I've owned several of the PCR series amps from Soundcraftsman.
They are OK for mids and highs, I will never use one for bass or full range use.
The PCR circuit reacts with time constants in the feedback loop of the amplifier to produce strong signals below 10hz when driven into clipping.
I destroyed a lot of woofers in vented boxes before I figured this out.
They are OK for mids and highs, I will never use one for bass or full range use.
The PCR circuit reacts with time constants in the feedback loop of the amplifier to produce strong signals below 10hz when driven into clipping.
I destroyed a lot of woofers in vented boxes before I figured this out.
You probably are using your VOM to measure voltage across the fuse. To set bias you need to measure current. Use your VOM as an ammeter not a voltmeter.
Sound "quaility" is often in the ears of the listener. I categorize music into two general categories:
1. Music and sound produced by acoustic instruments in their own acoustic space, and
2. Music, or sound, produced by electronic or amplified instruments and that are mixed down and have no individual instrument acoustic space.
The Diana Krall small jazz ensemble or Jazz at the Pawnshop could be examples of the first. On Jazz at the Pawnshop, on a good stereo system, you can hear the ambience of the rooms, glasses tinkling, and the music from the various players seems to come from its own acoustic space.
Pink Floyd Dark Side of the Moon is an example of my 2nd category above.
To reproduce the sounds of these two categories often is best done with different types of amplifiers and speakers. I like subtlety and detail and its playback does not require a lot of watts and my first category does not need the watts for playback as does the sound from a rock concert.
Every amp has some residual distortion and when an amp is bridged much of the distortion of each channel is added together so a bridged amplifier has more low level distortion than a single channel. More watts do not produce a cleaner sound in most instances. But it all depends on what type of sound (or music) you are trying to produce and on how loud you are playing the stuff.
But, I am biased. I call a Mozart Piano Concerto "music" whereas Pink Floyd seems to be manufactured sound put together to produce sound effects. Heck, I would even call the sound from the Dixie Chicks "music" but stuff I've heard from rock concerts seems characterized mostly by loundness.
Let the flames begin . . . I am out of here . . . . .
Sound "quaility" is often in the ears of the listener. I categorize music into two general categories:
1. Music and sound produced by acoustic instruments in their own acoustic space, and
2. Music, or sound, produced by electronic or amplified instruments and that are mixed down and have no individual instrument acoustic space.
The Diana Krall small jazz ensemble or Jazz at the Pawnshop could be examples of the first. On Jazz at the Pawnshop, on a good stereo system, you can hear the ambience of the rooms, glasses tinkling, and the music from the various players seems to come from its own acoustic space.
Pink Floyd Dark Side of the Moon is an example of my 2nd category above.
To reproduce the sounds of these two categories often is best done with different types of amplifiers and speakers. I like subtlety and detail and its playback does not require a lot of watts and my first category does not need the watts for playback as does the sound from a rock concert.
Every amp has some residual distortion and when an amp is bridged much of the distortion of each channel is added together so a bridged amplifier has more low level distortion than a single channel. More watts do not produce a cleaner sound in most instances. But it all depends on what type of sound (or music) you are trying to produce and on how loud you are playing the stuff.
But, I am biased. I call a Mozart Piano Concerto "music" whereas Pink Floyd seems to be manufactured sound put together to produce sound effects. Heck, I would even call the sound from the Dixie Chicks "music" but stuff I've heard from rock concerts seems characterized mostly by loundness.
Let the flames begin . . . I am out of here . . . . .
The trick is, just dont run the Soundcraftsmens into clip! there clip indicators are very very accurate!
The SC amps are amazing for what they are. i have been fascinated with them since my first. the Haflers just never sounded as good to me! I have a DH-220 here now and a PCR-800 and the hafler does not handle the low end as well. Thats not saying much. the Soundcraftsmens dont handle the low end well when compared to my Bryston 4B!
I have used the Soundcraftsmens full range with my Vandersteen 2b's, KEF 105's, and my Hales Revelation 3's and they sound very good. Better then an Adcom 555II, and much better then any Hafler i have heard. The SC's are a bit soft in the top end. im sure this is due to the Old Mosfets...
The SC did one thing right IMHO, and that is they got the driver stage right, or at least better then most! Plenty of current to charge those big cap mosfets! and those old Hitachi Mosfets have pretty high gate capacitance! The hafler is almost the same circuit. except it has a double LTP input stage. but for some reason, they just never sounded as good.
