Adcom GFS speaker Selector

dcmeigs

If anyone has experience with the Adcom speaker selector GFS-3, -4, or -6, I would like to here about it.

Specifically, I am concerned about signal degradation.

I noticed the units use twist locks rather than naners, which I think might be a downside, although I cannot remember using them. Do the twist locks work out OK?

markmarc

I have the GFS-3. The speaker connection lock is a bit of a pain. You will notice volume loss when two or more sets are engaged. It does do a solid job protecting the amp IMHO when dealing with two different type of speakers. FYI, I didn't go above 80db.

dcmeigs

markmarc wrote: »

I have the GFS-3. The speaker connection lock is a bit of a pain. You will notice volume loss when two or more sets are engaged. It does do a solid job protecting the amp IMHO when dealing with two different type of speakers. FYI, I didn't go above 80db.

A guy could solve that problem by either spending about $230 on the new model, the GFS-300, or he could retrofit these:

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=091-1150

These require a 1/4" hole. Can you tell what hole size they have drilled? If they have drilled larger holes it would be a pain in my arse to do it properly.

Yashu

I have the 3, it's pretty good. Once you get past the posts, it really is the best speaker selector for the money. The only one that I know that is better, costs much more, a Bryston selector, and you don't get impedance matching (though, if you get a Bryston 2, you don't need that really)

Anyway, the Adcom is good, but I eventually just got an amp with a/b selectors. It is not as easily modded as you think. The posts are quite complicated and need care to remove and replace, if you are going to.

The thing is, they make a very secure connection to bare wire. These are NOT typical clips. 12g is the largest wire you can stuff in there, but they do make a *very* secure conection.

dcmeigs

OK, I'll hold off on ordering the binding posts until I get the switch in my possession and have a chance to see how well the existing twist locks work and how difficult the mod will be. I can live with 12 gauge so I might just live with the twist locks too.

Several on ebay right now.

Thanks for the help.

dcmeigs

Well, I couldn't help myself. I modified one by adding the five-way posts. I was pretty satisfied with the outcome so I have posted some pictures in case anyone has a similar interest.

First, I think the Adcom speaker switches are very good gear. They have large 2.5 ohm resistors which can be switched into the circuit to keep the power amp stable when using multiple pairs of speakers at once and nice quiet switches. They sell on eBay for about $50. Problem is, I really prefer to use banana plugs in five-way posts in hi-fi applications. I just couldn’t abide those stock quarter-turn style of terminals in the circuit to the freshly tricked out SDAs.



The stock wire terminals are soldered to a circuit card and are easily removed in sets of four.

I decided to add six low cost five-ways pairs from Parts Express to keep the cost under control. In addition to the inputs, this provides connections for two sets of hi-fi speakers with bananas at the "one' and "two" taps while using the four remaining quarter-turns for the mid-fi stuff like pool speakers. One could easily do them all.



The holes left by the stock components are a little too large, but by using the pairs, one can bridge the holes and just call it extra ventilation. The result is snug and secure.

The new terminals are connected with point to point wiring. The switches have unused ears suitable for soldering which accept 14 gauge wire. One must also solder a jumper from the new inputs to the existing circuit card tracks to reconnect the remaining stock terminals..



I also added some additional wire between switches to supplement the solder tracks, but that's probably not necessary.

Once finished, I gave it a good listening and I could not hear any degradation in SQ at the "one" and "two" taps. Perhaps the biggest surprise was just how little difference in sound pressure level is made by switching in the 2.5 ohm resistors, even with just a single pair of speakers.

1CDRO1

Most interesting , that's what i need done for both of my GFS-3.

jim 249

I have the 6. Sounds fine and the twist locks are not that hard to work with. Once the wires are in you don't mess with it anyway.

mantis

I have the 3 and if you insert your wire in correctly there is no problems. I think it works just fine. I also have a Jamo 6 way which is in use, the Adcom doesn't get any use anymore. If you would like to have it , make me an offer and I'll strike a deal with you. It's in great shape. I can post pic's if you wish.

1CDRO1

Well i really want banana plugs, that's why the modification sparked my interest.

dorokusai

I think the mod is a must as the twist lock connections have more loss than an upgraded binder. In addition, you may not have the best connection even when it's locked properly.

I'd rather be stuck with screw terminals than that style and always replace them if possible. Even they have adapters. I've had a couple pieces of gear that it wasn't an option and I just ended up upgrading some other components and selling them.

dcmeigs

This is not a difficult mod. If you decide to do it, you should consider using single 5 ways rather than the dual type as I did. I used the dual style simply because I had some good ones on hand. Pomona makes a very high quality single 5-way post that you can get from mouser or digikey and they are pretty economical. I think the singles make the installation a little easier. Good luck with it.

DaveHo

Just get the GFS-4, it has 5 way posts. They can be hard to find, but are the best of the Adcom bunch. There is absolutely nothing in the signal path other than switches & wire. If you're going to drive multiple pairs of speakers, make sure you have a stoudt amp as there is no impedance matching or protection circuitry.

-Dave

dcmeigs

That's kind of the point of the mark 3. It has those big resistors that can be switched in or out for impedance matching, thus allowing you maintain a proper load on your amp.

soundfreak1

I've had one for some time , very nice unit, use it for multi room opperation on my main amp works fine with both 4 and 6 olm speakers.