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purpose of a preamp?

post #1 of 9
Thread Starter 

Is there any reason for me to use the preamp feature of my LD MK III for my m-audio av40 speakers?  Im not exactly too sure what the purpose of a preamp is.  Based on the wikipedia description (which isn't too helpful), I don't need it since the gamma-2 provides a line out?

post #2 of 9

Generally, pre-amps are used in conjunction with power amplifiers to power a set of speakers. Dedicated pre-amps give the power amplifiers more juice, and generally have volume controls (unlike the power amps).

 

Your av40s don't need a preamplifier - they have a built-in integrated amp designed to work with a line-level signal such as the one your Gamma 2 outputs. You can try using the pre-amp out of your LD if you want and see how it sounds - I've found that using the pre-amp out of my HP amp actually doesn't help the sound on my powered Audioengine A2s.

post #3 of 9

Preamps do this:

 

Select the input

Adjust the volume

Provide output 'drive'

 

In addition they can also do this:

 

Convert balanced to unblanced signal transmission and vice-versa

Adjust left / right balance

Provide a mute function

Provide signal polarity inversion

Have fancy displays to indicate source, volume level, etc.

 

 

I don't know your set-up or the LD specification, so it's simply going to come down to volume control. Ask yourself how are you going to do that? Remember that digital volume controls reduce resolution with signal level, so doing it in with an anolog control (as is likely in the LD) is sometimes best. Then again some cheap analog volume controls are of very poor quality with poor left / right channel matching. Try it and see.

 

post #4 of 9
Thread Starter 

there are volume controls on the speakers and i didnt notice any sound quality change when i added the LD as a preamp.

 

Thanks for both responses!

post #5 of 9

I have a similar question but with a slight twist.

Would using the LD as preamp to a MiniWatt powering B&W CM1's (to a decent volume I must say) provide a boost of watts? If so how much and how is that calculated?

Thanks

post #6 of 9
Quote:
Originally Posted by sluker View Post

I have a similar question but with a slight twist.

Would using the LD as preamp to a MiniWatt powering B&W CM1's (to a decent volume I must say) provide a boost of watts? If so how much and how is that calculated?

Thanks


There are a number of issues that you need to consider.  First, what is the gain from the LD?  If it acts as a passive preamp (aka a passive line stage) with unity gain, then there will be not "boost" in the signal.  Second, you need to consider the output impedance of the preamp and the input impedance of your MiniWatt.  The general rule of thumb is at least a 10x differential.  Even still, some preamps and amps just do not play well together.

 

Also note that if you do hook things up, I believe that you will be running your signal through two preamps, the LD and the MiniWatt (assuming that the MiniWatt is an integrated amp).  Are you at all able to bypass the preamp on the MiniWatt and feed the signal directly into the amplifier portion of the unit?

 

--Ken

post #7 of 9

Ken,

Thanks for that, I would not know how to bypass the preamp stage of the MiniWatt and I am not planning to take it apart. What would happen if I run the signal through two preamps? could this cause permanent damage to the Miniwatt or the speakers? Or would it just result in clipping/sound distortion?

Stan

post #8 of 9

Hi Stan,

 

First, a disclaimer.  I am not an electronics geek, so my advice comes to you as an owner of tube and solid state gear.  So, while I have researched this issue a bit in the past, I cannot explain any potential issues in any detail.  Having said that, it appears from the specs. that I could find on the web, the output and input impedances for the two units should be acceptable to each other.

 

Also, having briefly looked at the specs on your equipment, I do not think that your proposed set up will solve your problem.  You have a very low powered amp driving relatively inefficient speakers (84dB), and I am not certain if any additional gain, if available, will really solve your problem.  I see two solutions - buy more efficient speakers, or use a more powerful amp in place of the Miniwatt.  Perhaps you could use the LD to power some type of affordable solid state amp?

 

Good luck,

 

--Ken

post #9 of 9

Thanks Ken,

I have hooked up LD as preamp and it does seem to work OK. However, It does sound a bit distorted at really loud volumes (+110db, needless to say I do not listen to it at that volume in the room it is in) and a bit too "tubey" (if that is even a word) at regular volumes. Based on my reading I have come to the conclusion you advise as well. In fact I am looking at buying the marantz pm5003 (I can get a factory refurb for $330). 

The one reservation I have is that I really enjoy the MiniWatt by itself driving the CM1's (to surprisingly decent volumes) and with the headphone adapter it really has been a little gem. However, I am dying to see what the CM1' can do properly amped.

This hobby is definitely wallet draining.

P.S. If you know anything about the 5003  or other SS amps you can suggest (<$500) any advice would be welcome.

Thanks in advance.

Stan

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