The DH-220, at least the one i have, uses the Hitachi 2SK134/J49 mosfets where as the SC amps use the slightly larger 2SK135/J50 mosfets. Both are rated well above the rail voltage. i think the 134's are 160V devices if i remember correctly and the 135's 180V devices, both at 7 amps!
The Input transistors may not have high enough rating.... But they both use the 2N3440/2N5416(MM4403) drivers at those are 300V devices so i would bet, that with a little coaxing, you could get 200watts out of the DH-220 circuit. if the input transistors can handle the +/- 70VDC rails...
Zero
The SC amps are amazing for what they are. i have been fascinated with them since my first. the Haflers just never sounded as good to me! I have a DH-220 here now and a PCR-800 and the hafler does not handle the low end as well. Thats not saying much. the Soundcraftsmens dont handle the low end well when compared to my Bryston 4B!
I have used the Soundcraftsmens full range with my Vandersteen 2b's, KEF 105's, and my Hales Revelation 3's and they sound very good. Better then an Adcom 555II, and much better then any Hafler i have heard. The SC's are a bit soft in the top end. im sure this is due to the Old Mosfets...
The SC did one thing right IMHO, and that is they got the driver stage right, or at least better then most! Plenty of current to charge those big cap mosfets! and those old Hitachi Mosfets have pretty high gate capacitance! The hafler is almost the same circuit. except it has a double LTP input stage. but for some reason, they just never sounded as good.
The DH-220, at least the one i have, uses the Hitachi 2SK134/J49 mosfets where as the SC amps use the slightly larger 2SK135/J50 mosfets. Both are rated well above the rail voltage. i think the 134's are 160V devices if i remember correctly and the 135's 180V devices, both at 7 amps!
The Input transistors may not have high enough rating.... But they both use the 2N3440/2N5416(MM4403) drivers at those are 300V devices so i would bet, that with a little coaxing, you could get 200watts out of the DH-220 circuit. if the input transistors can handle the +/- 70VDC rails...
Zero
Hi Dick,
Thanks again for your kind advice. I'm sure you are right about the ammeter. I had better read the manual again.
I know just what you mean in your first example. I love that experience. Unfortunately, most of the music I deal with falls into the second example.
I see what you mean about the noise level when bridging. For some reason, I thought it would be less since I don't need to run the amp as hard.
I grew up on jazz. Played the bari sax all through school. Attended two Stan Kenton clinics. Gerry Mulligan was my favorite artist for years. I would love to have my old vinyl collection back.
Hi Zero,
I see that my ears don't deceive me then. My Soundcraftsmen is running two different filter caps right now and it still sounds better than those Haflers. I have caps on the way and am looking forward to hearing it with them installed. The Haflers sound better to me bridged than they did before, but that may be because of the additional power.
I would lov to have a Bryston 4B. That's pretty much standard here where I work. Way out of my price range. I do have a .4B preamp though.
I wondered how the Soundcraftsmen was able to put out 200WPC with 4 MOSFET's per side and the Hafler Pro230 only puts out 115wpc with 6 MOSFET's per side. I didn't realize there was that much difference between the 2SK134/J49 and the 2SK135/J50 . Exicon sells the same part numbers for both. Weird.
Thanks again, Terry
Thanks again for your kind advice. I'm sure you are right about the ammeter. I had better read the manual again.
I know just what you mean in your first example. I love that experience. Unfortunately, most of the music I deal with falls into the second example.
I see what you mean about the noise level when bridging. For some reason, I thought it would be less since I don't need to run the amp as hard.
I grew up on jazz. Played the bari sax all through school. Attended two Stan Kenton clinics. Gerry Mulligan was my favorite artist for years. I would love to have my old vinyl collection back.
Hi Zero,
I see that my ears don't deceive me then. My Soundcraftsmen is running two different filter caps right now and it still sounds better than those Haflers. I have caps on the way and am looking forward to hearing it with them installed. The Haflers sound better to me bridged than they did before, but that may be because of the additional power.
I would lov to have a Bryston 4B. That's pretty much standard here where I work. Way out of my price range. I do have a .4B preamp though.
I wondered how the Soundcraftsmen was able to put out 200WPC with 4 MOSFET's per side and the Hafler Pro230 only puts out 115wpc with 6 MOSFET's per side. I didn't realize there was that much difference between the 2SK134/J49 and the 2SK135/J50 . Exicon sells the same part numbers for both. Weird.
