Gain Issue

[Mcbrion]

Hi Guys:
I have a Classic 1 SE, ASL Hurricanes and Nola Contenders, Valhalla 2s interconnects and Shunyata Cobra cables.

I'm getting significant noise out of the speakers, due to their being 90db and the ASL is a very sensitive amp, and the CJ has 25db of gain. I can barely turn the volume past 8 o'clock. Any suggestions? The noise level when music is not playing is quite high. I'm thinking i need a preamp with less gain, (say, around 15), but not before asking for suggestions.

Thanks...

[admin]

You can put a resister in the chain. I have most often seen this done on the input stage of the Amp, especially if it as "very sensitive amp" as you put it. It's an easy and inexpensive mod.

[wynnytsky]

if it's just tube hiss then it would get louder with the volume
I noticed one day my ET3's noise floor shot up and so I knew something changed. I sent it to CJ and they returned it with a new tube -- said my other one was "dirty". That definitely solved my issue.

if your noise floor has a trace of buzz, and doesn't appear to be a function of volume then try lifting the ground. I have grounds lifted on all my stuff and I needed to do this for each device plugged into my P3 power re-generator -- just lifting the ground on the P3 itself wasn't enough.

[Mcbrion]

Thanks for the suggestion. I usually ground the preamp and lift the ground on everything else, but I'll give it a try anyway.
I originally posted nearly a year ago, and became disillusioned about the problem. Decided to sell the preamp, and someone bought it - only to return it saying that there was a hum problem. I sent him new tubes directly from CJ, but according to him, it didn't help, so he returned it.

Finally sent it off to CJ a week ago. Right after I first posted, I became a little "mental: a family member was diagnosed with pancreatic cancer, and I wasn't even as analytical as usual. And then, of course, I forgot about audio altogether.

Fortunately, she beat it and the cancer's gone (yeah, I know: who survives pancreatic cancer?? Well, she did, and I thank God for it). CJ just called and can find nothing wrong with the preamp, which makes me wonder about the buyer's statement that it was defective, but I prefer to believe him, as i heard the slight hum when rubbing my finger across the bottom of the preamp the day I got it back. AFter that, all hell broke loose and audio was put aside for 7 months.

Also, I neglected to mention something: the Hurricane (only one was changed) is also being restored to its original condition. It had been rewired in 2010. Apparently (and I guess this was part of the original design, but I never saw anyone mention any problems with their Hurricanes), if something - a resistor, maybe? - (too technical to remember now, but my tech was adamant about the danger to me, and I'm one of his favorite customers) on tube 8 failed, the voltage would transfer to tube 1, and if I happened to touch the metal part of the KT88 when the amp was on, I'd get a lethal shock, so I had my electronics repair guy rewire it (Mr. Lau, the designer, sent along a diagram on what to do), but the amps never sounded the same after that ( almost no dimensionality, dynamic range highly reduced, imaging went to hell, low-level detail was minimal, etc) for the past 5 years, so perhaps that re-wiring caused the issue and it's not the preamp. (Don't even bother wondering, 'well, why'd he do one and not the other'? I have NO idea what I was thinking at the time, except it cost well over a grand for the repair and at the time, money was an issue, so when I found out, I decided I could only have one rewired. At least, I GUESS that's what I was thinking…can't even remember now). And then, I bought a 2nd pair later because the first pair sounded so "dead", but they'd been changed to worked with 6550s, and they did NOT like the KT88s, so that didn't work out too well, either, in the end. I recently decided to have my first pair rewired to original specs, because, after I reflected on it, when the crisis ended, I thought to myself: you would never touch anything (tubes especially) when the amp is turned on, anyway, so why not just have it put back to its original wiring, be aware (I live alone, so no fear of any child putting themselves in danger) and see if that resolves the issue (not to mention, I want to see if the amps return to their original "magical" presentation. Doing only one could have thrown the synergy out of whack, but I'm just speculating). I'll get the amp back in a week or two, but the preamp will arrive around Friday. The only thing I have on hand to use for amplification with the Classic at the moment is an NAD integrated - which never hummed when used with the Classic, by the way. I can just use the amp section for now.

