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Old 6th December 2003, 01:07 AM   #1
gyusher is offline gyusher  United States
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Default "Enhanced" Forte' Model 3

I am selling this recently upgraded Forte" Model three. Email me for the details as too many to list here. gyusher@wowway.com Price is 750.00 plus shipping. Amp is in MINT condition and sounds incredible, most of the upgrade can be seen in my pic but as I said email me for details. A great Christmas present for yourself.
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File Type: jpg forte- hotrod-1a.jpg (72.2 KB, 636 views)
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Old 6th December 2003, 03:35 AM   #2
gyusher is offline gyusher  United States
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Default Upgrade details

listed below are some of the upgrades to this amp. . .This was done in October of this yesr.
“Forte’ Model 3 enhanced” 10-18-03
1) Replaced the stock 700 VA toroidal with two 600VA units for dual mono operation.

2) Replaced the 12000mfd per side (24000 total) capacitance to 40,000mfd per side (80,000 total). The replaced caps are superior grade Cornell Dubilier 100 volt types (stock were 45/90 volt types

3) Replaced the two 25 amp bridge rectifiers with 50amp parts. This upgrade was recommended by Nelson Pass for all his amps i.e. (Threshold, Forte and Pass labs).

4) Performance was enhanced to Dual mono, power into 8 ohms from 200 to 250 watts and 4 ohms from 300 to 410 watts.

Turn on rush will be about the same as the 565 you have. The 565 have about 70,000 to 75000 mfd's while the Forte has 80,000 mfd's.
The Forte can be used with a Variac to up the voltage without any problems (i.e. 140 volts AC instead of 120) in such a mode, it will give you about 380 watts RMS into 8 ohms. That means it will act like 2 565's. However in that mode it should not be driven into 2 ohms whilst the 565 can. Under normal voltages, the Forte CAN be paired up with 2-ohm loads. (i.e. 120v ac not 140 v ac)

Caution: Do not try to up the voltage on any Adcom, you will fry the outputs. They are rated at 90-0-90 volts DC Max while the ones in the Forte are rated at 100-0-100 volts DC. (The nominal rails on the Forte is about 79-0-79 and after you up the AC side to 140VAC, the DC rails will go up to 92-0-92) as you can see at 92-0-92, the Adcom's outputs will blow yet the Forte's will be OK.

Funny thing, Toshiba invented the perforated emitter technology and came up with the devices used in the Adcoms (D424/B554) then sold it to Motorola. The replacement devices that Toshiba made were the first "Super-Beta" devices i.e. do not lose current drive into lower impedance’s, and these are what are used in the Forte's (A1302/C3281).
Infact many Luxman, Carver, Sunfire etc. amps use these same devices. They have the reputation in the industry to keep constant distortion even into lower impedance.

Well, by virtue of installing 2 toroids instead of 1, the amp will clip at higher levels than before because the 2 Toroids can give more current than 1. So by default, the amp is more like a 250wpc amp rather than a 200wpc amp. (Actually it clips at 282 watts into 8 ohms).
What I did not do is increase the voltage by much, If I did that, then heat build-up would have been an issue. So reliability is as default while current drive is increased.
The same is the case with the Adcom 555 and 565. Both have DC rails of 82-0-82 but the 555 has a 675 VA toroidal and makes 200wpc while the 565 has the same rails i.e. 82-0-82 but makes 300 watts, well because it has a 2500VA power supply.
The other way to increase power is by increasing VOLTAGE, so to make the 555 a 300wpc amp, they would have needed to increase the rails to 90-0-90.
Back to the Forte, The voltage is now 78-0-78 instead of the stock 76-0-76, so that’s not an issue, (depending on your Home AC mains, the rails can be from 75-0-75 to 80-0-80, however at 120VAC, the rails are 78.5 -0-78.5) the real power comes from its 1200VA power supply compared to the original 700VA supply because it is better regulated and does not drop under load. Lastly because all circuits in the Forte are rated to run at 100-0-100 volts, we can increase the rails higher without any issues. (However currently the are not as high as they can be.)
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Old 7th December 2003, 10:08 PM   #3
gyusher is offline gyusher  United States
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Default Fort'e model 3

This guy is going on eBay tonight. I will post the link as soon as I do it.
Makes me sad as I have owned many Amplifiers costing many times the price I paid for this one but never one that sounded as good. . .Not even close. . .But in my 9x9 room it is a bit of overkill and I found a Aragon 4004 II that I want real bad. I have listened to both and this Fort'e beats the Aragon hands down, however the Aragon is priced right and I want to fool around with it for awhile.
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Old 7th December 2003, 11:35 PM   #4
gyusher is offline gyusher  United States
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Default Here goes

Well shes on eBay now 699.99 BIN. . .
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3064246664
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Old 15th December 2003, 12:21 AM   #5
gyusher is offline gyusher  United States
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Default SOLD

WoooooHoooooooo
SOLD!!!
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Old 15th December 2003, 01:07 AM   #6
K-amps is offline K-amps  United States
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Default NO biggie there's an Adcom on sale now that Dual Mono'ed

Woohoo check it out!

http://cgi.ebay.com/ws/eBayISAPI.dll...ory=39783&rd=1
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Old 22nd December 2003, 01:10 AM   #7
KBK is offline KBK  Canada
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And me...I've upped my Belles 450 from 40,000uf to about 260,000 uf.......
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Old 22nd December 2003, 01:12 AM   #8
K-amps is offline K-amps  United States
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Pics please. Also what did you do to the rectifiers... cause the stock ones will blow sooner or later...
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Old 22nd December 2003, 01:16 AM   #9
gyusher is offline gyusher  United States
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Default Yes PICs please

I too would like to see this. . . . .GREAT!. . .
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Old 1st January 2004, 05:19 PM   #10
KBK is offline KBK  Canada
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OK. I make photo. This is one of my Belles 450 units. (yes I know, the photo is not attached yet!)The other was some other brand but is just a re-labelled 450. Will attach a photo soon. The other amp is modded as well. I want to do the whole puppy over as this amp is quite expressive and -explosively ballsy- when you do mods to it. A 6-inch signal path from input to output does not hurt either! Beat that with a stick!

The bass is insane (speed my man, speed--combined with low impedance PS), with that double 750VA-paralell run transformer. It is possible to run it as a pair of mono channels with some tracing changes on the board, going to a pair of rectifiers or double set of fast recovery diodes on a heat sink, etc. As a stock transformer implementation, the double run paralell 750's does make for a incredible bottom end though...

I very much suspect that Dave Belles' recent brushes with 'designer fame' come off of this design and model. I've been bugging Dave to do maxed out versions of this unit for 10 years now. It looks like it is happening....in whatever version it now sells as a 'Power Modules' unit. The claim is the bass in his new units is 'reference quality'

Now you see why I like the 450 for modifying! If you can find a Belles 450, they are VERY much worth modding and respond incredibly well to such work. I'm still wanting a third unit.

I bought the last set of 4 100volt-47000uf sig-safco caps that Sonic Frontiers had in stock, when they moved to Oakville (about 8 years ago now!!). The amplfier is still working fine. The caps are rated at about 22-24amps ripple at 120 hz, I believe?
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