As far as the input FETs go, you could have nearly any workable parts. As opposed to the NEC 163/44 my second amp has Toshiba JFETs, but they are not 147/72 nor 170/74 - the part numbers are buried here at DIYaudio in one of my old posts, I just remember they were oddball.
Ideally, the best FETs for Q1-Q4 are the 147/72 with 163/44 right behind.
The blue Seacor PP film caps were all over my 110 and my 280(s). I only mentioned the higher-than-spec voltage because some think this could have an effect on the overall 'sound' of the cap. Higher voltage is usually thought to be better when it comes to film caps.
Every Seacor film cap that I traded out for Panasonic PP/foil or MPP had a negative affect on the sound. The Panasonics made everything 'smoother', so, less dynamics/ less sparkle.
I learned enough to leave all the film caps alone in my 110...
Side note: The polycarbonate caps in the 280 are gold. You cannot get them anymore. I swapped them for 2 different kinds of PP caps and never got as good a sound.
IC electros are Illinois Capacitor electrolytics, ironically, I live in Illinois. The circuit card 470uF and 100uF were IC's on my amps, the 1000uF BiPolar cap was a Nichicon on one amp and Taepo(?) on the other amp. Nichicon sounds better.
IC's were also used in my 110 pre, and having thrown away the old caps, I can honestly say my 110 may never be 'up to par' again.
No matter what the forum members keep shouting at me, I do not believe todays electrolytics are suitable for music equipment. Every 'large-can' 80's cap I have ever heard sounded better than its modern replacement. Sorry you guys, I know I'm nuts.
Stock bias is a bit low at 330 mA, go for 400mA or so is my suggestion.
Yes, the 280 was an 80's creation, I bought mine as a floor model in 1989.
Ideally, the best FETs for Q1-Q4 are the 147/72 with 163/44 right behind.
The blue Seacor PP film caps were all over my 110 and my 280(s). I only mentioned the higher-than-spec voltage because some think this could have an effect on the overall 'sound' of the cap. Higher voltage is usually thought to be better when it comes to film caps.
Every Seacor film cap that I traded out for Panasonic PP/foil or MPP had a negative affect on the sound. The Panasonics made everything 'smoother', so, less dynamics/ less sparkle.
I learned enough to leave all the film caps alone in my 110...
Side note: The polycarbonate caps in the 280 are gold. You cannot get them anymore. I swapped them for 2 different kinds of PP caps and never got as good a sound.
IC electros are Illinois Capacitor electrolytics, ironically, I live in Illinois. The circuit card 470uF and 100uF were IC's on my amps, the 1000uF BiPolar cap was a Nichicon on one amp and Taepo(?) on the other amp. Nichicon sounds better.
IC's were also used in my 110 pre, and having thrown away the old caps, I can honestly say my 110 may never be 'up to par' again.
No matter what the forum members keep shouting at me, I do not believe todays electrolytics are suitable for music equipment. Every 'large-can' 80's cap I have ever heard sounded better than its modern replacement. Sorry you guys, I know I'm nuts.
Stock bias is a bit low at 330 mA, go for 400mA or so is my suggestion.
Yes, the 280 was an 80's creation, I bought mine as a floor model in 1989.
So IC's refers to Illinois Capacitor electrolytics? I got it!
The only 470uF I see are are C201 & C202, the front ends PS caps. I believe* the 100uF, C17 & C18, provide add'l filtering for the front end from its PS.
* don't take my word on this
The 1000uF BiPolar cap, C8, on my best day I couldn't imagine what it does. I think one of mine uses them as I recall a Nichicon on PCB about where C8 is. BTW, are these caps available?
Yes I've read that in another thread. The author had his bias over 400ma; loved the "airy, balsey, but 'dirtier' sound." My goal, when I get the time, is to adjust "all 4 channels" to be as close to each other as possible; hopefully between 330ma & 400ma. Then do some careful listening. Thankfully the DC offset is in "all 4 channels" is in the single digits.
As a side note to DC offset-I have 2 Belles 1 amps. Awsome brutes w/6 bi-polars per channel, 66000uf PS capacitance, transformer 2-3 times that of our beloved 280s. They "make less watts" (80 @ 8 ohms). Where they shine is peak current @ 30 amps per channel!* Belles "A's" offset measures well below 100ma in both channels. Belles "B" has one channel measuring 1.03V! When this channel pops, it tries to suck the mid & woofers into the cabinet. I've posted this @ Club Rotel on a HT forum; Glen B is helping me with this.
* I'll PM my plans to drive just the subs in my Polk RTi A7s
untill next time...
cheers tony
HF:
I've been meaning to send you a couple of links of good stuff right up your ally. BTW Most of my replies are by Blackberry! Its tough for me to get internet time @ home.
One link to TnT-audio.com pointing you to their section on bias adjustment & PS upgrades. The other, that I'm seriously considering purchase, is to an ebay link marketing an XL-280 "upgrade kit." He also sells other PS caps that I'm sure my Belles amps would like.
