?

Thanks!  

B

I sure hope you are not posting while at work....

hmm...uh....wait a minute.....

never mind.

 Hey Richard!  Actually, no I was not posting at work - but I am now!  Flexibility is a good thing, and I have it in abundance right now.  Need to have you come over and check out the set-up, will look a lot different come Thanksgiving though, just got the stuff for the "home theater" and I am pretty excited.

What do you think about the BB question?  You have a Peach, do you find it to be kind of noisy?  I think I might have asked you this before...

B

Kriton:

First, can I hurt my speaks doing this?  Am I driving the amps too hard to produce this signal?  What technically am I doing here?  Have any of you tried the 4 ohm tap for any modern speakers, say for the RF7 with the deep impedance drops?  I am experimenting right now with my line arrays thaat while they are not as efficient as Klipsch, they are relatively decent.

I don't see how you can damage your speakers, but I would need to know some more about your signal chain (components and order of hookup) and also some info on Dodd speakers to analyze your problem. Also, when you have your other speakers hooked up to the same equipment do you see the same problems?

I do have a Peach, I do have some noise issues but primarily when I'm in (what I beleive to be) HiZ mode.  I always get the two screwed up so it might be LoZ mode... when I switch to the other, the background noise that I might hear, pretty much goes away.

Looks like you have some nice amps there....  maybe one day when you're REALLY curious....we can....

Don Richard:

info on Dodd speakers

Don, I was thinking those were amps?

http://doddaudio.com/mono_amp.aspx

 Well I am afraid I can't be much help with any of those questions - what I know is that i am using a Jolida 100 tube CD into a Juicy Music Blueberry Extreme2, hooked to a pair of Dodd Audio 120 watt Mk2 monoblock amps (utilizing each a quad of matched KT-77's, and three 5687's) out to the GR Research LS-6 line arrays.  The pair of speakers which were tested on the StereoMojo site, are *these* speakers (I got them after the write up) -

I can find no futher information on the Dodds, and no specifics on the LS-6 prototypes except the graphs that were added to the review here: http://www.stereomojo.com/LS6%20review/AV123LS6review.htm 

I have not hooked up the LaScalas yet, or the RF7's or the Cornwalls for that matter, as they are all still *boxed up* - and driving me nuts.  I will rememdy that shortly, but they are upstatirs and this system down - and moving the system into a new room is going to cuase its own set of problems, and lugging La Scalas downstairs right now is just not in the WAF factor, I am afraid.

Past that I am awash.  Did that help?

B

Ah, the Dodds are amps, driving the line arrays.

Equipment matching is the key to good performance in a sound system. It seems like you may be having grounding issues causing noise. Also, the higher impedances in tube equipment, relative to solid state, may be coming into play here. High impedance devices tend to be more susceptable to noise pickup.

First, with the power off check your interconnects to ensure that they are plugged in properly. If they are, try different interconnects. Power up. If there is no improvement, power the equipment down then unplug all of the inputs from the preamp and leave the preamp hooked up to the power amp and the power amp hooked to the speakers. If the noise improves the CD player and/or another source is contributing to the noise problem. If the noise doesn't change then, plug all of your electronics into a power strip so that they are all on the same ground.  Then use one of those little three-light AC circuit testers to ensure that the house wiring is correct, at the wall socket. Power up and then, if the noise is the same, try touching a known good ground to the chassis of the preamp, then to the power amp and see if the noise changes. Be careful here, because if there is a wiring problem or other fault in the pre or power amp, high voltage AC may be present, and a spark will result.

If the noise does not change, power down and reconnect the CD player and power up. Try increasing the preamp gains and volume control to see if the noise lessens. If the power amps have input attenuators, try adjusting them, and readjusting the preamp controls and see if there is any improvement.

If none of this helps there may be an issue within the pre or power amp, or a compatibility issue between the different brands of equipment.

As for the sound changing when using different impedance taps, the speakers you are using have a widely varying impedance curve. from 8 ohms or so minimum, to around 30 ohms or so maximum. This may cause a variation in the frequency response of the loudspeaker. Some tube amps are bad about that.

Hope this helps, let us know how the experiments work out.

 Cool - I will try it and check back with the results.

Thanks!

B

I have had some experience with hum, I'd thought I'd pass on some of the things that worked for me, I hate hum. My system(s) have to be dead quiet or something has to go!

Anyway, try your best to isolate what component is the source of the hum. If it's a two prong plug see if you can reverse the plug and flip it over. It sounds silly but it worked on a new pre-amp I had, it went dead silent just by flipping the plug. If it's a 3 prong, check with the manufacturer then try a cheater plug (know the risks of being ungrounded first). Good luck.

Thanx, Russ

 I think that the main hum is coming through the BlueBerry - and maybe just tube microphonics?  I was thinking about putting those *** Herbie's c*ck rings thingies...take the BB hum and add to it the Dodd tube hum (which you are gonna have with all those tubes) and it is less than quiet.  When I then turn on the turntable, the hum gets alot louder - you know, when you turn on the turntable and then turn up the volume?  The sound is really noticeable.

These components are all going through an APC line conditioner (that has worked very well by the by)...should I get the amps off the conditioner?

B

Is your BB your only preamp?

If no, might you swap out & see what happens?

If yes, then I have a Lexicon preamp that's currently laying around that you could experiment with....  I also have the Peach that you could try.  (I've been debating on switching them out for a while anyway)

Let me know if either of those interest you.  Also...let me know about 1 week in advance of when you plan on moving your LaScalas downstairs.  I think I have an old book report due that day but can't quite remember when it is....

You could always get a up to date amp...SS

Make sure that TT is grounded to the pre amp...

Ground hum can be a hard one to find...

 Nice!  No I am not going to call you to help me move them - I will make the wife do it!

Yes, I might try the Lexi out, if that is cool with you!

AND NO TREY - I have enough SS upstairs, these are my tube babies!!

B