Hi everyone.
Owner of an early 90 (apparently 91) Revox B77 mk2 1/4 (4) track NShere. Recently serviced (electrolytics, pinch roller,motor bearings etc) and properly callibrated. All good, clean and perfectly working.
But i’m only using the machine for hybrid recording (just some passes of tracks for analog flavour), so i was thinking about converting it to 2 tracks. Since i don’t care about listening to 4 track tapes.
1) Am i correct to think that a 2 track normal speed machine is better for recording than a 4 track normal speed?
That mod seems pretty straightforward. Just swapping the headblocks, the oscillator pcbs and maybe changing few small things on the recording-reproduce pcbs. I can find cheap used headblocks and i can sell or swap mine. Mine is used in great condition so i expect to find one in similar condition as well.
2) Is the HS conversion so difficult? There are used hs capstans in good prices ( i can also sell mine or swap), but there is a debate about different placement on the b77 chassis (modification) or not (people say that it can be done on the same location on the chassis) , different motor (i could sell or swap if needed) or not (people say that thevsame motor works well, and it’s really confusing. Of course the speed pcb needs simple mods but that’s easy.
It’s hard to undersand what can be modded in a diy way, when most opinions come from “audiophile“ people (and ultra detailed techs) who don’t like “down and dirty” diy (i mean i wouldn’t mind a revox with extra heads as an echo - dub machine), and it’s hard to figure out what’s “snake oil” and what’s doable.
In my eyes normal revox machines are great workhorses and not precious collector’s items.
3) is there any advantage from changing the recording eq from nab to iec? Is it doable in an easy way (i’m based in europe- so my mains is 230v, 50hz- i read about a mod that mains frequency matters)?
Thanks in advance
Owner of an early 90 (apparently 91) Revox B77 mk2 1/4 (4) track NShere. Recently serviced (electrolytics, pinch roller,motor bearings etc) and properly callibrated. All good, clean and perfectly working.
But i’m only using the machine for hybrid recording (just some passes of tracks for analog flavour), so i was thinking about converting it to 2 tracks. Since i don’t care about listening to 4 track tapes.
1) Am i correct to think that a 2 track normal speed machine is better for recording than a 4 track normal speed?
That mod seems pretty straightforward. Just swapping the headblocks, the oscillator pcbs and maybe changing few small things on the recording-reproduce pcbs. I can find cheap used headblocks and i can sell or swap mine. Mine is used in great condition so i expect to find one in similar condition as well.
2) Is the HS conversion so difficult? There are used hs capstans in good prices ( i can also sell mine or swap), but there is a debate about different placement on the b77 chassis (modification) or not (people say that it can be done on the same location on the chassis) , different motor (i could sell or swap if needed) or not (people say that thevsame motor works well, and it’s really confusing. Of course the speed pcb needs simple mods but that’s easy.
It’s hard to undersand what can be modded in a diy way, when most opinions come from “audiophile“ people (and ultra detailed techs) who don’t like “down and dirty” diy (i mean i wouldn’t mind a revox with extra heads as an echo - dub machine), and it’s hard to figure out what’s “snake oil” and what’s doable.
In my eyes normal revox machines are great workhorses and not precious collector’s items.
3) is there any advantage from changing the recording eq from nab to iec? Is it doable in an easy way (i’m based in europe- so my mains is 230v, 50hz- i read about a mod that mains frequency matters)?
Thanks in advance
First...... read the original spec´s on 4-track vs. 2-track.
Check for S/N, freq. response & distortion.
That should tell you, if it´s worth it 😉
Check for S/N, freq. response & distortion.
That should tell you, if it´s worth it 😉
This tech specs sheet shiws that the 2 track - 4 track conversion has some obvious advantages, and that the Normal speed to High speed one has only slightly better wow and flutter and distortion numbers.
https://www.reeltoreel.de/worldwide/B77.htm
Also after carefully studying the hs and ns motor constructions, apart from the capstan (and because it had a bigger diameter on the hs) the motor is placed a bit higher and a bit towards the right side.
And this happens with different placement of the motor screw holes.
So it’s only a careful drilling of new holes (enlargement of the existing ones and then very tight mounting) or being lucky and swap motors with hs owner who wants ns.
