Threshold s150 or Forte 4a amplifier?

I have a pair of 4 ohm speakers (2 Peerless High Def 5 1/4 Mid-woofer and Vifa Ring Radiator XT Tweeter in each cabinet) that are around 89 db/ in a fairly small listening room. I have a choice of either the Threshold s150 at 75 watts/channel or the Forte 4a at 50 watts/channel Class A. I am looking for some feed back on both of these amplifiers and suggestions on which amp I should Keep. Thanks in advance for all advise!
keep them both. two classic examples of ss.
The Threshold is in a different class, even though it's A/B. Not that the Forte is not a good amp too but, in my less than humble opinion that's a no brainer!

The Threshold in a different class? Wasn't Forte a Threshold Company? I am not sure of the relationship between the two but I know they are related in some shape or form. Can anyone fill me in?
I have not worked on any for almost 20 years, but I do not recall that much difference between them.

Actually......I like the output transistors in the Forte much better.
Yes, Forte was a Threshold company. Threshold was able to market products at a lower price point using the Forte name. I had heard the Forte 4A driving Thiel 1.5 and Martin Logan Aerius, and it was a great amp at that time for that price. Because of the power requirement of my Thiel 2.2s then, I ended up getting the Forte 6 (the 200 watt A/B version of the otherwise-the-same-design of 4A).

They share the same sound characteristics with their more expensive Threshold "cousins". Since you have both amps, why not trust your ears and make the judgment yourself?

I have been Listening to both and over all they seem to produce very similar sound. The Forte does produce a more definate lower end, the bass guitar in The Greatful Dead's "Working Mans Dead" each note stands out and rings as the strings hit the frets. When playing the same on the Threshold the notes on the bass guitar are a bit muddy. I have read things on power cord up grades and also somthing about moving the transformer away from the out put section. If anyone has some good advice on this I would like to hear it! Also I am currently using my Home theater Pre-amp Processor with these and would like to soon pick up a nice solid simple 2 channel preamp with in put for CD. Any suggestions?

Well I have had Both as well, My favorite for musicality out of all the thresholds still stands the best valued S150, I like the forte 4a A lot as well but I did not have the Class A' 50 watt version mine was configured in AB, and still very good, I had a s300 as well and the s150 always sounded much better to me, but could be the Synergy situation with certain components and speakers.
I have a S150 and a Forte model 6, I have not heard a model 4 but I know they have some very good reviews and are supposed to be a very very good amp. It was that reason why I bought model 6 and it is a very good amp. I got both amps within a month or so of esch other and have had not a lot of time to try them in my system, for the past 6 months due to health problems with my brother I have been at his place most of the time. I live in Vancouver and my brother lives in the Mountains the other side of Whislter B.C. No A/C there we run off a generator and no computer. I say this because I owe a few in this thread an email, sorry Jeff but I'm home for the winter now and Ar_t I owe a big email to and a big THANK YOU for telling me about how to Modifly my S150 by moving Transformer away from the circut board. The S150 has the Transformer bolted to the back of the faceplate and is butting up against the circut boards more the left ch. and I guess the magnetic field of the Transformer reacts with the circut boards. I moved the faceplate with the transformer a full 4" forward from the amp (circut board). The way I did it is one can put it back to stock without anyone being able to tell. But will I NO,NO,NO,NO, The S150 was Know as Thresholds lower powered amp in the S series but many thought it was the best sounding and as you can hear with your own ears it is a sweet sounding amp. OK,OK, you want to know how it sounds. Well it's like you went out and spent a lot more $$$$ on another Amp. The differance blew me away I didn't think the mod would have that much affect, was I wrong, the sound stage was much wider and grew in height and depth, placement of the instruments seemed better with more focus and the Bloom of the instruments is what really got me I was not prepared for that, it took a little getting used to there was so much more bloom. I run a pair of Maggies which are 4 ohm and my plan is to run the S150 on the top end + mid and the Forte 6 on the bottom of my Maggie III but my IIIs are down and over the winter I will do a rebuilt so right now the S150 is on my Maggies MG1 imp. I guess you know which amp I would pick, the S150 a very good amp made even better Thanks to Ar_t. I have on order some Vampire Pure copper female RCAs and just got some Eidson pure copper binding posts and a furtech IEC incert and when I was checking the fuses a good size piece of metal came off the inside of the fuse holder so I ordered some cryo jena labs fuse holders Although I might by pass the speaker fuses (output) and live dangerously. If you keep the S150 and want more info email me and I can help you with the Mod. Ofcourse you can talk to Ar_t who made this mod possible and I would just again like to Thank You Ar_t for helping me with this Mod. Oh one more thing can anyone tell me if the other S series amps have the Transformer on the back of the faceplate. Thanks Ken.
Another satisfied customer..........