Thanks again, Terry
Congrats on your bari sax and love of Mulligan. I have CDs of most of his recorded works, plus those of Stan Kenton, Chet Baker, and others of that era. I went to college in Utah and many fellow jazz lovers back then were of the "West coast school." And, then there was Dave Brubeck and Paul Desmond.
To hear the sublte nuances of Diana Krall's voice I would do it on my Musical Concepts PA3-B mod on a Hafler chassis. I would not do it with a P-230. Can't speak for the Soundcraftsman or Bryston, never listened to them.
Here are the Drain to Source voltage ratings of Hitachi Mosfets of that era:
2SK133 120
2SK134 140
2SK135 160
2SJ48 -120
2SJ49 -140
2SJ50 -160
I forget how to do the arithmetic, but output power depends on rail voltages and input impedance of the load to be driven. There is NO 200 watt per channel amp I know of that uses the same MOSFETS as your P-230 (2SK134/2SJ49). As you can see the SK134 is maxed out with +/- rail voltges of 70VDC (70+70 = 140 for drain to source voltage). It is unwise to run these devices at any higher voltage than +/- 65VDC as leeway must be built in for an occasional power service surge or spike. My house voltage here runs around 124 VAC which provides around 65 VDC to my amps.
Having more MOSFETs per channel does NOT increase output power as power is dependent on rail voltages, the amp's ability to swing the entire voltage from the - to the + rail, and the load impedance. Having the 6 MOSFETs per channel in the P-230 helps to lower its output impedance and allows the amp to push more current, especially at the lower frequencies.
The XL-280 runs the circuit cards at a higher voltage than the output stage MOSFETs. About 5 volts are required to turn on the MOSFET gates. So, a gate voltage of 5-7 volts higher with the XL-280 means it can get around 140 watts per channel. The XL-280 is a fully tricked out amp to derive about the max possible from the 2SK134/2SJ49 MOSFETs. One high end guy I know uses it to drive his subs.
You might think about bi-amping your rig with the P-230 driving the subs and woofers and the Soundcraftsman running the mids and tweets. This might be a good combo and you already have most of the parts to do so.
Dick...................
To hear the sublte nuances of Diana Krall's voice I would do it on my Musical Concepts PA3-B mod on a Hafler chassis. I would not do it with a P-230. Can't speak for the Soundcraftsman or Bryston, never listened to them.
Here are the Drain to Source voltage ratings of Hitachi Mosfets of that era:
2SK133 120
2SK134 140
2SK135 160
2SJ48 -120
2SJ49 -140
2SJ50 -160
I forget how to do the arithmetic, but output power depends on rail voltages and input impedance of the load to be driven. There is NO 200 watt per channel amp I know of that uses the same MOSFETS as your P-230 (2SK134/2SJ49). As you can see the SK134 is maxed out with +/- rail voltges of 70VDC (70+70 = 140 for drain to source voltage). It is unwise to run these devices at any higher voltage than +/- 65VDC as leeway must be built in for an occasional power service surge or spike. My house voltage here runs around 124 VAC which provides around 65 VDC to my amps.
Having more MOSFETs per channel does NOT increase output power as power is dependent on rail voltages, the amp's ability to swing the entire voltage from the - to the + rail, and the load impedance. Having the 6 MOSFETs per channel in the P-230 helps to lower its output impedance and allows the amp to push more current, especially at the lower frequencies.
The XL-280 runs the circuit cards at a higher voltage than the output stage MOSFETs. About 5 volts are required to turn on the MOSFET gates. So, a gate voltage of 5-7 volts higher with the XL-280 means it can get around 140 watts per channel. The XL-280 is a fully tricked out amp to derive about the max possible from the 2SK134/2SJ49 MOSFETs. One high end guy I know uses it to drive his subs.
You might think about bi-amping your rig with the P-230 driving the subs and woofers and the Soundcraftsman running the mids and tweets. This might be a good combo and you already have most of the parts to do so.
Dick...................
Thanks Dick,,
Man, Gerry Mulligan, Paul Desmond-"Two of a Mind". What an album!
Makes me sad I lost all of that. I envy you.
I've been looking at the Musical Concepts PA-3B kit. They have three. The "Modification kit", "Signature" & "Planitum". Which one are you using if you know? They vary quite a bit in price. I have a DH-200 as well as the two P230's. Do you think there would be any advantage to using one of the P230's over the DH-200 if I were to do the PA-3B kit? I think I would rather use the DH-200 for that if I would end up with the same thing after the mod.
