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回覆 (448): C59
Columbus aluminum frame, interesting, joints work are brilliant.  
http://www.ebay.com/itm/NEW-COLNAGO-DREAM-COLUMBUS-AIRPLANE-53-CM-FLASH-FOR-CAMPAGNOLO-FRAME-SET-BLACK-/221263326214?pt=US_Bicycles_Frames&hash=item3384526c06
Cadiver
13-08-06
12:41:22
回覆 (447): C59
This paint job is awesome !  
http://www.ebay.com/itm/NEW-Colnago-C59-Italia-56s-Carbon-Frameset-NR-C40-C50-Di2-EPS-/261259520343?pt=US_Bicycles_Frames&hash=item3cd447e957
Cadiver
13-08-06
12:12:13
回覆 (446): Cinelli Gazzetta
I missed my DeRosa .... Something I let go in 1996
Cadiver
13-08-06
12:00:55
回覆 (445): Cinelli Gazzetta
For your Cadiver,  
 
bobui
13-08-06
09:34:25
回覆 (444): Cinelli Gazzetta
Collnago or Prince, making Cinelli more & more attactive now. May be they are made in China now ....  
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Colnago or Dogma  
 
Made in Taiwan now........but still very nice.  
 
I feel the same too! Steel tubing and traditional geometry makes the bike look much more proportional and sensible. Dont hesitate la! Get one and go to a nice country to ride half an hour a day. More healthy than messing around with your amps and tubes!  
 
bobui
13-08-06
09:09:41
回覆 (443): Cinelli Gazzetta
 
Saw an awesome looking Cinelli Gazzetta city bike @ the office today, outstanding condition, not a scratch. Had the older style basic Cinelli letter instead of the big and loud funky label. You just don't see columbus tubing craftmanship too often these days ! It's not grossly expensive like those S-Works. It's a beauty everyday ride.... Make me wanting to get a bike again. At a fraction cost of the Collnago or Prince, making Cinelli more & more attactive now. May be they are made in China now ....
Cadiver
13-08-06
06:30:29
回覆 (442): DPA 300b
Does anyone know whether Allen Wright's DPA 300b a circlotron design?  
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no. it is a pp amp using differential topology thru out.
drwkng
13-08-05
12:09:50
回覆 (441): DPA 300b
Does anyone know whether Allen Wright's DPA 300b a circlotron design?
ackcheng
13-08-05
07:26:52
回覆 (440): The one and only- What is yours?
Choose one and may have to live with it forever from this moment. Here is how my list would look like for a start. What is yours?  
 
Meat: Fish  
Hi Fi: bobui DIY  
A friend: My CEO  
Music: This particular one below  
Woman: Chinese  
Place: I dont know  
Cartridge: Audio Technica 40th AT33  
Sexy: A smile  
Wine: Leroy  
Position: Concentrate on yours please  
 
 
 
 
bobui
13-08-03
18:07:06
回覆 (439): Output Valve working condition
Yes, you are thinking too much. You ought to buy Limage and me a few drinks each!  
 
 
 
 
 
bobui
13-08-02
19:29:37
回覆 (438): Output Valve working condition
guess i was thinking too much again. ^^
Welborne
13-08-02
18:57:04
回覆 (437): Output Valve working condition
according to Dhtrob:  
 
"I listened to this tube using different adjustments: In my opninion this tube is really magical at a 400V B+, 60mA Ip using a 1K kathoderesistor. The 60mA is the key here: If it is more pushed into current, its sound gets rougher, when lowered it sounds darker... Try it! What the TJ likes however, is a driver with balls (a real 300B after all). I first used the UX120 to drive my 45 and thus this tube. That sounds good, but if you use a real driver, you'll get instantaneously rewarded! Did I say driver? Try a powertube here! (45??), interstage 1:2 connected, and you don't believe that you could listen to all that previous, mediocre shit....  
To all 2A3SE owners: This can be a real upgrade!!"
http://www.dhtrob.com/impressies/tj300bmesh_en.php
Welborne
13-08-02
18:33:15
回覆 (436): Output Valve working condition
HelloBobui,  
 
It was all because my 300b amp was following Thorten's recommended operating point for using TJ 300B mesh at 350v/60ma/5k loading that he specially specified for getting 45 type of sound. I am just being curious about how critical the 350v is. ^^  
 
Welborne
13-08-02
18:28:42
回覆 (435): Output Valve working condition
 
 
Usually power supply to the output tubes is not regulated and as such, power line fluctuations would be ruthlessly reflected on the B+1. Mine wanders from 530V to 490V frequently and yet there is hardly any audible difference.  
 
