Well, I may, in fact, be nuts. BUT I found some NOS Signetics/Philips NE5534N chips (the original ICs that were used in the superb-sounding Neve consoles) and I'm gonna put them in the front end of my Otari MX-5050 MKIII-8 reproduce electronics. It was also tough (and expensive) to find suitable adapters to fit in the original HA12017's footprint. We'll see if it really makes a difference.....but, as one pundit, put it..."I LOVE the sound of open reel tape!!"
The 5534 was (is) a good performing chip and closer to what was originally in there, as you know I've had a pretty mixed experience with swapping op-amps in my 5050 MKIII, I have yet to undo it, but largely due to the op-amp mods it's retired.
My conclusion is the selection of op-amps was not accidental, and while cost was certainly a factor there were probably other much less obvious criteria not necessarily found in the data sheet. It's the second time I have made this mistake - like the time I swapped out OP285 for LM4562 - an immediately audible mistake in a PSA Ultralink II Dac.
I'd seriously start with a couple of channels and see where that gets you.
My conclusion is the selection of op-amps was not accidental, and while cost was certainly a factor there were probably other much less obvious criteria not necessarily found in the data sheet. It's the second time I have made this mistake - like the time I swapped out OP285 for LM4562 - an immediately audible mistake in a PSA Ultralink II Dac.
I'd seriously start with a couple of channels and see where that gets you.
Here's a quote from diyer Paul Bass:
"I upgraded from NJM4558 to NE5532 and it was a dramatic improvement in clarity and lower noise. I pushed my luck and tried LM4562 and it was oscillation city. The amp was screaming at me"
In your swaps, did you put 100nF caps between the rails and scope for oscillation?
I have also noted that the HA12017 used in my Otari has absolutely abysmal PSRR (only -45db on -V); that coupled with the (could-be-sold-as-a-noise-generator) 7815/7915 regulated power supply cries for some improvement.
"I upgraded from NJM4558 to NE5532 and it was a dramatic improvement in clarity and lower noise. I pushed my luck and tried LM4562 and it was oscillation city. The amp was screaming at me"
In your swaps, did you put 100nF caps between the rails and scope for oscillation?
I have also noted that the HA12017 used in my Otari has absolutely abysmal PSRR (only -45db on -V); that coupled with the (could-be-sold-as-a-noise-generator) 7815/7915 regulated power supply cries for some improvement.
Last edited:
I've also noticed that Studer, in their later-production tape recorders such as the A810, used NE5532s in their audio electronics. So they must have thought that tape deserved a better opamp than the old NJM 4558/9s that Otari used; and that it made a difference. Their machines are certainly among the best ever made.
Or it could simply be a matter of sourcing, what with them located in Europe and Japanese parts probably were not cost competitive.. The 5532 is somewhat better than the 4558/4559 - whether that is audible or not is another question. (I have gear with both, and no question I would select the 5532 over the 4559 - that said I have not noticed differences between the two practically speaking.)
It's a good choice overall, not sure if the 8 track has 18V supplies or not but check the supply voltage rating of anything you stick in there.
The MX-50 has +/-20V supplies and doesn't use any 4558/4559, instead using some mystery chip from Matsushita that I cannot even find a data sheet for.
It's a good choice overall, not sure if the 8 track has 18V supplies or not but check the supply voltage rating of anything you stick in there.
The MX-50 has +/-20V supplies and doesn't use any 4558/4559, instead using some mystery chip from Matsushita that I cannot even find a data sheet for.
I can understand your difficulty; the OP285 is a 9 MHz chip, whilst the LM4562 is a 55 MHz one. Much more difficult to harness and certainly prone to oscillation. That's the reason I have decided to stick to NE553x ICs for my Otari--they are 10 MHz chips. I have found some NE5532AN ON Semis in PDIP-8 form, and I'll be putting those in place of the NJM 4559s, and the NE5534As in place of the HA12017s in the front end. It's certainly possible that it won't make a noticeable improvement in tape circuitry, but at least I'll know I tried and I'll feel better!
I also received my denoiser power supply boards today and I'll see if I can fit them in place of the noisy 78/7915 regulator boards.
Last edited:
I've been studying the Otari audio circuit schematics, and I am impressed with the attention they obviously paid to the choice of capacitors---they used bi-polars for all the higher value couplers and also used a number of polystyrenes as well.
I was doing some service on my MX-5050 BII when I discovered that it's missing one of the two slip washers that go on either side of the pinch roller. Either a previous owner or yours truly must have forgotten to reinstall it. I could use some suggestions for where to source a replacement. I know McMaster Carr would likely have something, though I'd probably need to order a hundred.
The washers seem to have been used as much for height alignment of the pinch roller. And it is likely given that the pinch roller must be removed to lubricate the capstan motor front bearing that a previous owner may have lost one or more.
None of mine are the same! I try to make sure the tape is centered on the pinch roller. I now use rollers with ball bearings so less of a concern as long as the height is right.
