bblackwood
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Had to mod the input of my X250 and thought you guys would like to see what it looks like...
Anyone want to build me another one of these?
- Thread starter bblackwood
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Kev
Well-known member
eih :roll:
... they were off to a good start with multiple output devices ... 8 up and 8 down, I think , then again this is ClassA and it might be 16 total per side, can't quite see if these are all the same device
Most of mine have 6 up and 6 down.
That review says, it is heavily biased into ClassA mode and has +/-47volts so it ends up about 25 watts per channel.
This thing does double into 4 ohms so it looks like it has plenty of power supply.
1.2kva and 20 X 10k uf.
All in all a great amp ... I just think you need 75 volt minimum and prefer to get up towards 100. BUT ... in Class A mode that would make for lots of heat in the equipment room. Probably too much :shock:
Is ClassA worth all the trouble for a recording control room.
Brad is into mastering so it might make sense.
... they were off to a good start with multiple output devices ... 8 up and 8 down, I think , then again this is ClassA and it might be 16 total per side, can't quite see if these are all the same device
Most of mine have 6 up and 6 down.
That review says, it is heavily biased into ClassA mode and has +/-47volts so it ends up about 25 watts per channel.
This thing does double into 4 ohms so it looks like it has plenty of power supply.
1.2kva and 20 X 10k uf.
All in all a great amp ... I just think you need 75 volt minimum and prefer to get up towards 100. BUT ... in Class A mode that would make for lots of heat in the equipment room. Probably too much :shock:
Is ClassA worth all the trouble for a recording control room.
Brad is into mastering so it might make sense.
thermionic
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All those ops and only 25 watts? Class a is a cruel mistress (cheese icon, Ron Manager)
For curiosity, do you have an idea of the idle temperature Brad? Any idea what type of protection is used?
Where was that egg-frying picture, does he really slam the dc-bias that hard? I was told that for consumer-gear (Pass?s gear would be between pro and home in CE terms I presume), CE regs state no outer casing can exceed 35degC, anyone confirm? Modern lateral fets can work fairly comfortable above 100degC I believe? Pass would be going for long-term reliability and therefore wouldn't cook the ops on a commercial product??
I know this isn?t scientific, but I did my best not to give off visual clues:
My monitoring mono-blocs have a bias switch installed and I tried an A/B test on 3 associates with ears I trust (none of them know what class a stands for, they are muso types and to them it might as well be a drug reference). On each occasion they came out with all the class a clichés: ?silky?, ?more punch?, ?less fatiguing? etc etc? Don?t know what to say, I was a bit flabbergasted? Not a clinical test I admit.
The review also claims 250w into 8ohm, how can it do that at +/-47?? :roll: Am I missing a point? Is it due to single-endedness?
Is it safe for journos to think how it ?might? be performed?
:shock:
Here?s to more power-amp discussions
:guinness:
Justin
(pls excuse any grammar, no kip last night and hard day today)
For curiosity, do you have an idea of the idle temperature Brad? Any idea what type of protection is used?
Where was that egg-frying picture, does he really slam the dc-bias that hard? I was told that for consumer-gear (Pass?s gear would be between pro and home in CE terms I presume), CE regs state no outer casing can exceed 35degC, anyone confirm? Modern lateral fets can work fairly comfortable above 100degC I believe? Pass would be going for long-term reliability and therefore wouldn't cook the ops on a commercial product??
I know this isn?t scientific, but I did my best not to give off visual clues:
My monitoring mono-blocs have a bias switch installed and I tried an A/B test on 3 associates with ears I trust (none of them know what class a stands for, they are muso types and to them it might as well be a drug reference). On each occasion they came out with all the class a clichés: ?silky?, ?more punch?, ?less fatiguing? etc etc? Don?t know what to say, I was a bit flabbergasted? Not a clinical test I admit.
The review also claims 250w into 8ohm, how can it do that at +/-47?? :roll: Am I missing a point? Is it due to single-endedness?
Is it safe for journos to think how it ?might? be performed?
