Just got done playing with both, thought I'd share a few observations concerning differences.
The Pioneer SX-1250 is Kim G's unit that blew itself up. The KR-9600 is one that I have just received from an eBay sale.
Mechanical Construction: The Pioneer is ultra clean inside, at least on the top side. All the components mounted on the top side of the frame are covered with a steel shield, which may or may not be useful. The entire FM section (RF and IF) are shielded, being mounted on the squeaky-clean top frame assy. Considering that the front half of the receiver cover is wood, Pioneer engineers may have thought it necessary. The underside is where the ugly comes out, but it still is a much cleaner than most.
The Kenwood is butt-ugly inside - top and bottom, but wire routing is logical and reasonably easy to follow. Rather than have the entire FM section shielded, only the RF section is shielded. Shielding of the remainder is probably not necessary since the 9600 has a steel cover.
Opening up the cover on the 1250 is like popping the hood on a new Acura to peek at the motor. The Kenwood, on the other hand, is all business and makes few concessions to internal appearance. Kinda like opening up a Tektronics oscilloscope.
Disassembly is definately easier with the Pioneer...the core boards (amps, protection board, and power supply regulator) all are connected with plugs. Plugs are great for servicing, but tarnish over time and really should be cleaned every five years or so, especially the ones carrying high current (cleaned the male pins on Kim G's with Brasso and a Q-Tip, and sprayed with DeOxit on reassembly). The Pioneer uses solder and wire-wrap for other boards.
The Kenwood uses a combo of old-fashioned soldering and the dastardly wire-wrap. Of course, the wire wrap makes an ideal connection but removing a board is a nighmare (if indeed it must be completely removed...access can usually be gained without complete removal). Heat-sinking looks adequate for both.
Electrical and Electronic Design: Pioneer has pulled no punches in the design of the SX-1250. The transformer (a toroidal) is nearly as large as the one in my 700M, and it uses 88,000µf of filtering for both channels along with a soft-start circuit to prevent power switch failure due to inrush current. The FM section is fitted with a 5-Gang variable cap, two RF amp sections, one RF mixer, and four IF ceramic filters, identical to the Kenwood. The overall FM design of both is quite similar.
(Note: Although the circuits used in the Pioneer are pretty standard stuff looking at them from the eyes of a year 2003 critic, in the late 70's some of this was cutting edge.)
The Pioneer uses a pretty straightforward design for preamp and tone amp. The phono amp (there is only one) uses a bipolar input rather than the usual FET input, and the entire preamp assembly is capacitor coupled from stage to stage. The high and low filters are active style using an emitter follower, wheras the Kenwood uses a passive setup (no matter anyway...no one uses these things). The only drawback of Pioneer's active design is that the standard emitter follower leaves a bit to be desired as far as linearity goes. The low voltages are all regulated, and the power amp stage is well thought out with only the minimum number of stages to get the job done. Output is through paralleled TO-3 power devices and a 4PDT relay on the DC protection board. The amplifier allows both adjustable BIAS and DC-Offset (with cheap-ass little pots that won't stay where you put them for 5 minutes...Kim G's were replaced with nice expensive Bourns trimpots).
The Kenwood is overall an older design using older components and transistors that have been unavailable since 1977 (perhaps someone can help me out with the years here, but the Kenwood screams '1974-75' and the Pioneer '1977'...maybe that doesn't sound like much but if you were there and remember, those two/three years encompassed a lot of changes). Nothing terribly wrong here, and it usually has been a Kenwood hallmark to utilize tried-and-true designs in an effort to build a bulletproof product rather than attempt to wow the crowd. The power supply is what I would term 'adequate', with a 'plane-Jane' transformer and 40,000µf of filtering (less than half of that supplied on the Pioneer) and does not use a soft-start...the power switch takes all the inrush current. The FM section is quite like the Pioneer, again with a 5-Gang variable cap, two RF amp sections, one RF mixer, and four IF ceramic filters. The preamp and filter amp are again very similar to the Pioneer, with the Kenwood cutting a gain and buffer stage to help with simplicity (the 'KISS' rule). Low voltages are all regulated like on the Pioneer. The Kenwood gives you a bit of a choice on the phono...two full phono amps are employed, one using a FET input (rated at 2.5mV/76db), the other a bipolar input (rated at 5mV/80db). I prefer the sound of a FET input for phono, but others may not. Neither the Pioneer or the Kenwood has enough gain for a MC cartridge.
