Preamp Question!

Lab_Rodent · 28th November 2007, 02:36 PM

I have build some active monitors. Problem is that the levels dont go high enough to match the audio level of my other speakers. Only single phono/RCA channel preamps I can find all say that they are for turntables. Will they still work if my input is not from a turntable?

I found this one, and in all of the specs it says "allows you to adjust preamp gain for a wide variety of input sources".

I dont want to buy a 10 channel rack mount preamp for this one channel.

PigletsDad · 28th November 2007, 04:45 PM

Pre-amps for turntables are not suitable. They have a special frequency response, and follow the RIAA curve, with masses of bass boost and some treble cut.

I think you just want a standard line stage. The simplest thing I can think of is 1 opamp, about three or four resistors, some coupling capacitors, and some sort of power supply.

Google for line stage.

paulb · 28th November 2007, 05:02 PM

This will work:
http://headwize.com/projects/showfil...=cmoy2_prj.htm
Also see this for general information
http://tangentsoft.net/audio/

Lab_Rodent · 28th November 2007, 08:04 PM

I cant find much of anything on "Stage Lines" (in english). Did find a few though, they are all high dollar.

I thought about using a headphone amp and just using some RCA converters. I dunno' about building my own though.

Lab_Rodent · 28th November 2007, 08:12 PM

I found a couple of things that maybe you amp guys can tell me about.

This guy seems to make just what I need, and its THD% rating is great.
"The Pure III" preamp/headphone amp

I would make something like this, seeing all of the parts come with it. Getting all of the correct parts is the biggest issue for me. Do you all know much about these Ramsey kits? Sound quality is very important to me. Think this is good?
Ramsey Headphone amp kit
I figured I could change the 1/4" jack to RCA's when I made it.

Gordy · 28th November 2007, 11:27 PM

Although I don't know about the Ramsey company, the unit looks fine for $30 (/ £15). (Don't forget to buy the power supply too).

Lab_Rodent · 28th November 2007, 11:48 PM

I have 6 or so "wall wort" power adapters ranging from 9 to 12 VDC. This says it works on 9 to 15 VDC, so one of mine should work.

paulb · 29th November 2007, 12:35 AM

Quote:

Originally posted by Lab_Rodent
The-Pure-III-DC-Coupled-Extreme-Low-Noise-Headphone-Amp

This is the same as the Cmoy amp project I posted. You could build one yourself, especially following the guide in the other link I posted.

Quote:

Ramsey-SHA1C-Stereo-Headphone-Amplifier-Kit

This is based on an LM386 low power speaker amp, and is not very good quality. Not recommended.
If you do want to buy something, the Cmoy-type would be better. You can use your wallwarts for it.

nogoodboyo · 29th November 2007, 12:49 AM

There are some very nice looking pre-amp kits at www.twistedpearaudio.com

Lab_Rodent · 5th December 2007, 11:14 PM

Thought I would go ahead and share my slightly modified Ramsey Preamp/headphone amp. As you can see I made it so I can just plug in RCA's instead of having to use the headphone jack. It works great, just what I needed.

28th November 2007, 02:36 PM	#1
Lab_Rodent diyAudio Member Join Date: Nov 2007	Preamp Question! I have build some active monitors. Problem is that the levels dont go high enough to match the audio level of my other speakers. Only single phono/RCA channel preamps I can find all say that they are for turntables. Will they still work if my input is not from a turntable? I found this one, and in all of the specs it says "allows you to adjust preamp gain for a wide variety of input sources". I dont want to buy a 10 channel rack mount preamp for this one channel.

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28th November 2007, 04:45 PM	#2
PigletsDad diyAudio Member Join Date: Jul 2007 Location: South Worcestershire	Pre-amps for turntables are not suitable. They have a special frequency response, and follow the RIAA curve, with masses of bass boost and some treble cut. I think you just want a standard line stage. The simplest thing I can think of is 1 opamp, about three or four resistors, some coupling capacitors, and some sort of power supply. Google for line stage.

28th November 2007, 05:02 PM	#3
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	This will work: http://headwize.com/projects/showfil...=cmoy2_prj.htm Also see this for general information http://tangentsoft.net/audio/

28th November 2007, 08:04 PM	#4
Lab_Rodent diyAudio Member Join Date: Nov 2007	I cant find much of anything on "Stage Lines" (in english). Did find a few though, they are all high dollar. I thought about using a headphone amp and just using some RCA converters. I dunno' about building my own though.

28th November 2007, 08:12 PM	#5
Lab_Rodent diyAudio Member Join Date: Nov 2007	I found a couple of things that maybe you amp guys can tell me about. This guy seems to make just what I need, and its THD% rating is great. "The Pure III" preamp/headphone amp I would make something like this, seeing all of the parts come with it. Getting all of the correct parts is the biggest issue for me. Do you all know much about these Ramsey kits? Sound quality is very important to me. Think this is good? Ramsey Headphone amp kit I figured I could change the 1/4" jack to RCA's when I made it.

28th November 2007, 11:27 PM	#6
Gordy diyAudio Member Join Date: Nov 2006	Although I don't know about the Ramsey company, the unit looks fine for $30 (/ £15). (Don't forget to buy the power supply too).

28th November 2007, 11:48 PM	#7
Lab_Rodent diyAudio Member Join Date: Nov 2007	I have 6 or so "wall wort" power adapters ranging from 9 to 12 VDC. This says it works on 9 to 15 VDC, so one of mine should work.

29th November 2007, 12:49 AM	#9
nogoodboyo diyAudio Member Join Date: Dec 2004 Location: SF Bay Area	There are some very nice looking pre-amp kits at www.twistedpearaudio.com

5th December 2007, 11:14 PM	#10
Lab_Rodent diyAudio Member Join Date: Nov 2007	Thought I would go ahead and share my slightly modified Ramsey Preamp/headphone amp. As you can see I made it so I can just plug in RCA's instead of having to use the headphone jack. It works great, just what I needed.

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