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主旨寄件者更新日期
回覆 (336): Cloned Pass X 0.2 前級
dd845
11-11-07
09:54:57
回覆 (335): Cloned Pass X 0.2 前級
十足十照跟
dd845
11-11-07
09:53:56
回覆 (334): Cloned Pass X 0.2 前級
期待親耳一聽
dd845
11-11-07
09:49:32
回覆 (333): Cloned Pass X 0.2 前級
dd845
11-11-07
09:48:52
回覆 (332): Cloned Pass X 0.2 前級
真的一樣!  
_________  
 
据聞聲音都係...
dd845
11-11-07
09:48:24
回覆 (331): Cloned Pass X 0.2 前級
真的一樣!
dd845
11-11-07
09:47:25
回覆 (330): Chinese speaker
ackcheng
11-11-04
14:02:26
回覆 (329): Chinese speaker
So professionally done!  
 
http://www.hifidiy.net/index.php?action-viewthread-tid-447228
ackcheng
11-11-04
14:02:02
回覆 (328): A DIYer long kept secret
Making a 28mm perfectly rounded hole for your 300B 4 pin socket on your lovely looking copper chassis without getting your hand bleed, easy! A rectangular hole for the IEC socket, easy! Want your next killer amp look professional and sexy, easy la!  
 
Order a hydraulic hole puncher is all you need, it's handy, reliable and comes with over 40 different cutter sizes and shapes.  
 
Now you know a long kept secret of me! Good luck!  
 
http://www.stainelec.com.au/2.html
bobui
11-10-16
18:12:39
回覆 (327): diy pwr amp
Thanks to 朋友 for the recommendation of a cheap and cheerful dinner. However, there is just one minor insignificant detail I like to bring up. To squeeze in 12 big lads together under such romantic dim lighting which I could hardly see where my fingers were heading when the food arrived......emmmmm! Perhaps, we should have considered bringing some 小師妹!!!! then I know better where my fingers should not be heading!  
 
 
Picture time, show off time and Quiz time:  
Built for RAF for aircraft communicationaround WWII  
Can withstand up to 1,500 volts  
Only GEC and Mazda ever made them  
It can be used in Single ended similar to the American 211 setting with slightly less current.  
 
And the model number is?  
 
 
 
bobui
11-10-13
12:33:05
回覆 (327): diy pwr amp
e jai :  
do u know any of you going to sell a pair of EAR 549?  
___  
 
no bor! ^^
icefox
11-10-13
12:18:29
回覆 (326): diy pwr amp
e jai :  
do u know any of you going to sell a pair of EAR 549?  
 
haha!
GAS
11-10-13
08:50:39
回覆 (325): diy pwr amp
GAS sir,  
 
與其東碰西碰,不如一個電話打去代理,送套 CJ GAT前,ART MONO後過來!閉關練功!假以時日出關,必有一番作為!^_^  
 
小弟不才加莫財,才流連 ebay,Audiogon呢D鬼地方!!!@@
icefox
11-10-13
01:35:16
回覆 (327): DC Restorer
Please just ignore the previous one.  
 