You're welcome.

(Don't know about the others, but since the chassis is deeper, it may be further away.)
Thanks for the good info! I would like to here about the mods on the s150! I always welcome advice. I think I will try that transformer move before I decide. Any thing I should be cautious with?

Thanks again to all who have spoke up!
Although I plan on refining the mod cosmetiely some I also wanted to hear what it sounded like before I put to much work into it. So I looked in the PH.Book for someone who sells metal and I got a piece of 1/8" plate Aluminum channelling 8" long by 4" wide by 2" and cut it in half length wise and ended up with 2 8" pieces sort of U shaped like this ]. I trimed some of the inner flange after I took measurements with the faceplate removed. Unbolt the faceplate and just let it lie in front of the amp. The transformer wires will have some tie wraps holding them together which you may need to cut to give you more room to pull the transformer out. Measure to be sure you have enough room to put your new Aluminum extention between the amp and faceplate(4") You might want to measure first before you get you Aluminum some Transformers might have shorter wires. 4" was the max on mine with a just a bit extra. Line up the Aluminum to the amp and take mesurements to drill holes in the flange to line up with amp threaded holes. Once done bolt the extention to the amp useing org. faceplate bolts now move the faceplate in place and line up useing wedges now take measurements for drilling holes to mount faceplate. Next unbolt extention from amp and drill holes, now bolt it all back together ( I used stainless steel nut + bolt to mate faceplate to extention). Now you have a 4" gap on the top and bottom between the amp + faceplate. While I ponder what to do with that I just put plexey glass in place. Will probably get some Aluminum cut for a whole new top piece was thinking of a plexey glass top put who knows. Was wondering weather to add some heat sinks but as my amp runs cool I didn't bother. The nice thing about this mod is you can go back to stock if you want. After your done Let me kow how it compares to the Model 4 but believe me if you like the S150 now you will love it after. If you have any questions click on my user name and email me. Happy Modding Ken.
Thanks Gundam91, I was wondering how does the Proceed AMP5 compare to the Forte 4A? I heard the 4A's when my dealer was auditioning them in 1994 and they sounded awesome.
I decided to keep the Threshold! I went back and forth between the two. I couldn't decide! After pulling the transformer away from left side on the Threshold.... Ok I have decided to keep the Threshold! The Mod was only Temp. I will have to search for heat sinks and find a good machine shop to fabricate new Top and Bottom. I am going to have the top made from brushed aluminum! I think it will finish out nice! If any one is interested in the Forte Model 4 I just listed it on Audiogon! Thanks Benie and A_rt for you help! A-rt keep spreading the wealth!!!
The brushed aluminum top sound like a good idea it will match the faceplate. I think I will do that as well, my mod was a litte crude (prototype) now that I know this mod is for real it's time to refine it some. I'll keep alook out for some donar heat sinks but as my amp runs cool that can wait a bit I have a piece for the bottom. Maybe I should have kept my mouth shut and bought your S150 as a thought acurred about tri-amping in the future. lol Good luck with the Mod Grizzly.
Contact Jon Soderberg []. He might be able to help you getting the heat sinks.
He used to work at Threshold and repairs/modify all Threshold/Forte equipment.
He is a great guy and does avery good job. He had worked on my Threshold T2, DAC 1e and a S450e that I had.
Thanks for the info!
I switched to Forte Model 4/4a amps many years ago and have never looked back. Few amps can truly "outclass" them, and even then... at MANY TIMES the price. The only drawback I can pereceive is their handling of low bass, which is just a tiny bit thin and, well... lacks a modicum of control. Many will argue this point... please have at it :^)

For my subs, I use Adcom 555's, which are fabulous sub-bass amps... though they're just a smidge gritty on mids/highs... IMHO. Some will disagree... and that's okay :^)

Few truly affordable amps can faithfully reprodruce all frequencies extremely well. My solution is to bi-amp as above. It works for me.