Inna, that's a very bad idea; what you are talking about is "line level" signals, tape, tuner, etc.
Preamp out is what goes to amp in, not a line level signal.
Reel to reel deck directly to power amp ?
Thinking about my totally new future system. The main source is going to be reel to reel deck, most likely Otari two track, possibly Studer A810. I will keep the turntable and run the phono thru deck. So I will need only one input, decks have volume control and preamp. I don't think I will need separate preamp. Do you ?
Power amps could be both transistor and tube, maybe even hybrids - Lamm, as an example, would very much depend on speakers. Don't know what speakers, could be as different as Harbeth and Kharma.
Power amps could be both transistor and tube, maybe even hybrids - Lamm, as an example, would very much depend on speakers. Don't know what speakers, could be as different as Harbeth and Kharma.
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Yes, I was thinking about output/input match, but Ralph didn't mention there might be a problem. It should be fantastic sound, especially if you play good two track master tape dubs. But even recordings from vinyl will sound excellent. I make a lot of compilations, play them on my Nak 682ZX, I rarely play entire albums, I don't have many that I would want to play entirely and I don't enjoy moving the needle all the time. Nak recordings sound okay but far from vinyl, with reel to reel deck I will fix it, this should be very close. When playing records thru deck by way of separate phono you can adjust volume with both volume control and recording level knobs. The you use tape monitor switch to listen to either deck or turntable. There may be a slight drop in the resolution compared to running phono signal to top level preamp instead of a deck, sure, but at the same time you will lose some resolution when playing deck connected to preamp as opposed to running it directly into power amps. Unless, of course, power amps have two inputs, so you could run deck directly and phono thru preamp and then to amps. But in this case I would need to connect phono and deck directly, not thru preamp's tape-outs, to make best quality recordings from vinyl. Not too much work, though. Anyway, I will start without preamp. There is currently a pair of Clayton M70 monoblocks for sale on usaudiomart. That would work with my current and almost certainly future speakers. I keep my hands off credit cards, you won't find overall better amps for $2200, I guess. |
Yes, I was thinking about output/input match, but Ralph didn't mention there might be a problem.With any pro audio or semi-pro reel to reel, you have a volume control to control output. On my Otari 8-channel, not so easily accessed as you have to put a screwdriver though a hole in a panel. But the two channel machines have a regular volume control and are typically set to at least +4 dbm at full volume (some might be at +10); either way that's more than plenty to clip any amplifier made, and the output is robust enough to drive any amplifier made. IOW just do it :) I of course prefer tubes, and used to do this with my Ampex 351 machine. It was a bit harder, as the volume controls were on each channel and so a bit harder to adjust. But more modern machines have made that bit easy. |
Adjusting volume with a big bloody screwdriver would be cool ! I prefer tubes as well, we'll see. Next step could be asking Ralph to custom make playback head tube preamp or maybe playback head/phono stage unit, and match it precisely to his amps, and match the amps to speakers. Now that would be high end. |
I took a look at the manual for the Studer A810 that was mentioned in the OP. (The manual can be found at hifiengine.com if one is registered at the site). Depending on the version of the deck and on how the magnetic flux reference level is defined the maximum output is either +10 dbm, +16 dbm, or +24 dbm. Apparently only balanced outputs (and balanced inputs) are provided. Ralph, would I be correct in thinking that these dbm values, as well as the ones you referred to, mean decibels above a milliwatt into 600 ohms? If so, +10 dbm corresponds to about 2.45 volts; +16 dbm corresponds to about 4.9 volts; and +24 dbm corresponds to about 12.25 volts. The lowest of those numbers won’t be enough to drive the balanced inputs of **some** power amps to full power, although it would be enough for many and probably most of them. Output impedance, btw, won’t be any problem at all in this case, as the deck is specified as having an output impedance of 50 ohms max across the frequency range, and as being capable of driving a load impedance as low as 200 ohms. However the line-level input impedance is only 10K, which would not be optimal for some sources, especially some tube-based ones. Orpheus10 11-13-2018 To be sure it’s clear, preamp output specs that are stated to be in the tens of volts, or even in the high single digits, represent the preamp’s maximum output voltage **capability.** A preamp’s actual output voltage will be the input voltage it is provided with multiplied by its gain (expressed as a ratio, rather than in db), and reduced by the amount of attenuation the volume control is set to provide. No preamp in any home audio system would ever be called upon to provide an output of more than a few volts balanced, and usually not more than one or two volts unbalanced. From my point of view, this is a case of the blind leading the blind, and then running with it.From my point of view, this comment is uncalled for as well as inaccurate. I commend Ralph for not responding in kind. Regards, -- Al |