Thanks, Terry
Musical Concepts PA-3B
Man, Gerry Mulligan, Paul Desmond-"Two of a Mind". What an album!
Makes me sad I lost all of that. I envy you.
I've been looking at the Musical Concepts PA-3B kit. They have three. The "Modification kit", "Signature" & "Planitum". Which one are you using if you know? They vary quite a bit in price. I have a DH-200 as well as the two P230's. Do you think there would be any advantage to using one of the P230's over the DH-200 if I were to do the PA-3B kit? I think I would rather use the DH-200 for that if I would end up with the same thing after the mod.
Thanks, Terry
Musical Concepts PA-3B
Personally I would use a DH-200 for this mod as it has the lowest resale value so you are investing less in this mod. As for which MC kits, I would begin with the $299 circuit card kit and add in the power supply capacitor kit, LC-200 Kit: $89, (2"dia.x 4.125" high with low post screw mount).
I have an extra pair of the LC-200 PS caps that I flip in and out of a couple of Haflers here and I can distinctly tell the difference. The MC caps have more capacitance, which helps with bass heft, and they are also low ESR and help each instrument to find its own spot and stay there across the soundstage.
The higher priced kits with all the exotic caps quickly reach the point of diminishing returns unless one has a very highly resolving system and super sensitive ears, and a good imagination that tells him all the extra money made a difference. Go with the basic PA-3B kit for $299 and include the LC-200 kit for $89.
Use the hookup wire included. It is good stuff.
You may need a new on/off switch, depending on the amp rating of the present one in your Hafler DH-200. The extra capacitance can weld switch contacts on the older switches.
Initially you may find the modified amp to be bass defiicient. I did. Then, after longer listening to a variety of material I found that the bass was there and the amp actually played a little lower than the DH-200. What these new circuit cards do is provide harmonic integrity and a clear and balanced sound at all frequencies. The original Hafler amps had a "boom and tizz" sound as that was what sold back in the early 80s. Back then speakers were often a little weak in the bass and tweeters were not as developed as they are today, so the Hafler compensated with its boom and tizz.
Many think the PA3-B mods create an amplifier that compares with some of the best in the $1000 (or more) category. But, do include the PS cap kit.
The PA3-B mod does not allow for bridging, in case you wondered.
I think there is a thread or messages here at diyaudio about the MC mods. Also, go to the Audio Asylum and ask around. I think you will find many who think the MC mods are great.......
I have an extra pair of the LC-200 PS caps that I flip in and out of a couple of Haflers here and I can distinctly tell the difference. The MC caps have more capacitance, which helps with bass heft, and they are also low ESR and help each instrument to find its own spot and stay there across the soundstage.
The higher priced kits with all the exotic caps quickly reach the point of diminishing returns unless one has a very highly resolving system and super sensitive ears, and a good imagination that tells him all the extra money made a difference. Go with the basic PA-3B kit for $299 and include the LC-200 kit for $89.
Use the hookup wire included. It is good stuff.
You may need a new on/off switch, depending on the amp rating of the present one in your Hafler DH-200. The extra capacitance can weld switch contacts on the older switches.
Initially you may find the modified amp to be bass defiicient. I did. Then, after longer listening to a variety of material I found that the bass was there and the amp actually played a little lower than the DH-200. What these new circuit cards do is provide harmonic integrity and a clear and balanced sound at all frequencies. The original Hafler amps had a "boom and tizz" sound as that was what sold back in the early 80s. Back then speakers were often a little weak in the bass and tweeters were not as developed as they are today, so the Hafler compensated with its boom and tizz.
Many think the PA3-B mods create an amplifier that compares with some of the best in the $1000 (or more) category. But, do include the PS cap kit.
The PA3-B mod does not allow for bridging, in case you wondered.
I think there is a thread or messages here at diyaudio about the MC mods. Also, go to the Audio Asylum and ask around. I think you will find many who think the MC mods are great.......
hafler bias
thought I would add my two bits worth . I worked thru the 80s
at a repair shop here in utah and worked on many hafler units.
and have a dh 110 ,dh200 and a dh 220.
rarely did I ever see bad mosfets, usually it was the drivers.
the later dh220s had 2n5551-2n5401 for inputs they are rated
for much higher breakdown.
adding an inrush limiter is a very wise move as the most common breakdown was the power switch.