Buying hs motor is way too expensive (around 300-400 euros)for what the benefits are.
Also after carefully studying the hs and ns motor constructions, apart from the capstan (and because it had a bigger diameter on the hs) the motor is placed a bit higher and a bit towards the right side.
And this happens with different placement of the motor screw holes.
So it’s only a careful drilling of new holes (enlargement of the existing ones and then very tight mounting) or being lucky and swap motors with hs owner who wants ns.
Buying hs motor is way too expensive (around 300-400 euros)for what the benefits are.
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I did just the opposite. I bought a Revox B77 two track machine in 1981 and later converted it to a four-track machine. It wasn't difficult, they just removed the two-track heads and replaced them with four-track heads and realigned the tape path. I think I did it because I had some commercial four-track tapes I wanted to play.
I used to do warranty on these. I had a 1/2 track also (Tascam BR-20).
I wouldn't convert it. It is expensive and you have some electronic changes to make. You do gain some signal to noise ratio, maybe 2 dB from memory. Going to high speed works, but tape is pricy and you'll burn through a pancake pretty quickly. Again, a s/n ratio increase. If you were working with a mastering machine I can see it. But simply going to high speed will buy you the most bang for the buck, and you can still flip the tape over and get more time.
As for the motor, I never noticed it was positioned differently, but we didn't convert low speed, high speed often (rare). The capstan shaft is the only difference I recall, plus electronic EQ changes. The motor itself runs at the same speed exactly.
So for 1/2 track, you rewind the tape (stored tails out), then play it off. That way the tape lays down with controlled tension and an even pack. This may reduce tape edge damage and does extend tape life. The procedure gets old pretty fast. I'd rather play LPs with that dance.
I wouldn't convert it. It is expensive and you have some electronic changes to make. You do gain some signal to noise ratio, maybe 2 dB from memory. Going to high speed works, but tape is pricy and you'll burn through a pancake pretty quickly. Again, a s/n ratio increase. If you were working with a mastering machine I can see it. But simply going to high speed will buy you the most bang for the buck, and you can still flip the tape over and get more time.
As for the motor, I never noticed it was positioned differently, but we didn't convert low speed, high speed often (rare). The capstan shaft is the only difference I recall, plus electronic EQ changes. The motor itself runs at the same speed exactly.
So for 1/2 track, you rewind the tape (stored tails out), then play it off. That way the tape lays down with controlled tension and an even pack. This may reduce tape edge damage and does extend tape life. The procedure gets old pretty fast. I'd rather play LPs with that dance.
Thanks Anatech. I need it for good recordings of seperate instrument tracks (i would say 95% mono tracks) so i always keep in mind the term 1/2 track, even if i don’t do the modification. I even think of whole track mono, but it seems a rare breed to find a decent good priced mono machine.
The only use for a mono machine I can think of is a full tape width unit for creating test tapes (calibration tapes).
You do need to calibrate the machine to standards. So don't get creative. Figure out the track width for a 2", 24 track Studer running at 15 or 30 ips. Now 30 ips is problematic as the "head bumps" are well up in the audible range. Studer EQ's them out, but no so with smaller machines.
My point is that much original bed tracks were laid down on these Studer or MCI machines and a few others. If you want to do the same, a Studer would be my recommendation. They made two track machines for mastering. You really can't do better than that with tape. They released a B-77 recently, modern electronics. That would really give you a quiet machine. Too bad Nakamichi and Studer never collaborated, that would have been an awesome machine! Nakamichi made very quiet electronics. A Sendust head would have probably improved things further (Nakamichi).
You do need to calibrate the machine to standards. So don't get creative. Figure out the track width for a 2", 24 track Studer running at 15 or 30 ips. Now 30 ips is problematic as the "head bumps" are well up in the audible range. Studer EQ's them out, but no so with smaller machines.
My point is that much original bed tracks were laid down on these Studer or MCI machines and a few others. If you want to do the same, a Studer would be my recommendation. They made two track machines for mastering. You really can't do better than that with tape. They released a B-77 recently, modern electronics. That would really give you a quiet machine. Too bad Nakamichi and Studer never collaborated, that would have been an awesome machine! Nakamichi made very quiet electronics. A Sendust head would have probably improved things further (Nakamichi).