Almarg, if you're saying that .775 volts is enough to drive an amp, you're more mistaken than the rest. If all of youse chip in, you might be able to round out that square peg you're trying to fit in a round hole by chipping of the corners, or maybe you can square the hole a bit. Almarg, what do you think "MAX" is? Do you drive 120 MPH or whatever the max speed your car will go? |
Almarg, if you’re saying that .775 volts is enough to drive an amp, you’re more mistaken than the rest. I certainly didn’t say that, and I was not addressing the Technics deck you referred to. (Although there are in fact some amps that can be driven to full power by less than 0.775 volts, the Coincident Frankenstein and Coincident Dynamo being examples). And for that matter I didn’t express agreement with Ralph’s statement that +4 dbm would necessarily be adequate. Regarding Inna’s questions that followed my post, let’s wait for Ralph to confirm (or correct) my understanding of what the dbm numbers mean, which I’m not completely certain of. Regards, -- Al |
Next step could be asking Ralph to custom make playback head tube preamp or maybe playback head/phono stage unit, and match it precisely to his amps, and match the amps to speakers. Now that would be high end. I have an Atma-Sphere MP-3 that has switchable RIAA and IEC (15ips) EQ settings. While the linestage has the standard gain, Ralph has mentioned a number of times that this can be configured as a unity gain tube buffered output. Seems like this would meet your needs. I have used mine for a number of years now with the transport section of an Otari MX-5050, the signal taken directly off the tape heads. I also have the pro-sumer version of the deck that has the integrated preamp circuit with volume control. I can’t recall if I ever ran that directly into an amp, but guess I can check and report back here if anyone is interested. |
Ralph hasn’t responded yet about the dbm question I raised, so I did some further research and it appears that what I said was correct. dbm in this context represents decibels above 1 milliwatt into 600 ohms. So the voltage numbers I calculated were correct. It also happens that the 0.775 volt maximum output of the Technics deck that was referred to corresponds to 0 dbm, since 0.775 volts into 600 ohms corresponds to 1 milliwatt. So the bottom line is that with some combinations of tape decks and power amps it will be possible for the power amp to be driven to full power, and with some combinations it will not be possible. Generally speaking a problem is likeliest to arise in cases in which the amp is high powered (and most or all of its power capability is actually required by the user, at least occasionally), since there tends to be a **loose** correlation between the power capability of various amplifiers and the input voltages required to drive them to full power. Although there are many exceptions to that, of course, where a higher powered amp may require less input voltage to be driven to full power than a lower powered amp. Regards, -- Al |
Ralph will probably respond tomorrow. Right now it appears that all this would require a careful match, which is not bad but can be complicated. Would you spend $5k more on deck or on power amp ? Studer A810 is at least that much more expensive. But it should be more versatile in terms of match They are both toys compared to this, I guess. https://www.ebay.com/itm/EAR-Yoshino-STUDER-C37-One-Inch-Two-Track-Tube-Master-Reel-Recorder-SUPERB/... |
Tape One has always been able to get blank tape for $50 dollars a reel. Two reels are needed at 15 IPS to drop down an album. This is about passion for involvement with the medium. And if one thinks playing vinyl is alot of work ...try playing albums on 15 IPS tapes for 8 hours.
https://photos.app.goo.gl/B7CnGER12vuBEpQZA |
potential turn on thumps. Turn on thumps from the deck in question, might be a problem. Consider investigating that firstly with a preamp and some headphones. If no combination of reel deck output levels at turn on of said deck, are capable of producing a thump that might damage speakers (if connected directly to the power amp), then you are good to go. Not all decks are built equal in this, some have thumps of various levels some are designed to have no thump issues of any kind. They are not meant to be hooked up to any power amp directly, even if this can easily be done. Some companies will build with this thump issue in mind, some will build with minimum to no thump concerns at all, and thus some thump of some sort may occur, based on how the given deck is turned on vs it's output level settings. It’s always wise to check this before going forward. Only takes a few minutes.... |
That's a very good question Inna, and I hope someone has an answer in regard to the best tape. I have been so glad to get Quantegy 456, that I haven't scrutinized it. I dream of "Maxell EE"; that tape was so good that you could record at 3 3/4 and get the same results as recording on regular tape at 7 1/2. |
