Using Adcom GFS-4 Speaker switch backwards to compare SS amps - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 3Likes
  • 1 Post By m. zillch
  • 1 Post By 18Hurts
  • 1 Post By brandtlj
 
Thread Tools
post #1 of 21 Old 10-18-2018, 08:25 AM - Thread Starter
Member
 
brandtlj's Avatar
 
Join Date: May 2006
Posts: 148
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked: 24
Using Adcom GFS-4 Speaker switch backwards to compare SS amps

I have a GFS-4 speaker selector switch which has been great for a/b'ing different sets of speakers. This is the passive model (no load protection), which is supposed to maintain the purest signal through its wires and switches.


My question is, can this unit be used backwards, by hooking 2 amps to the speaker outputs and a set of speakers to the amp input? Looking to A/B a couple SS amps with the same set of speakers.


Want to get some feedback before I fry any of my equipment.
brandtlj is offline  
Sponsored Links
Advertisement
 
post #2 of 21 Old 10-18-2018, 10:22 AM
AVS Forum Special Member
 
jcmccorm's Avatar
 
Join Date: Mar 2001
Location: Madison, AL, USA
Posts: 4,519
Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 607 Post(s)
Liked: 459
I had one of these a long time ago and if I remember correctly, it's strictly a mechanical switch, so theoretically, it should work exactly like you want.

What I would worry about it whether or not it does a "break-before-make" when switching. I'm betting that it does but don't know for sure (if it does "make-before-break" then there'd be a moment when the outputs of both your amps are connected. Not good. Doesn't matter as much when it's just speakers that you're switching out).

I don't know of an easy way to test it. I'd just do it if it were me.
jcmccorm is offline  
post #3 of 21 Old 10-18-2018, 12:08 PM - Thread Starter
Member
 
brandtlj's Avatar
 
Join Date: May 2006
Posts: 148
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked: 24
I think I might be okay with the GFS-4 then. The buttons on the front panel independently switch on/off the connected devices to their respective binding posts, so they can all set to off(break) before turning one on, i.e. "break-before-make".
brandtlj is offline  
Sponsored Links
Advertisement
 
post #4 of 21 Old 10-21-2018, 01:06 AM
AVS Forum Addicted Member
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 12,576
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 5145 Post(s)
Liked: 3737
I was an Adcom dealer so I know this unit. It is not an A/B switch so the concept of make before break does not apply. It will indeed work in reverse but obviously don't accidentally select two amps simultaneously or KABOOM.
brandtlj likes this.
m. zillch is offline  
post #5 of 21 Old 11-26-2018, 10:10 AM - Thread Starter
Member
 
brandtlj's Avatar
 
Join Date: May 2006
Posts: 148
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked: 24
Quote:
Originally Posted by m. zillch View Post
I was an Adcom dealer so I know this unit. It is not an A/B switch so the concept of make before break does not apply. It will indeed work in reverse but obviously don't accidentally select two amps simultaneously or KABOOM.
Update:
So I tried connecting some t-amps to the GFS-4 switch (with the speakers connected to the AMP terminal) and I was getting some weird (by steady) clicking noises from the t-amps. I read this could possibly be a protection relay. I double checked all the speaker wire connections and could not find any issues. Any idea why this might have happened?
brandtlj is offline  
post #6 of 21 Old 11-26-2018, 10:22 AM
AVS Forum Addicted Member
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 12,576
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 5145 Post(s)
Liked: 3737
Quote:
Originally Posted by brandtlj View Post
Any idea why this might have happened?
Nope.

If you take a screwdriver to the GFS-4 and open it up I'm 99% sure you'll see that other than switches it has zero electronics. it is just a bunch of passive switches wired in parallel. Unlike other speaker selectors such as Adcom's GFS-3, GFS-6, and GFS-300 there are no resistors or anything else to possibly engage for impedance protection.

"Description

The GFS-4 is truly an audiophile grade loudspeaker switching system. It was designed to be the best product of its type available regardless of price.

During its design and construction particular attention was paid to the critical internal wiring and connections to insure that no degradation of sound quality would be audible in use.

Among the many important construction details in the GFS-4 are:

Extremely low internal resistance for minimum power loss; well below the contact resistance of the amplifier output connectors.

