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Background noise problems

Hi,

I posted around 2 months ago on this issue, but like an idiot, I was due for vacation in Bali a few days after I posted and missed most of the conversation. Anyways, I have tried a few more things and was hoping for some feedback....

Here is my situation: I am getting upper-frequency "snow" coming out of my speakers. My current setup is a Gold-level McCormack DNA-125 amp, Herron VTSP-1a/166 preamp, and Sony 9000es CDP that has been upgraded to VSE Level 6, with Tyler Acoustics Linbrook Signature speakers. Except for the snow that I am getting (sounds like a snowy TV) the system sounds great. Unfortunately, I am hearing the hiss around 20 feet away.

Here is what I have tried so far:
1) substituting a Eastern Electric Minimax preamp for the Herron: less of the hiss sound, but still present. I am assuming the preamp has less gain?
2) Substitute a Consonance CDP for the Sony. Not much change in background hiss
3) substitute a Jolida integrated amp for the Herron/McCormack combo, input from the Sony: this virtually eliminated the hiss

I have had the Herron checked over by Keith, replaced tubes, and everything has checked out. The McCormack was recently upgraded, but it is possible something is wrong there. The Sony unit was also recently upgraded from Level 5 to Level 6, but the hiss was there before the upgrade and still remains.

A few notes: I hear the hiss as soon as the Herron is engaged, whether or not it is receiving an input. The hiss is the same on all inputs, whether or not they have an active input or are not connected. The speakers are basically dead silent when only the amp is engaged.

It makes me think that I have some issue with compatibility in my system with the Herron, but as I am still getting some background noise on the substitute preamp, I am wondering where to go from here. The Jolida intergrated was basically quiet, which is a good sign.

Where should I go from here? I have the makings of a superb-sounding system, but need to get rid of this background noise. It can be heard easily in the music. Thanks in advance!
dawgcatching
mlsstl
1,436 posts
 
The specs on the McCormack show a 98 dB S/N ratio with a 1 volt input sensitivity for full output. The Herron has an 80 dB S/N ratio (for moving coil input) and the speakers show a sensitivity of 92 dB.

The rushing noise you hear is white noise and is typical of the residual background noise you get from gain circuits. All electronics produce this noise, but it is usually inaudible.

Since all the electronics have been checked or recently upgraded, the assumption is they are working correctly. (You also didn't mention any channel imbalance with the noise which could indicate an aging or faulty tube in one channel.)

That leaves the strong suspicion that you have a gain mismatch at work. Speakers a bit more sensitive than usual. A relatively powerful amp. A tube preamp (which often tend to have a bit more residual noise than solid states).

Are there any internal gain setting switches in either the preamp or amp? If there are, try some different settings. If that doesn't help, I'd simply try some different preamps and see if the noise disappears. You'd also want to try some different power amps with the Herron. (Looks like you've already tried different music sources.)

While each piece of equipment you listed is good stuff and has excellent reviews, it may be they are just not suited for each other.
dawgcatching OP
139 posts
 
Thanks for the replies. I also suspect it is related to the preamp, as I have pretty much tried everything else. Keith noted the gain may be an issue, but he couldn't put his finger on a "this is definitely causing the noise" problem. I checked all of the tubes (as did Keith when he had it in) and they have all checked out.

Thorman: I did try changing interconnects, so that wasn't it.

Tvad: The system sounds great except for the hiss, which is so loud that is audible at least 15 feet away. It really detracts from the music, which is why it is really bothering me. It is like looking outside through a really dirty window. My old system used to have a minor hiss, which was slightly annoying but not a deal breaker, but this can be heard through the music at all times.

Mr_hosehead: well, the Jolida was quiet, which was terrific. With regard to musicality, it was really flat and lacking detail. My current components are great, except for that loud hiss that I can't seem to get rid of.

MIsstl: If I need to look at a different preamp, what range would I be looking at for a gain to reduce the noise? If the Herron is 80db, then what would be better, or ideal? Is there a general rule, or is it something I will just have to try and compare? The EE Minimax I tried again last night (which got a bit quieter after I swapped the rectifier tube, and wasn't bad) actually looks higher at a 96db s/n ratio, but that may not compare directly with the 80db you were speaking of (I wasn't familiar with the moving coil input term) .

Also, is there an input resistance mismatch that could be causing this?
mlsstl
1,436 posts
 
Actually, 80 dB for the Herron is a pretty good noise figure (just reading from their spec sheet). That was for the moving coil input option and that circuit has a lot of gain. I would think that figure would improve with a line level input.

And a 1 volt input sensitivity on the power amp is perhaps a shade low, but certainly not an unusual figure.

Really, there is nothing about those numbers that suggests your setup should have the level of white noise you indicate. (You didn't say, but I gather you checked both amp and preamp for any additional gain-setting switches?)

If I were you, I think I'd have the preamp tested for output noise. I think I'd also contact the manufacturer and ask them if they have any insight. And, have you tried this preamp in another system? That might be revealing.
dawgcatching OP
139 posts
 
MIsstl,

Yes, I didn't see any gain-setting switches to play around with. I just got the preamp back from Keith at Herron, where he tested the preamp and didn't find anything out of the ordinary. He gave me some things to try (which I did) and it didn't solve the problem). He was very helpful, but in the end, couldn't figure out what was happening, except that it wasn't a faulty preamp, which leads me to believe there is a compatiblity issue with the amp.

I will give the preamp a go in another system.

dawgcatching OP
139 posts
 
Perhaps another thought: does anyone think there could be an issue with speaker cable? I don't see why there would be (I am using Signal Cable bi-wire) but thought I would throw that out there as something I hadn't yet pondered.
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