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SWR Fan Club
- Thread starter iriegnome
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Hi fellow SWR fans.
My SM-900 (arond 1992) is a bit sick. Can anybody help me find a schematic for it so that I can get it all up and running again?
David
My SM-900 (arond 1992) is a bit sick. Can anybody help me find a schematic for it so that I can get it all up and running again?
David
[email protected]
They've been less than brilliant in their support, but they have been good with supplying me with links to archival SWR schematics.
Good luck!
Okay my SM-900 is working again, but I've also gone and bought an M2 along witha QSC PLX1804.
I've been playing with fdeck's Invalid Link Removed to compare the aural enhancers on my three working amps to see if my ears are telling me the same news that the literature is. I also checked out what the bass intensifier did.
I've attached a spreadsheet with some graphs of various findings.
Note that below 50Hz all these graphs will be meaningless, the bad bass response is my PC sound card's problem, not the SWR amps. Also note that the relative height of each line is meaningless, I am just using the PC to test between each the amp's input and the effects send, at whatever volume I liked, usually just below clipping but not very accurately.
Amps under test are:
1992 SM-900
1995ish Basic Black
2008 M2 preamp.
The first graph shows some basics:
- The M2 with the enhancer defeated is slightly bass-biased
- The bass intensifier gives about a 12dB boost to a low signal but this boost is subject to a compressor, as shown in my 'high signal' curve (just below the clip light lights up) where it only gets a 6dB bass boost.
- The starting points for my old SWR amps are about the same. The old enhancer's smiley curves has a 3dB cut at 200Hz and 5dB boost at about 3k, relative to the 50Hz response.
- The higher mid cut frequency of the M2 (about 3dB at 600Hz) cuts into the old 3k treble boost, effectively moving it up 2 octaves to 12k and making it more gentle (2dB more than the bass response).
I can see the bass intensifier being more useful live than in recordings. I'm seeing it as being useful like a multiband compressor - sort of - boosting bass without chewing headroom.
The second graph shows something I didn't expect. When the enchance knob is turned from zero to about half way all that changes is the volume!
The curve just moves up on the screen about 5dB without changing shape. All these years I thought it was something more interesting going on. Anyway on each amp at some point near the knob's midpoint the mid cut becomes more noticeable. It is centred around 200Hz as advertised.
The third graph shows the M2 enhancer's operation in action, and compares the curves between the Basic Black and M2.
My first impressions of the M2 are that it is even more hi-fi than previous SWR gear. I haven't really heard the 'sweet spot' warmth (just below input clipping) that I'm accustomed to. But the clarity is definitely there, it's surprisingly low-noise too. I can't imaging why the footswitch socket is on the rear in a piece of rackable equipment but the switch works well and I think I'll be making use of it.
I'm gigging with the M2 tonight and tomorrow and will post my thoughts in a couple of days.
I've been playing with fdeck's Invalid Link Removed to compare the aural enhancers on my three working amps to see if my ears are telling me the same news that the literature is. I also checked out what the bass intensifier did.
I've attached a spreadsheet with some graphs of various findings.
Note that below 50Hz all these graphs will be meaningless, the bad bass response is my PC sound card's problem, not the SWR amps. Also note that the relative height of each line is meaningless, I am just using the PC to test between each the amp's input and the effects send, at whatever volume I liked, usually just below clipping but not very accurately.
Amps under test are:
1992 SM-900
1995ish Basic Black
2008 M2 preamp.
The first graph shows some basics:
- The M2 with the enhancer defeated is slightly bass-biased
- The bass intensifier gives about a 12dB boost to a low signal but this boost is subject to a compressor, as shown in my 'high signal' curve (just below the clip light lights up) where it only gets a 6dB bass boost.
- The starting points for my old SWR amps are about the same. The old enhancer's smiley curves has a 3dB cut at 200Hz and 5dB boost at about 3k, relative to the 50Hz response.
- The higher mid cut frequency of the M2 (about 3dB at 600Hz) cuts into the old 3k treble boost, effectively moving it up 2 octaves to 12k and making it more gentle (2dB more than the bass response).
I can see the bass intensifier being more useful live than in recordings. I'm seeing it as being useful like a multiband compressor - sort of - boosting bass without chewing headroom.
The second graph shows something I didn't expect. When the enchance knob is turned from zero to about half way all that changes is the volume!
The curve just moves up on the screen about 5dB without changing shape. All these years I thought it was something more interesting going on. Anyway on each amp at some point near the knob's midpoint the mid cut becomes more noticeable. It is centred around 200Hz as advertised.The third graph shows the M2 enhancer's operation in action, and compares the curves between the Basic Black and M2.
My first impressions of the M2 are that it is even more hi-fi than previous SWR gear. I haven't really heard the 'sweet spot' warmth (just below input clipping) that I'm accustomed to. But the clarity is definitely there, it's surprisingly low-noise too. I can't imaging why the footswitch socket is on the rear in a piece of rackable equipment but the switch works well and I think I'll be making use of it.
I'm gigging with the M2 tonight and tomorrow and will post my thoughts in a couple of days.
With the exception of a few months after Katrina when I had no amp, I am now SWR-less for the first time since 1995. I sold my Basic Black last weekend. I feel kinda naked. I think I might need an SM-400 for a backup....or primary, who knows.
Mike
Mike
Well, on the weekend, the M2 / PLX1804 rig stood up well. I use a Warwick Infinity SN bass and a pair of Dr Bass cabs and the sound was great in both gigs.
