It's all AKer Ivan100000's fault. He sent me his ailing 400CX-2 preamp for repairs, and I promptly fell in love with the thing when I was finished. He had the unmitigated nerve to actually want it back, so that was that. I started looking for examples for sale, which were few and far between, and when they did come up, the price was simply absurd. They are a wonderful preamp to be sure, but their price -- like ALL such outrageously priced equipment -- is primarily a function of their rarity, rather than the unobtanium performance/features they deliver over other more common pieces of similar equipment.
So, I started mulling about for a nice 400C. This was Fisher's very first stereo effort of any kind, and represents the origin for some of the standardized design efforts that followed through to numerous succeeding models of various types (preamps, integrated amps, receivers, console tuner/preamps, etc.), some of which followed through to the very last vacuum tube units Fisher produced.
Topology wise, it is a slightly simplified version of the 80-C and 90-C premium mono preamp offerings that preceded it, but the 400C represents the point where standardized component values began for many of the future small signal audio circuits of all things Fisher. Specifically, with only minor exceptions, the component values used in the 400C phono preamp followed through to every single piece of Fisher stereo equipment that followed it that had a magnetic phono input, and the active tone control network component values followed directly on through to the 400CX and 400 CX-2 preamplifiers and X-202, X202B, and EL34 based X-1000 premium integrated amplifier offerings. This includes the typically wonderful tracking dual tap 100K volume control that Fisher used in these tone control circuits. With a vacuum tube rectifier and DC heater power supply, the 400C then contains the most important basic building blocks of its more famous later versions. That meant that if I could just find a decent one, then I could go through it and rather easily upgrade it to provide the wonderful performance I had measured and heard in Ivan's unit earlier.
But since the 400C is an older unit, it is often in worse physical shape when available. A current look on the auction site will prove that. And, it is the later version of the 400C I wanted that has the individual tone controls for each channel and dropped the somewhat goofy crossover feature, so that narrows the field down even further. Therefore, while going this route is certainly easier than going for a real 400CX-2, it is still challenging to say the least.
Enter my good friend and fellow AKer Audiodon, who just happened to have a 400C of the type I was looking for. So typical of Don, it was a good looking unit, and was the version I was looking for. But there was a catch. This particular 400C was in many, MANY parts an pieces, carefully stored in a box from a previous gutting/rebuild effort that went awry some years earlier when the low level selector switch was found to be broken. So there it sat, with copious notes, schematics, parts and pieces and a broken low level selector switch. In one of the previous equipment ventures Don and I have had, he had sent me that switch, which I was able to successfully repair and send back to him. But by that time, with all his current work and the requests for work he gets, the steam was gone behind the 400C project for him, helped in no small degree by the Preamp Output Jacks his X-1000 and X-101C integrated amplifiers now offer. So there it sat for yet another year, until my quest for a Fisher preamp began in earnest.
When I received it from Don, it was packed to the hilt as he so typically does, complete with all of his notes, a nice set of tubes, and various containers of removed parts, mechanical parts, and parts yet to be installed. It was going to be a formidable project to say the least, but I was undaunted.
It is always interesting to pick up someone else's unfinished project that stopped midway through the effort, and now has, er....some age on it. Nothing of the project is fresh for recall, and the available Sam's schematic was already known to not only not match the version I had, but have numerous inaccuracies for the version it did represent. And, I'd never worked on, used, or heard a 400C either to know of any of it quirks as originally offered -- just the promise of the sound I'd heard from Ivan's 400CX-2 that I wanted to achieve in this 400C.
After addressing a number of initial basic issues, developing a neat game plan for going forward, and nearly reassembling/rebuilding it from scratch for a common build style from beginning to end, it reached the point that some basic testing could begin. While the basic building blocks were good, and the plan could ultimately return the performance I wanted, it turns out that being Fisher's very first stereo offering, it did in fact come with a number of quirks and design/build "features" that to my mind left it lacking against the 400CX-2 performance I witnessed earlier. Most notably was various amounts and timber of hum depending on the various control settings and connections used.
To be honest, I'm very picky about any extra hum or noise over base circuit operation. I HATE it, and will pursue it to the ends of the earth to eradicate it. This unit had plenty of it by my standard, which always spoils the listening experience for me just knowing that it's there, even if I can't hear it while the music is playing. Judging from some other threads and folks I've talked to, it's apparently not uncommon with these units. To my mind, that's just not how a Fisher should operate. Cutting to the chase, I have prevailed -- but the fix is rather intricate and involved. However, my 400C now emits nothing but a soft hiss under any condition of use, and delivers all the sound and performance I had heard from Ivans CX-2.
