mbz, congratulations. You have a really good preamp in stock form, but once you upgrade parts, you'll have a unit that can compete with the 4 and 5 figure pre amps offered today, and beat most of them on noise....Yamaha spent a lot of engineering time on the CX-1, but the bean counters came into play with some of the parts selection, as well as limitations as to what was available at that time. Can't stress using the Vishay resistors strongly enough, even if only a few are used at the output loading stage and the inputs. If you are a vinyl person, then do the whole phono stage. Once Vishay'ed the CX-1 phono stage will compete with 5 figure phono stages; have tried several of them and have always been surprised at the outcome; the CX-1 is a performer...
Yamaha CX-1 Thread
- Thread starter Bratwurst7s
- Start date
mbz, congratulations. You have a really good preamp in stock form, but once you upgrade parts, you'll have a unit that can compete with the 4 and 5 figure pre amps offered today, and beat most of them on noise....Yamaha spent a lot of engineering time on the CX-1, but the bean counters came into play with some of the parts selection, as well as limitations as to what was available at that time. Can't stress using the Vishay resistors strongly enough, even if only a few are used at the output loading stage and the inputs. If you are a vinyl person, then do the whole phono stage. Once Vishay'ed the CX-1 phono stage will compete with 5 figure phono stages; have tried several of them and have always been surprised at the outcome; the CX-1 is a performer...
808_state
Super Member
I just put my Japan domestic CX-1 back into use last night and while it still feels a little clinical in the very top end, the amount of life I hear in vocal choruses is absolutely stunning. So rich and alive! It doesn't seem to go as deep into the bass as my C-2x can but it packs a similar overall punch and it is a joy to spend time with. Can't stress enough how much the remote spoils me.
Hi John, I've been looking for some of the Vishay VSR resistors that you recommended but they don't seem to be available at Mouser. Do you have a recommended source?
Cheers,
James
you can't get them from mouser or digikey.
only sources are percyaudio.com or elcopc.com
Thanks! I'll look into those sources.
My second CX-1 arrived today. I haven't had time to do anything other than unpack it and confirm that it's in excellent condition optically. Tomorrow I'll take a deeper look.
Cheers,
James
808_state
Super Member
Oh wow, a second unit! What amp will it go with?
Have owned several of the yamaha pre amps. The CX-2 is nice, but not in same group as CX-1. The C-2a is another one that can sing. Also owned a pair of hot rodded CX-800s. The weak point on the 800 is the tiny power supply and the logic circuit can be sensitive to static. one winter had one of the CX-800s playing away. walked across the room, touched the chassis, discharging the static and the display went wild, flashing all sorts of signals, making noise, finally the whole unit died. The other CX-800 I built an external power supply. Left the small OEM transformer in the case. Bought an external case and added a 600VA toroid transformer to it. The pre amp was such a light load on the transformer, it always ran above its loaded voltage secondary output rating. But that 800 had dynamics like nothing else, and had an ease to the sound that was tough to beat.
That clinical sound you describe is coming from all the eletrolytic coupling caps that in the signal path. If you bypass them with a film and foil cap, that clinical sound quality will go away.
J
The 2nd one will be part of my son's 30th birthday present next year. I still have to decide on a power amp. And I have a lot of work ahead of me restoring the Speakerlab S7WA's that will provide air movement. I have an M-70 that I'm trying to repair that I had planned to use for myself but lately I've been thinking of finding an MX-1. If that happens I'll only be using the M-70 until the MX-1 is re-capped and the M-70 will go go my son. Providing that I get the M-70 working.
Concerning your earlier comment, yes, I have to agree strongly that I wouldn't want to go back to not having a remote for volume.
Cheers,
James
808_state
Super Member
Thanks for sharing the wisdom J! That is exactly why I am paying close attention to this thread so once I'm satisfied that the CX-1 is fully broken in I can then begin to consider some mods. It definitely improves/relaxes with each listening session (on both the phono and line-in's).
808_state
Super Member
Ah, I think the MX-1 seems attractive too! I didn't consider it until I heard how well the CX-1 performs. I might pick one up from Japan so I can get it as clean as my CX-1. The M-70 reminds me that I need to try it with my M-85 (so far I've only tried with the B-2x). I hope your son realizes how lucky he is!