I ran a dh220 with a 1.2ohm fullrange riibon driver for over a year
at very high levels (they were very inefficent) the only damage was buckets of fuses, these are rugged amps.
Iam running about 400ma of bias , and can say that it does tame
some of the harsh hard sound that these amps deliver , but I dont reccomend this unless you know what you are doing and bring it up slowly letting the amp reach thermal equilibrum before
advancing further.
at these levels it will run very warm.
thought I would add my two bits worth . I worked thru the 80s
at a repair shop here in utah and worked on many hafler units.
and have a dh 110 ,dh200 and a dh 220.
rarely did I ever see bad mosfets, usually it was the drivers.
the later dh220s had 2n5551-2n5401 for inputs they are rated
for much higher breakdown.
adding an inrush limiter is a very wise move as the most common breakdown was the power switch.
I ran a dh220 with a 1.2ohm fullrange riibon driver for over a year
at very high levels (they were very inefficent) the only damage was buckets of fuses, these are rugged amps.
Iam running about 400ma of bias , and can say that it does tame
some of the harsh hard sound that these amps deliver , but I dont reccomend this unless you know what you are doing and bring it up slowly letting the amp reach thermal equilibrum before
advancing further.
at these levels it will run very warm.
"adding an inrush limiter is a very wise move as the most common breakdown was the power switch."
I always use a 2R5 thermistor, a Keystone CL-30.
"Initially you may find the modified amp to be bass defiicient. I did."
That is because the stock unit is kind of flabby in the bass, the mod unit is tighter and more accurate. Simply adding between 50µF~100µF across the stock filter caps will do 90%+ of the high dollar mod. If you have a DH200 you need to add a 0.1µF film cap in parallel with the 10µF input coupling cap and also the 470µF feedback cap (the DH220 and newer already have a film input and film bypass on the feedback caps, this really smooths out the high end and makes the bass more articulate).
"Having more MOSFETs per channel does NOT increase output power as power "
Actually, on low impeadance loads it does.
The RDS on the FETs used is 1R7 over temperature. A DH220 uses two pair, an XL280 uses three pair.
The RDS of the output stages would then be 0R85, and 0R56 respectively.
Both amps run on about ±63V at idle. On program material with a 2R load there is about 3dB difference between two pair and three pair(200W vs 450W).
There is a 1.4dB difference at 8R, but that is from the high voltage tier on the XL280, only 0.4dB of that is from the lower RDS.
I always use a 2R5 thermistor, a Keystone CL-30.
"Initially you may find the modified amp to be bass defiicient. I did."
That is because the stock unit is kind of flabby in the bass, the mod unit is tighter and more accurate. Simply adding between 50µF~100µF across the stock filter caps will do 90%+ of the high dollar mod. If you have a DH200 you need to add a 0.1µF film cap in parallel with the 10µF input coupling cap and also the 470µF feedback cap (the DH220 and newer already have a film input and film bypass on the feedback caps, this really smooths out the high end and makes the bass more articulate).
"Having more MOSFETs per channel does NOT increase output power as power "
Actually, on low impeadance loads it does.
The RDS on the FETs used is 1R7 over temperature. A DH220 uses two pair, an XL280 uses three pair.
The RDS of the output stages would then be 0R85, and 0R56 respectively.
Both amps run on about ±63V at idle. On program material with a 2R load there is about 3dB difference between two pair and three pair(200W vs 450W).
There is a 1.4dB difference at 8R, but that is from the high voltage tier on the XL280, only 0.4dB of that is from the lower RDS.
Where is this installed?
Is the 50µF~100µF just hooked up across the the screw terminals of the filter caps? I assume +to+ and - to -? One per cap?
Also, you say to add a 0.1µF film cap in parallel with the 10µF input coupling cap and also the 470µF feedback cap. This would only be on the DH-200, not necessary on my P230? Do I add the 0.1µF film cap to each? Where are these two caps located?
These mods look like something easy and I would like to try them before I spend the money on the PA-3B boards.
Thanks, Terry
One of the main mods to the original DH-200 was to bypass all electrolytic caps with small film caps, preferably polypropylene.
The DH-220 incorporated most of the then DH-200 published mods. There is no need to bypass the DH220 electrolytics as they are already bypassed. Study the schematics.
The P-230 uses the same circuit card as the DH-220 so there are few mods to be made to the P-230.