The pics show just how well this unit turned out. Don had already done some serious cleaning on it, but still various panels he had yet to get to told the tale of just how filthy this unit originally was, coming rather obviously out of a heavy smoker's home. The other pics show the significant changes made to eliminate the hum from this unit. The effort was quite effective. Some of them are obvious, some, not so much so. Maybe some of you other 400C owners can spot them. In any event, they'll be detailed in upcoming posts.
Stay tuned....
Dave
So, I started mulling about for a nice 400C. This was Fisher's very first stereo effort of any kind, and represents the origin for some of the standardized design efforts that followed through to numerous succeeding models of various types (preamps, integrated amps, receivers, console tuner/preamps, etc.), some of which followed through to the very last vacuum tube units Fisher produced.
Topology wise, it is a slightly simplified version of the 80-C and 90-C premium mono preamp offerings that preceded it, but the 400C represents the point where standardized component values began for many of the future small signal audio circuits of all things Fisher. Specifically, with only minor exceptions, the component values used in the 400C phono preamp followed through to every single piece of Fisher stereo equipment that followed it that had a magnetic phono input, and the active tone control network component values followed directly on through to the 400CX and 400 CX-2 preamplifiers and X-202, X202B, and EL34 based X-1000 premium integrated amplifier offerings. This includes the typically wonderful tracking dual tap 100K volume control that Fisher used in these tone control circuits. With a vacuum tube rectifier and DC heater power supply, the 400C then contains the most important basic building blocks of its more famous later versions. That meant that if I could just find a decent one, then I could go through it and rather easily upgrade it to provide the wonderful performance I had measured and heard in Ivan's unit earlier.
But since the 400C is an older unit, it is often in worse physical shape when available. A current look on the auction site will prove that. And, it is the later version of the 400C I wanted that has the individual tone controls for each channel and dropped the somewhat goofy crossover feature, so that narrows the field down even further. Therefore, while going this route is certainly easier than going for a real 400CX-2, it is still challenging to say the least.
Enter my good friend and fellow AKer Audiodon, who just happened to have a 400C of the type I was looking for. So typical of Don, it was a good looking unit, and was the version I was looking for. But there was a catch. This particular 400C was in many, MANY parts an pieces, carefully stored in a box from a previous gutting/rebuild effort that went awry some years earlier when the low level selector switch was found to be broken. So there it sat, with copious notes, schematics, parts and pieces and a broken low level selector switch. In one of the previous equipment ventures Don and I have had, he had sent me that switch, which I was able to successfully repair and send back to him. But by that time, with all his current work and the requests for work he gets, the steam was gone behind the 400C project for him, helped in no small degree by the Preamp Output Jacks his X-1000 and X-101C integrated amplifiers now offer. So there it sat for yet another year, until my quest for a Fisher preamp began in earnest.
When I received it from Don, it was packed to the hilt as he so typically does, complete with all of his notes, a nice set of tubes, and various containers of removed parts, mechanical parts, and parts yet to be installed. It was going to be a formidable project to say the least, but I was undaunted.
It is always interesting to pick up someone else's unfinished project that stopped midway through the effort, and now has, er....some age on it. Nothing of the project is fresh for recall, and the available Sam's schematic was already known to not only not match the version I had, but have numerous inaccuracies for the version it did represent. And, I'd never worked on, used, or heard a 400C either to know of any of it quirks as originally offered -- just the promise of the sound I'd heard from Ivan's 400CX-2 that I wanted to achieve in this 400C.
After addressing a number of initial basic issues, developing a neat game plan for going forward, and nearly reassembling/rebuilding it from scratch for a common build style from beginning to end, it reached the point that some basic testing could begin. While the basic building blocks were good, and the plan could ultimately return the performance I wanted, it turns out that being Fisher's very first stereo offering, it did in fact come with a number of quirks and design/build "features" that to my mind left it lacking against the 400CX-2 performance I witnessed earlier. Most notably was various amounts and timber of hum depending on the various control settings and connections used.
To be honest, I'm very picky about any extra hum or noise over base circuit operation. I HATE it, and will pursue it to the ends of the earth to eradicate it. This unit had plenty of it by my standard, which always spoils the listening experience for me just knowing that it's there, even if I can't hear it while the music is playing. Judging from some other threads and folks I've talked to, it's apparently not uncommon with these units. To my mind, that's just not how a Fisher should operate. Cutting to the chase, I have prevailed -- but the fix is rather intricate and involved. However, my 400C now emits nothing but a soft hiss under any condition of use, and delivers all the sound and performance I had heard from Ivans CX-2.
The pics show just how well this unit turned out. Don had already done some serious cleaning on it, but still various panels he had yet to get to told the tale of just how filthy this unit originally was, coming rather obviously out of a heavy smoker's home. The other pics show the significant changes made to eliminate the hum from this unit. The effort was quite effective. Some of them are obvious, some, not so much so. Maybe some of you other 400C owners can spot them. In any event, they'll be detailed in upcoming posts.
Stay tuned....
Dave
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