So, a few developments since I last posted here.
First, I did end up buying a MX-1 and putting it in my system...
http://audiokarma.org/forums/index.php?threads/yamaha-mx-1-thread.823308/
...and I love it. It has much better control over the woofers in my Speakerlabs and gives better bass than the M-70 while still sounding good in the highs and mids.
Second, the second CX-1 arrived in good condition. When I recapped it the newest cap had a date code of 9331, so 1993 week 31, and the oldest cap was 8924. So Yamaha wasn't shy about using 4 year old caps in a new product. But we can also see that the 2nd unit was made only a few months after the 1st one.
The 1st pre has S/N E015873PR and the 2nd has E03358VX. So when looking at the S/N spread between unit 1 and 2 and them being only a few months apart perhaps mbz's unit might not be so much newer after all. The cap date codes would reveal that.
The 2nd unit is as mbz notes, with complete silk screening on both sides of all pcb's. Most (but not all) of the components that were tacked on to the trace side of the boards have been given a proper place and the traces corrected where the hand cutting was done on the 1st unit.
Cheers,
James
First, I did end up buying a MX-1 and putting it in my system...
http://audiokarma.org/forums/index.php?threads/yamaha-mx-1-thread.823308/
...and I love it. It has much better control over the woofers in my Speakerlabs and gives better bass than the M-70 while still sounding good in the highs and mids.
Second, the second CX-1 arrived in good condition. When I recapped it the newest cap had a date code of 9331, so 1993 week 31, and the oldest cap was 8924. So Yamaha wasn't shy about using 4 year old caps in a new product. But we can also see that the 2nd unit was made only a few months after the 1st one.
The 1st pre has S/N E015873PR and the 2nd has E03358VX. So when looking at the S/N spread between unit 1 and 2 and them being only a few months apart perhaps mbz's unit might not be so much newer after all. The cap date codes would reveal that.
The 2nd unit is as mbz notes, with complete silk screening on both sides of all pcb's. Most (but not all) of the components that were tacked on to the trace side of the boards have been given a proper place and the traces corrected where the hand cutting was done on the 1st unit.
Cheers,
James
A few schematic & parts list corrections...
The schematic shows a 220 ohm resistor in the signal path of every input except Phono. But what was actually installed in both pre's was a 330 ohm in all of those inputs except for CD, which did have 220 ohm.
R234 & R242, CD Buffer, shown in schematic as 3.9k ohm, 1.6k ohm installed.
R195 & R202, MM EQ Amp, shown as 94 ohm, 2.2k ohm installed.
R346, R353, 0-DB Amp, shown 3.9k ohm, 2.0k ohm installed.
R369, R370, 0-DB Amp, shown 4.7k ohm, 6.8k ohm installed.
There are a number of resistors shown in the schematic and parts list as 1w MOX, such as R345, 347, 352 and 354 (100 ohm). But what is installed are not MOX, and look like the classic 1/4w fusible resistors, in green (in this case) or in brown for some others. I have no idea what the different colors denote.
Cheers,
James
The schematic shows a 220 ohm resistor in the signal path of every input except Phono. But what was actually installed in both pre's was a 330 ohm in all of those inputs except for CD, which did have 220 ohm.
R234 & R242, CD Buffer, shown in schematic as 3.9k ohm, 1.6k ohm installed.
R195 & R202, MM EQ Amp, shown as 94 ohm, 2.2k ohm installed.
R346, R353, 0-DB Amp, shown 3.9k ohm, 2.0k ohm installed.
R369, R370, 0-DB Amp, shown 4.7k ohm, 6.8k ohm installed.
There are a number of resistors shown in the schematic and parts list as 1w MOX, such as R345, 347, 352 and 354 (100 ohm). But what is installed are not MOX, and look like the classic 1/4w fusible resistors, in green (in this case) or in brown for some others. I have no idea what the different colors denote.
