DIY 自作派同好同學會 |
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回覆 (121): DIY 自作派同好同學會
or I shall connect the coupling cap to the 811 from the Cathode of the 6B4G instead of the Anode for lower impedence drive.  
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I for one certainly would go for the anode output. With a low mu & low anode resistance triode, the effect of different output impedance shouldn't be great between the anode & cathode esp when you intend not to draw any grid current, but you need every bit of gain & voltage swing to drive the 811. Down side on the cathode output, don't forget the 811 is direct heat, either your DC filament section is adequately filtered or you use center tap of the LT trans, you might run into the problem of hum. I can be wrong.  
Derek2A3
11-06-15
16:25:25
回覆 (121): DIY 自作派同好同學會
The last picture is the chassis that arrived last week from Germany for the 811 project
bobui
11-06-15
11:59:43
回覆 (120): DIY 自作派同好同學會
tough one I know for just a few or even a couple. I ask Sowter today and see if they response.  
 
Load curve, gain and basic circuit is done. Need to calculate correct value for a few resistors and desire cut off frequency for the various coupling caps.  
 
Want to run B+ at 700 to 730 on the 811-10, as higher as possible to avoid grid current or I shall connect the coupling cap to the 811 from the Cathode of the 6B4G instead of the Anode for lower impedence drive.  
 
bobui
11-06-15
11:58:32
回覆 (119): DIY 自作派同好同學會
in hong kong, go to po shan. in china, i don't know anyone is interested in doing only a couple.
drwkng
11-06-15
11:44:53
回覆 (118): DIY 自作派同好同學會
dwkng, was lining up all the major compontnets for my 811 project. Found that the power transformer does not give me enough current,. Any idea where nd who in HK/China I can talior made two transformers?  
 
Thanks in advance!  
bobui
11-06-15
11:21:57
回覆 (117): DIY 自作派同好同學會
No, don’t be stupid doc. It ought to be Indian god lotion over sprayed the night before. ''''  
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Isn't it a waste to apply the precious Indian god lotion to the finger instead of the most important organ, unless that organ is of little use.  
kh33
11-06-10
23:39:24
回覆 (116): DIY 自作派同好同學會
 
 
coated with his special body oil giving the characteristic limage sound  
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No, don’t be stupid doc. It ought to be Indian god lotion over sprayed the night before.  
 
 
limage
11-06-10
19:39:54
回覆 (115): DIY 自作派同好同學會
However, every cartridge seemed to sound better after Limage gave his blessing by performing his magic finger brush on the stylus!  
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Don't you know that limage's finger is coated with his special body oil giving the characteristic limage sound?
kh33
11-06-10
18:42:26
回覆 (114): DIY 自作派同好同學會
However, every cartridge seemed to sound better after Limage gave his blessing by performing his magic finger brush on the stylus!  
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I think Master Limage's hand can be trusted compared to "Soo wei wei" with his SPU @[email protected]
daiwok
11-06-10
17:55:45
回覆 (113): DIY 自作派同好同學會
Love to but not sure. Can pass them to you first. No deposit required.
bobui
11-06-10
17:29:41
回覆 (112): DIY 自作派同好同學會
 
Bobui, great! How about arrange a session next Sat (18 June)?  
 
thekong
11-06-10
17:28:06
回覆 (111): DIY 自作派同好同學會
Kong, I will bring the KT88s to the my office next week. Any objection, raise your arm.
bobui
11-06-10
17:25:03
回覆 (110): DIY 自作派同好同學會
 
>I also personally experienced a fainted heart incident of a broken vdh colibri many years ago in Kowloon Bay Richard's studio where KH and Kris were there as witnesses. <  
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Oh the Colibri, I can tell you it must be one of the most fragile cartridges on earth, but they do sounds excellent. While I think the Ortofon A90 bettered the Colibri overall, I still miss the high frequency air of the Colibri, which I have yet to hear in any other cartridges.  
 
