Preamplifier woes

[joetama 5,000+ posts]

What's the model and specs on it? Why are you selling it? And How Old is it?

I might pick it up because I need another pre-amp at home...

BTW, what's with the Anti-Fi in you sub thing there....

 

[Beat_Dominator 5,000+ posts]

It's a Parasound P3, they came out in '00 I believe. I am the second owner, dunno what model year mine is, they never returned my email about the serial # code.

 

[Beat_Dominator 5,000+ posts]

Oh, selling it because I wanted 2 pairs of balanced outs.

*edit* Balanced In I mean oops.

 

[thylantyr 10+ year member]

It doesn't //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
My stuff is based on designs that came about decades before stereo came into existence, you think I'm running balanced inputs? //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

I read the thread this time. lol

You have a tube front end and tube amp and arn't satisfied with the noise from

the tube preamp. You should look into my suggestion, reduce the gain... call

the company up? Fish for a schematic? You can probably reverse engineer

the wiring and draw up a schematic, it can't be that hard. How much stuff

is inside the rogue?

Right now the solution is to migrate from a tube preamp to solid state?

If so, does the tube amp support higher voltage preouts? or can you

adjust the gain on that tube amp, even if you need to mod it.

Basically, that's what I'm getting at. A high voltage SS preout and reduce gain

tube amp will offer less audible noise. The balanced issue is a secondary issue

not applicable to your situation.

I had a problem with a SS amp where it was too noisy for my taste. A simple

mosfet design that when you placed your ear inches away from the tweeter,

you can hear audible hiss. The root cause is the circuit design, the quick fix is

to reduce the amp gain and feed this amplifier a higher voltage 'clean' input

to compensate. All it took was a opamp preamp circuit on the front end, simple.

This cured the amplifier problems, you could place your ear right on the tweeter

and hear no hiss.

 

[Beat_Dominator 5,000+ posts]

thylantyr: I am handy with a soldering iron.....but that all sounds like a pain in the *** //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

 

[joetama 5,000+ posts]

^^^^^

Haha... Agreed....

 

[thylantyr 10+ year member]

Yoda: Help you I can. Yes, mmmm.

Yoda: You must unlearn what you have learned.

Yoda: No. Try not. Do... or do not. There is no try.

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[thylantyr 10+ year member]

I know this is hard, but check out this schematic, a common SS amp.

http://www.leonaudio.gr/images/4x50sch1.JPG

Text book design, 3 stage.

R6 and R8 ratio determine gain.

If you look closely, R8 connects to the output which makes it the feedback

resistor for the input stage. You can raise R6 in resistance to lower gain

or reduce R8 or any combination of the two. Common sense rule says

that increase R6 is ideal because decreasing R8 can drive transistor Q2 with

more current.

In other words, changing one resistor in a preamp or power amp

can allow you to opimize your noise and get better results.

Amplifier Mod Made Simple[tm] By John Basedow //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

http://fitness-made-simple.com/?source=adwords

 

[JimJ 5,000+ posts]

http://www.soundstage.com/revequip/rogueaudio_metis.htm

Thought this was interesting. A review of the Rogue Metis, a close relative of the Rogue Model 66, except with 6SN7 tubes...

When I hooked up the Metis to my Art Audio amp and ReTHM speakers, it was a bit noisy, producing easily heard hiss and low-level hum. The combination of a fairly sensitive amp input (0.7V) and very sensitive speakers (102dB) makes a very good noise detector. My standard noise remedy is to insert Rothwell inline attenuators between the preamp and amp, which reduces the signal to the amp by 10dB. The signal that is reduced contains the noise, so when the preamp volume control is turned to the desired setting, you’re getting more signal and less noise. The Metis has oodles of gain, so the Rothwell attenuators worked well. There was still a very slight buzzing from the Metis, audible only near the speakers. Yes, I tried floating the ground, but that just added some hum. Other preamps in my collection (deHavilland Mercury 2, Audio Note M2 Phono, and Audio Research SP9 Mk III -- all more expensive units) don’t exhibit a similar noise problem.

Describes my problem to a T.

 

[Beat_Dominator 5,000+ posts]

My MLs have a sens. of 84dB.....on a good day //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[thylantyr 10+ year member]

http://www.soundstage.com/revequip/rogueaudio_metis.htm
Thought this was interesting. A review of the Rogue Metis, a close relative of the Rogue Model 66, except with 6SN7 tubes...

Describes my problem to a T.

There's some comedy to this.

To explain.

An amplifier has gain, and it's fixed gain as shown on that schematic I linked

eariler.

But, amplifiers with gain knobs are not really gain adjustments, they are input attenuators to reduce the signal, gain remains fixed

in spite that the amplifier is labed as 'gain'. ... lol ... You probably know this already ...

By adding input attenuators you are essentially making a 'gain control' even

though it's not the real thing. This can help relieve the problem, but if you

want to solve the problem at the root level, you change the amplifier gain,

that feedback resistor I talked about. This method will give you the best

performance because a high gain amplifier with attenuated input is still

in 'high gain mode' which can amplify noise present, usually noise from the

amplifier itself can be annoying.

 

[joetama 5,000+ posts]

My MLs have a sens. of 84dB.....on a good day //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

What do they have on a bad day?? Does anyone actually read Thy's posts anymore?

 

[Beat_Dominator 5,000+ posts]

I think a rating of like 82dB would be more realistic. Good thing I have plenty of headroom.

 

[joetama 5,000+ posts]

Well 90 is better //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif....

 

[JimJ 5,000+ posts]

Well 96 is...wait, that's the reason I'm having this **** problem in the first place.

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