SDA-SRS 1.2tl Amp Suggestion

xoaphexox

I know this is a highly subjective question but I am going to ask it here anyhow.

Would there be enough of an audible difference between a Pioneer SPEC-4 and an Adcom GFA-555ii power amp as to warrant a switch?

I have read many places the SDA-SRS 1.2tl benefits sonically from a "high current" power amp and from all I can tell the Pioneer SPEC-4 I am currently using is not one.

The Adcom GFA-555ii is in my price range, and it is tax season after all.... just kicking the idea around in my head as to whether or not this would be a worthwhile "upgrade".

Also - if there is another "De facto" amp in that price range for these speakers I am all ears - Carver, Parasound, etc - I do not have any brand allegiance (except for Polk of course!).

Thanks

motorstereo

I know I wouldn't chance running my 1.2tl's on a 555II which has no speaker relay protection. I had one go belly up and send out some dc which didn't bode well with the voice coil on the woofer. I would keep an eye out for a carver tfm series amp which sounds great when paired up with the big polks.

xoaphexox

Oh wow, very good to know about the lack of relay protection in the GFA. I was not aware. I will say, though, that my SDA-SRS have passive woofers - no voice coil.

Regardless, There are still 12 active drivers per enclosure and frying even one of them would be unacceptable.

I will take a look at the Carver TFM series.

Thanks!

OldmanSRS

Carver TFM is a good choice.

nooshinjohn

Sunfire Stereo 300/2 is an even better choice, and it will allow for the only "bi-wiring" setup I have found that makes a difference. The amp has a voltage output and a current output. Use one for the low end and the other for the tweets.

Schurkey

xoaphexox wrote: »

The Adcom GFA-555ii is in my price range,

Acurus A-250

heiney9

555ii

H9

heiney9

motorstereo wrote: »

I know I wouldn't chance running my 1.2tl's on a 555II which has no speaker relay protection. I had one go belly up and send out some dc which didn't bode well with the voice coil on the woofer. I would keep an eye out for a carver tfm series amp which sounds great when paired up with the big polks.

Ludicris talk. FYI, 555 mark II's use a dc servo to block dc so that was not the issue. Real amps don't need speaker protection, when done inexpensively speaker protection is usually in the signal path and causes more issue than it solves.

Buying or not buying based on that single criteria is plain stupid, IMO.

H9

RickTfromAZ

Adcom GFA-5802.

I just upgraded to JC-1's from the Adcom GFA-5802. The JC-1's are wonderful amps. However, until I got the JC-1's, I never realized just how good the GFA-5802 is.

heiney9

The 5802 is NOT common ground so keep in mind you will need to use the AI-1 or strap the negative speaker terminals.

The 5802 is a stellar amp.

H9

twochannel

I have a GFA-5802 and GFA565 monos that I use on my SRS's with the grounds strapped."Not both at the same time"!!! I like the way both sound and often switch between them. The 565's have excellent bass response, the 5802 has a greater depth to the soundstage.These are really great amps. I also had used two original design 555's biamped which worked very well until purchasing the 565's. If $ is a problem, you can find a 555ii for about $350-$400.

motorstereo

heiney9 wrote: »

Ludicris talk. FYI, 555 mark II's use a dc servo to block dc so that was not the issue. Real amps don't need speaker protection, when done inexpensively speaker protection is usually in the signal path and causes more issue than it solves.

Buying or not buying based on that single criteria is plain stupid, IMO.

Well you must have a vastly different 555II than the pair that I had. Both of mine had 4 rail fuses on the back and no speaker relay. One day one of them was operating just fine. The very next day it was showing 6 volts dc at the speaker output which fried the vc in a vintage infinity woofer. None of those correct value fuses had blown. I'm just glad the damn thing didn't do this while I wasn't around as it probably would've started a fire. I consider that pretty good criterea when looking for an amp in not having a fire hazard in the house.

heiney9

You are talking about a speaker relay which has nothing to do with protecting against dc offset. 555II's have a dc servo control that protects against excess dc at the outputs. Speaker relays are usually for current in-rush protection and shorting speaker cables. The 4 rail fuses serve the same function (as a speaker relay). Rail fuses don't protect against dc at the output nor does a "speaker relay".

If your speaker died from dc, it wasn't beause of lack of a speaker relay. You had some other catastrophic event that no speaker relay would have prevented. You sure it was a MK II model?

You are getting the terms mixed up.

H9

heiney9

motorstereo wrote: »

I consider that pretty good criterea when looking for an amp in not having a fire hazard in the house.

There is no piece of electronic gear made that is 100% fool proof. A speaker relay wouldn't have prevented what happened. It may have prevented a fire as the VC shorted out, but then again that's what those 4 rail fuses are for.

My Pass Aleph has no fuses or muting circuit or speaker relay and you can short the outputs without damage. Never an issue.

All I'm saying is that, IMO, basing a purchase on that is silly because it's a non-issue unless you plan on shorting your speaker cables a lot.