A significant deviation from Kenwood's standard practice of using known standard designs is the use of the output power module. The 9600 replaces the standard current mirror/driver/output stage with a hybrid package where the output drivers, power transistors, bias servo and overcurrent protection network are bonded to a very large aluminium heat spreader - increasing the area of thermal contact between the semiconductors and heatsink by a factor of at least 5 (the KA-9100 integrated also uses a hybrid module output). This, although similar in looks, is very different from the various STK modules used by mid-fi amps, one can actually even test the output transistors measuring through the pins of the hybrid module - the point was just to achieve exemplary thermal integrity. An additional advantage is a fair degree of ripple rejection that is not possible by using a standard driver/output stage, which is why Kenwood is able to get away with using such a comparatively small value of power supply filtering. The additional cost of manufacturing the hybrid is more than offset by savings in power supply caps (big caps=$$$). The downside is the unavailability of the module in the year 2003 should it fail for some reason. The upside is that, should you decide to do so, a discrete arrangement can be fabricated to replace a dead module, and there is a KR-9600 up for auction right now on eBay where this has been done - although the seller says he knows nothing of it. The amp section has no BIAS adjustment (BIAS is set through a precision voltage reference in the hybrid) and no DC-offset adjustment. One thing I found in the Kenwood that I did not like was back-to-back electrolytics in the input of the power amp section, and these electrolytics were tantulum at that! Tantalums are generally not used in signal paths because of poor frequency characteristics and substandard sonics, and back-to-back electrolytics are also frowned upon (but in the mid 70's quality bipolar electrolytics simply did not exist) . Fair or not, I replaced the input capacitor with a Black Gate 'N' series bipolar...I hate tantulums. The output of the power amp travels through two 4PDT relays mounted on the DC protection board.
Both of these receivers use those shitty spring loaded speaker lead connectors. I hate those things!! And both have a preout/main-in jumper to allow the use of the receiver as a preamp, which no integrated amp or receiver should be without (IMHO).
Listening and Overall Impressions: Both the Pioneer and the Kenwood have exceptionally sensitive and selective FM sections, with the Pioneer seeming to have a bit of an edge in sensitivity, and the Kenwood having an edge in selectivity and AM rejection. Sound quality, however, is significantly better in the Pioneer. The Kenwood FM audio quality just isn't up to audiophile standards, and barely qualifies as Hi-Fi (mild exaggeration...) The problem here is a way substandard output opamp in the Kenwood IF section, a thread concerning which I started here. After the opamp change, the Kenwood FM quality is at least on par with the Pioneer, but lacking a really decent FM station here in Kansas City, I can only speculate as to what both of these receivers might be capable of regarding FM reception. In stock form, the Pioneer wipes the floor sonically with the Kenwood. Anyone with a 9600 that would like to make a serious and noticeable improvement should drop me a line.
The phono sections of both are quite well done, but since I prefer the sound of a FET input for phono, I have to give the Kenwood a nod here. Odd that Kenwood, cutting costs to manufacture the most inexpensive TOTL Japanese mass-market receiver, would opt for two complete phono stages. Nevertheless, it gives one a choice of sensitivities and sound.
Kickin' back with the Dynaudio speakers on each amp reveals that there is not an enourmous difference in sound quality (with the notable exception of the FM stage). Both sound like good quality solid-state amps, with power to spare. At low-to-medium volumes I kind of preferred the Kenwood...noise floor seemed lower and detail was more apparent, although soundstaging was superior with the Pioneer at all volume levels. At the highest levels, the Pioneer shines, missing nary a beat and seeming to have the ability to output much more than its rated 160WPC (I cannot test full output power at these levels unless I want to smoke my precision dummy loads...and I can't afford to replace them). The Kenwood, on the other hand, more than likely is pretty accurately rated at 160WPC. Even with the hybrid module on the Kenwood, there is simply no substitute for big-ass filter caps (although 88,000µf is probably serious overkill). Another nice mod to the Kenwood would be to add a bit of filter capacitance, perhaps 10,000µf per side. This could be risky since the Kenwood has no soft-start circuitry, and power switch or bridge rectifier failure could become an issue. Unless you regularly rattle the walls or have very inefficent speakers (like I do), this is not necessary.