Coleman, there is indeed no cause for alarm, nor even valid reasons to be overly meticulous.  
 
 
limage
13-08-02
16:34:14
回覆 (434): Output Valve working condition
Good!  
 
Buy me a drink.
bobui
13-08-02
16:28:07
回覆 (433): Output Valve working condition
Ok ^^ order received.  
 
Just for info, in my 300b amp there isca VR installed as the last resistor above the output tube's anode so that I am able to adjust the voltage supplied to anode without affecting the operating point for front tube.  
 
Ok I will not sweat for trying to get 350v from 369v :)
Welborne
13-08-02
16:22:24
回覆 (432): Output Valve working condition
OK! This is an order, my friend!  
 
DO NOT pay too much attention to the slight difference you can make to the anode/plate to cathode voltage.  
 
WHY?  
Ans: The B+ is determined by the secondary voltage on the power transformer, power transformer regulation and the internal impedance of the rectifier. In fact, the whole power supply impedance. There is not much you can do other than placing a very large variable resistor that run so hot in the B+. Even if you willing to do that, you must consider the whole circuit operation condition. Not just the output tube.  
 
Ans: Cathode resistor is there to adjust the current, not the anode/plate to cathode voltage.  
 
Ans: 350V working voltage is not too harsh to a 300B! 365V working voltage is not too harsh to a 300B! Just leave it! Its the current that kills, not the voltage!  
 
bobui
13-08-02
15:47:30
回覆 (431): Output Valve working condition
So does it imply that if i want the tube to run at lower anode-cathode voltage from now, I should aim at an even larger cathode resistor value than 1.2k instead of the otherway round?
Welborne
13-08-02
15:15:05
回覆 (430): Output Valve working condition
Dont say educate la! Sound like I am old an crumpy! Leave the educate part to the well qualified. Sharing is all good! You can teach me how to dance !  
 
Here is the catch:  
The grid is actually the one that control the flow of electrons. Thats why the full name is called Control Grid. You can either impose a negative voltage to the grid and leave the cathode at ground potential (Fixed bias). Or add a resistor to the cathode to raise the cathode voltage in respect to the grid (cathode bias).  
 
In your case, its cathode bias.  
 
The B+ should be the last thing you want to mess around because it not only alter the operating condition of the output tube. It changes the whole circuit operating condition.  
 
If the power supply is properly contructed and the power transformer is not close to exceeding its max power rating. A small increase to the output tube current should bring NO EFFECT to the B+.  
 
Example:  
Let say you want the 300B to operate at a slightly higher current. You then change the 1.2k cathode resistor to 1k. What you see is a lower cathode voltage and a current increase. Because the 300B cathode voltage is lower, the plate to cathode voltage is now higher than before. The current is also higher. The valve is working harder and a little closer to its max dissipation.  
 
bobui
13-08-02
14:46:48
回覆 (429): Output Valve working condition
Ok. :)  
 
But to educate me, what will likely be the change (direction) in plate voltage if the cathode resistor is reduced from 1k to 1220ohm?  
 
I assume...resistor becomes smaller, then more current pass through the tube, and cathode to ground voltage will go up, making Anode-cathode (plate voltage) smaller? Or...the other way round?
Welborne
13-08-02
13:48:17
回覆 (428): Output Valve working condition
369 Vs 350V, the difference is only around 5%. If I were you, I wouldn't care.  
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Absolutely!  
 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++  
 
OK, here is a bit more for your consideration.  
 