If the way how Dr F handle the cartridge even raised your heart beat, you would have a heart attack seeing Limage performed his finger trick on both of my Colibris no less :-) However, every cartridge seemed to sound better after Limage gave his blessing by performing his magic finger brush on the stylus!  
 
thekong
11-06-10
17:19:15
回覆 (109): DIY 自作派同好同學會
HI, Michael,  
 
I was close enough seeing Wadia's face turned pale, heard his heart beating like "take five" drumming and his mind still 死頂 when Dr F twisting his cartridge (or tonearm? not remember) with bare fingers during the alignment demo. I must admitted to myself I was quite enjoying the show and horror scene at that time. Sorry, Ah Wher.  
 
I also personally experienced a fainted heart incident of a broken vdh colibri many years ago in Kowloon Bay Richard's studio where KH and Kris were there as witnesses.  
 
I am sure gentleman like you and Limage will manage this hand-job well. Most of us have got fainted hearts.
dkyyu
11-06-10
16:54:03
回覆 (108): DIY 自作派同好同學會
 
>reminds me of the horrible scene when attending the cartridge alignment session led by Dr F in Wadia's studio last yr.<  
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Dennis, I can’t quite remember, but what was so horrible? No cartridge was damaged as I remember!  
 
When I said "have enough samples to go around", I meant we could mount different samples, of the same model of cartridge, on the arms so as to save time between switching!  
 
thekong
11-06-10
16:31:34
回覆 (107): DIY 自作派同好同學會
We should also have enough samples of the Midas Denon to go around!  
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This reminds me of the horrible scene when attending the cartridge alignment session led by Dr F in Wadia's studio last yr.  
 
Wadia,  
 
Was it your cartridge or someone else in demo last yr?
dkyyu
11-06-10
16:06:47
回覆 (106): Linear tracking vs pivoted type
Masters,  
 
Both types have weakness and strength in my humble opinion. There are lots of battles when setting up your T-T for good performance, the pivoted type serves me well as it saves me out from many maintenance issues.  
 
If any contest available, may I join in as pineapple chicken?
dkyyu
11-06-10
16:02:12
回覆 (106): DIY 自作派同好同學會
 
>There have been plans for a head to head contest between the linear and the conventional arm on the same type of turntable with the same model of cartridge, but then the date has to be postponed time and again owing to the complexities involved. <  
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Limage, once you finish fine tuning you new room, we can set up a head to head session without much difficulty. With Diawok’s modular Lenco, we can switch arms quite quickly. We should also have enough samples of the Midas Denon to go around!  
 
For linear trackers, we can gather the Kuzma Airline, Rockport 6000, Terminator, Airtech, and a couple of versions of the Souther/ClearAudio TQ1s among friends. Of course, we have no shortage on pivotal arms either. It would be great fun :-)  
 
thekong
11-06-10
16:01:39
回覆 (106): DIY 自作派同好同學會
There have been plans for a head to head contest between the linear and the conventional arm  
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That sound real fun. Count me in please. Any input and contribution i can offer. Give me a shout. I dont have Maggie speakers but I do have a Maggie tonearm.  
 
bobui
11-06-10
16:00:16
回覆 (105): DIY 自作派同好同學會
 
but i do think i need to listen and see more on how people get good results from linear tracking  
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I too have serious reservations over linear tracking arms which I believe create more problems than they have purported to resolve.  
 
There have been plans for a head to head contest between the linear and the conventional arm on the same type of turntable with the same model of cartridge, but then the date has to be postponed time and again owing to the complexities involved.  
 
It isn't that easy to ensure a conclusive result because there are simply too many variables at work.  
 
limage
11-06-10
15:38:14
回覆 (104): DIY 自作派同好同學會
this is my current DIY turntable with a linear tracking arm as well 8^)  
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You teasing me. I bet you were laughing at me when I had my home made turntable picture posted a while ago. You are in fact the MASTER in LP.  
 
Offer me a price or I shall for the Alphason.
bobui
11-06-10
14:36:48
回覆 (103): DIY 自作派同好同學會
bobui,  
 
this is my current DIY turntable with a linear tracking arm as well 8^)  
 
daiwok
11-06-10
14:28:51
回覆 (102): DIY 自作派同好同學會
However, after I switched out the stock pump (which can only output around 11psi max.) for an industrial pump with integral surge tank, and up the air pressure to 34psi,  
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Sound like success and you were having fun after investing in it.  
 
