[See final update. Distortion of the Breeze Preamp is comparable to the Emotiva so long as the Balanced Input on the Breeze is not used. Using only the RCA inputs, the distortion is 0.0006% or less through the RCA outputs, through the balanced outputs setting a new record at 0.0003% or less. The DC offset can be nearly zeroed in all conditions at the same gain level, but changes with different gain levels, though I've adjusted it to 3mV or less provided the volume control is not advanced beyond the 3PM point, which I should never need to do. At max, it's 14mV, which may not be OK for all amplifiers. This is acceptable for use in gain adjustment for blind testing so long as only the RCA inputs are used and volume kept below 3PM.]
Clearing off the audio bench, again, I finally figured out the R/L mismatch issue that's been preventing me from doing computer measurements for the last few months. One of the TRS to XLR balanced cables has gone bad. (The old one was a Belden from Blue Jeans, my usual cable supplier. TRS is not their usual thing. Perhaps not XLR so much either. Their specialty is premium 75 ohm Canare RCA's on Belden cable, and I've never had one like that in hundreds fail. I took a break right here to order a replacement set of Mogami Gold TRS to XLR cables from Sweetwater. Will be going that kind of route for TRS cables from now on, and perhaps XLR's as well. The Mogami XLR's look better strain relief'd than Blue Jeans does. I've now decided I like Gotham Audio the best for AES XLR, but they don't make TRS to XLR cables. Mogami has a different "CORE" line of "professional use" cables but they are not the optimal shielded cable, which I need for my instrumentation bench. Mogami Gold ought to be durable enough, I'm not doing daily gigs in beer joints.)
So, to finally measure the Breeze Preamp using RMAA, I borrowed a TRS to XLR from my keyboard.
First I measured my Emotive XSP-1. It is impeccable. Excellent construction with excellent design, including full balanced operation made possible by discrete resistor based attenuation with 0.5dB steps. This is the kind of technology you used to have to buy $6k (now $20k) Krell preamps for.
Actually I first measured the residual. It's 0.0003% distortion.
When the Emotive is hooked in, the distortion rises to a mere 0.0005% distortion. This suggests that the Emotiva actually has about the same THD as my residual, around 0.0003%. That's what decent (not stellar) engineering can do nowadays.
Then I hooked in the Breeze in place of the Emotiva. Distortion rises to 0.0068%. Despite being based on the fabled German MBL 6010, which was measured as having less than 0.002% distortion by Stereophile at 2V, and using even better IC's, the even more fabled AD797's.
I was hoping to use the Breeze as my measurement preamp, but clearly it's not good enough for that, while the Emotiva is. I'm not thrilled about using it in my living room system either. The plan was to use it to equalize the gain for ABX purposes. In fact, the original plan was to use it to convert the unbalanced output of the Denon DVD 5000 (which I was then using as my midrange DAC) to balanced for running the Krell FPB 300 on a different AC circuit, for which balanced operation is a really good idea.
Well, I ultimately decided the Denon DVD 5000, which measured 0.0038% distortion, though having much better S/N than the DVD 9000 for some not yet understood reason, wasn't clean enough. It doesn't have the ultimate "good" IC's opamps that are available now, it used an earlier generation which aren't very well regarded anymore. So I've switched to using all Emotive Stealth DC-1's, which have AES inputs, XLR outputs, and measured as good as good or better than I am able to measure, 0.0003% distortion. Emotiva uses the good IC's, and uses them in textbook quality engineering.
So, if a DAC with 0.0038% distortion isn't clean enough, a preamp with 0.0068% distortion certainly isn't either.
I may just have to get Emotiva preamps for all gain stages. My main quibble with the XSP-1 Mk 2 is it's rather large and has way more features than I need. The Breeze seemed to be exactly what I needed but it doesn't seem good enough. It has XLR and RCA inputs, selectable, and XLR and RCA outputs which are always running independently, and a volume control (based on a single high quality potentiometer, because the level adjustment is done in an unbalanced part of the circuit, with balanced to unbalanced converters preceding it, and unbalanced to balanced converters following it--but this is what you have to do if you are not using precision discrete attenuation like the Emotiva).
Also, I measured fairly high DC offsets from the Breeze. Around 30mV DC. Now, the Breeze actually looks fairly textbook also. I wonder why the distortion measures as high as it does. One particular point, the Breeze has pretty high 2nd harmonic, filling in the second harmonic that is virtually nil on my analyzer.
I didn't want to tinker with the DC offset trimpots which are clearly right there in the Breeze without measuring the distortion first, fearing that fixing the offset would make the distortion worse.
It's quite possible, I think now, that fixing the DC offset will also, at least to some degree, fix the THD as well, which looks like it may be generated by asymmetry at the summing point of the Breeze.
Update:
I have adjusted the offset(s) in the breeze. It did not lower the distortion.
The two pots near the input seem to control the unbalanced input. I adjusted those to reduce unbalanced-to-unbalanced offset to 0.01 mV or less.
The two pots near the volume control seem to control the balanced output. I adjusted those to balanced-to-balanced offset of 0.01mV or less. I went back and forth on these adjustments, after many preliminary attempts in which adjustments seemed to make no difference.
