adcom 585 - redundancy in circuit? - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 7th May 2004, 05:47 PM   #1
rhyno is offline rhyno  United States
diyAudio Member
 
Join Date: May 2004
Location: houston
Question adcom 585 - redundancy in circuit?

proceeding under the premise that there is no perfect part....
i was looking at the schematics of an older nelson pass design that i own (adcom 585) and i see that in addition to a slow start circuit, he also has wired a coupling capacitor (4.7uf) and resistor (1k) as the first things the input signal sees.

now i understand that the coupling cap is there to remove any DC that a preamp might send. but given the soft start circuit (and assuming good turn-on procedure: preamp 1st, amp 2nd), should this C-R network even be in the signal path? seems like a great way to lose transparency w/ no benefit to me...

also, given the coupling cap, i also see that the design has 4 dc-rail fuses on the output stage (which, i would assume, would blow prior to substantial DC being output to the speakers).

again, how redundant is all this? (i'm apt to leave the fuses, as i can get nice silver plated fuses that sound fast & nice, but remove the coupling cap, as i think that any cap will impact the sound more than the DC rail fuses will).

i'd like to pull the cap as i assume this will improve transparency, but i'd love some advice on if i should pull the cap, the C&R, or neither. (as i'm not sure the purpose of the resistor in this network). (and i can live w/ the risk of DC output from the preamp, as i'll always turn it on first.)

thoughts?

thanks!
rhyno
  Reply With Quote
Old 7th May 2004, 06:42 PM   #2
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
I don't recall designing a 585. More likely it was a modified
version of an earlier circuit I did, however some resistance
in series with the input is generally a good idea to prevent
oscillation in a system, either from a preamp that doesn't
want to look at the base of a transistor directly, or vice versa,
or to help reduce the possibility of pickup from the output
of the amp back to the input.
  Reply With Quote
Old 7th May 2004, 11:10 PM   #3
rhyno is offline rhyno  United States
diyAudio Member
 
Join Date: May 2004
Location: houston
Default thanks, one more question

thanks for the advice.

given the requirement of the resistor, is it still a safe assumption that the coupling cap can go?

best
rhyno
  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-555 claiborne Solid State 8 27th September 2007 10:20 AM
Trouble with speaker protection circuit (Randy Slone's circuit) whalefat Solid State 3 13th April 2005 10:13 AM
Adcom GFA-585 went bad - calling Adcom experts hangguy Solid State 14 24th December 2004 08:09 PM
Is Adcom GFP750 circuit same as BZLS or Aleph L? KT Pass Labs 14 6th October 2004 04:04 AM
Solution to redundancy PassFan Everything Else 1 21st January 2002 03:02 AM


New To Site? Need Help?

All times are GMT. The time now is 10:45 AM.


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