Studer is the way to go…but…Too expensive. Way too expensive. Unfortunately if it’s expensive for others, for me here in greece it’s imossible.
I’m lucky having my revox properly repaired (since i know my way around diy audio electronics).
Take a mono track out of an interface out, pass it on tape, send it back in the computer. The bigger the track width, the better the tape flavour. I don’t mind hiss and noise, but it’s better to control it.
I’m lucky having my revox properly repaired (since i know my way around diy audio electronics).
Take a mono track out of an interface out, pass it on tape, send it back in the computer. The bigger the track width, the better the tape flavour. I don’t mind hiss and noise, but it’s better to control it.
I agree, properly serviced is rare.
Okay, so keep the 1/4 track and run it at higher speed. This is the least expensive option. But if quality is important, Studer is the one and only way. There are very good reasons why those machines cost more. Tape handling is waaaayyyyyy better as well.
The Revox (I love them and still service them) is a toy by comparison.
Okay, so keep the 1/4 track and run it at higher speed. This is the least expensive option. But if quality is important, Studer is the one and only way. There are very good reasons why those machines cost more. Tape handling is waaaayyyyyy better as well.
The Revox (I love them and still service them) is a toy by comparison.
How could i disagree. Studer and otari are the industry standards.
As far as the higher speed goes, it’s not a very expensive mod if there are machinists contacts, but there is quite some work to be done and a little bit of risk. Buying a high speed motor is overpriced in europe is like 4 times the price of normal speed (in the sec. hand market ). If you want do some research about normal speed to high speed conversion.
Since you know tascam, how would you compare a small 22-2 to a revox b77? Tape duration is no issue since most of my work is no longer than 507 min.
As far as the higher speed goes, it’s not a very expensive mod if there are machinists contacts, but there is quite some work to be done and a little bit of risk. Buying a high speed motor is overpriced in europe is like 4 times the price of normal speed (in the sec. hand market ). If you want do some research about normal speed to high speed conversion.
Since you know tascam, how would you compare a small 22-2 to a revox b77? Tape duration is no issue since most of my work is no longer than 507 min.
Studer stands alone.
The only difference between high and low speed motors is the capstan shaft. The rest is identical. Replace the rear bearing and lubricate the front sleeve bearing when you change it out.
The B-77 is a much better machine. Tascam machines sound great (I did warranty for them also, and a couple others). But the basic differences are fundamental. With German machines, parts are diecast and milled. They fit exactly, their motors are AC. With all Japanese machines, the parts are stamped and everything pretty much is adjustable. Early machines used AC motors, later ones went to DC (and some capstan motors reversed - RUN!). Very basic differences in their thinking.
The 22-2 isn't in the same league as the B-77. I imagine you could really update the electronics in the B-77. It would be a fun project. I'm not talking about someone's idea of what sounds good, I'm talking about looking at how the best electronics were done and applying that to the B-77. Adapt a Nakamichi BX-300 head amp to the B-77 for example. This would perform much better and sound much better.
The capstan motor in a B-77 is an AC motor with a brilliant electronic drive. No brushes and very good speed control. You might be able to improve it, but it is pretty darned good now.
The only difference between high and low speed motors is the capstan shaft. The rest is identical. Replace the rear bearing and lubricate the front sleeve bearing when you change it out.
The B-77 is a much better machine. Tascam machines sound great (I did warranty for them also, and a couple others). But the basic differences are fundamental. With German machines, parts are diecast and milled. They fit exactly, their motors are AC. With all Japanese machines, the parts are stamped and everything pretty much is adjustable. Early machines used AC motors, later ones went to DC (and some capstan motors reversed - RUN!). Very basic differences in their thinking.
The 22-2 isn't in the same league as the B-77. I imagine you could really update the electronics in the B-77. It would be a fun project. I'm not talking about someone's idea of what sounds good, I'm talking about looking at how the best electronics were done and applying that to the B-77. Adapt a Nakamichi BX-300 head amp to the B-77 for example. This would perform much better and sound much better.
The capstan motor in a B-77 is an AC motor with a brilliant electronic drive. No brushes and very good speed control. You might be able to improve it, but it is pretty darned good now.
I trust your expertise anatech regarding tape machines.
