Guys,
Need to pick your brains as I am out of ideas.
Have two JVC turntables: QL-A7 and QL-7. Both carry the same motor assembly and the arm. QL-A7 has larger, heavier plinth, and is additionally equipped with "photokinetic end of play mechanism". Both have speed dead on, tested with test record and oscilloscope/frequency counter.
However, music from QL-A7 just sounds "slower". 🙁
Both tables were tested in the same environment, side by side, using the same phono preamp, and the same cartridge and arm settings, playing the same record. Results confirmed by multiple people.
I am aware of fast/slow preamps or amps that I believe may have something to do with slew rate but never heard about turntables doing such thing beside mechanical speed issue. It sounds like there is delay in decay of the sound (just guessing). Is it possible that additional weight of photo sensor mechanism that is attached to and carried by the arm creates some resonance issues ? 😕
See attached file showing tonearm assembly. The part in question is no 91 attached to the actual tonearm with two long posts.
Thanks
Need to pick your brains as I am out of ideas.
Have two JVC turntables: QL-A7 and QL-7. Both carry the same motor assembly and the arm. QL-A7 has larger, heavier plinth, and is additionally equipped with "photokinetic end of play mechanism". Both have speed dead on, tested with test record and oscilloscope/frequency counter.
However, music from QL-A7 just sounds "slower". 🙁
Both tables were tested in the same environment, side by side, using the same phono preamp, and the same cartridge and arm settings, playing the same record. Results confirmed by multiple people.
I am aware of fast/slow preamps or amps that I believe may have something to do with slew rate but never heard about turntables doing such thing beside mechanical speed issue. It sounds like there is delay in decay of the sound (just guessing). Is it possible that additional weight of photo sensor mechanism that is attached to and carried by the arm creates some resonance issues ? 😕
See attached file showing tonearm assembly. The part in question is no 91 attached to the actual tonearm with two long posts.
Thanks
What do you mean by »slower«? Lower BPM counts with the same record and longer playing time of the same track?
Best regards!
Best regards!
Mats are the same.
Playing time is the same, BPM as well.
"Slower" is definitely happening in our brains not on the oscilloscope or a timer. 1kHz test signal from both turntables is spot on with small 2Hz variation. Duration of the same track was timed on both turntables - again same. However, there is a perception of "slower music" caused by frequency shift or something else, and it must relay to the electrical/mechanical source in the turntable. I guess a good analogy would be to compare it to a fast and slow amplifiers. They just render/reproduce music in a slightly different manner where one "seems" fast, snappy, with good pace, and the other just sounds "slow", mushy.
Playing time is the same, BPM as well.
"Slower" is definitely happening in our brains not on the oscilloscope or a timer. 1kHz test signal from both turntables is spot on with small 2Hz variation. Duration of the same track was timed on both turntables - again same. However, there is a perception of "slower music" caused by frequency shift or something else, and it must relay to the electrical/mechanical source in the turntable. I guess a good analogy would be to compare it to a fast and slow amplifiers. They just render/reproduce music in a slightly different manner where one "seems" fast, snappy, with good pace, and the other just sounds "slow", mushy.
So it's just a matter of frequency and phase response. Are both cartidges of the same manufacturer and model?
Best regards!
Best regards!
Kay, thanks for your response.
Actually, for the test I was switching one DL-103 between two turntables. Mounted in the headshell, easy to remove, attach. What could be the reason for such phase response ? Could it be a difference in the arm assembly (additional parts/mass attached) creating unneeded resonance ?
Actually, for the test I was switching one DL-103 between two turntables. Mounted in the headshell, easy to remove, attach. What could be the reason for such phase response ? Could it be a difference in the arm assembly (additional parts/mass attached) creating unneeded resonance ?
Well, if you switched the same cart for comparison, the reason of the phenomenon reported has to be found somewhere else. And there are tons of possibilities in such an electromechanical device (arm and external cabling, different effective arm masses, arm geometry, just to name a few)!
Best regards!
Best regards!
Thanks Kay. Will investigate and let you know about my findings.
Been dealing with that for some time now.
Some pics of QL-7. It has been listed on Ebay since:
Victor JVC QL-7 TT-71 Direct Drive Turntable + Original Box + Shure M97AH | eBay
Been dealing with that for some time now.
Some pics of QL-7. It has been listed on Ebay since:
Victor JVC QL-7 TT-71 Direct Drive Turntable + Original Box + Shure M97AH | eBay
Mark,
I wish that was the case. We did test both decks side by side. Three people were listening. They were not told what to listen for in both decks. All of them reported exactly same results. Two said music on QL-A7 was "slower", third listener described it as more "syrupy and heavy", all pointing to the same deck.