The highest grade of heavy-duty, gold-plated, solid-brass, 5-way binding posts, found only in the finest quality instrumentation-grade equipment.

Glass fiber epoxy (NEMA FR-4 grade) circuit board construction with the widest signal traces for minimum power loss; resistance of less than 0.001 ohms; will not degrade the damping-factor of any amplifier.

Oxygen Free Copper (OFC), internal wire jumpers of 12AWG stranded cable to insure signal integrity.

Massive nickel-plated-copper ground buss-bar; to insure lowest connection resistance between grounds.

Designed to be wired between your amplifier and the loudspeakers, it may be used to connect from one to four pairs of loudspeaker systems simply and conveniently.

You can play more than one speaker system at a time by pressing the appropriate button on its front panel.

If you own an Adcom brand amplifier, you can safely drive one or two pairs of 8-ohm or 4-ohm speakers up to any reasonably tolerable home listening level.

Should you intend to operate three or more pairs of speakers simultaneously, we suggest the use of an Adcom GFS-3 or GFS-6 Speaker Selector with Minimum Impedance Protection.

Should you own another brand amplifier, you should consult its instruction manual, or ask your audio specialist dealer for guidance, before connecting two or more speaker systems simultaneously to your amplifier."

source: https://www.hifiengine.com/manual_li...om/gfs-4.shtml
m. zillch is offline  
post #7 of 21 Old 11-26-2018, 10:38 AM
AVS Forum Special Member
 
Join Date: Jan 2015
Location: United States
Posts: 2,583
Mentioned: 51 Post(s)
Tagged: 0 Thread(s)
Quoted: 1293 Post(s)
Liked: 2091
You have another option,

Just use one speaker with each amp (in glorious mono!) and switch back and forth between them. In reality, have someone else switch back and forth and get the speakers close together so you have no idea what is playing. Basically, do this in a larger room so it will be harder to get directional cues for the "tell".

Back in the day, I did this with three amps but we only had two pairs of of the same speakers and it worked very, very well. Statistically it was even but for fun, we also did two of the amps against each other with the two pairs of speakers.

It is a serious pain in the butt to get them level matched but very informative when using several people and getting the results. You can rotate the switch duty but make sure you also have someone doing the "disinterested party" duty...someone that does not care in the slightest. We used our neighbor but girlfriends can amaze you on how little they actually care about your audio hobby. My wife still don't care after over 20 years...she is at such a level of not caring that she leaves once I start the first sentence...

Statistics over the years indicate more accurate results using mono testing over stereo--and you can get a much more accurate setup that way. Give it a shot, at least you won't blow the amplifiers up! After all, any amplifier that works beats any amplifier that is destroyed...be careful out there.
brandtlj likes this.
18Hurts is offline  
post #8 of 21 Old 11-26-2018, 11:14 AM
AVS Forum Addicted Member
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 12,576
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 5145 Post(s)
Liked: 3737
Quote:
Originally Posted by 18Hurts View Post
In reality, have someone else switch back and forth and get the speakers close together so you have no idea what is playing. Basically, do this in a larger room so it will be harder to get directional cues for the "tell".
The tell will always give it away and it is not just the direct wave timing cues differences. There will always be a shift in the room's acoustical power response curve if you measure the same speaker but placed at two locations, even if very close, due to the changes in the constructive /destructive room boundary reflections.


Montser Cable actually took advantage of this in marketing their wire: [paraphrased] "Rotate your balance knob all the way to the left using our wire on one speaker and then all the way to the right using your existing, inadequate speaker wire. Hear that difference? That's what our better wire gets you!"

Most people would hear at least some change even though it has nothing to do with the wire: it is the room response change from different speaker locations [and to a small degree the expected changes between one serial number of a speaker and the next]. The proof I am correct is you also hear the same change when using the same wire on both speakers. Try it.