Cheers,
James
So for sure mcgjohn, you got my interest activated concerning low noise resistors and bypass caps. Enough that I did a fair amount of browsing concerning that, found an interesting white paper from Vishay for instance...
https://www.eetimes.com/document.asp?doc_id=1278251
http://www.vishaypg.com/docs/49997/49997.pdf
http://www.resistorguide.com/resistor-noise/
The thing is that I just can't begin to afford to buy those Z-film resistors. Even the CMF & RN addup pretty quickly, especially as I like to buy at least double what I need and sort them.
But I could afford Vishay's SFR25 series so I bought a potful of them, with some CMF & RN for use directly in the signal path. It was interesting to note that Yamaha shows higher watt ratings for some of the resistors in the CD and Tape-3 inputs than the same resistors in the other inputs. So I generally used 1/2w in the signal path and 400mW elsewhere, except for where it looked like Yamaha definitely used a 1/4w fusible.
I replaced the carbon film resistors with metal film in: the complete power supply, the -20-DB amp section, the 0-DB amp section, the entire phono section, and the CD, Tape-3 and Aux input/buffer sections, as well as a few more in the control section. I just counted and it added up to 244 resistors. Per pre-amp.
It's interesting to see that as well as the CD input/buffer section Yamaha strongly addressed the Tape-3 section, which has the 2nd best specs in the amp (not counting phono). The CD and tape-3 inputs appear to be the only ones that have a muting relay, all the rest have muting transistors (including phono). Tape-3 has dual 2-channel SIP-9 op-amps (and uses both op-amp channels, summed for each L & R channel) compared to the single Dip-8 for the other inputs. The CD input/buffer is entirely discrete.
Cheers,
James
https://www.eetimes.com/document.asp?doc_id=1278251
http://www.vishaypg.com/docs/49997/49997.pdf
http://www.resistorguide.com/resistor-noise/
The thing is that I just can't begin to afford to buy those Z-film resistors. Even the CMF & RN addup pretty quickly, especially as I like to buy at least double what I need and sort them.
But I could afford Vishay's SFR25 series so I bought a potful of them, with some CMF & RN for use directly in the signal path. It was interesting to note that Yamaha shows higher watt ratings for some of the resistors in the CD and Tape-3 inputs than the same resistors in the other inputs. So I generally used 1/2w in the signal path and 400mW elsewhere, except for where it looked like Yamaha definitely used a 1/4w fusible.
I replaced the carbon film resistors with metal film in: the complete power supply, the -20-DB amp section, the 0-DB amp section, the entire phono section, and the CD, Tape-3 and Aux input/buffer sections, as well as a few more in the control section. I just counted and it added up to 244 resistors. Per pre-amp.
It's interesting to see that as well as the CD input/buffer section Yamaha strongly addressed the Tape-3 section, which has the 2nd best specs in the amp (not counting phono). The CD and tape-3 inputs appear to be the only ones that have a muting relay, all the rest have muting transistors (including phono). Tape-3 has dual 2-channel SIP-9 op-amps (and uses both op-amp channels, summed for each L & R channel) compared to the single Dip-8 for the other inputs. The CD input/buffer is entirely discrete.
Cheers,
James
Concerning bypass caps. Again, the high end caps were/are simply outside what I could/can afford. But Panasonic ECW polypro caps work with my budget so I used them. I'll detail exactly where later. One thing. I did a brain fart and missed the recommended 0.047, 0.022 and 0.01 and instead used 0.47, 0.22 and 0.1 (also 2.2µF to bypass the main filter caps and to replace C206/211 in the 0-DB section). Afterwards I ordered some Wima MKS2 in 0.047, 0.033, 0.022 and 0.01 and will try using them later, but haven't found any polypro caps with long enough leads that I can afford.
More about all of this later. I don't mean to be a tease but I'm pretty burned out tonight and will post more tomorrow.
Cheers,
James
More about all of this later. I don't mean to be a tease but I'm pretty burned out tonight and will post more tomorrow.
Cheers,
James
My little update. I finished my CX-1, going more conventional, Nichicon UKL over MKS and Silmic II over KZ (maybe KZ next time).