would I be correct in thinking that these dbm values, as well as the ones you referred to, mean decibels above a milliwatt into 600 ohms?Yes. However: Generally speaking a problem is likeliest to arise in cases in which the amp is high powered (and most or all of its power capability is actually required by the user, at least occasionally), since there tends to be a **loose** correlation between the power capability of various amplifiers and the input voltages required to drive them to full power.Usually higher powered amps have more gain. This is because they are often used on lower efficiency loudspeakers, and the gain is need both to make use of the preamp signal and also to make the voltage swing needed to drive the output devices. The result is that with a pro audio tape machine usually has more than enough drive to work in most situations. Depending on the machine, if its output is not loaded at 600 ohms, it may well make more voltage. At any rate I've run tape machines directly into power amps many times with no worries. The exception as you correctly point out is that older consumer decks often do have lower outputs, the standard for many cassette machines was 1 volt. But I think we aren't talking about consumer machines here. Next step could be asking Ralph to custom make playback head tube preamp or maybe playback head/phono stage unit, and match it precisely to his amps, and match the amps to speakers. Now that would be high end.:) We offer tape EQ in our MP-1 and MP-3 preamps and they work pretty well with our amps... |
Ralph, that's good to know. Do you offer both IEC and NAB equalization ? Do I need both ? At least for pre-recorded tapes, I guess. In what way do they differ ? The deck must be modified to use outboard head preamp, I think it can be modified to include a switch for use with both internal and external playback head preamp. But..with Ralph's preamp I would have to use tape-outs to record from vinyl, something that I like to avoid, unless of course Ralph will guarantee that there will be virtually no signal loss. Ralph, do you think your 30 watt/ch amps would drive something like Harbeth or Dynaudio, thinking medium size room and not thinking insane dbs ? 60 tube watts should be no problem, not forgetting speakers' impedance curve. |
@inna Our 30 watt amps don't do very well if the impedance is less than 8 ohms. IEC and NAB are a good idea. At 15 i.p.s., the difference is basically where the turnover is; NAB is at 3150Hz while IEC is at 4500Hz. There has been debate over the decades about whether or not bass emphasis is needed for the NAB curve and some pretty good arguments for why its not seem to win out. So the playback curve is essentially a 6db per octave rolloff; the designer has to choose where that should start. We have enough gain that we can do it at 16Hz. To use your machine for record, you would need a switch on the playback head which directs the head signal to an XLR or uses the internal electronics. To use our phono circuit for recording onto this deck, I recommend a Jensen transformer to make the match- the phono section otherwise by itself will be bass-shy driving a 10K load. |
One more cable plus transformer - this will degrade the sound. Separate phono with appropriate output impedance will be better. What is the good range of output/input impedance proportion, 1/5-1/10 or so ? I still don't understand IEC /NAB real difference and whether or not I may need both. Both Studer and Otari electronics do have both. Anyway, there is so much that I don't know or even have no idea of when it comes to open reel decks. |
I have an "old" Crown SS800 reel-to-reel that I use in one of my systems. It has all of the inputs and outputs associated with a pre-amp and is what I run the amps with. The difference with your Studer / Otari concept is it/they don't have any tone controls (yeah, I know, audio purists don't "do" tone controls. I do. Even have a graphic equalizer in my esoteric system - gasp!), which may make your listening a little strained. The Crown also has Class-A inputs (courtesy of John Haynes, Goshen, IN - Wherever you are dear friend) that sound really great with older/vintage speakers. I'm partial to co-axial/coincidental speakers also. So good luck with the system and I look forward to hearing about what your hearing....brilliant! |
One more cable plus transformer - this will degrade the sound. Separate phono with appropriate output impedance will be better. What is the good range of output/input impedance proportion, 1/5-1/10 or so ?Ideally 1:10 or better is the rule of thumb. It will be tricky to come up with a tube phono section that is OK driving 10K ohms. While the output impedance might look low enough on paper, the defining spec is what the output impedance is at 20Hz, not 1KHz. That is why I recommended the transformers. BTW, input and output transformers are quite common in studio gear, from whence most of our recordings come. I don't like transformers, but they have their place and when they are needed, they can be really helpful! Where will the extra cable be used?? |
Ralph, unless I got confused - one cable goes from preamp's tape-out to transformer and another from transformer to deck, as opposed to from separate phono directly to deck. I think, my Nak's input impedance is around 50 kohm and my Acoustech's output impedance is close to 10 kohm, very high. They match very well, I can tell this. Hard to find phono stage to impedance match pro or semi-pro deck... Unexpected complication. |
Most line-level impedances are 600-1000 ohms. Tube amps input impedances are 50kohms to 100kohms. Should work well. Some solid state amps as low as 10kohms inputs .... not as much gain and frequency response issues if the nominal impedance rises sharply in the bass (as sometimes is the case). Tube amps should be a decent bet. |
Many preamps have 10kohm RCA line level input impedance, just like pro reel to reel decks. I haven't heard of many difficulties of matching separate phono's output impedance to that, though not all of them would match, of course. I think, both Al and Ralph exaggerated on this point. XLR line level input impedance, speaking of preamps not decks, can be much higher, I've seen figures of 40kohm. There are not many phono stages with XLR outs, though, and most that do are not inexpensive. Anyway, I see it as a very workable minimalist idea and will get to it at the right moment. My thanks to all participants. |
