Hello everyone. I recently got a hold of a nice otari 5050. It currently only kind of sort of works. The buttons, lights, motors, knobs, switches, and all that good stuff all works just fine. The thing actually will play music, but it is very quiet and has a lot of noise. And when I say quiet, I mean I have to stick my ear up to the tweeter quiet. Something in the amplifier section is not having a good day.
Rather than rooting around in the circuit boards trying to figure out where the problem is, I would like to build a quick and dirty tape head preamp and just cut out the middleman. I intend on building a proper tube preamp later on, but for now I just want something that will play music at adequate listening levels so that I can sort the rest of this otari out.
Would something like this work? Low noise tape head preamplifier | ElecCircuit.com
Do you guys have any other recommendations?
Rather than rooting around in the circuit boards trying to figure out where the problem is, I would like to build a quick and dirty tape head preamp and just cut out the middleman. I intend on building a proper tube preamp later on, but for now I just want something that will play music at adequate listening levels so that I can sort the rest of this otari out.
Would something like this work? Low noise tape head preamplifier | ElecCircuit.com
Do you guys have any other recommendations?
A very simple one here http://www.youspice.com/wp-content/uploads/2015/04/RIAANABequalizationAmp.png
I would try to wire the PB heads to a Tape deck recorder or even a phono preamp in order to test them first. Check PSU section, if power isn't getting to the circuits it won't play.
I would try to wire the PB heads to a Tape deck recorder or even a phono preamp in order to test them first. Check PSU section, if power isn't getting to the circuits it won't play.
Well the headphone jack more or less works. Its loud enough to get slightly higher than normal listening levels. However the volume knob doesn't do anything......so thats cool.
The other thing is that audio doesn't seem to be coming in on the right cable. There are only two headers coming from the tape heads. There is one header that has 8 individual cables/pins and another that has 4 pins.
According to the manual along with several other forum posts, the 4 pin cable is supposed to carry audio from the playback head. Yet when I pull out this cable, there is still a bunch of audio at the same level.
When I try to tap into the 4 pin cable, I see 0v regardless of how I connect to each pin. And sure enough when I plugged these cables into my phonostage, I got no signal.
Mysteries abound.
The other thing is that audio doesn't seem to be coming in on the right cable. There are only two headers coming from the tape heads. There is one header that has 8 individual cables/pins and another that has 4 pins.
According to the manual along with several other forum posts, the 4 pin cable is supposed to carry audio from the playback head. Yet when I pull out this cable, there is still a bunch of audio at the same level.
When I try to tap into the 4 pin cable, I see 0v regardless of how I connect to each pin. And sure enough when I plugged these cables into my phonostage, I got no signal.
Mysteries abound.
> Mysteries abound.
Indeed.
A phono preamp *will* bring a tape head to useful level. The EQ is a bit wrong but generally in the right direction. Tape heads are sometimes "weaker" than phono carts but it still should play well enough to tell.
The head output level may be too low to read on a common meter.
There is a lot of JFET switching but if you are coming right off the heads into a phono preamp then this is out of the picture.
Most models have SelSync. Have you tried playback that way?
It would be highly unusual for a play head to fail. For *both* Play and SelSync (Rec) heads to fail there would have to be some incredible accident.
Obviously you are sure your tape has signal? And that the Otari Erase system isn't wiping it?
Indeed.
A phono preamp *will* bring a tape head to useful level. The EQ is a bit wrong but generally in the right direction. Tape heads are sometimes "weaker" than phono carts but it still should play well enough to tell.
The head output level may be too low to read on a common meter.
There is a lot of JFET switching but if you are coming right off the heads into a phono preamp then this is out of the picture.
Most models have SelSync. Have you tried playback that way?
It would be highly unusual for a play head to fail. For *both* Play and SelSync (Rec) heads to fail there would have to be some incredible accident.
Obviously you are sure your tape has signal? And that the Otari Erase system isn't wiping it?
