Matching a commercial preamp - adcom - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 20th June 2005, 06:38 PM   #1
diyAudio Member
 
Join Date: May 2005
Location: Seattle, WA, USa
Default Matching a commercial preamp - adcom

Hi, does anyone have any experience matching a chip amp to an adcom preamp? I plan to build my first amp in the next month and want to buy a preamp to go with it. I don't have a lot of money, so a gtp-400 or 500 seems like a good choice. Of course, I know I should build my own preamp, but the convenience rules on this one.
Thanks,
Alex
  Reply With Quote
Old 20th June 2005, 09:22 PM   #2
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
It's mainly a question of matching the gain of your chip amp with the gain of the preamp so that you don't have too much. Too much gain would give you little useable range on your volume control.

Can you tell us what is the gain in your chosen preamp?
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 21st June 2005, 08:36 AM   #3
diyAudio Member
 
Join Date: May 2005
Location: Seattle, WA, USa
Default Gain

Well, that's a good question. The manual for the GTP-400 doesn't list gain, but it does list Loudness (volume at 9'oclock) - 100Hz.............+5dB
20Hz.............+10dB

I assume that's the same as gain, yes?
  Reply With Quote
Old 21st June 2005, 09:51 AM   #4
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
No, they are talking about a boost (optional) of the lower (bass) frequencies when listening at lower volumes.

It's not absolutely essential but if you want to do things properly, you will need to know how much the input signal to the pre-amp is increased (gain) before the output to the power amp. I'm not so sure I would trust a hi-fi component supplier that couldn't supply this basic information!

I know that you say 'convenience' is an issue here but why not just build your Gainclone, use it and when it is convenient, build a pre-amp? If you build the pre-amp shown on Decibel Dungeon, it has a unity gain so you wouldn't need to change the gain in the power amp section! But if you wanted gain in the pre-amp, you could easily change the gain of the power amp to suit. Having said that, you could probably just buy that pre-amp and tailor the gain of the GC accordingly.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 21st June 2005, 05:19 PM   #5
diyAudio Member
 
Join Date: May 2005
Location: Seattle, WA, USa
Default Gain

I'm trying to attach the specs page from the user manual.

How do you change the gain in chip amp? I'm planning to build BrianGT's LM3875kit.

Thanks for the answers Nuuk. Your website's been very helpful.
Attached Files
File Type: pdf gtp400manualspecs.pdf (75.2 KB, 48 views)
  Reply With Quote
Old 21st June 2005, 06:18 PM   #6
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
I can't tell from that spec what the gain is!

You can alter the gain on the GC by changing the feedback resistor or input resistor, providing that you don't lower the gain below 10 and keep a high enough input impedance.

If your heart is set on the pre-amp, put the two together as they come and see how they are together. If you find that it is hard to alter the volume precisely, lower the gain on the GC as described above.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 21st June 2005, 08:08 PM   #7
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Sofia
Quote:
I can't tell from that spec what the gain is!
Why?

It appears to be x6.45
  Reply With Quote
Old 21st June 2005, 09:08 PM   #8
Banned
 
Join Date: Mar 2003
Location: Lisbon, Portugal
Quote:
Originally posted by analog_sa
It appears to be x6.45
x6.45161290322580...

High gain...
  Reply With Quote
Old 21st June 2005, 09:10 PM   #9
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
OK we want no smart-***** here chaps. Tell us how please!
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 21st June 2005, 09:15 PM   #10
Banned
 
Join Date: Mar 2003
Location: Lisbon, Portugal
Quote:
Originally posted by Nuuk
OK we want no smart-***** here chaps. Tell us how please!
2V / 310mv.
  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
Adcom GTP-740 Preamp Problems john65b Solid State 5 15th January 2014 12:35 PM
FS Adcom GTP-600 Preamp/Tuner tomeh! Swap Meet 1 30th April 2011 05:51 PM
Adcom GTP 500 Preamp Request for Help bcrescen Solid State 7 26th December 2008 12:56 PM
Adcom preamp - scratchy pot Ty_Bower Solid State 8 28th April 2008 12:27 PM


New To Site? Need Help?

All times are GMT. The time now is 12:46 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