The calculations I do for this purpose involve logarithms, which I do using a scientific calculator. But a simpler method, which yields reasonably good results, would be to start with the following calculator. It applies to box-type dynamic speakers, and if the calculation is being performed for planar speakers such as Martin-Logans or Maggies that are listened to at typical distances (such as yours) add around 5 db or so to the results it provides. The reason being that as listening distance increases SPLs fall off more rapidly for box-type dynamic speakers than in the case of planar speakers. (And in fact the volume produced by a planar speaker may be greater at say 2 meters than at 1 meter, since the upper and lower parts of a planar speaker will generally be more on axis at 2 meters than at 1 meter). https://myhometheater.homestead.com/splcalculator.html Best regards, -- Al |
Hi Paul,
Happy New Year to you and yours as well.
Both the Maggies and your present speakers have the same nominal impedance, into which the reworked amp will be able to supply 300 watts. All three Maggies have specified sensitivities that are 5 db less than the specified sensitivity of your present speakers. The approximate maximum SPL at the listening position of 110 db that I calculated for your present speakers in my previous post did not take into account their powered woofers, which of course the Maggies don't have.
So it seems reasonable to me to simply subtract 5 db from the 110 db to derive an approximate estimate of the maximum SPL the revised amp would be able to generate with the Maggies at your listening position.
And 105 db at the listening position is certainly enough for most of us. Although I have a few classical symphonic recordings on labels such as Telarc, Sheffield Lab, and Reference Recordings which have been engineered with minimal or no dynamic compression, that can reach 100 to 105 db at my listening position on occasional brief dynamic peaks, while being listened to at average SPLs in the mid-70s. But recordings having such wide dynamic range are rarely encountered.
Best regards,
-- Al
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What were your thoughts on converting the amp to the V1 specs? Although I have no experience with Coda amps or ML speakers, it seems to me like it could very possibly be a worthwhile change. As you appear to realize, most of the time most users are just using a small fraction of an amp’s maximum power capability. And on brief dynamic peaks that may require close to full power, 300 watts into the nominally 4 ohm impedance of your planar speakers at your listening distance should result in a volume at the listening position of around 110 db! And that would apply even if the speaker did not incorporate a 200 watt bass amplifier, which of course it does. In saying this I’m assuming that the specified sensitivity of the speaker (91 db/2.83 volts/1 meter, which for its 4 ohm nominal impedance corresponds to 88 db/1 watt/1 meter) is reasonably accurate. Also, I note in the manual for the speaker that "power handling" of 250 watts per channel is specified. So the speakers apparently wouldn’t even be able to handle anything close to the 600 watt/4 ohm power capability of the amp in its present "v2.5" configuration, that you had described earlier. Regarding the comparison of volume control settings with the McIntosh amp that you mentioned, the volume control settings that are used are dependent on the gain of the amp, not on its maximum power capability. And while there tends to be a **loose** correlation between those two parameters among various amplifiers, there are a great many cases in which higher powered amps have lower gains than lower powered amps. Best regards, -- Al |
Hi Paul, I’m still here :-) And thanks for the update. Excellent news that the balanced input impedance is 10K, not 1K. So your DAC and almost all other DACs or other source components having solid state output stages will have no problem driving the balanced inputs of the amp. Although a goodly number of components having tube-based output stages would still experience some degree of deep bass rolloff and/or other sonic issues. ... it seems they still suggest to turn the volume down on the DAC and use the volume control on the amp. Didn’t say with balanced or RCA though? The voltages of the balanced and single-ended outputs of the DAC are both much higher than usual by similar proportions. So the DAC’s volume control should most likely be turned down in either case. And since you have found balanced interconnections to be preferable, it appears that you should continue with that approach, while experimenting a bit to determine an optimal setting of the DAC’s volume control. And happy holidays to you and your family! Best regards, -- Al |
Is there something I could ask Doug Dale at Coda to do to limit the output voltage of the balanced outputs?
I presume you meant to refer to the amp’s balanced inputs, not outputs. I would recommend against asking him to do anything to make the amp more optimal for use with the high output voltage of your DAC, because it would likely make it less suitable for use with whatever DAC or other source components a future purchaser of your amp may want to use with it. What you might ask him about, though, is if it would be feasible to drastically increase the input impedance of the amp’s balanced inputs. Very few tube-based source components can drive 1K properly, and many solid state source components would have trouble as well. So if it is practicable for him to make such a change, it would increase the amp’s versatility. Why do you think this voltage is so high here? What would be the intended equipment to run balanced at this voltage? I have no idea. (And btw the unbalanced output voltage of the DAC is also far higher than usual). My initial instinct was to suspect that the high output voltages of the DAC might be optimal for use with W4S’s own preamps and integrated amps, but looking at the gain and sensitivity specs for their currently produced models (which are fairly normal numbers) I doubt that is the explanation. Best regards, -- Al |
W4S finally got back to me with this response:
" So a 1k load is quite ridiculous really, not sure why they would release something like that but surely don’t drive that single-ended. Running balanced will drive it and whatever degradation would be common to both phases so likely to cancel out. I can test a DAC to see how it handles it if you wish but I suspect it would be fine".