:shock:
Here?s to more power-amp discussions
:guinness:
Justin
(pls excuse any grammar, no kip last night and hard day today)
SonsOfThunder
Well-known member
We've done listening tests on heavy bias versus just enough to get you out of class B. My opinion is that its not worth the extra heat and strain on the components, PCB, etc. for the additional bias. I wonder if anyone has ever done any measurements that show any real differences. I have never been able to see any differences in the measurements I have made on ALL the amps I have ever tested. (That's a "few" amps!)
btw, I recently brought a modified @lesis RA-100 into work to check the bias and mod it a little more. I need to document the mods cause the stock freq response is crap-ola! Maybe someone is interested. But after mods, its a pretty respectable amp for monitoring, makes about 150W/ch into 4 Ohms and you can pick them up for cheep (maybe USD$100) on evilbay. Its all discrete, no chips in the path and it modular so its easy to disassemble and mod. Stock. it was about 1.5dB down at 20k (and you CAN hear that!), I think I got it to go to within 1 dB @ maybe 60k or 80k.
That Pass amp sure is pretty!
Peace!
Charlie
btw, I recently brought a modified @lesis RA-100 into work to check the bias and mod it a little more. I need to document the mods cause the stock freq response is crap-ola! Maybe someone is interested. But after mods, its a pretty respectable amp for monitoring, makes about 150W/ch into 4 Ohms and you can pick them up for cheep (maybe USD$100) on evilbay. Its all discrete, no chips in the path and it modular so its easy to disassemble and mod. Stock. it was about 1.5dB down at 20k (and you CAN hear that!), I think I got it to go to within 1 dB @ maybe 60k or 80k.
That Pass amp sure is pretty!
Peace!
Charlie
thermionic
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That's funny Charlie. I'm highly cynical with regards to audiophoolery, but myself and others concur class a has an opiate quality to it in the case of my blocs, I'm looking forward to adding more ops and h/sinking - as things stand it takes care of heating in winter.
I will add that there could be an issue involving a particularly noxious x-over region in my amp config, which could explain things, but we're only talking about (at +/-75v push-pull) 400ma increases that seem detectable...
edit: I should add (before I go to bed) that I'm a big fan of Randy Sloane's pwr-amp books. He is suspect regarding any audiophoolery to the point where he recommends against class a designs. He even suggests using scrap parts, but as he comes from an academic perspective I learn a great deal and add whatever audiophoolery I fancy myself, on top of the fundamentals learned via the books.
J
I will add that there could be an issue involving a particularly noxious x-over region in my amp config, which could explain things, but we're only talking about (at +/-75v push-pull) 400ma increases that seem detectable...
edit: I should add (before I go to bed) that I'm a big fan of Randy Sloane's pwr-amp books. He is suspect regarding any audiophoolery to the point where he recommends against class a designs. He even suggests using scrap parts, but as he comes from an academic perspective I learn a great deal and add whatever audiophoolery I fancy myself, on top of the fundamentals learned via the books.
J
bblackwood
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[quote author="thermionic"]
For curiosity, do you have an idea of the idle temperature Brad? Any idea what type of protection is used?[/quote]No idea, but you sure can't touch it for long. I'd guess over 40 C...
I do know that not even the best AB amps I've tried sound as good as this one does in my mastering room.
Max Output Voltage +/- 65 volts
Max Output Current +/- 20 amps
If you read the manual, available here, he describes super-symmetry. These amps really are about doing as little as possible while keeping the signal as accurate as possible, and my ears tell me he struck a nice balance. I've not heard a better sounding amplifier...
For curiosity, do you have an idea of the idle temperature Brad? Any idea what type of protection is used?[/quote]No idea, but you sure can't touch it for long. I'd guess over 40 C...
I'd say it depends on a lot of things. For an amp designer like nelson Pass, I think it can make a diff as he's good enough to squeeze everything out of it.
I do know that not even the best AB amps I've tried sound as good as this one does in my mastering room.
This is what it says on the site:
Max Output Voltage +/- 65 volts
Max Output Current +/- 20 amps
If you read the manual, available here, he describes super-symmetry. These amps really are about doing as little as possible while keeping the signal as accurate as possible, and my ears tell me he struck a nice balance. I've not heard a better sounding amplifier...
bblackwood
Active member
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[quote author="Kev"]
... they were off to a good start with multiple output devices ... 8 up and 8 down, I think , then again this is ClassA and it might be 16 total per side, can't quite see if these are all the same device
Most of mine have 6 up and 6 down.[/quote]
16 per side, all the same.