Adding capacitance to the PS is an often used mod. Also adding bypass caps to the main PS caps, such as a 10 uF polypropylene film cap, is a frequent mod. For everyone who recommends all these bypasses you will find someone else who says they don't make a difference and can even add distortion because of the interaction between the resonances of several different value caps in parallel.
Bypass film caps to the PS can help to lower the PS's impedance at higher frequencies. However, many agree that more modern filter caps can maintain a low impedance at high frequencies without the need for bypasses.
My experience tells me that a pair of the LC-200 kit caps from Musical Concepts can be an excellent mod. MC uses only a small 1.0 bypass film cap on each large cap. I have tried different combo of caps, large and small, and the MC caps as MC uses them is the best -- for me.
There is a fairly new thread here on the use of the LC-30 thermistor to help blunt the initial turn-on surge. This thread has some good info in it.
Then, there are those who claim a high current capacity transformer used with only modest amounts of capacitance makes the best PS.
Well, we are getting into the hair splitting type of messages. You can't make a Bryston out of a P-230 and there are few mods (simple replacements of passive parts) that will work wonders with this amp.
The DH-220 incorporated most of the then DH-200 published mods. There is no need to bypass the DH220 electrolytics as they are already bypassed. Study the schematics.
The P-230 uses the same circuit card as the DH-220 so there are few mods to be made to the P-230.
Adding capacitance to the PS is an often used mod. Also adding bypass caps to the main PS caps, such as a 10 uF polypropylene film cap, is a frequent mod. For everyone who recommends all these bypasses you will find someone else who says they don't make a difference and can even add distortion because of the interaction between the resonances of several different value caps in parallel.
Bypass film caps to the PS can help to lower the PS's impedance at higher frequencies. However, many agree that more modern filter caps can maintain a low impedance at high frequencies without the need for bypasses.
My experience tells me that a pair of the LC-200 kit caps from Musical Concepts can be an excellent mod. MC uses only a small 1.0 bypass film cap on each large cap. I have tried different combo of caps, large and small, and the MC caps as MC uses them is the best -- for me.
There is a fairly new thread here on the use of the LC-30 thermistor to help blunt the initial turn-on surge. This thread has some good info in it.
Then, there are those who claim a high current capacity transformer used with only modest amounts of capacitance makes the best PS.
Well, we are getting into the hair splitting type of messages. You can't make a Bryston out of a P-230 and there are few mods (simple replacements of passive parts) that will work wonders with this amp.
Hopefullly you have a pair of 134s, not 133s.
Here are the Drain to Source voltage ratings of Hitachi Mosfets of that era:
2SK133 120
2SK134 140
2SK135 160
2SJ48 -120
2SJ49 -140
2SJ50 -160
Finding a pair of matched 2SJ49 MOSFETs will be very difficult (they must be matched). Perhaps some kind soul somewhere has a pair of them. I have an original Hafler MOSFET curve tracer that enables device matching but I don't have a sample of 10-20 MOSFETs to use in making matched sets.
Exicon sells an equivalent to the 2SJ49 but they do not match devices.
http://www.profusionplc.com/exicon.htm
You could rearrange your 6 MOSFETs to place 2 of them per channel. The amp will run this way with a careful rebiasing. It would then become a 60 watt per channel amp. Or, you could get another Hafler DH-200 amp for parts, make one good amp out of them, and sell the remainder for parts.
Soundvalves in the past has sold matched sets of Exicon MOSFETs but no longer seek this business. Now and then Soundvalves runs an auction for 8 or 16 MOSFETS at a time so if you had lots of buddies you could buy the lot and split them amongst you.
Here are the Drain to Source voltage ratings of Hitachi Mosfets of that era:
2SK133 120
2SK134 140
2SK135 160
2SJ48 -120
2SJ49 -140
2SJ50 -160
Finding a pair of matched 2SJ49 MOSFETs will be very difficult (they must be matched). Perhaps some kind soul somewhere has a pair of them. I have an original Hafler MOSFET curve tracer that enables device matching but I don't have a sample of 10-20 MOSFETs to use in making matched sets.
Exicon sells an equivalent to the 2SJ49 but they do not match devices.
http://www.profusionplc.com/exicon.htm
You could rearrange your 6 MOSFETs to place 2 of them per channel. The amp will run this way with a careful rebiasing. It would then become a 60 watt per channel amp. Or, you could get another Hafler DH-200 amp for parts, make one good amp out of them, and sell the remainder for parts.