And what you say sounds pretty encouraging helping understanding better the ideas i have,and i do appreciate your effort to help and show possibilities, to an inexperienced reel to reel user.
Without pretending that i know exactly what i’m talking about, some (audiophile) people say (in an absolute way) that because of the larger hs capstan (9mm diameter) to the smaller ns one (4.5mm diameter), the motor base has to move a bit higher, because the larger capstan gets in the way of the bottom tape guide and a bit to the right in order to get a bit away from the tape guide next the (larger) capstan. In general apparently the capstan size obstructs the tape path.
Here is a picture of the two capstan motor bases side by side (hs is the one with the offset mounting-screw holes, ns is the centered mounting-holes one).
That’s why i’m saying about mods. I don’t really know, since i’m no expert, or have any experience eith an hs b77. So i wonder if it’s just an audiophile search for perfection, removed from the recording world, or a necessary change?
If i could avoid that trouble and expense, it would be heaven sent.
And what you say sounds pretty encouraging helping understanding better the ideas i have,and i do appreciate your effort to help and show possibilities, to an inexperienced reel to reel user.
Without pretending that i know exactly what i’m talking about, some (audiophile) people say (in an absolute way) that because of the larger hs capstan (9mm diameter) to the smaller ns one (4.5mm diameter), the motor base has to move a bit higher, because the larger capstan gets in the way of the bottom tape guide and a bit to the right in order to get a bit away from the tape guide next the (larger) capstan. In general apparently the capstan size obstructs the tape path.
Here is a picture of the two capstan motor bases side by side (hs is the one with the offset mounting-screw holes, ns is the centered mounting-holes one).
That’s why i’m saying about mods. I don’t really know, since i’m no expert, or have any experience eith an hs b77. So i wonder if it’s just an audiophile search for perfection, removed from the recording world, or a necessary change?
If i could avoid that trouble and expense, it would be heaven sent.
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Well, as I said. Very rarely did we have to change between speeds. I have done it a couple times, but the entire motor came out and it probably mounted differently. But speed changes were decades ago for me. Most of the time we were maintaining them, and I have had to replace worn out capstan shafts keeping the same speed most often. Like, 99% of the time. You should see people dragging out logging machines (really slow speed) and trying to change to high speed machines. The main shaft is the same exact size in all motor versions. The basic motor was the same.
As for offset mounting holes, I would have to examine each one and the chassis to give you an answer for sure. That kind of work was done so long ago. I do not ever remember having to replace the motor - just the shaft. You serviced the motor at that time. I mean, we are talking the 1980's for speed changes. Maybe a couple through the 1990's and nothing afterwards. I've serviced a lot of machines between then and now.
About audiophiles. Very often, people fixate on tiny things that don't matter, and completely miss the things that do. It isn't uncommon for effects at RF frequencies to take focus over what happens at audio frequencies. I work in both areas of electronics, the parts are different. What is optimized for one thing is actually not as good as parts designed for something else. Fast recovery diodes vs normal ones a classic case in point. Parts have their applications, there is no one best kind of part. It depends greatly on what that part is doing. Bypassing a coupling capacitor is a waste of time, power supply bypass caps are different, and that does make a difference - in the right location! I pull tons of parts to install the correct ones, or remove unrequired parts to clean up the area.
So with this in mind, focus on what you are actually doing and how best to achieve it. Audio isn't special, it follows the same rules of physics as a guided missile or spacecraft, airliner or anything else. Each part designed for one application may not be suited for another (meaning audio). Different things are most important. No, as in ZERO parts are designed specifically for audio. Some are branded and marketed for audio, and they probably wouldn't cut it in real audio or industrial process. We only get (in audio) what industry needs.
So when you see 1 dB difference in noise or level, it may not be noticable to you - or it may be if you're talking about frequency response. For an industrial machine it may or may not be critical, for test and measurement it certainly is critical.
Try it at 7 1/2 ips and see. You will only see a couple dB difference to 15 ips. Your calibration will make much more of a difference, and calibration is done for the specific tape you are using. If you're using used tape, all bets are off. Check it before trying to record (rec-play calibration). Make certain you are playing back on specification before anything.