Then unbalanced-to-balanced has about 2mV offset, and balanced-to-unbalanced has about 4mV offset, not perfect, but not horrible.
None of this improved the distortion appreciably from 0.0065%. At one intermediate point, I measured 0.0061%. Adjusting the balanced output offsets seemed to make no visible difference on the distortion spectrum from the balanced outputs as I was watching it live. All my distortion measurements are balanced-to-balanced.
Maybe I need 3 Emotiva preamps, or more. I need at least one for the Living Room, and one for the Laboratory.
I wish I could buy something smaller and simpler, like the Breeze, with performance as good as the Emotiva.
Another Update:
The Breeze is absolutely fine for single ended inputs, except for an unfortunate tendency to change the offset as the volume control is turned.
The RCA output distortion is essentially at my residual at unity gain. Actually the number is 0.0006%, run through the "processor loop" of the Emotiva (to convert the balanced I/O of my Juli@ card to unbalanced) measured at around 2-3V output--and I can't read the exact number because RMAA is pulsing). At 4-6V output, distortion rises to 0.04%. And 1-1.5V, distortion is barely changed from unity. I would only need 3V or less with most amplifiers.
Adjusting the pots near the input seems to affect the RCA input balance. Adjusting the pots near the volume control seems to mainly affect the balanced input balance. Adjusting both, one can make both zero simultanously at unity gain, but both rising to 14mV at volume control maximum, and falling to just slightly below zero. Below 3PM on the volume control, RCA output offset is below 3mV for both inputs. For my ABX gain adjustment purposes, I should not need higher than 3PM on the volume control, which is more than a little over unity gain.
Neither set of controls seems to have any affect on distortion through the balanced input.
The balanced input measured even lower distortion. Taking the RCA output through the Emotiva processor loop, but then taking the balanced output of the Breeze, yields distortion measuring 0.0003%, lower than I see through the Emotiva balanced outputs, in fact, 0.0003% is precisely my residual...the Breeze is not raising the distortion number...meaning it can't be known but is probably significantly lower than 0.0003%.
The source of unnecessary distortion seems to be: high outputs (above 4V for single ended, unable to do this test for balanced) and use of the balanced input. The balanced output is fine.
It looks like I can use this for ABX gain adjustment after all, just always use the RCA inputs.
The Balanced Inputs aren't horrible, at 0.0065% THD, but it represents unnecessary distortion by today's easily achievable circuits (including LM 4562 op amps and AD 797 and OPA 211), which can achieve 0.0003% or much better.
The fact that the distortion occurs only for balanced input, and has majority 2nd harmonic, indicates that the issue is with the balancing of the input differential amplifier for the XLR inputs. One would need to fine-tune the gain of one of the two IC's used, and there are no pots for that. If MBL didn't use trimmers, they might have used more tightly matched resistors setting the input gains.
Clearing off the audio bench, again, I finally figured out the R/L mismatch issue that's been preventing me from doing computer measurements for the last few months. One of the TRS to XLR balanced cables has gone bad. (The old one was a Belden from Blue Jeans, my usual cable supplier. TRS is not their usual thing. Perhaps not XLR so much either. Their specialty is premium 75 ohm Canare RCA's on Belden cable, and I've never had one like that in hundreds fail. I took a break right here to order a replacement set of Mogami Gold TRS to XLR cables from Sweetwater. Will be going that kind of route for TRS cables from now on, and perhaps XLR's as well. The Mogami XLR's look better strain relief'd than Blue Jeans does. I've now decided I like Gotham Audio the best for AES XLR, but they don't make TRS to XLR cables. Mogami has a different "CORE" line of "professional use" cables but they are not the optimal shielded cable, which I need for my instrumentation bench. Mogami Gold ought to be durable enough, I'm not doing daily gigs in beer joints.)
So, to finally measure the Breeze Preamp using RMAA, I borrowed a TRS to XLR from my keyboard.
First I measured my Emotive XSP-1. It is impeccable. Excellent construction with excellent design, including full balanced operation made possible by discrete resistor based attenuation with 0.5dB steps. This is the kind of technology you used to have to buy $6k (now $20k) Krell preamps for.
Actually I first measured the residual. It's 0.0003% distortion.
When the Emotive is hooked in, the distortion rises to a mere 0.0005% distortion. This suggests that the Emotiva actually has about the same THD as my residual, around 0.0003%. That's what decent (not stellar) engineering can do nowadays.
Then I hooked in the Breeze in place of the Emotiva. Distortion rises to 0.0068%. Despite being based on the fabled German MBL 6010, which was measured as having less than 0.002% distortion by Stereophile at 2V, and using even better IC's, the even more fabled AD797's.
I was hoping to use the Breeze as my measurement preamp, but clearly it's not good enough for that, while the Emotiva is. I'm not thrilled about using it in my living room system either. The plan was to use it to equalize the gain for ABX purposes. In fact, the original plan was to use it to convert the unbalanced output of the Denon DVD 5000 (which I was then using as my midrange DAC) to balanced for running the Krell FPB 300 on a different AC circuit, for which balanced operation is a really good idea.
