Modifying Maplin preamp kit - Page 3 - diyAudio
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 16th June 2012, 09:54 PM   #21
diyAudio Member
 
Join Date: Jun 2012
Location: Devon
With the volume pot turned down almost all the way, just enough to hear, and with the power on, the signal does not sound distorted.

I hope that I made it clear that the signal was only distorted with low voltages connected to the opamp supply (1.5V and 3V, also from batteries), and was completely silent with a higher voltage battery (9V), as if the opamp was dragging the signal down.
  Reply With Quote
Old 16th June 2012, 09:57 PM   #22
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Ok,

So you are saying it works..but with 9V or more it shuts down?

At what voltage does it work up to and at what voltage point does it shut down?
I guess you are using pure DC batteries not a wall wart PSU?

Regards
M. Gregg
__________________
What is the sound of one hand clapping?
  Reply With Quote
Old 16th June 2012, 10:01 PM   #23
diyAudio Member
 
Join Date: Jun 2012
Location: Devon
Quote:
Originally Posted by M Gregg View Post
So you are saying it works..but with 9V or more it shuts down?
Yup, when unpowered it works, as the voltage is increased it becomes more distorted and quieter until becoming silent.
  Reply With Quote
Old 16th June 2012, 10:04 PM   #24
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
What happens if,

You remove R2 and R6?
Internal compensation for unity gain?
Is C3/C6 the right way around?
Output short protection cutting in?

Regards
M. Gregg
__________________
What is the sound of one hand clapping?

Last edited by M Gregg; 16th June 2012 at 10:08 PM.
  Reply With Quote
Old 16th June 2012, 10:06 PM   #25
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
A wiring error is probably causing the op-amp to stick to one supply rail as soon as it switches on, thus shorting the signal. Check for solder bridges or wrong resistor values. Measure the DC conditions and post the results here.
  Reply With Quote
Old 16th June 2012, 10:11 PM   #26
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Quote:
Originally Posted by DF96 View Post
A wiring error is probably causing the op-amp to stick to one supply rail as soon as it switches on, thus shorting the signal. Check for solder bridges or wrong resistor values. Measure the DC conditions and post the results here.
LOL,

you got to admit its interesting..Hopefully this is already checked..

Regards
M. Gregg
__________________
What is the sound of one hand clapping?
  Reply With Quote
Old 16th June 2012, 10:13 PM   #27
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
I guess,

R7 and R8 are equal values?

I have to sign off now..I'll be back..hopefully someone will pick up with you..

Regards
M. Gregg
__________________
What is the sound of one hand clapping?

Last edited by M Gregg; 16th June 2012 at 10:16 PM.
  Reply With Quote
Old 16th June 2012, 10:19 PM   #28
diyAudio Member
 
Join Date: Jun 2012
Location: Devon
Quote:
You remove R2 and R6?
They are soldered onto the PCB, shorting them seems to make no difference to the way the circuit behaves.

Quote:
Is C3/C6 the right way around?
Just triple checked and they are the right way around.


Quote:
Internal compensation for unity gain?
Output short protection cutting in?
I'm not sure how to check for these, however I don't think the output is shorted, as the volume of the signal is not massively reduced compared to being plugged straight in.

Thanks, Matt
  Reply With Quote
Old 16th June 2012, 10:22 PM   #29
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
R2 and R6,,


DONT short them remove them...LOL and give it a try..

I'll catch you laters..

The chip has unity gain compensation (internal)

Regards
M. Gregg
__________________
What is the sound of one hand clapping?

Last edited by M Gregg; 16th June 2012 at 10:24 PM.
  Reply With Quote
Old 16th June 2012, 10:30 PM   #30
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
R7 and R8 each channel,

They should be equal values...

I gotta go ...

Regards
M. Gregg
__________________
What is the sound of one hand clapping?
  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
Help! Modifying the Dayton RS1200K kit whbuchan Subwoofers 4 20th November 2010 06:11 AM
X-PRE musical fidelity preamp. need help modifying 04mac Tubes / Valves 10 26th August 2010 09:53 AM
goin 2 visit maplin 4 a pcb kit got any ideas 4 a super newbie Sord_Fish Introductions 23 21st October 2004 08:44 AM
Modifying DoZ Preamp to unity gain PaulHilgeman Solid State 5 28th April 2003 12:28 AM
Modifying preamp power supply Peter Daniel Pass Labs 5 2nd April 2002 09:48 PM


New To Site? Need Help?

All times are GMT. The time now is 07:09 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