So that you know my final destination: when I'm finished w/ALL the upgrades for ALL my amps including a 5th '280 I have yet to buy, I hope by then to have connected w/someone who can guide me to convert one channel in 3 of my 280s to Class A to drive tweeters XO'd @ 2K. Yeah I'll need new transformers beause that channel's finals will need much lower rail voltage.
I anticipate new toroidals for all my amps along w/slightly lowered rail voltage. All that is for another day.
The 2 remaining 280s need balanced inputs for HT duty as side & rear channel amps. In my 30+ years in audio & now home theatre, again & again I realize the value of speaker wire as short as posible. I've measured several different routes. The shortest posible distance measures 30'.
You inspire & help me as many others have on this forum w/this crazy hobby we love.
Until I can get ona computer @ home, Tony
I've been meaning to send you a couple of links of good stuff right up your ally. BTW Most of my replies are by Blackberry! Its tough for me to get internet time @ home.
One link to TnT-audio.com pointing you to their section on bias adjustment & PS upgrades. The other, that I'm seriously considering purchase, is to an ebay link marketing an XL-280 "upgrade kit." He also sells other PS caps that I'm sure my Belles amps would like.
So that you know my final destination: when I'm finished w/ALL the upgrades for ALL my amps including a 5th '280 I have yet to buy, I hope by then to have connected w/someone who can guide me to convert one channel in 3 of my 280s to Class A to drive tweeters XO'd @ 2K. Yeah I'll need new transformers beause that channel's finals will need much lower rail voltage.
I anticipate new toroidals for all my amps along w/slightly lowered rail voltage. All that is for another day.
The 2 remaining 280s need balanced inputs for HT duty as side & rear channel amps. In my 30+ years in audio & now home theatre, again & again I realize the value of speaker wire as short as posible. I've measured several different routes. The shortest posible distance measures 30'.
You inspire & help me as many others have on this forum w/this crazy hobby we love.
Until I can get ona computer @ home, Tony
tnt-audio links:
Solid State Power Amplifier Supply Part 1
Adjusting the Bias Of Your Amp [English]
ebay: hafler XL-280 Power Amplifier Upgrade Kit
Hafler XL-280 Power Amplifier Upgrade Kit - eBay (item 260691159381 end time Dec-10-10 21:12:05 PST)
cheers tony
Solid State Power Amplifier Supply Part 1
Adjusting the Bias Of Your Amp [English]
ebay: hafler XL-280 Power Amplifier Upgrade Kit
Hafler XL-280 Power Amplifier Upgrade Kit - eBay (item 260691159381 end time Dec-10-10 21:12:05 PST)
cheers tony
carity on the '280 front end FETs and IC caps
So that I'm chrystal clear. I'm ready to shop, soldering iron hot!
Also some of my 280s have the Nichicon & IC caps you mention in earlier posts. Any suggestions to obtain more?
My [Hafler] focus is on 3 of my 280s. BTW, I'm shopping for a 5th, another story for another day. If all else fails, I'll swap caps & FETs to make those 3, the "chosen ones."
My main focus is on fixing those 2 Belles amps w/those nasty DC offset** problems** I mentioned in an earlier post. I've traced them** to a "6 pack" of bi-polar transistors in the front end. Looking for a source of GE S6016 & S6017 transistors. Need minimum 4, likely 12 each. For grins I've attached my updated parts list, some readings I took this weekend, and a link to the thread where you can get a look "my drawing." (reply #20) Go to reply #24 for a few (verbal) important corrections to "my drawing."
thanks tony
haflerfreak said:
So that I'm chrystal clear. I'm ready to shop, soldering iron hot!
Also some of my 280s have the Nichicon & IC caps you mention in earlier posts. Any suggestions to obtain more?
My [Hafler] focus is on 3 of my 280s. BTW, I'm shopping for a 5th, another story for another day. If all else fails, I'll swap caps & FETs to make those 3, the "chosen ones."
My main focus is on fixing those 2 Belles amps w/those nasty DC offset** problems** I mentioned in an earlier post. I've traced them** to a "6 pack" of bi-polar transistors in the front end. Looking for a source of GE S6016 & S6017 transistors. Need minimum 4, likely 12 each. For grins I've attached my updated parts list, some readings I took this weekend, and a link to the thread where you can get a look "my drawing." (reply #20) Go to reply #24 for a few (verbal) important corrections to "my drawing."
thanks tony
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The only time I could actually hear a difference in power supply caps was when replacing 20 year old leaky nichicons with brand new ones. Better bass , more headroom , all were quite apparent. The only other place that type and quality of cap can be actually heard is in the bootstrapped current source of my BX amp module. The panasonic FC can deliver a sound that the nichicon or Xicon's can not , really. Different input caps of the same value ,I can not hear ... perhaps my ears are not "golden enough".
OS
John Curl says we should buy 2SK170BL if we can.
Because JFETs works better at higher current.
And John Curl should know.
Depends on definition of "better"
Back to the OT: electrolytic caps can be viewed as a long line that contains diodes. Diodes are non-linear thingies.
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