Preamp gain ???


What gain will work well with my Classe CA400, 12db or 24db through balanced outs ???
slikric3000
This will depend a lot on the your speakers. How efficient are they?

Depending on the speakers, high gain might mean that you are only able to use a small fraction of the range of your volume control (which would be the case if your speakers are very efficient). On the other hand, low gain might mean you are not able to get your system to play as loud as you want (if your speakers are not very efficient).
I have the Dali Grand 90db/2.83v but I live in an apartment which I tought I would be into a house by now but the economy took a dive shortly after I bought it. I am guessing 24 would be ok maybe but may sound harsh. I am looking at Audio Research pre's.
this is the second preamplifier gain thread that has popped up in recent days...

it seems to me that preamplifier gain is generally irrelevant: what i would think should matter to you is what is the input sensitivity of the preamplifier, what is the maximum output level from the the preamplifier and what the clipping voltage is for your power amplifier. if your sources provide signal levels (typically around 500mv) to the preamplifier that hit the input sensitivity level then you can hit the maximum output level at the output of the preamplifier. in all likelihood, that maximum output level from the preamplifier is more than enough to drive your power amplifier into clipping (which i think might typically occur at around 4v or 5v).

the other topic that i have frequently seen commented concerns impedance matching between the preamplifier and power amplifier. as a practical matter, i don't know how much that really is an issue. the preamplifier specifications should tell you what input impedance it needs to see to drive maximum voltage and that should be way below the input impedance of most power amplifiers. for example, i have a bryston bp-20 preamplifier - according to the specifications, it can drive a maximum voltage (15v) into impedance loads as low as 600 ohms. my power amplifier (a bryston 4b-st) has an input impedance of around 50kohm, so you can see that impedance matching isn't really an issue in my case.

in any event, you can check the specifications on this stuff to be sure in your case but hopefully you have a better idea of what kinds of data to check.

there is the whole area of passive preamplifiers but i don't know anything about that kind of equipment so there may be a different set of considerations for which to account.
For many people the issue is too much gain, resulting in operating the pre w near max attenuation and at the lower end of the volume control's range. Under these conditions you may be in that portion of the attenuator where channel matching is not v. good and, particularly in the case of a stepped attenuator, where the "steps" are too coarse to give you good level control. Step x, too soft, step x+1 too loud. typically, the perceived volume difference between steps is less as you go to less and less attenuation (higher spls). Not knowing much at all about the technical side of electronics/circuits, I am guessing that this is due to the logarithmic relationship between power output and spls- Need 10x the power (wattage) to sound 2x as loud. So it really does NOT matter much as long as you are able to operate in the middle of the controls range. Believe me, I had a CAT SL-1 w stepped attenuator and 2 clicks up from 0 was too soft and 3 clicks up was "kick out the jams"! A real PITA.
Swampwalker is corrent! My current setup is a little less of the volume control than i would like. Icurrentlu USE the balance out, and if I switched to the RCA out, I would probably be right in the corrent range. Problem is i bought a 7 meter balance Hero, and to buy another one in RCA is a bit expensive. I may ask to have the balanced changed to RCA by Kimber Cable some time down the road!
Slikric,
It depends on the output of your source i.e. how many volts and also the sensitivity of your amplifier and speakers.The higher the source out put, the less gain needed from your preamp. The more senitive the amp(for example an amp with a sensitivity of .5volts would require less preamp gain than an amp with a sensitivity of say 1.5 volt to reach a given volume level). The same with speakers, 95db sensitivity would need less gain than a 88db speaker to reach a given sound volume. Most digital sources will be 2 volts or higher and often high gain preamps are`nt needed, 10 db of gain should be plenty. With too much gain in a system your useful range on the volume control will be quite limited i.e. 7-9 oclock, as above that level the sound becomes to loud, and fine tuning is very difficult.
And Charles1dad summarizes all of the issues perfectly on either side of the pre-amp. They all contribute to the "problem" of excess gain which manifests itself in having to operate the attenuator in a non-optimal part of its range. The pre-amp is also the place where you can (usually) have the manufacturer easily resolve the "problem". You can easily experiment w low cost line attenuators at the amp's input to determine how much the pre-amp gain needs to be reduced or use one the better 10 dB attenuators like the Rothwell for a slightly more expensive, easily reversible fix. If you do that and use heavy cables, make sure you provide some support under the attenuator or else, IME, you are likely to have a failure of one of the jacks.
i would say this: i think it unnecessarily complicates the problem is you are trying to solve amplifer-speaker interface problems at the preamplifer. it is more manageable to decompose the problem; with regard to the preamplifier the focus should be on the input signal levels from the sources. you can then focus on the output signal from the preamplifier but most reasonable preamplifiers should be able to drive a power amplifer into clipping at maximum output voltage (such that in reality you would likely never get anywehere near the maximum output voltage). then you deal with issues of speaker sensitivity sepearately but that is more concerned with whether the power amplifier is up to snuff to drive the speaker load.

