preamp with GC

[windsonian]

Hi there,
I've been looking around, but am still a little vague.
Can someone please explain to me in layman's terms:
Why do I need a preamp with a gainclone amp?

[preiter]

It's not strictly necessary, you can just put a pot on the input for volume control. That's how I am running mine right now.

They seem to sound better with an active buffer feeding them, however. I just finished the electronics for my pre-amp / active crossover. Just have to build the chassis now

[windsonian]

Originally posted by preiter
It's not strictly necessary, you can just put a pot on the input for volume control. That's how I am running mine right now.

They seem to sound better with an active buffer feeding them, however. I just finished the electronics for my pre-amp / active crossover. Just have to build the chassis now

Thanks, that's kind of what I figured, but could find nowhere that anyone said you don't need one.

If I've got sources with controllable volume to begin with (eg a PC), does this mean I can plug straight into a GC that I make for $100?

[preiter]

It will work, it may or may not sound good. The problem with attenuation at the source is that you then have an attenuated signal traveling through the interconnect cable.

Generally you want the strongest possible signal travelling through the long wires.

But you can set it up that way initially, see how you like it, and add a pre-amp or pot on the GC later if you want to. Such is the flexibility of DIY.

[windsonian]

Originally posted by preiter
It will work, it may or may not sound good. The problem with attenuation at the source is that you then have an attenuated signal traveling through the interconnect cable.

Generally you want the strongest possible signal travelling through the long wires.

But you can set it up that way initially, see how you like it, and add a pre-amp or pot on the GC later if you want to. Such is the flexibility of DIY.

attenuation, meaning the volume control?

so the only reason for a preamp (in a basic system) is so you can decrease the distance from volume pot to power amp?

is there any concern regarding the voltage output from the source to the power amp input (noting that many preamps have a 6dB gain for example)?

which leads me to another question....
i was looking at a preamp (maybe on esp, can't remember), where the CD input bypasses the gain stage. it said that the gain stage is to bring all the other inputs up to CD level. I understand this for phono, mic etc... but why would AUX inputs need gain when CD input doesn't? Is a CD output usually higher than other sound sources (PC etc)?

[billdinva]

I used a modified version of ESP's OP2134 for a preamp and DS1802 pushbutton digital vol/balance contol on the same board as two 3875's. Sound's great.

Although the 100% level for a CD player is supposed to around 2Vrms. Most CD's come nowhere close to this level 300mVrms is about the max. And some are recorded even lower.

Note that the min GBW for the 3875 is only 2MHz. I used resistors or 22k and 1k for feedback giving gain of 23x. I set the gain of the preamp of such that a 150mV rms signal at full volume would reach the maximum output level.

If you check the specs of a typical receiver (integrated preamp/tuner/amp), you will see that the sensitivity is around a couple hundred millivolts, even on the CD input.