Go to that "gas-wasting" 8 x KT88 thread at R33 ( which drwkng has once visited). Someone has explained its basic structure. To be brief, it takes some of the signal AC current right from the coupling cap and convert it into positive DC to offset part of the negative bias of the following tube, thus, whenever there is signal coming, reducing the negative bias and therefore raising the following tube's current. It solves a problem while creating several others.
ThomasC2
11-10-13
01:07:22
回覆 (326): DC Restorer
Go to that "gas-wasting" 8 x KT88 thread at R33 ( which drwkng has once visited). Spmeone has explained its basic structure. To be brief, it takes some of the signa ACl current right from the coupling cap and convert it into positive DC to offset part of the negative bias of the following tube, thus reducing the negative bias and therefore raising the following tube's current. It solves a problem while creating several others.
ThomasC2
11-10-13
01:01:10
回覆 (325): diy pwr amp
Thanks to GAS for an interesting topic and latest listing link in bay watch. Seems to be a lot of money for a foreign DIY!
bobui
11-10-13
00:30:14
回覆 (324): diy pwr amp
hahahah ! foreign diy!
GAS
11-10-12
21:58:33
回覆 (323): diy pwr amp
the workmanship of this amp is really ...Hmm
drwkng
11-10-12
19:37:05
回覆 (322): diy pwr amp
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=180734640414&category=50593&_trksid=p5197.c0.m619
GAS
11-10-12
18:53:28
回覆 (321): diy pwr amp
yes. i think so. so for us class A folks, it does not mean much.
drwkng
11-10-12
17:10:32
回覆 (320): diy pwr amp
ah, he wants to limit DC shift so he can run the amp more stabe towards Class B.
bobui
11-10-12
16:47:09
回覆 (319): diy pwr amp
Wait a minute, wait a second. Are we talking about Class AB or Class B here? in If in Class B operation, it has zero DC bias as the valves or whatever would be biased at the cut-off, the valve bascailly only conducts when the input signal is greater than the grid voltage. And if one phase is in Class A, the other phase is not. The amp really is not in Class B, right?  
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it is a PP amp. my friend.
drwkng
11-10-12
15:48:00
回覆 (318): diy pwr amp
a CLass AB amp does go into CLass B  
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Wait a minute, wait a second. Are we talking about Class AB or Class B here? in If in Class B operation, it has zero DC bias as the valves or whatever would be biased at the cut-off, the valve bascailly only conducts when the input signal is greater than the grid voltage. And if one phase is in Class A, the other phase is not. The amp really is not in Class B, right?
bobui
11-10-12
15:38:16
回覆 (317): diy pwr amp
So, you saying the DC restorer is to shift the amp tp Class B by allowing grid current but without affecting the bias level which in turn extend the output power. And if I am correct, this also enable the amp to drive lower impedence speaker a bit more effective because you bascially push the amp/output valves to class B region.  
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no. a CLass AB amp does go into CLass B when it is driven past the class A region. this being a PP amp, onlyone phase is at class B while the other phase is still at class A.
drwkng
11-10-12
15:16:26
回覆 (316): diy pwr amp
dc restorer which shifts the DC of the output stage will allow the class B to behave like a class B.  
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So, you saying the DC restorer is to shift the amp tp Class B by allowing grid current but without affecting the bias level which in turn extend the output power. And if I am correct, this also enable the amp to drive lower impedence speaker a bit more effective because you bascially push the amp/output valves to class B region.  
bobui
11-10-12
14:53:20
回覆 (315): diy pwr amp
Not sure why artifically extend the curve to class AB2.  
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at CLass AB, when one tube is driven into class B, the output is cut off but the driver stage is not. the average DC after the coupling cap might affect the bias level of the tube. hence the dc restorer which shifts the DC of the output stage will allow the class B to behave like a class B.
drwkng
11-10-12
13:53:04
回覆 (314): diy pwr amp
My sharing and my summary as follow  
 
Not sure if the DC restorer is to control the voltage or current by artificially inject a regulation kind of circuit in the bais or HT.  
 
Not sure why artifically extend the curve to class AB2.  
 
Not sure if majority owners have real big concern on the durablibity of their Eastern Europrean, Chinese or Russian made replica KT88s. Only ladies prefer men to be gentle. Hence "Gentlemen", not "Gentletubes". Right?  
 
Not sure how he measure distortion. At full output or idle.  
 
Sure for one thing, a junior inexperience stubborn short sighted blow-water DIY such as bobui. I just dont get it.  
 
 
 
bobui
11-10-12
13:23:43
回覆 (313): diy pwr amp
i'm kind of busy these few days so can't get into too much of this. but enough to say that if you are into Class AB amp with capacitor coupling, you might benefit from this DC restorer. i think this mod is from Stu Hegeman and not bob carver. and i think it has nothing to do with the low bias of the tubes. the tubes can run at lower bias with the DC restorer since it gives lower distortion. but it is not a causation. bob completely lost me when he talks about the lower bias and the way he describes how a CLass AB amps work. Ah! but then i never am quite capable of understanding high audio marketing anyway^-^
drwkng
11-10-12
11:36:53
回覆 (312): diy pwr amp
DC restorer  
---------------------------------  
Sound like a regulated circuit that control the DC working voltage. Lower when at idle (no signal) and restore to normal when you apply signal. Nothing more I can add without reading the circuit. And it sound like an automatic stand by switch to me! But then... please read below.  
 
"Good to have"  
Emmmmmmmm! So let say you just finished listening to one of Art Pepper CD and is in the right mood to continue your night with more Miles, Bach or whatever you fancy but somehow need to put it on hold so you can run to the kitchen to fill up your wine glass and then back to the drawer to pick your next CD or LP. Of course, you may also want to make a quick call to your high hand friend to blow water for a few minutes. You know what I mean! Do you think it is necessary to switch your amp to stand by mode to save your electricity bill or for your valves to live longer?  
 