so the issue at the preamplifier is the input sensitivity of the preamplifier and the input signal levels from the soruces. i would expect that the input sensitivity of a preamplifier is going to be around 500mv, which is the line voltage signal level that you tend to get from many sources. cd players tend to be a bit higher. where you really need to watch out is when using phono sources. here you have to make sure that the phono stage provides sufficient gain for the given cartridge. ideally you want the output signal level from the phono stage to come in at around the input sensitivity of the preamplifier.

so once you have managed the input signal levels from the sources then you want to make sure that the preamplifier can drive the output voltage to the power amplifier. as i stated, the voltage amplitude should be sufficient but you probably want to check the preamplifier manual to find out what is the minimum input impedance that the preamplifier expects to see at the power amplifier, then check the input impedance of the power amplifier to make sure that the specified input impedance is considerably higher than the minimum needed by the preamplifier.

that's the analysis that you should do at the preamplifier. what you want to determine is whether the sources are providing adequate signal levels to the preamplifier and that the preamplifier is providing an adequate signal level to the amplifier. a side benefit of this analysis is that the signal being provided to the power amplifier will likely have a better signal to noise ratio, which, if the amplifier is up to snuff, will result in a better sounding system. issues related to the interface between the power amplifier and the speakers should be addressed in an analysis of the capabilities of the power amplifier.
Paperw*- Nothing that you have said is incorrect but you have neglected the attenuation/gain (if active) provided by the pre-amp, which then is added to the gain of the amp. That can result in excessive overall system gain which results in the user having to operate his pre-amp w excessive attenuation which can have negative effects on the sound. The speaker/amp interface is not usually a decision based on max gain provided by the amp vs. speaker sensitivity, and room size, source output and volume preference all vary. Therefore, god in her infinite wisdom invented the pre-amplifier. Some have adjustable gain for each input. Some do not. Some are passive and provide attenuation only. some are active and have varying amounts of gain. Some of have stepped attenuators and some do not. Some have tape loops and some do not. Some have line and phono stages. some of those w phono stages can accommodate LO MC carts, some only MM or MI carts. Not all line level sources have the same output voltage (some CD players can deliver 2V!) The ability to alter the overall gain/attentuation of a pre-amp may be vital under some circumstances. IN fact some manufacturers have recognized this by incorporating separate gain controls via front or rear panel toggle switches (e.g., Supratek); front panel rotary controls (e.g., Joule), internal dip switches/jumpers (e.g., Nagra) or internal resistors that are designed to be switched out or bypassed (some ARC).

I for one cannot imagine that sensitivity would be the primary criterion I would use to pick a speaker. Of course, that does not mean that you don't need to make sure that you don't get a serious mismatch between speaker and amp but I don't think that you are going to go w a 84 db/w/m speaker instead of a 92 dB/w/m just to provide proper volume control.