I mean Im getting plenty of signal out of the headphone jack. I can actually listen to music quite comfortably if I only use headphones. (of course I am also hearing music played in reverse from the other side of the tape, so there is that).
So I know for a fact I am getting a decent signal. It just clearly isn't getting to the right place
For the moment the real question is where am I getting the signal from because its definitely not the wire that goes to the playback head. And of course the obvious follow up question is why am I not getting audio from the playback wire.
My meter is a half decent fluke that can measure down to 0.01mv ac. Something like that. I feel like the tape head signal should be a little higher than that, but if Im wrong, please correct me.
And lastly, I don't think the erase head is doing anything. If I play music, then rewind and listen to it again, its still there.
I tried reading the manual in hopes that this might be a case of RTFM, but no luck so far.
I will say that the selsync is new to me and didn't seem to be in the manual. Can you explain it a bit more?
So I know for a fact I am getting a decent signal. It just clearly isn't getting to the right place
For the moment the real question is where am I getting the signal from because its definitely not the wire that goes to the playback head. And of course the obvious follow up question is why am I not getting audio from the playback wire.
My meter is a half decent fluke that can measure down to 0.01mv ac. Something like that. I feel like the tape head signal should be a little higher than that, but if Im wrong, please correct me.
And lastly, I don't think the erase head is doing anything. If I play music, then rewind and listen to it again, its still there.
I tried reading the manual in hopes that this might be a case of RTFM, but no luck so far.
I will say that the selsync is new to me and didn't seem to be in the manual. Can you explain it a bit more?
SelSync: record guitar on one channel. Playback, and sing on the second channel. With a standard deck the two tracks would be out of sync by the distance from record to play heads. In SelSync you play from the record head. Fidelity is down but your singing is exact sync with the guitar on the tape.
Not all models have this. It isn't relevant to a play-only situation unless the complaint is weak highs over 5KHz.
Not all models have this. It isn't relevant to a play-only situation unless the complaint is weak highs over 5KHz.
Hi. I had the same dilemma, but I opted for tweaking the amp inside because I realized that not only NAB/IEC tapes sound different but that also every studio has different taste or flavor and the Otari caries NAB/IEC plus three bias levels which is a neat trait and very useful to fine tune my old tapes to my liking, so it would be much work to reproduce every function on a new amp. So I will take my time and build a discrete one in the future, with Low Thermal Memory distortion circuit.
To your problems:
If you have phones out working then: head-->common gate JFET-->501 opamp-->101 opamp-->502 opamp path should be OK.
You can use this phone out to connect to your power amp
or take a direct unbalanced out from opamp 101.The problem must be on the balanced output section which normally has lots of parts and very high output V. I replaced it for a THAT balanced line driver chip.
The volume pot issue must be very easy to fix. I assume that you checked the "SRL" function...just check with multimeter if the pot is OK and if everything is well soldered. I forgot to mention that as with all these old machines you must use a good cleaning aerosol for electronics...lots of it...
I found the original pot to be muddy sounding and I replaced it for a SMD resistor based pot with which I cannot distinguish between SRL and pot. I lost independent channel volume control though...
I remember the signal after the common gate JFET Q105 is around 20mV max with normal programme material. So better use a scope instead of a Vmeter. Connector 9(4) must be OK. I doubt you have signal from elsewhere.
If you want to mod your amp I can tell the many mods I carried out as the sound of the stock machine is so so...
I never started the thread I considered...
What you MUST do is the mod for the tape path:
Otari MX-5050/BII/BIII Tape Path Modification Kit Specs | Bottlehead
With ten bucks you can do it: eBay 6x3x3mm miniature ball bearings and M3 iron bolt and nuts. The washers should be non-metallic though.
Cheers,
M.
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I have a 5050 and I have to use the balanced outs to get much volume out of it. Of course you need a balanced preamp or a balanced line convertor. An alternative is an older preamp that has tape head inputs. I have a Mcintosh MA 6100 integrated that has such inputs and a Harman Kardon Citation A, neither of which have I tried.
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