Last edited by m. zillch; 11-26-2018 at 11:35 AM.
m. zillch is offline  
post #9 of 21 Old 11-26-2018, 11:23 AM
AVS Forum Addicted Member
 
DonH50's Avatar
 
Join Date: Feb 2010
Location: Monument CO
Posts: 12,271
Mentioned: 67 Post(s)
Tagged: 0 Thread(s)
Quoted: 3240 Post(s)
Liked: 3288
Some amplifiers do not like to be unloaded (open circuit). It might not take much to stabilize them; a 50 - 100 ohm resistor across each amplifier speaker output might be enough and would not impact your test results. I would expect class-D amps to be more sensitive to open circuits.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
DonH50 is online now  
post #10 of 21 Old 11-26-2018, 11:34 AM
AVS Forum Addicted Member
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 12,576
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 5145 Post(s)
Liked: 3737
Quote:
Originally Posted by brandtlj View Post
Update:
So I tried connecting some t-amps to the GFS-4 switch (with the speakers connected to the AMP terminal) and I was getting some weird (by steady) clicking noises from the t-amps.
Oh, sorry, I may have misread this. Do you mean when you hold your ear up to the amp itself you are hearing clicking noises or do you mean the sound coming out of the speakers connected to it?
m. zillch is offline  
post #11 of 21 Old 11-26-2018, 11:44 AM - Thread Starter
Member
 
brandtlj's Avatar
 
Join Date: May 2006
Posts: 148
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked: 24
Quote:
Originally Posted by m. zillch View Post
Oh, sorry, I may have misread this. Do you mean when you hold your ear up to the amp itself you are hearing clicking noises or do you mean the sound coming out of the speakers connected to it?
It is the amps themselves making the steady clicking noises. No need to put my ear to it, as it is very audible.
brandtlj is offline  
post #12 of 21 Old 11-26-2018, 11:47 AM - Thread Starter
Member
 
brandtlj's Avatar
 
Join Date: May 2006
Posts: 148
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked: 24
Quote:
Originally Posted by DonH50 View Post
Some amplifiers do not like to be unloaded (open circuit). It might not take much to stabilize them; a 50 - 100 ohm resistor across each amplifier speaker output might be enough and would not impact your test results. I would expect class-D amps to be more sensitive to open circuits.
I knew this was an issue with tube amps but didn't realize digital amps would be sensitive to this as well...I'll test the tripath amps tonight by running without speaker wires attached to see if I get the same result. Thanks
brandtlj is offline  
post #13 of 21 Old 09-12-2019, 10:49 AM
AVS Forum Addicted Member
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 12,576
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 5145 Post(s)
Liked: 3737
Quote:
Originally Posted by brandtlj View Post
I knew this was an issue with tube amps but didn't realize digital amps would be sensitive to this as well...I'll test the tripath amps tonight by running without speaker wires attached to see if I get the same result. Thanks
What was the result of your test? Does the amp make clicking noises when not connected to speakers?
m. zillch is offline  
post #14 of 21 Old 09-12-2019, 12:26 PM
AVS Forum Addicted Member
 
Ratman's Avatar
 
Join Date: May 2002
Location: Collingswood, N.J.
Posts: 19,263
Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 2320 Post(s)
Liked: 2173
brandtlj hasn't been at AVS since:
Last Activity: 04-17-2019 01:19 AM


Maybe send a PM or Email. His last post in this thread was:
11-26-2018, 02:47 PM



If you can’t explain it simply, you don’t understand it well enough – Albert Einstein
Ratman is offline  
post #15 of 21 Old 09-12-2019, 12:29 PM
AVS Forum Addicted Member
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 12,576
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 5145 Post(s)
Liked: 3737
@brandtlj You still around these parts?
m. zillch is offline  
post #16 of 21 Old 09-21-2019, 06:59 PM - Thread Starter
Member
 
brandtlj's Avatar
 
Join Date: May 2006
Posts: 148
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked: 24
Quote:
Originally Posted by m. zillch View Post
What was the result of your test? Does the amp make clicking noises when not connected to speakers?
Zero clicking noises when the tripath amp was not connected to speakers. The cause was somehow related to the Adcom.
brandtlj is offline  
post #17 of 21 Old 09-21-2019, 08:00 PM
AVS Forum Addicted Member
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 12,576
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 5145 Post(s)
Liked: 3737
Quote:
Originally Posted by m. zillch View Post
If you take a screwdriver to the GFS-4 and open it up I'm 99% sure you'll see that other than switches it has zero electronics. it is just a bunch of passive switches wired in parallel. Unlike other speaker selectors such as Adcom's GFS-3, GFS-6, and GFS-300 there are no resistors or anything else to possibly engage for impedance protection.
To confirm my advice was correct I have now opened and photographed mine. It is exactly as I said in post 6:


I suppose if a lot of conductive dust fell inside and landed on its very beefy, copper signal traces on its circuit board, which immediately then get converted to thick wires sent to the gold plated 5-way binding posts on the back panel, a partial short could be occurring and your amp may be reacting to that partial short. Other than that I have no idea what is happening.