Again, this also assumes that you have a reasonable match btwn amp and pre-amp based on impedance and input sensitivity. Just my opinion; worth the proverbial $0.02. IME, YMMV, do not try at home, professional driver on closed course, LSMFT, etc, etc. ;~)

02-21-11: Swampwalker
Paperw*- Nothing that you have said is incorrect but you have neglected the attenuation/gain (if active) provided by the pre-amp, which then is added to the gain of the amp. That can result in excessive overall system gain which results in the user having to operate his pre-amp w excessive attenuation which can have negative effects on the sound. The speaker/amp interface is not usually a decision based on max gain provided by the amp vs. speaker sensitivity, and room size, source output and volume preference all vary. Therefore, god in her infinite wisdom invented the pre-amplifier. Some have adjustable gain for each input.
what i am stating is that if you manage the signal levels at the input of the preamplifier, the gain of the preamplifier is largely irrelevant [i appreciate that there is a gain relationship between the input sensitivity level and the maximum output level from the preamplifier]. that is why i am stating that you should look at the signal levels from the sources and the input sensitivity of the preamplifier and manage the problem at the input of the preamplifier. in the case of a phono source, you want to adjust the gain of the phono stage so that the phono preamplifier provides an input voltage level that hits the input sensitivity level for the preamplifier. on the other hand, if you have a source that produces a "hot" signal (like the CD that you mentioned) that is way above the input sensitivity, then the adjustment is to reduce the signal level at the input of the preamplifier. that's what an attenuator would do. some preamplifiers have trimming resistors that allow you to accomplish the same thing on a per-input basis. for my own part, i have never made use of an attenuator but YMMV.

the problem with the focus on gain as a selection criteria for a preamplifier (and, btw, i would expect that the input sensitivity of the preamplifier would vary according to the gain) is that if you select a gain level based on a "hot" signal, then the other signal levels are likely to be below the input sensitivity level for the preamplifier. in that case you are more likely to experience degraded signal to noise ratio for those weaker signals.

as i stated, you also want to make sure that you know what the minimum input impedance the preamplifier needs to see in the amplifier, which is something that you should be able to get if the manufacturer supplies good product specifications. but, in practice, i think impedance matching is rarely an issue. yeah, i suppose you should check the input sensitivity of the amplifier for completeness, but power amplifier input sensitivities tend to run between 1v and 2v, so i would rarely expect that to be an issue either. but, of course, it is always a good idea to check this stuff just in case...

the point is, if you ensure that you provide appropriate input signal levels to the preamplifier from the sources, you are not likely to have a problem in providing an appropriate input signal level to the power amplifier from the preamplifier. then the task becomes one of whether the amplifier is up to the task of driving the speakers. but if you have to take on the amplifier-speaker interface issues from the preamplifier, then you've probably got some problems in your system in general.
what if the gain in the pre-amp section is too high and, as a result, generating excessive hiss or residual noise? I have this problem and even the manufacturer states it is coming from the pre-amp section on my integrated. What else can one do if not reduce the gain?
if your integrated has pre out and main in jacks or a tape/processor loop, you could insert attenuators in the loop.
Hi Bobrock

I like Swampwalker's idea. I don't if your integrated has XLR Outputs and inputs but this is the line level attentnuator I use. The possible problem is that it lowers gains in increments of 10db. They are about $40 each but are well built IMO.

Audio-Technica AT8202 Attenuator with 10, 20 or 30 db of Selectible Attenuation - In-Line XLR Barrel
Rothwell sells well regarded 10 dB attenuators in RCA and xlr termination.
The Rothwell Attenuators will change (lower) the load impedance his BAT VK5 preamp will see, and being tube it (the load) may come down too far for it to perform at it's optimum, and could roll of the bass early as it is capacitor coupled.

[url]http://www.stereophile.com/content/balanced-audio-technology-vk-5-preamplifier-vk-6075-power-amplifiers-vk-5-measurements[/url]

Cheers George