I’m afraid all this technical lingo is above me, could I please trouble you to comment on this response? Is the fact they "suspect it would be fine" acceptable in your mind? First, to be sure it’s clear, you would not be driving 1K with a single-ended connection, as the input impedance of the single-ended inputs of your amp is 50K. Regarding ... Running balanced will drive it and whatever degradation would be common to both phases so likely to cancel out. ... My understanding is that balanced operation tends to cancel even order distortion components (e.g., 2nd, 4th, 6th harmonics, etc.), but not odd order distortion components (e.g., 3rd, 5th, 7th harmonics, etc.). And generally speaking odd order distortion components are more objectionable than even order harmonic distortion components. However, given that he "suspects it would be fine," and given that you are happy (or at least encouraged) with the results you are getting at this point, I suppose it is reasonable to put this issue aside. Regards, -- Al |
Just this week I saw Paul McGowan of PSA audio imploring viewers to ALWAYS turn DACs up all the way and leave the volume control to the pre-amp. However Paul’s DACs (and the vast majority of others) do not put out maximum voltages anything like 10.5 balanced and 5.2 unbalanced, as the OP’s DAC does. Which can certainly cause problems for some preamps and integrated amps, ranging from having to set their volume controls too low (where depending on the specific design the resolution of volume changes may become too coarse and channel balance may suffer); to some degree of sonic degradation; to outright overload and severe distortion. The very different and more conventional specs on Paul’s DirectStream DAC: Output level, low: 0.282 VRMS Balanced; 0.141 VRMS Single Ended Output level, high, maximum: 2.818 VRMS Balanced; 1.414 VRMS Single Ended Also, there are a number of very different approaches to volume control implementation that are used by various DACs, which have differing susceptibilities to sonic degradation at settings that are below max. As is usual in audio, it all depends :-) Regards, -- Al |
This was the manufactures response to your suggestion Al: “The DAC has hot outputs that may be too much for your integrated. I would suggest a level of 55 and if that is still too much then go RCA at that level.” I tried RCA and what I got was a lower volume and a little less detail (lackluster sound ) than with balanced connections. Definitely a little brighter, but in a nice sort of way. I turned the volume down to 55 (from 65) as the manufacturer suggested and have left it at that for now. Any comments?
Hi Paul, I would also ask W4S how much sonic degradation they would expect, if any, when the DAC is asked to drive a balanced load impedance of 1K. If their answer is that audibly significant degradation is likely to result then I would continue to use RCA interconnections, in which case the DAC is presented with a vastly more benign 50K load impedance, as I had indicated. And I would look elsewhere for the cause of the lackluster sound quality you referred to. It’s usually best, IMO, to try to determine and address the root cause of an issue rather than compensating for it by introducing a different issue. On the other hand, if they feel that 1K would be no problem for the particular DAC, perhaps it would be best to return to the balanced cables and turn the DAC’s volume control down a bit further. Of course, another variable in all of this is the relative sonic quality of the balanced vs. unbalanced interface circuits of the two components, which can probably be determined only by listening (if a 1K load is suitable for the DAC). Good luck. Regards, -- Al |
1. I have balanced connections between my DAC & amp.
2. The W4S DAC volume is set to maximum, which is 65. Either or both of those factors could very conceivably be the entire cause of the problem, IMO, given the 1K balanced input impedance of the amp and the 10.5 volt maximum balanced output of the DAC. And if so, changing speakers will of course not help. Definitely try using RCA interconnects, and definitely try lower volume settings on the DAC. Good luck. Regards, -- Al |
Some questions that are unrelated to speakers, but depending on the answers might be related to the problem:
1) Is the connection between the DAC and the Coda integrated amp balanced or unbalanced? It appears that the amp has an unbalanced input impedance of 50K, but a balanced input impedance of only 1K. I wouldn’t be at all surprised if the DAC would have major sonic problems driving 1K, especially at high volume.
2) What do you have the DAC’s volume control set to? When it is set to max it outputs **very** high signal levels (5.2 volts unbalanced and 10.5 volts balanced, when the audio data is at "full scale"), and I wouldn’t be surprised if those levels could over-drive a circuit stage in the amp that is "ahead" of the amp’s volume control, such that significant distortion occurs on musical peaks. On the other hand, though, using a low setting of the DAC’s volume control might degrade its sonics somewhat. If you already haven’t done so, experimenting with various settings of the DAC’s volume control may be in order.
3) It appears that three versions of the amp exist, V1 (150/300 W for 8 and 4 ohms, respectively); V2 (250/500 W); V3 (400/800 W). Which is yours?
Regards,
-- Al |
Looking at the photos linked to above, and also at the photo in your system description thread which shows the speakers, my suspicion is that the major contributors to the problem are:
1) The listening chairs are too far off center, assuming you don’t relocate them when listening.
2) The speakers are too close together. It appears that there is not much more than five feet between them, while the listening distance is significantly greater than that.
I would expect that moving the speakers further apart and listening from a centered position would result in much better separation of multiple instruments and much less of the garbling you referred to.
Regards,
-- Al
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