... they were off to a good start with multiple output devices ... 8 up and 8 down, I think , then again this is ClassA and it might be 16 total per side, can't quite see if these are all the same device
Most of mine have 6 up and 6 down.[/quote]
16 per side, all the same.
It runs hot, but just about everything in my rack is class A, so the AC just runs all the time, summer or winter...
NewYorkDave
Well-known member
"Class A is a cruel mistress", indeed.
I once worked on a Krell two-channel amp, class-A, something like 50W per channel. That thing was a beast: it took two or three guys to heft it up on the workbench. It was two complete amplifiers, with their own power supplies, inside one huge box. Cooling was provided by forced air and massive heatsinks. My lower back tingles just thinking about it.
Me? I monitor with an old Crown D75 :thumb:
I once worked on a Krell two-channel amp, class-A, something like 50W per channel. That thing was a beast: it took two or three guys to heft it up on the workbench. It was two complete amplifiers, with their own power supplies, inside one huge box. Cooling was provided by forced air and massive heatsinks. My lower back tingles just thinking about it.
Me? I monitor with an old Crown D75 :thumb:
Kev
Well-known member
[quote author="bblackwood"]This is what it says on the site:
Max Output Voltage +/- 65 volts
Max Output Current +/- 20 amps
If you read the manual, available ...
.... he describes super-symmetry.
I've not heard a better sounding amplifier...[/quote]
65 volts is getting up there for a ClassA
I'll try to get a look at that pdfs file
I'm sure this is a good sounding amp and for Brad, probably a cool choice in his mastering duties.
For many of us though, I think it might be a little light on for grunt and level ... unless you have very efficient speakers.
[quote author="NewYorkDave"]Me? I monitor with an old Crown D75 :thumb:[/quote]
cool
that's got the headphones covered
... what about the main monitoring
:green: :green:
Max Output Voltage +/- 65 volts
Max Output Current +/- 20 amps
If you read the manual, available ...
.... he describes super-symmetry.
I've not heard a better sounding amplifier...[/quote]
65 volts is getting up there for a ClassA
I'll try to get a look at that pdfs file
I'm sure this is a good sounding amp and for Brad, probably a cool choice in his mastering duties.
For many of us though, I think it might be a little light on for grunt and level ... unless you have very efficient speakers.
[quote author="NewYorkDave"]Me? I monitor with an old Crown D75 :thumb:[/quote]
cool
that's got the headphones covered
... what about the main monitoring
:green: :green:
What about the DIY stuff on Pass' website, like the Zen amp? A bit overkill for my Radio Shack/RCA Horrortone wannabe's? I know those amps would have enough power for those speakers, but maybe I should just do a one-chip and spring for the C-37 . . .
And Kev, when you're talking about powering the mains, you're talking about soffit mounted big boys, not NS-10's, right?
Bear
And Kev, when you're talking about powering the mains, you're talking about soffit mounted big boys, not NS-10's, right?
Bear
NewYorkDave
Well-known member
Arrggh... NS10s. The devil's speaker! I hate 'em!
Kev: I mix in a spare bedroom on a little pair of JBLs (and also check for "crap system translation factor" on a pair of Minimus 77s). If I ever have the room for a "real" studio, I do have a DC300A waiting in the wings... Well, at least I have the hulk of a DC300A that I might rebuild someday. :wink:
Being a broadcast engineer, I'm partial to old Crown amps. They're the standard in my field. Treat 'em right and they'll go for a very, very long time.
Kev: I mix in a spare bedroom on a little pair of JBLs (and also check for "crap system translation factor" on a pair of Minimus 77s). If I ever have the room for a "real" studio, I do have a DC300A waiting in the wings... Well, at least I have the hulk of a DC300A that I might rebuild someday. :wink:
Being a broadcast engineer, I'm partial to old Crown amps. They're the standard in my field. Treat 'em right and they'll go for a very, very long time.
HiString
Well-known member
Charlie,
Re the RA-100.
I have an RA-150 that could benifit from some attention so any and all details of what was done to the RA-100 would be appreciated.
ChrisO
Re the RA-100.