The big difference may be at 20 KHz or so, again very dependent on calibration and tape path alignment. Assuming tensions are correct. The more advanced machines (A-700 I think) use active back tension, most other things use brakes and do not sense back tension. This can matter. Studers absolutely use active tension sensors. Same as a Tascam 52 (50 series) and the BR-20. You will have more consistent speed and high frequency performance with better machines.
So try it. If it's good, use it the way it is. If it isn't even close to what you want, you need a better machine. If it is nearly there, maybe changing speeds or head type may do it. But then you may be further ahead purchasing the machine configured the way you need it. Changing speeds isn't cheap, changing head configuration even more expensive. Above all, make certain the machine is calibrated and also calibrated to the tape you are using. Use new tape. It is dependent on the performance you are looking for.
As for offset mounting holes, I would have to examine each one and the chassis to give you an answer for sure. That kind of work was done so long ago. I do not ever remember having to replace the motor - just the shaft. You serviced the motor at that time. I mean, we are talking the 1980's for speed changes. Maybe a couple through the 1990's and nothing afterwards. I've serviced a lot of machines between then and now.
About audiophiles. Very often, people fixate on tiny things that don't matter, and completely miss the things that do. It isn't uncommon for effects at RF frequencies to take focus over what happens at audio frequencies. I work in both areas of electronics, the parts are different. What is optimized for one thing is actually not as good as parts designed for something else. Fast recovery diodes vs normal ones a classic case in point. Parts have their applications, there is no one best kind of part. It depends greatly on what that part is doing. Bypassing a coupling capacitor is a waste of time, power supply bypass caps are different, and that does make a difference - in the right location! I pull tons of parts to install the correct ones, or remove unrequired parts to clean up the area.
So with this in mind, focus on what you are actually doing and how best to achieve it. Audio isn't special, it follows the same rules of physics as a guided missile or spacecraft, airliner or anything else. Each part designed for one application may not be suited for another (meaning audio). Different things are most important. No, as in ZERO parts are designed specifically for audio. Some are branded and marketed for audio, and they probably wouldn't cut it in real audio or industrial process. We only get (in audio) what industry needs.
So when you see 1 dB difference in noise or level, it may not be noticable to you - or it may be if you're talking about frequency response. For an industrial machine it may or may not be critical, for test and measurement it certainly is critical.
Try it at 7 1/2 ips and see. You will only see a couple dB difference to 15 ips. Your calibration will make much more of a difference, and calibration is done for the specific tape you are using. If you're using used tape, all bets are off. Check it before trying to record (rec-play calibration). Make certain you are playing back on specification before anything.
The big difference may be at 20 KHz or so, again very dependent on calibration and tape path alignment. Assuming tensions are correct. The more advanced machines (A-700 I think) use active back tension, most other things use brakes and do not sense back tension. This can matter. Studers absolutely use active tension sensors. Same as a Tascam 52 (50 series) and the BR-20. You will have more consistent speed and high frequency performance with better machines.
So try it. If it's good, use it the way it is. If it isn't even close to what you want, you need a better machine. If it is nearly there, maybe changing speeds or head type may do it. But then you may be further ahead purchasing the machine configured the way you need it. Changing speeds isn't cheap, changing head configuration even more expensive. Above all, make certain the machine is calibrated and also calibrated to the tape you are using. Use new tape. It is dependent on the performance you are looking for.
Everything so well said. Thank you Anatech for your time and effort to share such insight. Food for thought and research. You shared so easily your vast knowledge on audio tech repair, and on the few things i also know i couldn’t agree more. What i strongly believe in, are the phrases “whatever works” and “if it’s not broken don’t fix it”
In my case the machine works well. It’s well calibrated. But since i’m only recording, i was thinking about probable real world (not “ideal” - not testing) recording improvements.
So it seems like it’s a matter of few changes. And i think now i have a much clearer idea.
In my case the machine works well. It’s well calibrated. But since i’m only recording, i was thinking about probable real world (not “ideal” - not testing) recording improvements.
So it seems like it’s a matter of few changes. And i think now i have a much clearer idea.
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Okay, try recording and playback. You'll need an audio oscillator or tone from a sound card. You will need an AC voltmeter, NOT A DVM! You need a real AC voltmeter, one with a pointer may be easier. It needs to be flat well above the highest frequency. Hewlett Packard meters are about the best. A 3400A would be superb.
