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Is there such a thing as a "black quiet" amp?


eth2

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I just got my VAC PA80/80 amp hooked up and expected to hear...nothing. However there is noise when there is no music playing. A slight sssshhhhhhh. Also, there is a slight power hum for the first 20 seconds or so when first powering the amp up. The sshhh and the power hum occur even when the preamp is not connected. My B&K exhibits the same sssshhhing. (but not the short power hum)

Is this "normal?"

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Both.

I called a friend who told me to buy a VAC, and has the VAC 450's. His are silent...but also outrageously expensive and not in the universe of what I would ever pay for an amp (or even a car). He told me I should try different tubes as some are quieter than others. So I guess what I would like to know is should my PA80/80 be quieter, and in the realm of what most of us would consider reasonably priced, are tube amps silent?

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I've been able to get the Jubilee's pretty near dead silent (zero hiss unless you are about 12" from the horn.

I can adjust my gains to make it work.

When I had fixed input amps (various tube amps as well as some solid state) hiss was just part of my life.

I think I've come to understand that if you have an amp with low input sensitivity (a high number, NOT "1" for example but maybe 2.5) you might find it more friendly.

I'm sure others will explain where I'm off base.

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I've been able to get the Jubilee's pretty near dead silent (zero hiss unless you are about 12" from the horn.

I can adjust my gains to make it work.

When I had fixed input amps (various tube amps as well as some solid state) hiss was just part of my life.

I think I've come to understand that if you have an amp with low input sensitivity (a high number, NOT "1" for example but maybe 2.5) you might find it more friendly.

I'm sure others will explain where I'm off base.

Just listen to your speakers at 11 for a period of time and everything will seem quite. :D

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I have to get right up to the tweeters on my LS to hear any thermionic noise from my 2A3 amps. However, when powering up, they have hum (gets louder and then fades away) until warmed up. BUT, they are DHTs and the heaters are AC. It's not enough that it bothers me.

Bruce

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I had a power hum with my setup, I very faint hum with the Heresies. When I had the chance to hook them up to a pair of Lascalas it was unbearable. I later found out there was some cold solders, and the power transformer was wired wrong. Once I re soldered some joints, and wired the transformer correctly my preamp was dead quite.

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Black quiet dose exist in a galaxy far far away and is alied with the force. :rolleyes: I have the Reference speakers so I can't related to Heritage speakers but, that is one of the things that I enjoy about my amps. They have a black noise floor that even if you put your ear right up on the speaker they are dead silent.

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Are tube amps silent? No. I have several and have heard several more and my experience is that tube amps are not silent. Especially with very high efficiency speakers like your Khorns.

Not true at all, I have had SEVERAL quiet tube amps and indeed have one right now that at max volume on headphones is dead quiet. The problem is design NOT tubes

Unfortunately Earl you have found one of the MANY amps that are not good on efficient horn speakers. the low level hiss you are hearing is likely to be there forever its just the way the amp was designed, I would bet if you look up specs on the amp they claim it can power speakers in the low 90 to even the 80's db sensitivity. and if you were to hook that amp to those speakers the hiss would be inaudible to very low

the short initial HUM you describe sounds like the transformer settling in

I found that most of the higher power PP design tube amps i tried were noisy (one exception was Craigs NOS VRD's )

Edited by joessportster
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I just got my VAC PA80/80 amp hooked up and expected to hear...nothing. However there is noise when there is no music playing. A slight sssshhhhhhh. Also, there is a slight power hum for the first 20 seconds or so when first powering the amp up. The sshhh and the power hum occur even when the preamp is not connected. My B&K exhibits the same sssshhhing. (but not the short power hum)

Is this "normal?"

Noise is never easy to trouble shoot and maybe my post will get a few of the more technical people to weigh in. Here are a few links that are fairly good in helping understand noise.

http://sound.westhost.com/noise.htm

http://www.rane.com/note145.html

http://www.computerworld.com/s/article/56253/Signal_to_Noise_Ratio?taxonomyId=015

Essentially, all audio components create some level of 'noise' in the audio signal and it is important to understand how to keep the noise in the singal as low as possible. In general, the 'analog' audio gear (i.e. amps, turntables, tape decks, etc.) typically have a much lower signal-to-noise ratio than digital components such as the DVD & CD players used today.

I believe that tape hiss in an old cassette has a signal-to-noise ratio of about 40 dB and dolby c would be about 75 dB. In comparison, even an inexpensive CD player produces a signal-to-noise ratio of 100 dB or higher.

I believe that the noise floor of the amplifier determines the amount of 'hiss' (i.e. circuit noise) that you will hear through the speakers. In addition, the higher electrical sensitivity of the speakers (i.e. Klipschorns), the more acoustic energy the speaker makes of any electrical energy input, the higher the noise floor level will appear against the music signal, as the noise is constant, and only another signal played at higher levels (i.e. music from the recording) cover it up.

In looking at the manual for your amplifier, it has a signal-to-noise ratio of < 1.5 mv at the output, S/N ratio > 84 dB, which will most likely give you a low level 'hiss' from the high frequency tweeters. I suspect that the amplifer may not be the best match for extremely sensitive speakers.

Link to the VAC manual for the PA80/80 for specifications reference.

http://www.vac-amps.com/manuals/Manual_PA80-80.pdf

Does the 'light sssshhhhhhh' increase with volume?

If noise increases with volume, it could be components (i.e. tubes, resistors, cold solder joints, loose connections, dirty tube sockets, bad filter cap, etc.) of the amp may be deteriorating and drifing out of spec or going bad.

Does the 'light sssshhhhhhh' stay constant?

If noise stays constant, see above. While you cannot overcome the noise floor spec, this is one area where I believe that a thicker gauge cable with better conductors/connectors could result in less noise in signals as it helps eliminate cross talk between components. In addition, keep the interconnect cables away from the power supplies of the equipment.

You probably will not completely eliminate the hiss; however, you just need to reduce it below the audible threshold of your normal listening volume levels.

Is the 'light sssshhhhhhh' at the lower frequency levels (i.e. woofer mid bass)?

This is probably a ground loop. If so, eliminate any possible groud loops and pull any lamps or lights, especially lights with dimmers, out of the outlet you power your system with.

If you are a classical music listener and the noise can be heard from your typical listening position, it will probably drive you nuts as the noise will easily be heard between the movements or during the quieter passages. Then you have the aspect of knowing the noise is there and this often develops into a focus on the noise over the music. Now if it is just a matter of hearing the noise when you are an inch from the speaker, the only thing I can ask is 'will that be where you intend to be while you listen to music'?

Edited by Fjd
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My experience with Jolida tubes resulted in tube noise......... My experience with Cary tubes was clear of tube noise. My experience with SS is no extraneous noise, reliability and performance. The SS equipment is older Adcom gear and newer ACCUPHASE. Oddly I had system hum I could not lay hands on until recently when I learned it was coming from a Balanced Power line conditioner. It was very low frequency transformer hum. In my experience tubes were a poor experience rife with failures and oddities such as tube artifact. Guess I'm just not esoteric enough for tubes as such things seem to just come with the territory.

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