It's still a bit of a mystery to me, though, what is going on. I don't think it's grounding, as I've always tested ground configurations, but now that Life is stable again, I'll have more time to investigate. I would've thought the CJ and the ASLs should have been fantastic, as that's the combination HP used back in 2003 when he first reviewed the Hurricanes, and their realism surpassed anything I'd ever heard, including my Jadis, Goldmunds, VTLS or anything else and, since I've actually owned two pair of Hurricanes.... So, now I'm thinking it can't be the gain issue, but at the time I posted, things were pretty intense, so I wasn't thinking clearly. In any case, CJ says the Classic has no discernible problem, so, they'll send it out in two days.

So, thanks for the suggestions, guys, and I'll report back once everything's back in the house.

[admin]

Mcbrion,
Nice to see you back. Sorry to hear about the difficulties but I'm glad to hear that things turned out ok. Must be nice to be back to the music after a hiatus. Definitely let us know how things turn out.

I know it's super basic, but did you ever try to use a RCA-to-RCA plug ground loop isolator to see if the hum is a ground loop issue vs something intrinsic to the electronics? I find these devices to be very helpful in hunting down hum from grounding issues.

Again, welcome back!

[Big Dog RJ]

G'day mate, came across your gain issue.

This does seem to be an annoying aspect with certain tube preamps. I could relate based on the following:
1. CJ tube preamps do have certain amounts of hiss, usually from just one channel and very minimal hiss. Usually apparent when you're very close to the speaker, not so much from a distance.

2. If there is a significant hiss from both channels and it increases upon level adjustments then a tube change is in order even though the tubes may have very few hours on them. Typical tube problem & very tricky to find quiet tubes. You may have to try several in order to keep hiss at a minimum.

3. If it is a hum you're experiencing then this is definitely a grounding issue. Some where along the chain there is a ground leak... could be caused by several things (poorly laid out power strip, bad mains grounding, power amp grounding not stable or some other component's ground is not grounded properly. Mono amps have this issue.

4. I wouldn't think it would be the preamp because cj preamps are usually designed with solid grounding circuits, all it requires is a proper grounding into a power strip with a primary earth. The Nordost Qbase is one exceptional power base, similarly there are other high quality power bases available that I would try before changing preamps.

5. By the way you have described it, certainly sounds like the amplification is not grounded properly, causing the sensitive speakers to pick up unnecessary hum or noise and the amps are further amplifying this unwanted noise.
If cj is saying that your classic preamp is fine then that would be correct because they would be testing it in lab conditions, that are well grounded. These types of conditions are not available in the average home. Therefore, there are so many factors that affect the electrical circuit where the system is plugged into.

I remember once there was a nasty hum/buzz coming on & off during the nights. I could distinctively hear it because at nights things are much quieter. After careful investigation I realized it was the dam fridge which was actually plugged into the same ring circuit of the system.

Solution: I got an electrician to install a completely separate line with circuit breaker just for the system. A dedicated line for the system solves MANY grounding issues, and a good quality power base adds to the overall refinement.

That's just my 50 cents, hope it helps or at least gives you an idea of what maybe going on with the system's interaction with AC mains. The NAD not humming or making a noise is obviously a more stable design and simple amplifier circuit. The so called highend gear is temperamental, that's why it's called highend. On certain days the Ferrari starts and on other days it craps itself!

Whereas my old mitsubishi always starts... I can relate to your NAD; I used an 80 watt power amp with a matching NAD preamp, lovely piece of gear for the money. Soon as I ventured into the high-end, yep all the hums & buzzes came out to play. Dedicated circuit sorted it out but what an annoying investigation it was... Sometimes I truly miss those NAD days...

Cheers mate, and I hope you get to the bottom of identifying that problem. It can be solved with the right attention.
RJ