Compared to my old SM900 there's a more solid bass feel about the whole sound, yet the same sense of clarity. Highs have gone from "clear but ever so slightly harsh" to "clear verging on glassy" from the same speakers.
I made use of the M2's supplied footswitch (I'm not normal a switches and pedals kinda guy but that could change) to turn the bass intensifier on an off for a few tunes, used the compressor very gently, the whole time (ratio of 2, threshold set high enough to only catch louder notes, attach and release set straight up).
I have to use bass intensifier sparingly or not at all, since I like a lot of clarity. I think I used about 3dB of a possible 12dB boost, on about 3 songs each night. These gigs were an acoustic covers trio and an 80s covers/concept show band. I used the boost function for the bass solo in "Call me Al" and got an enthusiastic applause from the sound guys, who'd been checking the rig out with beforehand with great interest.
Being more used to the old SWR sound, I'm glad I did the exercise that led to my last post, which helped me experiment with occasional mid boosts. I'm also glad I read the Invalid Link Removed in my old SM900's manual because it is very informative on how to use the semiparametric EQ, which seems virtually the same in the M2. I recommend that for anyone with a variable midrange control.
If it's not obvious, I'm a very happy SWR customer.
Compared to my old SM900 there's a more solid bass feel about the whole sound, yet the same sense of clarity. Highs have gone from "clear but ever so slightly harsh" to "clear verging on glassy" from the same speakers.
I made use of the M2's supplied footswitch (I'm not normal a switches and pedals kinda guy but that could change) to turn the bass intensifier on an off for a few tunes, used the compressor very gently, the whole time (ratio of 2, threshold set high enough to only catch louder notes, attach and release set straight up).
I have to use bass intensifier sparingly or not at all, since I like a lot of clarity. I think I used about 3dB of a possible 12dB boost, on about 3 songs each night. These gigs were an acoustic covers trio and an 80s covers/concept show band. I used the boost function for the bass solo in "Call me Al" and got an enthusiastic applause from the sound guys, who'd been checking the rig out with beforehand with great interest.
Being more used to the old SWR sound, I'm glad I did the exercise that led to my last post, which helped me experiment with occasional mid boosts. I'm also glad I read the Invalid Link Removed in my old SM900's manual because it is very informative on how to use the semiparametric EQ, which seems virtually the same in the M2. I recommend that for anyone with a variable midrange control.
If it's not obvious, I'm a very happy SWR customer.
I just got my first SWR (workingpro 700) since I first played on one in 1992. With all the anticipation, I ordered it to arrive by 2 day air. When I plugged it in, the Master volume knob is scratchy and wont come clean with numerous workouts, and the Intensifier switch on the pedal box wont work. Has things gone to crap since fender? I thought I was buying the best brand out there....
I recently did some mods to my sm900. Its disgusting now.
Replaced the opamps with opa2604's but will go with 2134's soon.
Replaced the 6800uf caps with 15,000uf, in the power supply.
Replaced the .02 tube caps with .033 orange drops.
put in a stero volume control vs. the single knob.
The amp is realy sick now. =)
Im not familiar with the fender/swr quality. My sm900 is from 92.
Replaced the opamps with opa2604's but will go with 2134's soon.
Replaced the 6800uf caps with 15,000uf, in the power supply.
Replaced the .02 tube caps with .033 orange drops.
put in a stero volume control vs. the single knob.
The amp is realy sick now. =)
Im not familiar with the fender/swr quality. My sm900 is from 92.
Hey Chicago_Mike can you please spare a few words for what the sound is actually like now due to the mods? What's changed?
Haven't seen a Goliath Sr here yet:
Got it in trade for an Ampeg 810. I love the SWR sound, glad to have access to it.
Got it in trade for an Ampeg 810. I love the SWR sound, glad to have access to it.
The mods help with low notes, especially the B string. Its sustains better.
If you are inclined. I would first change the power supply caps.
15000uf at 80volts are around 13 to 40 bucks depending who you go to. I got some unknown ones but will swap to panasonics soon.
Also I am going to change the 5watt Xicons to some 10watters I have. unless I can find some dale 10 watts cheap.
The cap in the preamp section is more of a personal test than anything proven.
Im also making a tonal balance control and might find a way t put that in too. Taking it off the amp schematic I have and just doing some minor tweaking to it.
The opa's are quiter than the tlo72's. But Ill be using opa2134's soon or something even more hi-fi.
I cant leave sh*t alone......
If you are inclined. I would first change the power supply caps.
15000uf at 80volts are around 13 to 40 bucks depending who you go to. I got some unknown ones but will swap to panasonics soon.
Also I am going to change the 5watt Xicons to some 10watters I have. unless I can find some dale 10 watts cheap.
The cap in the preamp section is more of a personal test than anything proven.
Im also making a tonal balance control and might find a way t put that in too. Taking it off the amp schematic I have and just doing some minor tweaking to it.
The opa's are quiter than the tlo72's. But Ill be using opa2134's soon or something even more hi-fi.
I cant leave sh*t alone......
Nice rig Dargov!
I saw this thread and need to update my Pic since I put my head in a different rack and changed the Poweramp. Though I have changed the Poweramp again but havent taken any good pics.
I saw this thread and need to update my Pic since I put my head in a different rack and changed the Poweramp. Though I have changed the Poweramp again but havent taken any good pics.
I'm in! Love these cabs, the only thing that really bothers me is that they don't stack well on each other.
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