If your answer is Yes, then you have one more option to choose from as your next toy. If your answer is No, then it's hard to qualify as "good to have".  
 
The thing is there was no mentioning that the design can offer better sound quality. Its all about cost savings, right?  
bobui
11-10-11
14:46:21
回覆 (311): diy pwr amp
Every vacuum tube amp in the world suffers from shifting DC operating points, and this, unfortunately, has remained a functional limitation and maddening sore point for amplifier designers ever since the very beginning of vacuum tubes. Consequently, I had to invent a DC restorer circuit using a 6AL5 / 5726 tube; it eliminated every last vestige of DC shift, while simultaneously reducing distortion three-fold and vacuum tube idle power by the same amount. As Tim would say, "Nothing new under the sun", just the same, it's never been done before, and it works flawlessly.  
The answer is the DC restorer. Here's how. Most amps idle the output tubes at an average of 32 watts or so. Now the DC restorer allows the tubes to idle at about 9.75 watts. Since tube longevity is roughly proportional to the plate dissipation raised to the 2.3 power, we have 32 divided by 9.75 raised to the power of 2.3 = 15.4. Finally, 15.4 X 3 years = 46 years. I have also noticed that many console amplifiers have 50 year old tubes right here on eBay, and those tubes check out great. Great question, hope this helps.(quoted from bob carver)  
 
dc restorer? that interesting any high hand cna expalin more to this? better in chinese if possible haha  
 
GAS
11-10-11
08:49:11
回覆 (310): diy pwr amp
Hi GAS,  
 
I am always happy to have the chance to share my thoughts on valve amp circuits with many high hands here. Surely is fun trying out new stuff! I have heard stories about people having success from turning transmitting tubes into audio use.  
 
Englighten us with your thoughts and plan on the 838/805. I am sure you are well aware of the fact that many of the 8 series American big tubes are meant for high power Class C radio frequency tranmission. They require grid current, high power drive and not very linear which only improve slightly when driven hard on the HT voltage.  
 
Good luck and share with us when you have time!
bobui
11-10-07
17:48:50
回覆 (310): diy pwr amp
yup
GAS
11-10-07
17:34:58
回覆 (309): diy pwr amp
Improved tubes  
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Meaning higher power?
bobui
11-10-07
11:58:39
回覆 (309): diy pwr amp
yes. 838 looks better but only slightly. it is still a very non-linear tube.
drwkng
11-10-07
11:57:01
回覆 (308): diy pwr amp
ops actually is 838 not 805 ! the later and improved tubes from 805
GAS
11-10-07
11:48:33
回覆 (307): diy pwr amp
why 805? it looks awfully non-linear by any stretch of imagination and it is very difficult to drive as well. but of course if you want to torture yourself then go for it.
drwkng
11-10-07
11:07:48
回覆 (306): diy pwr amp
805 (838) triode push pull  
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Sound exciting! It's always a positive feeling to me seeing high hands trying out new stuffs or circuits.  
 
I may have a SE 805 circuit hidden somewhere in my den which I can dig out if you think it may offer you some inspirations. Oh, just a gentle reminder of the grid current and the high capacitance between grid and anode
bobui
11-10-07
10:50:20
回覆 (305): diy pwr amp
hi all c-hing  
 
planning to built a pair of 805(838) triode push pull pwr mono,  
single end 300b as driver stage, solid state retifiers.  
 
any c hing got any schematic diagram ?
GAS
11-10-06
21:11:58
回覆 (304): What I did last night?
Bobui, how did you manage to get all those good looking chassis for you DIY projects? Respect!  
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Thanks a lot for your kind words and encouragment! Its may be Ok burt from from good looking la.  
 
Yes, its always a bit tough. For the chassis, I first got a sheet of copper, 4 X 8 feet and send over to someone in Monk Kok to have them made to my required size. The welding usually very rough when done. So I need to rub and sand before grilling, punching holes and cutting squares for the transformers. Spray is the last process.  
 
 
bobui
11-10-06
18:06:15
回覆 (303): What I did last night?
looks tasty ! 8^)  
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I changed the circuit to cap coupling which gives less chance for failure. It only loss out to the 6B4G/2A3 PP amp I've always been using because of its lower power.  
 
Please take it home and try it. Its on 16 ohms now but wont be a problem if you connect it directly to a 32 ohms speaker.  
 
I will start working on the Tannoy preamp tomorrow which should be ready by the time you guys coming over to my den and please also take home for a run. It will be two completely seperate mono preamps with the various bass roll off for ffrr, columbia, RCA etc.
bobui
11-10-06
17:54:52