You might ask on a forum dedicated to t-amps and ask "What causes a mechanical clicking noise?"
Attached Thumbnails
Click image for larger version

Name:	IMG_1077.JPG
Views:	10
Size:	414.3 KB
ID:	2618462  

In A/V reproduction accuracy, there IS no concept of "accounting for personal taste/preference". As art consumers we don't "pick" the level of bass, nor the tint/brightness of a scene's sky, any more than we pick the ending of a novel or Mona Lisa's type of smile. "High fidelity" means "high truthfulness", faithful to the original artist's intent: an unmodified, neutral, accurate copy of the original master, ideally being exact and with no discernable alterations, aka "transparency".

Last edited by m. zillch; 09-21-2019 at 08:05 PM.
m. zillch is offline  
post #18 of 21 Old 09-21-2019, 08:43 PM
AVS Forum Addicted Member
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 12,576
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 5145 Post(s)
Liked: 3737
Another thing which can cause a partial short [if I haven't mentioned in already] is if a stray strand of speaker wire happens to have snapped off and fell into the binding post. Often when stripping speaker wire a few strands get cut off inadvertently and sometimes some get damaged but seem to stay in place. . . . But then when the wire is twisted they fall off and become dangerous.

I guess a close examination with a magnifying glass and some quick bursts of compressed air into all the binding posts, not just the ones you use, might be in order.
m. zillch is offline  
post #19 of 21 Old 09-21-2019, 09:01 PM - Thread Starter
Member
 
brandtlj's Avatar
 
Join Date: May 2006
Posts: 148
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked: 24
Quote:
Originally Posted by m. zillch View Post
Another thing which can cause a partial short [if I haven't mentioned in already] is if a stray strand of speaker wire happens to have snapped off and fell into the binding post. Often when stripping speaker wire a few strands get cut off inadvertently and sometimes some get damaged but seem to stay in place. . . . But then when the wire is twisted they fall off and become dangerous.

I guess a close examination with a magnifying glass and some quick bursts of compressed air into all the binding posts, not just the ones you use, might be in order.
If a short was the issue, wouldn't there have been problems using the switch previously as a speaker selector - as it was intended?
brandtlj is offline  
post #20 of 21 Old 09-21-2019, 09:25 PM
AVS Forum Addicted Member
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 12,576
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 5145 Post(s)
Liked: 3737
Quote:
Originally Posted by brandtlj View Post
If a short was the issue, wouldn't there have been problems using the switch previously as a speaker selector - as it was intended?
Maybe.

It's not a short: it's a partial short. High grade amps [like an Adcom] can sometimes blast through them and just sees it as a difficult load yet they can still drive the speaker and play music, to a point. The tiny, barely touching (poorly connected), single strand of copper is just too skinny to carry much current and it may not be enough to trip the amp's protection circuits or blow a fuse.
m. zillch is offline  
post #21 of 21 Old Yesterday, 05:58 AM - Thread Starter
Member
 
brandtlj's Avatar
 
Join Date: May 2006
Posts: 148
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked: 24
Quote:
Originally Posted by m. zillch View Post
Quote:
Originally Posted by brandtlj View Post
If a short was the issue, wouldn't there have been problems using the switch previously as a speaker selector - as it was intended?
Maybe.

It's not a short: it's a partial short. High grade amps [like an Adcom] can sometimes blast through them and just sees it as a difficult load yet they can still drive the speaker and play music, to a point. The tiny, barely touching (poorly connected), single strand of copper is just too skinny to carry much current and it may not be enough to trip the amp's protection circuits or blow a fuse.
Well, for whatever reason, using the switch backwards did not work for me. The good news is that I have decided on an amp I really like.
18Hurts likes this.
brandtlj is offline  
Sponsored Links
Advertisement
 
Reply Audio Theory, Setup, and Chat



Forum Jump: 

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