I did allocate MKS/UKL/Silmic to TAPE 1 PB/TUNER/AUX ie, just on the input opamps, it's just 1 cap, doubt I would pick the difference.
Only had a brief listen, certainly good, however I prefer my unrestored CX-1000, worth a listen if you have one in the shed.
I did allocate MKS/UKL/Silmic to TAPE 1 PB/TUNER/AUX ie, just on the input opamps, it's just 1 cap, doubt I would pick the difference.
Only had a brief listen, certainly good, however I prefer my unrestored CX-1000, worth a listen if you have one in the shed.
I can't help you with the math. I was just interested in the concept and decided to give it a try. I had the luxury of having 2 CX-1's sitting here and decided to take advantage of that to find if I could hear a difference.
With the freshly recapped 1st unit in the system, I reworked the 2nd unit completely, caps, resistors, and bypass caps in the signal path and on the main filter caps. Then I sat and listened to a cd with the 1st unit (John Fogerty, Blue Moon Swamp, 20th anniversary edition), swapped out the pre's and listened again. To my ears there is a definite and nice SQ improvement. I'm quite happy with the way it sounds, enough that I went ahead and replaced the resistors and added the bypass caps in the 1st unit.
Working the 2nd CX-1 took me roughly 50+ hours to do the complete job. Having all of the components marked on both sides of the pcb's was a luxury. A good part of the time involved was because I measured/tested each and every component as I removed it, and measured each and every new component. I bought at a minimum double what I needed for everything and cherry-picked the best parts, and did the best possible L&R matching that I could. In general doing this I was able to stay under +/-0.5% tolerance with the resistors.
Reworking the 1st unit was a lot harder because the pcb's aren't marked at all, so it took a lot more time. Rough guess is about 70 hours total including the previous re-capping.
Was it worth the time and cost involved? For my purposes, yes, no question. The SQ improvement was worth it for me. YMMV.
I'll post some photos starting tomorrow.
Cheers,
James
With the freshly recapped 1st unit in the system, I reworked the 2nd unit completely, caps, resistors, and bypass caps in the signal path and on the main filter caps. Then I sat and listened to a cd with the 1st unit (John Fogerty, Blue Moon Swamp, 20th anniversary edition), swapped out the pre's and listened again. To my ears there is a definite and nice SQ improvement. I'm quite happy with the way it sounds, enough that I went ahead and replaced the resistors and added the bypass caps in the 1st unit.
Working the 2nd CX-1 took me roughly 50+ hours to do the complete job. Having all of the components marked on both sides of the pcb's was a luxury. A good part of the time involved was because I measured/tested each and every component as I removed it, and measured each and every new component. I bought at a minimum double what I needed for everything and cherry-picked the best parts, and did the best possible L&R matching that I could. In general doing this I was able to stay under +/-0.5% tolerance with the resistors.
Reworking the 1st unit was a lot harder because the pcb's aren't marked at all, so it took a lot more time. Rough guess is about 70 hours total including the previous re-capping.
Was it worth the time and cost involved? For my purposes, yes, no question. The SQ improvement was worth it for me. YMMV.
I'll post some photos starting tomorrow.
Cheers,
James
Thanks for the update. I've used the SFR25's before, while I didn't pickup any significant improvement
I feel comfortable with that work knowing they have better thermal drift properties and lower noise.
Certainly use them in bias circuits (temp drift) and also on collectors (noise), use them elsewhere
if you have the time etc... Will try and dig deeper into rationale behind bypass caps, however all
that matters is you've got 2 great sounding pre's
I feel comfortable with that work knowing they have better thermal drift properties and lower noise.
Certainly use them in bias circuits (temp drift) and also on collectors (noise), use them elsewhere
if you have the time etc... Will try and dig deeper into rationale behind bypass caps, however all
that matters is you've got 2 great sounding pre's
Bypass caps on the volume control...
Cheers,
James
Cheers,
James
Before removing the main and tone control boards I measured them for clearance under the boards and then took a fine marker and marked where the mounting frame cutouts were on the boards so that I wouldn't have any clearance problems when mounting bypass caps to the trace side of the boards...
Cheers,
James
Cheers,
James