If they both start a 0 and attunuate at .5db to max all it means is that the 50 'volter will drive a far more insensitive amp and or long runs of cables with out degredation. Beware however, some amps have large initial steps of attenuation, as much (or more?)as 3db. With those you could easily run out of usable attenuation with an amp which is very sensitive or a source which is high level.
I realized I aksed my question incorrectly. What I am wondering is if given the conditions described above, will the preamp that outputs 50 vrms sound louder than the preamp that outputs 20 vrms, assuming both are set at the same volume level????
No. It won't sound louder. By using the attenuator you will have effectively reduced the output to the amp to the same level, you'll just have a lot of power in reserve that you will never use unless you have a grossly insensitive amp or one specifically designed for that pre-amp output (balanced design perhaps?).
No, it wouldn't be louder. In fact, I am willing to bet you wouldn't even use any of the gain in either one! Many preamps don't need to be set past unity gain for the loudest music level used. Exceptions are preamps with post attenuators or those mated to a highly insensitive amp, like Newbee says.
Ok, so if this is the case, why does preamp a (50 vrms) play significantly louder than preamp b (20 vrms)? Is all due to the gain??? I am really confused because the only thing I have changed in my system is the preamp I am auditioning and the sound is already above my listening levels at volume setting "1" on the preamp (preamp a). Please explain so I can better understand what is causing the signficant difference in volume I am hearing.
Everything else being equal (and I doubt that it is) if preamp a has a lower output impedance than b it will play louder at the same setting.
What are the specs on the preamps? (BTW, 50Vrms is EXTREMELY high for a pre amp, are you sure about that?)
Do they really have the same gain?
Do they have the same taper on their volume controls?
Are you using them both balanced?
Why do you have this same basic question posted in several different threads? I think you'll get better answers if we don't have to follow 2 threads on the same topic.
Perhaps it would be helpful if you listed the preamps instead of having us guess what the problem is?
herman, I currently have the Classe CP-700 pre. The other pre I am auditioning is the new BAT VK-52se.
I checked their web sites but can't find any specs for gain on either of the preamps.
In addition to the output voltages being different (the headroom is there to keep distortion down at the levels you *do* play BTW) the preamps also have different *gain*. The two are not the same, although it sounds like the unit with the higher voltage also has more gain.
herman, i was told by BAT that the max gain is 17db. I am going to check the gain for the classe today...i will report back.
It does sound like they have different gain. If you can't find the gain, you can also use the input sensitivity voltage to get your answer.
I seem to recall you can change the gain in the new Classe Delta preamps. I remember my old CP50 had this feature. It is a very practical feature to get the most resolution out of your volume control.
Ok, I switched to the single ended output on my Cary which is supposed to be at 3vrms. And even though the volume has decreased by a bit, it is still pretty loud even with the preamp at the lowest possible setting.
Also, the output impedance of the BAT CVK52se is listed as 200ohms and the Classe CP-700 is 100ohms.
Now I am really confused why their is such as big difference in volume between the BAT and Classe preamps.
That difference in output impedance isn't enough to make any difference. Until you find out what the gain of the Classe is we are wasting our time speculating about the difference.
Quite simply a higher gain will result in a louder sound. The volume dial alows you to adjust the gain. A higher maximum ouput implies nothing unless you know the maximum input level.
Suppose that all signals are RCA line level and unbalanced; input is designed for a max of roughly 2 Vrms and therefore the gain at maximum output appears to be at least 25.
Suppose that all signals are line level and balanced; input is designed for a max of roughly 4 Vrms and therefore the gain at maximum output appears to be at least 12.
These high gains are unusual for a hi-fi pre-amp as most pre-amps are close to unity gain at maximum levels...the advantage will be better immunity to RF/EM noise (likely a lower noise floor downstage of the preamp).
To get back to normal volume levels you need to;
1) reduce the power amplifier gain stages to compensate for a large signal at the input of the power amplifier
2) attenuate the signal so that it matches the input capabilities of the power amplifier.
3) get a power amplifier that is specifically designed to accept this higher range of input signals
Good power amplifiers will often have potentiometers to provide flexibilty to handle various input level ranges.
Ok, I found out the gain of the classe is 14db, the bat is 17db. any ideas?
I got a response from BAT that explains the difference in volume control between my Classe preamp and the VK-52se even though they both have similar gain. I guess it comes down to digital volume control (Classe) vs discrete volume control (BAT). By the way, what is a "Discrete" volume control? Can someone explain why discrete volume control does not have as much attenuation as digital control?
Below is an exerpt from the email I got BAT sent me:
"...integrated digital volume controls give
you more room - they have 180 or more steps, allowing you to achieve greater
attenuation. I don't have solid information on Classe, but what you are
telling me is consistent with a use of such a volume control.
High quality discrete volume controls usually stop sooner. Reasons are
practical - cost and complexity...It is many times more expensive
than the integrated circuit attenuator. The reason we use that expensive
solution is the sound, of course.
Our volume attenuator has linear range of 70dB. We do not go further as
doing so would degrade the signal way too much. -60dB attenuation means you
are throwing away 99.9% of signal, letting just 1/1000 of it go through -
hardly good situation."
The maximun gain is within 3dB, not enough to explain the difference.
The output impedance is essentially the same compared to the input impedance of the amp.
The input impedance of each compared to the output impedance of the CDP should make no difference.
That leaves us with the taper of the volume controls. The only logical explanation I can see is that the louder one's steps are bigger at lower volumes than the other one. Have you contacted the manufacturers to see what they have to say?
If you want to ship them both to me I can measure the gain at the different control settings. You could do this yourself with a test CD and a cheap multimeter if you really want to know.
ok, i think i figured out what BAT meant when they replied to me. My Classe has a gain range of -84db to 14db. The BAT has a range of 70db, from -53db to 17db. So on the lower end, the Classe is attenuating by more than -30db which explains why on the lowest volume settings, music sounds so much louder. This doenst help but at least I understand what is going on.
Thanks for the follow up. It helps in the sense that when it comes to gain you now know what you are looking for in a preamp. If you want to stick with the rest of your components you either need one with a lot of attenuation like the Classe or you will need extra attenuators.
50 vrms from a preamp? Absurd! The industry standard for a CD player (line level signal capable of driving most power amps to near max volume) is 2 vrms. Most preamps can put out about 10 vrms, which is overkill.