In the looks department, this is a matter of taste (Duh!). I have always loved what I called the 'white-faced' Pioneer receivers. The Kenwood, OTOH, has the cool-blue front panel and chrome handles that I like. Suffice it to say that the Pioneer is probably more 'wife-friendly' (as long as she doesn't have to lift it) with the attractive walnut case and straightforward panel layout. The Kenwood appeals to the 'techno-gadget-freak' in me, and looks at home next to a HP signal generator and a Tek scope. Both are beautiful units, but I usually give in to the tech side of me, so on looks I prefer the Kenny.
In some ways this was not a totally fair test. The Pioneer was at the top of the food chain for Japanese receivers, and the Kenwood at the bottom. Indeed, once you start looking closely at the construction, places where Kenwood cut corners to keep costs down start to become apparent. The Pioneer is a 'balls-to-the-wall' design, and the Kenwood occupied the bargan basement. Regardless, both do the job and do it quite well. The KR-9600 would not be so desirable after all these years if it did not still sound good all this time.
I find it unusual that the SX-1250 tends to sell on eBay for a bit less than the KR-9600. If I didn't have a thing for Kenwood gear, and if I didn't have the ability to tweak the gear to sound the way I want, this would be a no-brainer...I'd snag a mint SX-1250 and head down da road. Perhaps because the KR-9600 is not quite as common as the SX-1250, and because the SX-1250 lives in the shadow of the SX-1280 and the SX-1980, it it not as sought after.
Whatever the reason, the SX-1250 is clearly the winner of a heads-up match between it and the KR-9600. Massive power with huge reserve, coupled with great looks and no glaring faults...unlike the Kenwood with it's 'so-so' FM audio quality, and irreplaceable power hybrid module (not so much a fault as a point of worry). Admittedly with a few minor tweaks the Kenwood can hold its own in most respects, but for the average Joe lookng for a decent TOTL vintage receiver, the Pioneer SX-1250 is tough to beat.
The Pioneer SX-1250 is Kim G's unit that blew itself up. The KR-9600 is one that I have just received from an eBay sale.
Mechanical Construction: The Pioneer is ultra clean inside, at least on the top side. All the components mounted on the top side of the frame are covered with a steel shield, which may or may not be useful. The entire FM section (RF and IF) are shielded, being mounted on the squeaky-clean top frame assy. Considering that the front half of the receiver cover is wood, Pioneer engineers may have thought it necessary. The underside is where the ugly comes out, but it still is a much cleaner than most.
The Kenwood is butt-ugly inside - top and bottom, but wire routing is logical and reasonably easy to follow. Rather than have the entire FM section shielded, only the RF section is shielded. Shielding of the remainder is probably not necessary since the 9600 has a steel cover.
Opening up the cover on the 1250 is like popping the hood on a new Acura to peek at the motor. The Kenwood, on the other hand, is all business and makes few concessions to internal appearance. Kinda like opening up a Tektronics oscilloscope.
Disassembly is definately easier with the Pioneer...the core boards (amps, protection board, and power supply regulator) all are connected with plugs. Plugs are great for servicing, but tarnish over time and really should be cleaned every five years or so, especially the ones carrying high current (cleaned the male pins on Kim G's with Brasso and a Q-Tip, and sprayed with DeOxit on reassembly). The Pioneer uses solder and wire-wrap for other boards.
The Kenwood uses a combo of old-fashioned soldering and the dastardly wire-wrap. Of course, the wire wrap makes an ideal connection but removing a board is a nighmare (if indeed it must be completely removed...access can usually be gained without complete removal). Heat-sinking looks adequate for both.
Electrical and Electronic Design: Pioneer has pulled no punches in the design of the SX-1250. The transformer (a toroidal) is nearly as large as the one in my 700M, and it uses 88,000µf of filtering for both channels along with a soft-start circuit to prevent power switch failure due to inrush current. The FM section is fitted with a 5-Gang variable cap, two RF amp sections, one RF mixer, and four IF ceramic filters, identical to the Kenwood. The overall FM design of both is quite similar.
(Note: Although the circuits used in the Pioneer are pretty standard stuff looking at them from the eyes of a year 2003 critic, in the late 70's some of this was cutting edge.)