H9

motorstereo

Sorry; there is no mix up on the adcoms. The speaker wires were not shorted as that's the first thing that I thought of also. The dmm showed 6 volts at the speaker outputs. Pass didn't believe in using a relay in the 555II's because he believed it may have detracted from the sound. This may have been fine when these units were new but now that they're getting some age on them there's starting to be failures.

The relay click we hear on most gear with speaker relays means there's no dc present at the outputs and it won't engage if there is. I consider this a very important feature.

heiney9

Complete bollocks, You also aren't reading for comprehension.

You are incorrect about what speaker relay does. Pass revised the original and Adcom changed it around so it no longer resembled what he gave them as a prototype. Lots of really well regareded high end amps should never be bought based on your logic.

I am not going to argue anymore about it. If the OP has to have an amp with a speaker relay based on your post, then that's cool. It's a ridiculous way to choose an amplifier.

H9

heiney9

motorstereo wrote: »

The relay click we hear on most gear with speaker relays means there's no dc present at the outputs and it won't engage if there is. I consider this a very important feature.

No, only if the amp has something like a DC servo to detect DC. That is a separate function from a typical speaker relay which as I have stated twice now protects against current in-rush and/or shorted outputs. Just because you hear a click doesn't mean you are protected from DC.

When all gear gets long in the tooth it can fail. I find it funny that the amp in question DID have dc protection, yet it failed. And you are saying it failed because it didn't have DC protection. It had DC protection, just not a speaker relay. Electronic gear, like cars needs maintenance too.

H9

motorstereo

Sorry to the original poster for drifting so far off course. There's plenty of choices out there in some fine amps to drive your 1.2tls. In my experience a protection less 555II isn't one of them and I'll just leave it at that.

heiney9

The 555II has a dc servo system to protect against dc at the outputs.

H9

motorstereo

Is the B+ and B- resettable circuit breakers the dc servo system you're talking about h9?

xoaphexox

Thanks for the suggestions. That Sunfire sure does look nice! None on the 'bay right now, however. I'll put in a saved search for a few of these models and see if I can net any one for less than the 'average' closing price.

I realize that any amp can die and fry speakers. Luckily I have never had that happen. Having owned a Nakamichi Stasis PA-7AII, I am fond of Nelson Pass's work, but I don't take this hobby as seriously as I used to since having children so I (read: my wife) don't want to spend that kind of cash.

Thanks again everyone.

xoaphexox

Okay I will toss one last question out there. These amps appear to be plentiful and the same price: Carver TFM-35 or Adcom GFA-555ii.

Any pros/cons to either one? Thanks for all feedback. I don't make quick decisions and every ounce of anecdote helps out.

F1nut

These amps appear to be plentiful

That should tell you something.

motorstereo

I've owned both of those amps you mentioned. For sound quality it was hands down the tfm. I'm not a big fan of Carver's hokus pokus and his explanation behind the tfm amps but they do sound really good. I'm actually listening to a tfm45 right now. The 45 sounded great paired up with my 2.3s but I've never had any carvers on my 1.2s. Sal (Lazarus) had a pair of them bi-amping his 1.2tl's and I thought his set up sounded fantastic.

xoaphexox

F1nut wrote: »

That should tell you something.

I see

F1nut

Sal (Lazarus) had a pair of them bi-amping his 1.2tl's and I thought his set up sounded fantastic.

He replaced them, sounds way better now.

motorstereo

I can imagine they do with the new Musical Fidelity.

SDA SRS 1.2

Started out with the TFM-45 on my 1.2's (non-TL) which sounded great and upgraded to the Sunfire Signature 600~Two which sounded even better.

xoaphexox

Sounds like there are many viable options out there ranging in price from several hundred to several thousand. I just picked up a Burson HA-160D preamp/DAC and will eventually determine a power amp to pair with it for these speakers.

Lots of good suggestions here. I will see what kind of budget I'm working with after I sell my Pioneer gear. I admit it sounds great already but I am ready for something new.

That Sunfire stuff looks great - will definitely keep an eye out for it.

Thanks again

heiney9

You have a excellent start with the Burson, be sure to pick a worthy amp when you can. Don't skimp on the amp now that you have a solid pre/dac to make a really nice system.

H9

FTGV

motorstereo wrote:

Well you must have a vastly different 555II than the pair that I had. Both of mine had 4 rail fuses on the back and no speaker relay. One day one of them was operating just fine. The very next day it was showing 6 volts dc at the speaker output which fried the vc in a vintage infinity woofer. None of those correct value fuses had blown. I'm just glad the damn thing didn't do this while I wasn't around as it probably would've started a fire. I consider that pretty good criterea when looking for an amp in not having a fire hazard in the house.

The servo will only compensate for offset produced at the input stage ,so DC can certainly be present at the outputs if a component failure occurs.Yes it could have resulted in a fire since the rail fuses did'nt blow,that voice coil would have been getting extremely hot being fed a continous diet of DC and could have ignited a paper cone.