Soundvalves in the past has sold matched sets of Exicon MOSFETs but no longer seek this business. Now and then Soundvalves runs an auction for 8 or 16 MOSFETS at a time so if you had lots of buddies you could buy the lot and split them amongst you.
Do you folks know if the LC200 kit will work in the DH200 without doing the PA-3B mod? That seems like a better place to start to me not to mention it sounds like a good bang for the buck.
Another thing. I keep hearing good things about the Blackgate caps. Would they be a better investment than the LC200 caps? i know they are more money but even MC talks them up pretty good.
Thanks, Terry
Another thing. I keep hearing good things about the Blackgate caps. Would they be a better investment than the LC200 caps? i know they are more money but even MC talks them up pretty good.
Thanks, Terry
Terry,
MC searches for the best sounding passive parts. They did this to locate the caps they now have MC branded. Who makes these caps I don't know. Can one buy the same thing with a different label for less money? I don't know. I do know that these have been the best sounding PS caps I have found, and I have tried half a dozen varieties at that location.
The LC-200 caps are the same size as those presently in your DH-200 or P-230. They are drop-in replacements. You can try a pair in your DH-200 and listen for a few days to determine if they make a difference. Then, move them over into your P-230 for a listening and comparison test. I predict you will find them to be "keepers."
Note that MC uses a 1.0 uF film cap in parallel with each capacitor, and also installls a bleeder resistor (6000 ohms?) across each capacitor. The bleeder has no sonic benefit but it helps safeguard against inadvertant shock by bleeding off most of the cap's charge when the amp is turned off. Be very careful when messing with PS caps to make sure they are fully discharged before handling. They can hold a lethal charge!!
There is lots of controversy about Black Gate caps. I would try and study up on the comments about them before putting down what is some serious money for them. People using them have reported a difference in the sound, both good and bad, they mention long break in times, and other comments. But, they usuall do not produce a "wow" effect and one must consider the overall value of the device being modified before putting in such expensive upgrade items.
Go to the Tweak/DIY form at the audioasylum:
http://www.audioasylum.com/audio/tweaks/bbs.html
Check their archives, ask some questions about black gates.
Good luck.
Dick
MC searches for the best sounding passive parts. They did this to locate the caps they now have MC branded. Who makes these caps I don't know. Can one buy the same thing with a different label for less money? I don't know. I do know that these have been the best sounding PS caps I have found, and I have tried half a dozen varieties at that location.
The LC-200 caps are the same size as those presently in your DH-200 or P-230. They are drop-in replacements. You can try a pair in your DH-200 and listen for a few days to determine if they make a difference. Then, move them over into your P-230 for a listening and comparison test. I predict you will find them to be "keepers."
Note that MC uses a 1.0 uF film cap in parallel with each capacitor, and also installls a bleeder resistor (6000 ohms?) across each capacitor. The bleeder has no sonic benefit but it helps safeguard against inadvertant shock by bleeding off most of the cap's charge when the amp is turned off. Be very careful when messing with PS caps to make sure they are fully discharged before handling. They can hold a lethal charge!!
There is lots of controversy about Black Gate caps. I would try and study up on the comments about them before putting down what is some serious money for them. People using them have reported a difference in the sound, both good and bad, they mention long break in times, and other comments. But, they usuall do not produce a "wow" effect and one must consider the overall value of the device being modified before putting in such expensive upgrade items.
Go to the Tweak/DIY form at the audioasylum:
http://www.audioasylum.com/audio/tweaks/bbs.html
Check their archives, ask some questions about black gates.
Good luck.
Dick
Terry,
I had hoped someone else with more precise info might have answered your question but now here is mine.
The stock Hafler transformer is rated around 4 amps or 480VA and has a 80VAC center tapped secondary. The pair of 40VAC secondaries can provide +/-65VDC supply to the rails (40 * 1.64= 65VDC) after rectification. Under load the rail voltages will sag depending on the load. As you have seen with ~124VAC home service and under the load of a P-230 amp you get rail voltages of ~65VDC.
I had hoped someone else with more precise info might have answered your question but now here is mine.
The stock Hafler transformer is rated around 4 amps or 480VA and has a 80VAC center tapped secondary. The pair of 40VAC secondaries can provide +/-65VDC supply to the rails (40 * 1.64= 65VDC) after rectification. Under load the rail voltages will sag depending on the load. As you have seen with ~124VAC home service and under the load of a P-230 amp you get rail voltages of ~65VDC.
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