1audio said:
The Kenwood L07D is taking care of this, at least in two ways:
1. The PLL loop has some sort of hysteresis (or dead zone) so that it does not correct the speed "live". Inside the dead zone, its the large platter inertia momentum that regulates the speed.
2. The PLL loop is designed as critically dampened, so that the correction is not overshooting.
Direct drive can potentially have amazing objective performances, unfortunately it was compromised by way to many 556 PLL implementations, toy DC motors and lightweight platters. A good Direct Drive DC motor would have to combine the DC motor quality with an excellent bearing, not easy or cheap to find.
If I could source such a motor, I would be interested in such a DIY project. Retrofitting an existing platter, providing a good plinth and adding some well designed electronics shouldn't be that difficult.
syn08 said:
I'm not sure that the dead zone story isn't a marketing spin around an undocumented feature (bug). I measured some direct drive turntables for speed accuracy a long time ago and found a double hump distribution with almost no signal on frequency, where a Linn had a norma distribution on speed. I used a CD4 test record with its 30 KHz (?) carrier and a Tek 7L5. It wasn't hard to see the issue. I have not looked at the issue since (30+ years) but I think its worth exploration.
I'm also interested since I have ways of obviating the bearing issue, we just need the motors. With the resurgence of Vinyl and DJ tables is should be pretty easy to get a suitable motor from China if someone has suitable contacts.
demian:
i'm curious - do you extend this view to the denons of the mid '80s (e.g. dp-37f, dp-47f, ...)
mlloyd1
i'm curious - do you extend this view to the denons of the mid '80s (e.g. dp-37f, dp-47f, ...)
mlloyd1
1audio said:
I can assure you it is not. This is very well developed in the control theory and maps to an exponential factor in the Laplace transform of the transfer function. In practice, it is the huge mass of the platter and the motor torque that are providing this kind of behaviour; think of short pulses of current through the motor that have virtually no instantaneous effect in the time (speed) domain. It's your measured dual hump curve, but with the peaks greatly attenuated.
What rate would those enegy "bumps" happen? Could they be audible in a 'rhythm or timing" sense?
1audio said:
Well, I am the last person to get reliable subjective opinions from, but to me the Kenwood L07D is at par to any high end belt drive modern TT. Don't know much about other DD TT's... except of acknowledging that each and any other I've ever seen and seriously listen to, sucks big times.
Another low noise bipolar pair
I found these Sanyo devices 2SC3504E/2SA1433E in a local chinese store. They are in the same FBET process as 2SC3601/2SA1407, so I gambled and got the entire stock.
Lucky guess - they are at par with the lowest noise devices from Hitachi and Rohm (see the previous measurements in this thread http://www.diyaudio.com/forums/showthread.php?postid=1834943#post1834943 ) at obout 0.23nV/rtHz. Only Beta is lower (around 100 instead of 400+ for the Hitchi devices). One to another, excellent low noise devices, grap them if you can. Although they appear to be in production at Sanyo (according to the web site), a Sanyo representative is telling me they are discontinued 🙁
I found these Sanyo devices 2SC3504E/2SA1433E in a local chinese store. They are in the same FBET process as 2SC3601/2SA1407, so I gambled and got the entire stock.
Lucky guess - they are at par with the lowest noise devices from Hitachi and Rohm (see the previous measurements in this thread http://www.diyaudio.com/forums/showthread.php?postid=1834943#post1834943 ) at obout 0.23nV/rtHz. Only Beta is lower (around 100 instead of 400+ for the Hitchi devices). One to another, excellent low noise devices, grap them if you can. Although they appear to be in production at Sanyo (according to the web site), a Sanyo representative is telling me they are discontinued 🙁
Re: Another low noise bipolar pair
syn08:
those look to be a nice find!
do you have any opinions on the 2sb716/2sd756 from hitachi?
(not necessarily low noise parts, so perhaps i'm off topic 😱 )
mlloyd1
syn08:
those look to be a nice find!
do you have any opinions on the 2sb716/2sd756 from hitachi?
(not necessarily low noise parts, so perhaps i'm off topic 😱 )
mlloyd1
syn08 said:
Re: Re: Another low noise bipolar pair
Jamais couché avec, but according to the datasheet, there's nothing really special or oustanding with this pair. Good quality small signal complementary devices.
mlloyd1 said:
Jamais couché avec, but according to the datasheet, there's nothing really special or oustanding with this pair. Good quality small signal complementary devices.
Re: Another low noise bipolar pair
Ovidiu, deci chiar n-a mai ramas nimic? Was it Honson, BTW? I noticed they have quite an inventory of Sanyo parts.
syn08 said:
Ovidiu, deci chiar n-a mai ramas nimic? Was it Honson, BTW? I noticed they have quite an inventory of Sanyo parts.
Re: Re: Another low noise bipolar pair
Honson, moved at College and Spadina. That's the place, I left a few pairs in behind (about ten, I guess), 0.45/pc.
ikoflexer said:
Honson, moved at College and Spadina. That's the place, I left a few pairs in behind (about ten, I guess), 0.45/pc.
The Hitachi devices might not be a problem to obtain in the future, british company is cloning them under licence, it is however at this point unclear if large production run will be made but some devices were put on the market.
AndrewT said:
A DIYaudio member sent me pictures of what he got as Hitachi 2SC2547/2SA1085 devices from Dalbani. Based on those pictures, I now have serious concerns regarding this company's ability to deliver original parts.
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