Power dissipation: Is 40W (WE 300B original spec.). Max anode is 450V. I prefer to run it at 400V and 75ma which is still only 30W or 75% of its Max.  
 
Higher current or voltage: I prefer at around 90% of its max voltage. Hence the 400V. Valve loves voltage but not as easy when it comes to dealing with current. Just be a little bit more gentle with them on the ma meter. I prefer not to go beyond 75% of their max current. Dont go ver the red line or they may short live.  
 
Additional notes:  
Some output valves are more forgiving than others when it comes to handling excessive amount of voltage or current but not the 300B lor! The 300B has a very long W shape faliment and is famous for being easily break up from overheat or external vibration. You shouldnt get too aggressive with them!  
 
Others such as the Svetlana 811-3, 811-10 or KT88s, .....wow, ar! They just love being hard push and pull! The hotter they get, the better they sound! Best when you see a 811 anode go red. So sexy lor!  
 
bobui
13-08-02
12:01:11
回覆 (427): 6C33C - Is it the best?
369 Vs 350V, the difference is only around 5%. If I were you, I wouldn't care.
Derek2A3
13-08-02
09:58:02
回覆 (426): 6C33C - Is it the best?
To change the dc working condition of the output tube, best and most proper is to adjust the cathode resistor. Not at B+ because it also change the driver tube working condition.  
 
bobui
13-08-02
07:50:09
回覆 (425): 6C33C - Is it the best?
oh, sorry, forgot to menton it is a question in relation to 300B
Welborne
13-08-01
16:57:18
回覆 (424): 6C33C - Is it the best?
I got a couple of questions:  
 
My question is: 1) now when I adjust the b+ (voltage taken at anode) to 441v, I get 72v at cathode (72/1.22k, hence 60ma), and it means 369v (441v - 72v) plate voltage. BUT I am trying to target at 350v plate voltage with 60ma. How can I do that? Shouldn't I use 1k instead of 1.22k ohm?  
 
The next question is: 2) for the same 60ma plate current, what will likely be the difference in sound for a higher plate voltage 369v vs a lower 350v? or it does not matter much, it is the current that matters most.  
 
Enlighten me if you can.  
 
Welborne
Welborne
13-08-01
16:56:44
回覆 (423): 6C33C - Is it the best?
A bit sceptical about the reliability of the two OA2 in the bias circuit. Question on maintaining a correct -3.4vdc grid bias.  
 
Choke input offer better regulation but not as effective as pi filter. Need to specify to your transformer maker the chokes are for choke filtering.  
 
I can recommend you to my copper chassis maker in HK but you still need to get someone to handle the drill, cut, punch and final finishing. Very tough work!  
 
Go go go! Things will always turn out ok la!  
 
 
bobui
13-07-30
08:11:12
回覆 (422): 6C33C - Is it the best?
For anyone interested in building, the website has a user support forum answering questions for people and sharing sources of part.  
 
so far I have only collected the 6e5p and OA2..
Welborne
13-07-29
17:54:31
回覆 (421): 6C33C - Is it the best?
Basically the amp is based on the russian 6e5p tube, capacitor coupling ti 6c33, all in fixed bias. Each 6e5p has two OA2 gas regulators used to provide bias. Output transformers use something like 950-1000 ohm with double c-core amorphous. 6c33 biased at 200ma or something like that. There are built in timer switches to switch on each stage at preset time interval to ensure filaments are preheated enough before HV is applied.
Welborne
13-07-29
17:48:06
回覆 (420): 6C33C - Is it the best?
schematics can be found on the following page. There are two versions, one is a single end one channel version, the other is a 3-channel version with built in crossover for the designer's own horn system. The former is the one that we should look at.  
 
I already obtain quotes for making all the transformers (about 7 per channel, total 14) and they are not expensive as most are power supply chokes and filament supply. Finding soneone to build and the right chassis is beyond my capability and patience....  
 
http://www.goodsoundclub.com/Melquiades.aspx
Welborne
13-07-29
17:41:05
回覆 (419): 6C33C - Is it the best?
Bobui,  
 
When I pulled tube from the socket, I found one leg was left in the socket between the clamps. It looked as if the entire metal leg came off.  
 