Anyway, spending enough time trying to figure out everything else and being suspicious about optical sensor arm assembly, I went ahead and did fiddle with the arm. Removed two long brass posts and the plate (part 91 on the drawing) attached to the arm. There were parts of the optical sensor mechanism. That was almost 50g pulling the arm at its pivot point. Weight was distributed vertically and for sure not balanced. I guess that must have been causing some arm resonance issues resulting in frequency/phase shift because that did the trick. Music became more lively, "slow" feeling went away. Again, that was confirmed by others.
Can't imagine that issue applies to all QL-A7 as it would have been too easy to notice it on new decks at the time they were introduced. Therefore, I assume it only happened to my deck due to its age, arm misalignment or other factors. All good now. Thank you for your help.
I wish that was the case. We did test both decks side by side. Three people were listening. They were not told what to listen for in both decks. All of them reported exactly same results. Two said music on QL-A7 was "slower", third listener described it as more "syrupy and heavy", all pointing to the same deck.
Anyway, spending enough time trying to figure out everything else and being suspicious about optical sensor arm assembly, I went ahead and did fiddle with the arm. Removed two long brass posts and the plate (part 91 on the drawing) attached to the arm. There were parts of the optical sensor mechanism. That was almost 50g pulling the arm at its pivot point. Weight was distributed vertically and for sure not balanced. I guess that must have been causing some arm resonance issues resulting in frequency/phase shift because that did the trick. Music became more lively, "slow" feeling went away. Again, that was confirmed by others.
Can't imagine that issue applies to all QL-A7 as it would have been too easy to notice it on new decks at the time they were introduced. Therefore, I assume it only happened to my deck due to its age, arm misalignment or other factors. All good now. Thank you for your help.
Fascinating problem with an interesting fix. 
Too bad you weren't able to make a good digital recording of it.
The same effect has struck me on some speakers. They sounded so "slow" on familiar tracks that I've checked and double checked playback speed - on digital files! After awhile you get used to it, but at first it's perplexing. Knowing what part of our perception is causing the sensation would go a long way.
Too bad you weren't able to make a good digital recording of it.The same effect has struck me on some speakers. They sounded so "slow" on familiar tracks that I've checked and double checked playback speed - on digital files! After awhile you get used to it, but at first it's perplexing. Knowing what part of our perception is causing the sensation would go a long way.
Hi Pano,
Good idea. I should have made good quality recordings of both decks. At the time I was not thinking, "obsessed" to fix the issue.
That would let for frequency analysis and potentially shed some light as to what causes such phenomenon.
Good idea. I should have made good quality recordings of both decks. At the time I was not thinking, "obsessed" to fix the issue.
That would let for frequency analysis and potentially shed some light as to what causes such phenomenon.
I have an QL-A7 and never noticed anything like that but than again I wasn't A/B testing it either. I also have a two arm Victor plinth with a UA-7045 tonearm on it and it sounds fantastic. I know the UA-5045 tone arm found on the QL-7 is considered a top notch arm as well. Although the arm on the QL-A7 looks very similar to the arm on the QL-7 I do know that there are some differences and that long tube and plate may be causing what you hear. Very interesting........
BillWojo
BillWojo
Think it has to do with the way, you perceive/experience the music from the two TT´s, and the heavier plint could very well make that difference. One of my friends changed his TT from a Mitchell Orbe to a Verdier La Platine. Same arm, same cartridge, same cables, but the sound of the Verdier....... (which was the only difference) gave milestones of ways to better reveal what was hidden in the grooves, in a way, the Orbe never did. Pace, rythm, timing.... you name it 🙂
Could be perhaps related to frequency response, since slowing things down usually means a lower pitch. Upper high frequencies could be being masked or lower being emphasized.
A digital copy would perhaps shed the light on it. There are people who can hear the difference of cables. I can't since I've never heard Cryo-treated or one direction only cables.
A digital copy would perhaps shed the light on it. There are people who can hear the difference of cables. I can't since I've never heard Cryo-treated or one direction only cables.
BillWojo,
That was just coincidence to have QL-A7 and QL-7 at the same time.
Both decks share the same arm indeed. However, because of the optical sensor QL-A7 arm is mounted to the plinth differently, using additional hardware.
That was just coincidence to have QL-A7 and QL-7 at the same time.
Both decks share the same arm indeed. However, because of the optical sensor QL-A7 arm is mounted to the plinth differently, using additional hardware.
Boydk,
Possibly, heavier plinth may have something to do with the issue. Also, both decks use different phono output cables. I bet there a couple of more differences. QL-7 rendered music closer to its digital version, though. At least that what my brain tells me ... 🙂
Possibly, heavier plinth may have something to do with the issue. Also, both decks use different phono output cables. I bet there a couple of more differences. QL-7 rendered music closer to its digital version, though. At least that what my brain tells me ... 🙂