The Pioneer uses a pretty straightforward design for preamp and tone amp. The phono amp (there is only one) uses a bipolar input rather than the usual FET input, and the entire preamp assembly is capacitor coupled from stage to stage. The high and low filters are active style using an emitter follower, wheras the Kenwood uses a passive setup (no matter anyway...no one uses these things). The only drawback of Pioneer's active design is that the standard emitter follower leaves a bit to be desired as far as linearity goes. The low voltages are all regulated, and the power amp stage is well thought out with only the minimum number of stages to get the job done. Output is through paralleled TO-3 power devices and a 4PDT relay on the DC protection board. The amplifier allows both adjustable BIAS and DC-Offset (with cheap-ass little pots that won't stay where you put them for 5 minutes...Kim G's were replaced with nice expensive Bourns trimpots).
The Kenwood is overall an older design using older components and transistors that have been unavailable since 1977 (perhaps someone can help me out with the years here, but the Kenwood screams '1974-75' and the Pioneer '1977'...maybe that doesn't sound like much but if you were there and remember, those two/three years encompassed a lot of changes). Nothing terribly wrong here, and it usually has been a Kenwood hallmark to utilize tried-and-true designs in an effort to build a bulletproof product rather than attempt to wow the crowd. The power supply is what I would term 'adequate', with a 'plane-Jane' transformer and 40,000µf of filtering (less than half of that supplied on the Pioneer) and does not use a soft-start...the power switch takes all the inrush current. The FM section is quite like the Pioneer, again with a 5-Gang variable cap, two RF amp sections, one RF mixer, and four IF ceramic filters. The preamp and filter amp are again very similar to the Pioneer, with the Kenwood cutting a gain and buffer stage to help with simplicity (the 'KISS' rule). Low voltages are all regulated like on the Pioneer. The Kenwood gives you a bit of a choice on the phono...two full phono amps are employed, one using a FET input (rated at 2.5mV/76db), the other a bipolar input (rated at 5mV/80db). I prefer the sound of a FET input for phono, but others may not. Neither the Pioneer or the Kenwood has enough gain for a MC cartridge.
A significant deviation from Kenwood's standard practice of using known standard designs is the use of the output power module. The 9600 replaces the standard current mirror/driver/output stage with a hybrid package where the output drivers, power transistors, bias servo and overcurrent protection network are bonded to a very large aluminium heat spreader - increasing the area of thermal contact between the semiconductors and heatsink by a factor of at least 5 (the KA-9100 integrated also uses a hybrid module output). This, although similar in looks, is very different from the various STK modules used by mid-fi amps, one can actually even test the output transistors measuring through the pins of the hybrid module - the point was just to achieve exemplary thermal integrity. An additional advantage is a fair degree of ripple rejection that is not possible by using a standard driver/output stage, which is why Kenwood is able to get away with using such a comparatively small value of power supply filtering. The additional cost of manufacturing the hybrid is more than offset by savings in power supply caps (big caps=$$$). The downside is the unavailability of the module in the year 2003 should it fail for some reason. The upside is that, should you decide to do so, a discrete arrangement can be fabricated to replace a dead module, and there is a KR-9600 up for auction right now on eBay where this has been done - although the seller says he knows nothing of it. The amp section has no BIAS adjustment (BIAS is set through a precision voltage reference in the hybrid) and no DC-offset adjustment. One thing I found in the Kenwood that I did not like was back-to-back electrolytics in the input of the power amp section, and these electrolytics were tantulum at that! Tantalums are generally not used in signal paths because of poor frequency characteristics and substandard sonics, and back-to-back electrolytics are also frowned upon (but in the mid 70's quality bipolar electrolytics simply did not exist) . Fair or not, I replaced the input capacitor with a Black Gate 'N' series bipolar...I hate tantulums. The output of the power amp travels through two 4PDT relays mounted on the DC protection board.
Both of these receivers use those shitty spring loaded speaker lead connectors. I hate those things!! And both have a preout/main-in jumper to allow the use of the receiver as a preamp, which no integrated amp or receiver should be without (IMHO).