For well known 6c33 amp, I can only speak about the "Melquiades" design from Roman (Romy the Cat). King will know about it as I posted the circuit and other stuff on r33 and he made some comments on the schematics. That would be the monoblocks I would want to have someone built for me.  
 
http://www.goodsoundclub.com/Forums/ShowPost.aspx?PostID=741
Welborne
13-07-29
17:33:12
回覆 (418): 6C33C - Is it the best?
one of the pins came off when i pulled it from the socket.  
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that is to be expected. just consider the heat and the filament current. but then they only rated for 600 hours.
drwkng
13-07-29
16:25:57
回覆 (418): 6C33C - Is it the best?
one of the pins came off when i pulled it from the socket.  
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What happened when you pushed the 6C33C back into the socket? I mean, did the pin felt back in??  
 
 
 
+++++++++++++++++++++++++++++++++++++++++  
For bobui, basically it never stops! :-)  
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You drink, I drink lor!  
 
 
 
+++++++++++++++++++++++++++++++++++++++++  
Can u recommend a 6c33 amp I should pay attention (to shop), beside the Graff  
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I had a 6C33C connected to a test bench power amp for some lovely hours when I first got the valves and a pair of Tango a few years back. Since then, I have never really mess with this valve or heard of it in a proper system set up.  
 
To be honest, I am not a big fan of 21st century valve amp and I never seen a well constructed 6C33C push pull amp in front of my eyes. There just so few around!  
 
The only one I have heard is the Tenor 75W. But then, its an OTL!  
 
I am sure there are some good ones out there. I am just not knowledgeable enough to comment.  
 
Welborne, may be try to clean the pins of a new valve before you insert it into the socket. When new, you can see the pins have some kind of corrosion residual. Sand and get rid of them and make the pins smooth because when the valve become hot, the corrosion residual would melt together with the socket pin clamp.  
 
bobui
13-07-29
16:21:43
回覆 (418): 6C33C - Is it the best?
 
 
I couldn't remember exactly. There was a song sung in Taiwan dialect which resembled something like 無奶食。  
 
I cannot stop laughing whenever I see the 6C33. Who on earth could have the crazy vision of a Big Fat Ma Ma with 3 nipples?  
 
He must have been the weakest of the triplets!  
 
limage
13-07-29
16:10:57
回覆 (417): 6C33C - Is it the best?
I would want 2 pairs (4 pcs) if possible.  
 
Know what, on one of the 6c33 tubes I have on hand which is far from reaching its end of lifespan, one of the pins came off when i pulled it from the socket.
Welborne
13-07-29
15:39:20
回覆 (417): 6C33C - Is it the best?
>Isn't it time to start drinking already ???! Or already started ...<  
_________________________________________  
 
For bobui, basically it never stops! :-)  
 
thekong
13-07-29
15:39:11
回覆 (416): 6C33C - Is it the best?
OK.  
Can u recommend a 6c33 amp I should pay attention (to shop), beside the Graff  
 
Isn't it time to start drinking already ???! Or already started ...
Cadiver
13-07-29
15:21:36
回覆 (415): 6C33C - Is it the best?
[email protected], can I have 10 after your slow brew burn in configuration ?  
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Sure! But there is just one tiny insignficant detail I forgot to tell you. After conducting my run in process, the final billing would be US$350 each!  
 
Dont worry, since we all have one thing in common, namely as 1pk high hands lor! I would make an exception for you and let you off with a few glasses of Premier Cru White as fees for me! OK, my friend?  
 
bobui
13-07-29
15:01:52
回覆 (414): 6C33C - Is it the best?
[email protected], can I have 10 after your slow brew burn in configuration ?
Cadiver
13-07-29
14:08:34
回覆 (413): 6C33C - Is it the best?
Like!
Welborne
13-07-29
13:18:46
回覆 (412): 6C33C - Is it the best?
typo - should be "accept refund".
bobui
13-07-29
09:07:41