Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 5th August 2013, 11:53 PM   #1
Jsixis is offline Jsixis  United States
diyAudio Member
 
Join Date: Feb 2011
Location: Columbus Ohio
Default LME49720 Pre amp PCB/Kit

I ordered this pre amp kit and it arrived today.

Stereo Tone Control 3 Way Audio Preamplifier Kit Bass Mid Treble Analog | eBay.

the documentation is here www.siliconwiz.com/k330/doc.pdf

Really small 2 1/2" by 3 3/4". Almost too small for my plans.

I ordered this because to me it looked like a decent pre amp.
It uses LME49720 which seem to be great chips, seems to have above average capacitors.
I like the tone controls where they are (60hz 1k and 8 k), and it came from New York.

I may need to order a power transformer since this thing only requires 65ma and they recommend a 17 volt which would be hard to find so I'll probably look for a 15-0-15 supply.

Suggestions greatly appreciated, I'm a noob who prefers to just assemble kits and leave the designing to those who enjoy all of that math.

Thanks
  Reply With Quote
Old 6th August 2013, 01:35 AM   #2
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
The LME49720 is a great opamp and has a maximum rating of 36v (-/+18) and anything up to +/-17v is good.

A simple supply can be made using a LM7815 and a LM7915 TO-220 packaged regulators.

The LME49860 is even better and is good for +/- 22v max.

jer
  Reply With Quote
Old 6th August 2013, 01:50 AM   #3
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: South Florida
I just ordered one of these to add line inputs to a guitar amp I am building. I'll probably run it on +/- 15 volts derived from the heater supply.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 6th August 2013, 11:24 PM   #4
Jsixis is offline Jsixis  United States
diyAudio Member
 
Join Date: Feb 2011
Location: Columbus Ohio
I'll have to read up about using LM7815 and a LM7915 for a power supply.
I'll probably start off minimal gain but still want a power supply 15-17 volts.
  Reply With Quote
Old 6th August 2013, 11:26 PM   #5
Jsixis is offline Jsixis  United States
diyAudio Member
 
Join Date: Feb 2011
Location: Columbus Ohio
Quote:
Originally Posted by tubelab.com View Post
I just ordered one of these to add line inputs to a guitar amp I am building. I'll probably run it on +/- 15 volts derived from the heater supply.

I've thought about this for a small practice bass rig going to a tda2050 or LM1875 chipamp. On that I would change the crossovers, maybe use slider pots to imitate an eq .

Have to build this one 1st.
  Reply With Quote
Old 7th August 2013, 12:44 AM   #6
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
The LM78xx and 79xx regulators are very easy to work with and don't require huge filter capacitors.

bipolar power supply - Google Search

Radio shack has some small 25.2v center tapped transformer that will work.

http://www.radioshack.com/product/in...1&locale=en_US

This one should be able to power your preamp and a small chipamp,

http://www.radioshack.com/product/in...tent=CT2032230

jer

Last edited by geraldfryjr; 7th August 2013 at 12:53 AM.
  Reply With Quote
Old 7th August 2013, 11:22 PM   #7
Jsixis is offline Jsixis  United States
diyAudio Member
 
Join Date: Feb 2011
Location: Columbus Ohio
I have several of those 2 amp radio shack transformers, when they decided to get out of electronics they were selling them for 2 bucks, even today they are a good price and they are shielded too.
I'll probably go buy one of the smaller MA transformer since this is suppose to draw a maximum of 65ma.
I have a choke but it is only rated for 50ma.
  Reply With Quote
Old 7th August 2013, 11:45 PM   #8
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
WoW.....2 bucks !!!
That is a good deal.....Had I known that I would have gotten a bunch more of them!!!
I have used those for years in many projects and I just used my last one in my variable 0v to 13.5Kv power supply.


The Opamp won't draw any more than about 25ma. worst case and typically about 10ma. under normal use as a preamp.

That transformer will give you +/- 17.8V I used a couple of diodes in series feeding each rail of the opamp to drop the voltage for a safe level in order to not fry the chip.

Two diodes in series will give you aproximately 1.1v to 1.3v drop.

Do measure the voltage First by loading the supply with a 1K to 5K resistor to ground before hooking up the preamp and if it is to high add another diode.

That is the cheap and quick method should you not have any regulators on hand.

Here is the schematic,

how can test the stator insulation and mylar coating?


jer
  Reply With Quote
Old 9th August 2013, 01:48 AM   #9
Jsixis is offline Jsixis  United States
diyAudio Member
 
Join Date: Feb 2011
Location: Columbus Ohio
here in Ohio those 2 amp 12.6-0-12.6 are giving me 30 volts with 125 volts at the outlet.
I stopped at 2 radio shacks today. The 1st one had 0 transformers, the guy took me to the wall wart section. The send store had an older clerk and took me right to them so I bought 1.

I'll start soldering on this project in the morning.
I should order some better pots.
  Reply With Quote
Old 9th August 2013, 02:41 AM   #10
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
Hmmm.......... Your line voltage is high in your area.
If it fluctuates that much your better off using some regulators.

Is that 30V AC out of the transformer?
If so that will give you +/- 21.2Vdc, a bit to high!!

+/- 15V is plenty enough for a preamp.
You can get as much a 25Vp-p on that much voltage and I doubt you will ever need more than half of that.
Even +/-12v is enough using a LM7812/7912 regulators.
You could even use a simple zener diode regulator as well using a pair of 15v zener's and two resistors.

jer

Last edited by geraldfryjr; 9th August 2013 at 02:55 AM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Best Pre amp Kit on the market domtweaker Analog Line Level 30 19th September 2013 07:01 PM
Pre amp kit Vrystaat Analog Line Level 1 12th April 2013 12:06 PM
New LM1875 pcb and kit pre-order special BrianGT Chipamp 43 17th August 2012 01:33 PM
Anyone built the phono pre from LM4562/LME49720 datasheet? Tolu Analog Line Level 26 5th January 2011 12:14 PM
RCA Jack/Plug Selection/Switches Pre-amp & 3875 Premium kit Destroyer OS. Chip Amps 15 22nd August 2006 06:43 PM


New To Site? Need Help?

All times are GMT. The time now is 07:50 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2