I would look in the McMaster Carr catalog and perhaps check with Athan Corp as well.
None of mine are the same! I try to make sure the tape is centered on the pinch roller. I now use rollers with ball bearings so less of a concern as long as the height is right.
I would look in the McMaster Carr catalog and perhaps check with Athan Corp as well.
I've sent a note to Athan. We'll see what they say.
After a search of McMaster Carr, the closest washers I can find to the measured dimensions (10mm O.D., 5.75mm I.D., 0.26mm thickness) are in brass. While that would be fine for the height aspect, I'm concerned that I won't be getting the same slip as I would from nylon or PTFE (which is what I assume the originals are/were). Thoughts?
After a search of McMaster Carr, the closest washers I can find to the measured dimensions (10mm O.D., 5.75mm I.D., 0.26mm thickness) are in brass. While that would be fine for the height aspect, I'm concerned that I won't be getting the same slip as I would from nylon or PTFE (which is what I assume the originals are/were). Thoughts?
Ok, I found PTFE washers at McMaster Carr. After replacing them, I spun the roller a bit and was surprised by the amount of drag I felt. I know people switch to the ball bearing rollers for this reason, but I'm curious how normal (or not) this is for the original roller. In other words, how free-spinning should I expect the original to be?
That makes sense about the motor torque vs. roller drag. It does spin relatively freely, just not so freely that any momentum from me turning it quickly with my finger will keep it going for more than a second. I'm not going to worry about it.
Re the capstan, I actually just recently finished pulling out the motor and opening it up to secure the sensor coils with epoxy. They were still in place, but I thought it wise to follow your lead from this earlier post.
So you think you want to play with tape: An Otari Story
At the same time I cleaned out the top bearing and added fresh oil there and to the foam ring once the motor was reinstalled. But after some testing, one thing is now bugging me a little. With the deck in the vertical position, I can hear a very faint/slight irregular tick as the capstan motor turns. However, when the deck is laying flat, the noise disappears. I just pulled the motor again and am right now considering opening it up to see if I can spot anything amiss, though I'm not sure what it could be other than just wear in the rear bearing.
Re the capstan, I actually just recently finished pulling out the motor and opening it up to secure the sensor coils with epoxy. They were still in place, but I thought it wise to follow your lead from this earlier post.
So you think you want to play with tape: An Otari Story
At the same time I cleaned out the top bearing and added fresh oil there and to the foam ring once the motor was reinstalled. But after some testing, one thing is now bugging me a little. With the deck in the vertical position, I can hear a very faint/slight irregular tick as the capstan motor turns. However, when the deck is laying flat, the noise disappears. I just pulled the motor again and am right now considering opening it up to see if I can spot anything amiss, though I'm not sure what it could be other than just wear in the rear bearing.
I pulled the motor again and separated the halves. The noise is coming from the bottom half. Nothing appears to be scraping anywhere--there's definitely no contact between the head and the flywheel--but there are areas around the perimeter I can't see and where it's possible that very slight contact is being made between the flywheel and housing. I think the lower bearing itself is fine, as the capstan shaft has a long spin-down time after giving it a flick with my fingers.
Unless anyone has any other suggestions, I'm probably just going to reassemble the motor and live with it/accept that it's just a wear or tolerance issue. Fortunately, the noise is inaudible until I get my ear close to the deck.
Unless anyone has any other suggestions, I'm probably just going to reassemble the motor and live with it/accept that it's just a wear or tolerance issue. Fortunately, the noise is inaudible until I get my ear close to the deck.
I was just surfing and came across the service manual for an Otari MTR-12---one of their later machines that has earned quite a good reputation among the R-R audiophile crowd. Looked up the audio electronics schematic and noted that they switched the opamps in the record path to NE5532s from the previously used New Japan Radio chips. I cannot help but wonder why they didn't also change the reproduce chips; but....it does show that Otari thought that better ICs made a difference, at least in the record side. That's why I'm putting all Philips/Signetics NE5534/32s in my Otari.....
Brings back some fond memories of a demo studio my friends had with an Otari 8 track. I also remember mixing down to a 2 track Otari and a magnificent Studer A800 24 track 2" machine - digital eventually replaced it all. Best part of the ad copy is "Try anything and everything and always roll tape".
Is there still a source for new 1/2 (and 2") magnetic tape?
Is there still a source for new 1/2 (and 2") magnetic tape?
Yes, 1/2 inch, 1 inch and 2 inch tape are available from RTM and ATR.
I use RTM's SM900 but obviously in 1/4 inch tape - my machines are all 2 track.
ATR available here and elsewhere: Dealers — ATR Magnetics
and RTM from here: Dealers - RecordingTheMasters
I get RTM tape from Splicit.
I use RTM's SM900 but obviously in 1/4 inch tape - my machines are all 2 track.
ATR available here and elsewhere: Dealers — ATR Magnetics
and RTM from here: Dealers - RecordingTheMasters
I get RTM tape from Splicit.