Input cap on Adcom 555II - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 8th April 2009, 02:54 AM   #1
diyAudio Member
 
Join Date: Apr 2004
Location: NYC
Default Input cap on Adcom 555II

I have a couple 2uF Sonicaps I that I would like to substitute for the stock 1uF that are installed. What cons would there be with doubling the value of the input coupling caps? What would be the effects on the response of the amp?
I had installed some bypass .01uF caps on the stock caps and found the sound to be much improved, which leads me to the conclusion that the stock caps may be poor quality. Also I noticed that the stock caps were rated at 50v. whereas the schematic called for 100v.
Thoughts?
  Reply With Quote
Old 10th April 2009, 03:25 AM   #2
gni is offline gni  United States
diyAudio Member
 
gni's Avatar
 
Join Date: Sep 2006
Cap in series is a high pass filter at 6dB per octave); frequency will depend on
input resistance.

Increase value will lower the cut-off. (2x value = down an octave)

Decrease value will increase the cut-off. (1/2x value = up an octave)

10k input with 1.06 microFarads is 15Hz cutoff (down 3dB).
10k input with 2.12 microFarads is 7.5Hz cutoff (down 3dB).

10k input with 0.01 microFarads (10 nF) is 1,592 Hz cutoff (down 3dB).
Good amp for running a tweeter since the amp will mainly amplify frequencies
above 1500 Hz; it will attenuate frequencies at 6dB per octave below 1500Hz
and be down 36 dB at 23 Hz and -66 dB at 0.73 Hz.

C1 (fd) = 1,000,000 / (6.283 x Impedance x Crossover Frequency)

The cap will effectively block DC (you DO NOT want to amplify DC. . .BAD thing happen). Too high a value and low frequencies (below 20Hz down to DC might
be amplified more and consume more power at frequencies you can't hear and
your amp will run higher.

Probably won't matter but try to replace the cap with same or higher voltage.
Some engineer calculated it to be the right value. Some preamps (tube) can
produce greater than 20V! I have a mixer (SS) that can put out 12.3V.

I think I got the math right. Please, anyone, corrections.

A very good discussion with types also:
Input capacitor
  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 GFA-555II badfireguy Solid State 8 1st March 2012 05:02 AM
Adcom GFA-555II the apostate Solid State 32 2nd September 2011 08:41 AM
Looking for schematic for Adcom GFP-555 (not GFP-555II) dougzilla Solid State 8 18th August 2011 05:51 PM
Adcom GFA-555II with DC Offset sjdemark Solid State 19 28th February 2009 01:33 PM
Adcom GFA-555II problem oscarav098 Solid State 2 10th November 2005 03:47 PM


New To Site? Need Help?

All times are GMT. The time now is 03:10 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