Bias and bias EQ, set your zero level at 1 KHz, reduce the level from the source by about 20 dB. I forget what the manual specifies, but this is close enough. R-R bias is typically set at higher level, lower will be fine. Set your AC voltmeter to read something convenient but reasonably close to that level. Compare the 20 KHz to 1 KHz levels, reduce bias slightly to increase the high frequency level. Make them equal or maybe 1/2 a dB higher at 20 KHz to add "sparkle". Check at various frequencies once you have that done. We are assuming azimuth is fine, you check phase at 1 KHz, 10 KHz and 20 KHz to make sure azimuth is okay. Once your bias is set, go back to 1 KHz or 400 Hz and your 0 dB level. Make the source and monitor levels the same. Note that azimuth is the first adjustment, if it was off your highs will be better once corrected.
Don't attempt to use the meters on the B-77. They are not flat, they are not calibrated or linear in many cases. Machines with less quality have even worse meters. The meters on any recorder are rough guides. Studers are okay for level, better meters. I wouldn't trust them to be flat with frequency though.
So before trying to improve anything at all, make sure the machine is bang-on. Note tape distortion can be quite high, so don't try to chase 0.00x % THD, you'll never get there.
Bias and bias EQ, set your zero level at 1 KHz, reduce the level from the source by about 20 dB. I forget what the manual specifies, but this is close enough. R-R bias is typically set at higher level, lower will be fine. Set your AC voltmeter to read something convenient but reasonably close to that level. Compare the 20 KHz to 1 KHz levels, reduce bias slightly to increase the high frequency level. Make them equal or maybe 1/2 a dB higher at 20 KHz to add "sparkle". Check at various frequencies once you have that done. We are assuming azimuth is fine, you check phase at 1 KHz, 10 KHz and 20 KHz to make sure azimuth is okay. Once your bias is set, go back to 1 KHz or 400 Hz and your 0 dB level. Make the source and monitor levels the same. Note that azimuth is the first adjustment, if it was off your highs will be better once corrected.
Don't attempt to use the meters on the B-77. They are not flat, they are not calibrated or linear in many cases. Machines with less quality have even worse meters. The meters on any recorder are rough guides. Studers are okay for level, better meters. I wouldn't trust them to be flat with frequency though.
So before trying to improve anything at all, make sure the machine is bang-on. Note tape distortion can be quite high, so don't try to chase 0.00x % THD, you'll never get there.
Thanks a million for the advice. All can be folliwed, but voltmeters are rare and expensive. 500 euros for a second hand hewllet packard. I’ll do my best.
You don't have to get the 3400A, many HP meters would be fine. An older THD meter, like a 331A, 332A, 333A or 334A are also very accurate AC voltmeters. Plus they read distortion. This is something you need if you work on amplifiers. An HP 339A contains an even better THD meter and a very low distortion oscillator. The 8903A or B is digital with a small analogue meter, it would also work well. Note the "C" versions on most distortion test sets do not include an oscillator (avoid).
Options.
Options.
"Too bad Nakamichi and Studer never collaborated,"
Now that is funny. I also have a Nakamichi 1000X which I haven't used in years. I used that for my cassette tapes but now it's just collecting dust.
Now that is funny. I also have a Nakamichi 1000X which I haven't used in years. I used that for my cassette tapes but now it's just collecting dust.
Hi Ray,
Very good machine. Is it a 1000 Tri Tracer, or 1000ZXL? The 1000ZXL (& limited) were the best ones. I have a Dragon, CR-5 and BX-300. The electronics on the units like the BX-300 and CR-5, probably the Dragon were slightly more advanced. If you have a 1000ZXL, you have the very best machine. Use it!
I fired up the CR-5 and realised there is no reason to let them sit. I forgot how amazing they sound. I made tapes for my TD-700 in the car.
Very good machine. Is it a 1000 Tri Tracer, or 1000ZXL? The 1000ZXL (& limited) were the best ones. I have a Dragon, CR-5 and BX-300. The electronics on the units like the BX-300 and CR-5, probably the Dragon were slightly more advanced. If you have a 1000ZXL, you have the very best machine. Use it!
I fired up the CR-5 and realised there is no reason to let them sit. I forgot how amazing they sound. I made tapes for my TD-700 in the car.