I have an RA-150 that could benifit from some attention so any and all details of what was done to the RA-100 would be appreciated.
ChrisO
orson whitfield
Well-known member
I like this stuff! Jeff Roland makes a nice mono block too.
Kev
Well-known member
[quote author="Bear"]And Kev, when you're talking about powering the mains, you're talking about soffit mounted big boys, not NS-10's, right?
[/quote]
yeah but even with NS10's I think you can afford to have a little more ... not so much about the shear wattage but the volts ... all about the volts.
[quote author="NewYorkDave"]Being a broadcast engineer, I'm partial to old Crown amps. They're the standard in my field. Treat 'em right and they'll go for a very, very long time.[/quote]
oh yes
we do like our old Crowns.
... could be a good DIY project
... a rethink of the old Crown 300 or 75 with the modern flatpack 3305 - 2955 .... TIP3055/2955 I think ??
I started this a while back and even had a PCB laid out ????
[/quote]
yeah but even with NS10's I think you can afford to have a little more ... not so much about the shear wattage but the volts ... all about the volts.
[quote author="NewYorkDave"]Being a broadcast engineer, I'm partial to old Crown amps. They're the standard in my field. Treat 'em right and they'll go for a very, very long time.[/quote]
oh yes
we do like our old Crowns.
... could be a good DIY project
... a rethink of the old Crown 300 or 75 with the modern flatpack 3305 - 2955 .... TIP3055/2955 I think ??
I started this a while back and even had a PCB laid out ????
Infernal_Death
Well-known member
@ SonsofThunder
I would be very interested in the mods you did since i also have a Alesis RA-100 amp. Was the best thing i could afford when i started.
Until can afford something better i guess it really would be cool to mod the Alesis. So i would appriciate it if you can share any informations you have.
Flo
I would be very interested in the mods you did since i also have a Alesis RA-100 amp. Was the best thing i could afford when i started.
Until can afford something better i guess it really would be cool to mod the Alesis. So i would appriciate it if you can share any informations you have.
Flo
I have an old, very nice sounding amp design that I've been using for years.
It's basically 125w, AB, comp/sym, low feedback, opamp in, fairly unique voltage gain, darlington out.
I can give the old schematic, some suggested improvements, and let y'all have at it, if you'd like.
By nice sounding, it beats a Bryston 4B, if that's good enough.
It's basically 125w, AB, comp/sym, low feedback, opamp in, fairly unique voltage gain, darlington out.
I can give the old schematic, some suggested improvements, and let y'all have at it, if you'd like.
By nice sounding, it beats a Bryston 4B, if that's good enough.
Kev
Well-known member
Dan,
I'm into that. :thumb: :thumb:
Can we swap a few idea in PMs or emails.
I'll send you my old stuff and PCB layout and we can chose the best DIY project.
I'd be very happy to have this at my new place.
Let me know what you think ??
I'm into that. :thumb: :thumb:
Can we swap a few idea in PMs or emails.
I'll send you my old stuff and PCB layout and we can chose the best DIY project.
I'd be very happy to have this at my new place.
Let me know what you think ??
SonsOfThunder
Well-known member
[quote author="orson whitfield"]Jeff Roland makes a nice mono block too.[/quote]Now yer talkin! I will admit that Mr. Pass is an intelligent designer, though a little quirky or esoteric for my taste. (A bunch of giant light bulbs on top of an amp is just a nice novelty and nothing more, imo...) Jeff Rowland's designs really impress me!
As far as the @lesis mod goes, I'll gather up the info and post in a new thread. The RA-150 is a different thing, I think, based on the frequency response specs...I think they were disappointed with the RA-100 as well. Its really a good base to start with, imo. Sorry to drag this high-end thread down with the name. We've seen Rowland, Bryston, Krell, and Pass names thrown in here already...that's quite a "who's who" in amp design!
Peace!
Charlie
As far as the @lesis mod goes, I'll gather up the info and post in a new thread. The RA-150 is a different thing, I think, based on the frequency response specs...I think they were disappointed with the RA-100 as well. Its really a good base to start with, imo. Sorry to drag this high-end thread down with the name. We've seen Rowland, Bryston, Krell, and Pass names thrown in here already...that's quite a "who's who" in amp design!
Peace!
Charlie