Concept and principal are important facts but i do think i need to listen and see more on how people get good results from linear tracking. Thats has always been a downside to me because I hardly pay visit to others in the past. Daiwok and Kong dens are the two set up I am deeply interested. Honest, purely because Diawok make his own turntable and your precious LP set up. The Imedia too, of course.
bobui
11-06-10
14:24:22
回覆 (103): DIY 自作派同好同學會
I thought we were talking about bearings.  
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All bearings have a degree of friction, it all depends how you over come the friction.
daiwok
11-06-10
14:18:43
回覆 (102): DIY 自作派同好同學會
if there is no gap, it would not be a bearing. the gap is there by definition. for oil bearing, there is thin film of oil. for air bearing, there is cushion of air. when there is relative movement between two non-parallel surface, the pressure differential of the lubrication film will generate force to separate the two surfaces hence the bearing. the air bearing in this application is to ensure the horizontal movement with least friction which it seems to be doing quite well. since the two surfaces can never be perfectly concentric, i think when you increase the pressure, the vertical movement which translates into a rotational motion is countered by the pressure differential of the non-parallel surface. so if you want to restrict the rotational motion yet using a low pressure tank, you can also try to increase the rotational moment of inertia of the arm. just my bs.
drwkng
11-06-10
14:11:01
回覆 (101): DIY 自作派同好同學會
 
>Why air bearing “contradicts the use of good bearings”? <  
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Well, I suppose what Bobui refers to is that airbearing always have an air gap, so it just can’t be as rigid as conventional bearings. I believe this could be somewhat true, but if you could up the pressure to 30+ psi, or 60+ psi as in the case of the Kuzma Airline, then the problem would be minimized.  
 
I believe Kuzma claimed that you could pick up the whole turntable by holding on to the armtube of the Airline, and the bearing would still not be grounded!  
 
thekong
11-06-10
13:45:20
回覆 (100): DIY 自作派同好同學會
> Why air bearing “contradicts the use of good bearings”?  
> What are good bearings?  
 
I thought we were talking about bearings.  
 
feikeung
11-06-10
13:24:30
回覆 (99): DIY 自作派同好同學會
Bobui, what you said is true for airbearing arms, but then pivotal arms also have their own sets of problems, like only having 2 tangential points when tracking through the disc.  
 
Also, some of the pivotal arms, like the Dynavector, purposely designed to have a much higher horizontal than vertical effective mass, which the designer believe would result in better bass performance. Theories aside, I always find linear tracking arms present a bigger and airier soundstage, which are important factors to me!  
 
Some people think airbearing arms are not good at the bass, and I can relate to that. When I started out using the Rockport arm, the bass was certainly not its strong suite. However, after I switched out the stock pump (which can only output around 11psi max.) for an industrial pump with integral surge tank, and up the air pressure to 34psi, I don’t have any more complain on the bass. In fact, I think it is better than many pivotal arms in this area.  
 
thekong
11-06-10
13:08:56
回覆 (98): DIY 自作派同好同學會
What are you getting at precisely?  
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Linear tracking have very different effective masses in horizontal and vertical planes: in the horizontal plane the cartridge has to react against the whole mass of the moving assembly - air bearings and stuff, entire mass of the counterweight and arm tube with none of the mechanical advantage of a pivoted arm and all this reacts against the cantilever. Given that there is hardly a record without some degree of eccentricity this can add up to large forces.  
 
Correct and share as I am learning too.
bobui
11-06-10
12:33:47
回覆 (98): DIY 自作派同好同學會
the drag is purely a natural effect with the stylus on the the groove.  
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the point i was trying to make is that without the gap, the force need to overcome will be the dynamic friction of the two surfaces. it is no mean task for a stylus!
drwkng
11-06-10
12:23:31
回覆 (99): DIY 自作派同好同學會
I can fit an air bearing arm on your Lenco for you Good Doctor. But you need to buy a pump which will cost between HKD 300 to HKD 1200. HKD 1200 is japanese brand and HKD 300 is a China brand which will last about 1 year. The arm will be low pressure type.  
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great! may be i should go back to my mechanical engineering background to start designing an turntable arm^-^
drwkng
11-06-10
12:21:31
回覆 (97): DIY 自作派同好同學會
> The fact that linear tracking arm always need to have an air gap to allow pressured air to cushion the movement is contradict to the use of good bearings.  
 
