Does a preamp attenuate?

[doctorcilantro]

I've got a question rolling around in my skull about 2vrms standard for CD players.

Since each output for stereo is essentially a separate circuit, does this mean that each channel outputs 2vrms as the standard, or are specs given per channel?

i.e.

• Output level: 2VRMS +/-0.5dB (typical); 2VRMS +/-1dB (limit); 1KHz, 0dB (condition)

I ask because my amps input sensitivity is 1vrms. It would seem that if 2vrms is going to the preamp, and using 1vrms input sens. for the amps with high efficiency speakers would mean that I am attenuating the signal with the preamp, and limiting the volume control range on the pre. Does this attenuation color the sound? I have currently adjusted the output of my DAC1 (which run to the preamp), so that with preamp at max volume with a 0dbfs sine wave, the vrms output of the preamp is .99 vrms. I now have a much more refined volume control.

Thoughts?

DC

[Don Richard]

You are getting 2 V per channel at maximum output. With high level sources the preamp is indeed attenuating the signal. The electronics serve mostly to match the impedance of the source to the input impedance of the amp. What you are doing to get more range from your volume control is OK as long as it doesn't increase noise. Some folks are hooking CD players with built in volume controls straight to the amp, eliminating the preamp, and report less noise and distortion as a result.

[doctorcilantro]

Very interesting. So would it be correct to assume that with a CD player, which hads avolume control, that if the knob is cranked to max, it's output is 2vrms?

If so, I wonder if people are outputing a lower output signal. I was using something like .5v out of my DAC1 and I think at 2pm the volume on the Sunfire>Mini-Mites is LOUD....more than I would ever need.

Like I said, the sensitive speakers combined with sensitive input on the mini-mites almost forces me to attenutae at the DAC1 with the calibrated trim pots on the back.

thanks

Jon

[Don Richard]

Very interesting. So would it be correct to assume that with a CD player, which hads avolume control, that if the knob is cranked to max, it's output is 2vrms?

Correct

If so, I wonder if people are outputing a lower output signal. I was using something like .5v out of my DAC1 and I think at 2pm the volume on the Sunfire>Mini-Mites is LOUD....more than I would ever need.

Adjusting the levels of multiple components is called gain staging, and one reason to do that is to get a better volume control range

Like I said, the sensitive speakers combined with sensitive input on the mini-mites almost forces me to attenutae at the DAC1 with the calibrated trim pots on the back.

Good job, you've solved your problem

thanks

[doctorcilantro]

Maybe Mr. Deneen has some input on why Quicksilvers have 1v instead of 2v for the input sensitivity?

dc

[LarryC]

Wasn't the QS owner and designer familiar with Klipschorns and designed some of his electronics for them? From my somewhat limited experience, 1 V in for only 25 watts out is a fairly low gain, which has one great advantage for me: it doesn't seem to amplify pre-amp noise as much as 1 V or 0.5 V in for humongous power out. That can be a problem with 104-db efficient speakers like Klipschorns.

As Don said, the different maximum voltage levels may be useful for gain matching. My CD player output can be varied between 0.5 and 9 (!) volts. In my former CAT preamp, I set it to 0.52 V out to keep the volume control close to the same setting for phono and CDs, since the CAT had high (26 db) linestage gain but low (46 db) MC phono gain. I now have a Joule preamp with only 11 db linestage gain but 61 db MC phono gain, so I moved moved the CD output up to 1.04 V, again to bring volume control settings on CD and phono closer together. It also closely matches my tuner, rated at 1 V out.

For me, these maximum voltage ratings are mostly useful for gain-matching and noise issues. Also, impedance apparently can be part of the gain picture in ways I don't understand.

[djk]

Most preamps run the signal from the input selector switch into the volume control, from there it goes into the line amp and/or tone controls.

The 2V signal from the CD is only at digital zero, assuming they leave no headroom.

Many amps have some headroom, 3dB or so. If the amp is rated at 2V for nominal power you will never be able to clip it with a passive preamp. This could be good or bad, depends on your system. 88dB speakers at 10ft with a 100W amp only hit 98dB peaks. When they try and play it 'loud' they are probably driving their amps 6dB into clipping.

Klipsch systems with certain brands of electronics with 30dB linestages may have problems with excessive noise, poor volume control tracking at low levels, etc.

[SET12]

There was at one time a quasi-standard sensitivity of around 2V for HiFi power amps. This came about in an age of phono cartridges and tuners which did not have the high output of CDPs, and a preamp was an assumed component. Many amp makers now move much of the preamp gain into the amp and therefore lower the sensitivity to 1V or even .5V on some amps. I suppose they are doing this so you can plug certain CDP direct into the amp.

If all you have is one source, and you like the sound of the CDP plugged directly into the amp, then you are done.

mdeneen makes a good point!

Its exactly what I do but I do have more than one source but all my sources have volume controls I could just wire up some additional jacks with high quality switchs but I mostly have been listening to CD as of late and occasionally run my DVD direct as well.

My amps have are about a 1/2 volt in for 10 watts out my CD player will clip my amp at the 1-2 o'clock range on its volume control which goes from 7-5 most of my listening is from 9-11 with 12 o'clock being pretty loud 95db+.

Of course I always knew direct was possible and I'm quite aware that preamps can add life and drama to music.

I'm also quite aware that they can subtract as well which is what I found with a good FET line stage that I had that now has been sitting in my closet for several yrs now as I found that my CD direct was hands down far more dynamic and revealing so much so that I'm afraid its going to take a 5-$10,000 line stage to convince me to use one!

I recently had a good $2,000 tube line stage that a friend brought over for a listen. I held my breath as I knew if I liked it I'd be designing one for myself! But as it was, It just couldn't compete in my system which has a high degree of resolve. Its amazing what simple signal paths can reveal!

Doing direct allows one to sink more funds towards a better source as well.

It really works well for me!

Good Thread!

Cheers

SET12