Well, I ultimately decided the Denon DVD 5000, which measured 0.0038% distortion, though having much better S/N than the DVD 9000 for some not yet understood reason, wasn't clean enough. It doesn't have the ultimate "good" IC's opamps that are available now, it used an earlier generation which aren't very well regarded anymore. So I've switched to using all Emotive Stealth DC-1's, which have AES inputs, XLR outputs, and measured as good as good or better than I am able to measure, 0.0003% distortion. Emotiva uses the good IC's, and uses them in textbook quality engineering.
So, if a DAC with 0.0038% distortion isn't clean enough, a preamp with 0.0068% distortion certainly isn't either.
I may just have to get Emotiva preamps for all gain stages. My main quibble with the XSP-1 Mk 2 is it's rather large and has way more features than I need. The Breeze seemed to be exactly what I needed but it doesn't seem good enough. It has XLR and RCA inputs, selectable, and XLR and RCA outputs which are always running independently, and a volume control (based on a single high quality potentiometer, because the level adjustment is done in an unbalanced part of the circuit, with balanced to unbalanced converters preceding it, and unbalanced to balanced converters following it--but this is what you have to do if you are not using precision discrete attenuation like the Emotiva).
Also, I measured fairly high DC offsets from the Breeze. Around 30mV DC. Now, the Breeze actually looks fairly textbook also. I wonder why the distortion measures as high as it does. One particular point, the Breeze has pretty high 2nd harmonic, filling in the second harmonic that is virtually nil on my analyzer.
I didn't want to tinker with the DC offset trimpots which are clearly right there in the Breeze without measuring the distortion first, fearing that fixing the offset would make the distortion worse.
It's quite possible, I think now, that fixing the DC offset will also, at least to some degree, fix the THD as well, which looks like it may be generated by asymmetry at the summing point of the Breeze.
Update:
I have adjusted the offset(s) in the breeze. It did not lower the distortion.
The two pots near the input seem to control the unbalanced input. I adjusted those to reduce unbalanced-to-unbalanced offset to 0.01 mV or less.
The two pots near the volume control seem to control the balanced output. I adjusted those to balanced-to-balanced offset of 0.01mV or less. I went back and forth on these adjustments, after many preliminary attempts in which adjustments seemed to make no difference.
Then unbalanced-to-balanced has about 2mV offset, and balanced-to-unbalanced has about 4mV offset, not perfect, but not horrible.
None of this improved the distortion appreciably from 0.0065%. At one intermediate point, I measured 0.0061%. Adjusting the balanced output offsets seemed to make no visible difference on the distortion spectrum from the balanced outputs as I was watching it live. All my distortion measurements are balanced-to-balanced.
Maybe I need 3 Emotiva preamps, or more. I need at least one for the Living Room, and one for the Laboratory.
I wish I could buy something smaller and simpler, like the Breeze, with performance as good as the Emotiva.
Another Update:
The Breeze is absolutely fine for single ended inputs, except for an unfortunate tendency to change the offset as the volume control is turned.
The RCA output distortion is essentially at my residual at unity gain. Actually the number is 0.0006%, run through the "processor loop" of the Emotiva (to convert the balanced I/O of my Juli@ card to unbalanced) measured at around 2-3V output--and I can't read the exact number because RMAA is pulsing). At 4-6V output, distortion rises to 0.04%. And 1-1.5V, distortion is barely changed from unity. I would only need 3V or less with most amplifiers.
Adjusting the pots near the input seems to affect the RCA input balance. Adjusting the pots near the volume control seems to mainly affect the balanced input balance. Adjusting both, one can make both zero simultanously at unity gain, but both rising to 14mV at volume control maximum, and falling to just slightly below zero. Below 3PM on the volume control, RCA output offset is below 3mV for both inputs. For my ABX gain adjustment purposes, I should not need higher than 3PM on the volume control, which is more than a little over unity gain.
Neither set of controls seems to have any affect on distortion through the balanced input.
The balanced input measured even lower distortion. Taking the RCA output through the Emotiva processor loop, but then taking the balanced output of the Breeze, yields distortion measuring 0.0003%, lower than I see through the Emotiva balanced outputs, in fact, 0.0003% is precisely my residual...the Breeze is not raising the distortion number...meaning it can't be known but is probably significantly lower than 0.0003%.
The source of unnecessary distortion seems to be: high outputs (above 4V for single ended, unable to do this test for balanced) and use of the balanced input. The balanced output is fine.
It looks like I can use this for ABX gain adjustment after all, just always use the RCA inputs.
The Balanced Inputs aren't horrible, at 0.0065% THD, but it represents unnecessary distortion by today's easily achievable circuits (including LM 4562 op amps and AD 797 and OPA 211), which can achieve 0.0003% or much better.
The fact that the distortion occurs only for balanced input, and has majority 2nd harmonic, indicates that the issue is with the balancing of the input differential amplifier for the XLR inputs. One would need to fine-tune the gain of one of the two IC's used, and there are no pots for that. If MBL didn't use trimmers, they might have used more tightly matched resistors setting the input gains.
Hello
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