What are you getting at precisely?  
Why air bearing “contradicts the use of good bearings”?  
What are good bearings?  
 
feikeung
11-06-10
12:17:43
回覆 (98): DIY 自作派同好同學會
the air gap together with the shaft and arm form some kind of bearing. NO?  
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I can fit an air bearing arm on your Lenco for you Good Doctor. But you need to buy a pump which will cost between HKD 300 to HKD 1200. HKD 1200 is japanese brand and HKD 300 is a China brand which will last about 1 year. The arm will be low pressure type.
daiwok
11-06-10
12:15:40
回覆 (97): DIY 自作派同好同學會
i don't know much about arm design. but without the air gap, what kind of force is required to drag the arm along the shaft. the air gap together with the shaft and arm form some kind of bearing. NO?  
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the drag is purely a natural effect with the stylus on the the groove. Air bearing arms come in several forms but generically can be separated into 2 - either high pressure like Rockport / Kuzma Airline or low pressure Airtech MG1 / Terminator T3pro.  
 
in fact there is a possibility of an air bearing shoot out in the horizon this year 8^)
daiwok
11-06-10
12:10:31
回覆 (96): DIY 自作派同好同學會
vibration measurement rig  
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actually Good Doctor, its actually just the rig only @[email protected] no measurement. I did intend to upgrade the ADJUST + from Dr Feikeung to PRO version which claims it can measure vibration of the tonearm. I asked Dr Feikeung and he said easy, just pay the extra online ! no trial or test first ! so I decided to put this on the back burner.  
 
To be honest like I said before isolation can be achieved in many forms, given the number of carts and tonearms I have played with, most of the so called top end arms are very similar yet you will find even older arms from the golden period of Japanese turntables and tonearms will out perform current new so called high end arms.
daiwok
11-06-10
12:07:28
回覆 (97): DIY 自作派同好同學會
The fact that linear tracking arm always need to have an air gap to allow pressured air to cushion the movement is contradict to the use of good bearings.  
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i don't know much about arm design. but without the air gap, what kind of force is required to drag the arm along the shaft. the air gap together with the shaft and arm form some kind of bearing. NO?
drwkng
11-06-10
12:07:16
回覆 (96): DIY 自作派同好同學會
may be it is just me. i don't like things hanging.  
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Count me in. In tradtional bearing arm, the design concept usually center around material reasonce frequency, bearing tolerence, gravity etc. Most of the linear tracking arm ignore these parameters and emphasis on tracking ability alone. The fact that linear tracking arm always need to have an air gap to allow pressured air to cushion the movement is contradict to the use of good bearings.  
 
bobui
11-06-10
12:00:27
回覆 (95): DIY 自作派同好同學會
what does arm pods mean? I mean was to have the shaft that the arm slides on supported on both sides. may be it is just me. i don't like things hanging.  
i think you should ditch out some serious money to set up a vibration measurement rig^-^  
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arm pod means a separate independent island for the tonearm.  
 
Ah supported on both sides - then you are looking at the Clearaudio Statement tonearm !  
 
vibration measurement rig ........ you must have heard ....... I bought one .....but it is so big that you can fit 2 x Linn Sondek LP12 on it and still have room for a Hornby train set or Scaletrix to run rings around the turntables @[email protected] ...... never mind you need 3 people to carry it @[email protected]
daiwok
11-06-10
11:45:20
回覆 (95): DIY 自作派同好同學會
 
>wouldn't it better to have the arm suspended on both ends? <  
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I think Dr King is referring to the airbearing spindle of the arm. The arm’s spindle on the Rockport Sirius 3 is supported on both ends, while my 6000 arm only has support on one side. I believe supporting the spindle on both sides would make it more stable, and I am thinking of a way to modify my 6000 arm! It shouldn't be too hard, but it probably would need a CNC machine!  
 
thekong
11-06-10
11:44:14
回覆 (93): DIY 自作派同好同學會
Daiwk, almost missed the details. Your first turntable. Gosh, its very good looking. You seems to have a way with turntable.  
 
Guys, just imagine a few of us put some hours and hard work together to produce a series of turntable and amps project. It will be so much fun and make HK Hi Fi community look real cool. Knowledge is power. Quality is money. And is not blowing water lor simply because we already seeing them in this site.
bobui
11-06-10
11:43:56