Listening and Overall Impressions: Both the Pioneer and the Kenwood have exceptionally sensitive and selective FM sections, with the Pioneer seeming to have a bit of an edge in sensitivity, and the Kenwood having an edge in selectivity and AM rejection. Sound quality, however, is significantly better in the Pioneer. The Kenwood FM audio quality just isn't up to audiophile standards, and barely qualifies as Hi-Fi (mild exaggeration...) The problem here is a way substandard output opamp in the Kenwood IF section, a thread concerning which I started here. After the opamp change, the Kenwood FM quality is at least on par with the Pioneer, but lacking a really decent FM station here in Kansas City, I can only speculate as to what both of these receivers might be capable of regarding FM reception. In stock form, the Pioneer wipes the floor sonically with the Kenwood. Anyone with a 9600 that would like to make a serious and noticeable improvement should drop me a line.
The phono sections of both are quite well done, but since I prefer the sound of a FET input for phono, I have to give the Kenwood a nod here. Odd that Kenwood, cutting costs to manufacture the most inexpensive TOTL Japanese mass-market receiver, would opt for two complete phono stages. Nevertheless, it gives one a choice of sensitivities and sound.
Kickin' back with the Dynaudio speakers on each amp reveals that there is not an enourmous difference in sound quality (with the notable exception of the FM stage). Both sound like good quality solid-state amps, with power to spare. At low-to-medium volumes I kind of preferred the Kenwood...noise floor seemed lower and detail was more apparent, although soundstaging was superior with the Pioneer at all volume levels. At the highest levels, the Pioneer shines, missing nary a beat and seeming to have the ability to output much more than its rated 160WPC (I cannot test full output power at these levels unless I want to smoke my precision dummy loads...and I can't afford to replace them). The Kenwood, on the other hand, more than likely is pretty accurately rated at 160WPC. Even with the hybrid module on the Kenwood, there is simply no substitute for big-ass filter caps (although 88,000µf is probably serious overkill). Another nice mod to the Kenwood would be to add a bit of filter capacitance, perhaps 10,000µf per side. This could be risky since the Kenwood has no soft-start circuitry, and power switch or bridge rectifier failure could become an issue. Unless you regularly rattle the walls or have very inefficent speakers (like I do), this is not necessary.
In the looks department, this is a matter of taste (Duh!). I have always loved what I called the 'white-faced' Pioneer receivers. The Kenwood, OTOH, has the cool-blue front panel and chrome handles that I like. Suffice it to say that the Pioneer is probably more 'wife-friendly' (as long as she doesn't have to lift it) with the attractive walnut case and straightforward panel layout. The Kenwood appeals to the 'techno-gadget-freak' in me, and looks at home next to a HP signal generator and a Tek scope. Both are beautiful units, but I usually give in to the tech side of me, so on looks I prefer the Kenny.
In some ways this was not a totally fair test. The Pioneer was at the top of the food chain for Japanese receivers, and the Kenwood at the bottom. Indeed, once you start looking closely at the construction, places where Kenwood cut corners to keep costs down start to become apparent. The Pioneer is a 'balls-to-the-wall' design, and the Kenwood occupied the bargan basement. Regardless, both do the job and do it quite well. The KR-9600 would not be so desirable after all these years if it did not still sound good all this time.
I find it unusual that the SX-1250 tends to sell on eBay for a bit less than the KR-9600. If I didn't have a thing for Kenwood gear, and if I didn't have the ability to tweak the gear to sound the way I want, this would be a no-brainer...I'd snag a mint SX-1250 and head down da road. Perhaps because the KR-9600 is not quite as common as the SX-1250, and because the SX-1250 lives in the shadow of the SX-1280 and the SX-1980, it it not as sought after.
Whatever the reason, the SX-1250 is clearly the winner of a heads-up match between it and the KR-9600. Massive power with huge reserve, coupled with great looks and no glaring faults...unlike the Kenwood with it's 'so-so' FM audio quality, and irreplaceable power hybrid module (not so much a fault as a point of worry). Admittedly with a few minor tweaks the Kenwood can hold its own in most respects, but for the average Joe lookng for a decent TOTL vintage receiver, the Pioneer SX-1250 is tough to beat.
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, but it is indeed looking like they are almost on par regarding pricing of late. The recent auctions show what you have found, but I have been watching auctions for both for the last 6 months or so, and in general the 9600 has been commanding a slightly higher price. The latest auctions have bucked this trend a bit, as you have discovered. As much as I like the Kenwood (and I am indeed a fan of their stuff), the top SX receivers are tough to beat. For $250 - $300, the SX-1250 or SX-1280 are a steal.
