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回覆 (306): Valve LCR phono preamp
Hi,  
 
A preview of my long on going LCR phono preamp. The chassis is pretty much completed except the lettering. A dual mono power supply with valve shunt regulator. Total six transformers in the power supply.  
 
bobui
15-09-17
13:48:20
回覆 (305): 6C33 SE Test Report
Yes, but cathode bias can take care of this neatly, though power will be lowered.  
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The reason I use Fixed bias is more to do with maintaining a desire operating voltage than maximize output power. I have very little intension to drive the 6C33 hard into A2 grid current. The power supply transformer I have gives out roughly 210Vdc under load. If I use cathode bias (minus roughly 60 to 70v at cathode voltage), the 6C33 would be operating at roughly 140Vdc which is far too low from my desire operating voltage. Hence the fixed bias. You know what I mean!  
 
Few elements I like about the 6C33 than many other popular output tubes:  
1. The indirect heat cathode is a nice addition that eliminate unwanted 50hz when connect AC to the Faliment  
2. The lower impedance allow a much lower winding ratio for the output transformer. As you can see from my below screens. The high frequency response is much better than the one from my PX25SE amp. The PX25SE amp has a Tamura F2004 output. I really don't think Tamura output is more inferior than Tango lor! To, me, they are equally well made.  
3. The price of a single 6C33 is still way much less than nearly all mid to large triode output tubes. When search for 6C33 for sales in the web, please take not that some selling use 6C33 original Russian code, 6S33S.  
 
I just made an order to Sowter for a pair of custom output. Specification is for 6 pairs of 6C33 in Push Pull per channel that can handle 500Watts using their larger iron core.  
 
Time to stock up some more 6C33!
bobui
15-06-20
09:25:29
回覆 (304): 6C33 SE Test Report
The tube together with the chassis act as a heatsink for the extremely hot 6C33. Other than more spare 6C33 I need, I am also looking for better made socket for the 6C33. Only Chinese, Russian, USA and Japan have manufactured 6C33 socket. What you see in my amp is ceramic from the Russian. I just bought two NOS USA made socket made by Johnson.  
 
I have tried four pins Japanese made Telfon in my SV811 amp in the past which run nearly as hot as the 6C33. The durability is not as super as I expected. The four cylinder pins in the socket which holds the SV811 turned black after roughly one year of regular use. Mine was the gold plated version. Fortunately, the pins can be unscrewed for a cleanup. The cylinder pins also have the tendency to collect unwanted debris and dust. Users at 1pk, please watch out for that.  
 
Johnson made sockets are probably one of the best available. Be it four pins, octal, 9 pins or others. They are mostly ceramic made with silver plated contact pins. They don't appear to hold the valve as strongly as the more recent developed Telfon from Japan but their durability and rigidity is second to non.
bobui
15-06-20
08:56:09
回覆 (303): 6C33 SE Test Report
perfect contact may often prolong tube life as the tube would not get into vicious cycles which often damage the tube one way or the other.  
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Yes, but cathode bias can take care of this neatly, though power will be lowered.  
 
Anyway, we better leave this for bobui to consider.
Derek2A3
15-06-19
15:44:58
回覆 (302): 6C33 SE Test Report
 
 
Well, if we look at it from a different perspective, perfect contact may often prolong tube life as the tube would not get into vicious cycles which often damage the tube one way or the other.  
 
limage
15-06-19
14:05:33
回覆 (301): 6C33 SE Test Report
In case the 6C33 really has a short life span (word on the street 500 hours only), keeping the socket might be a better idea for easy replacement. But then direct welding or soldering of the input and driver tubes should always be encouraged.
Derek2A3
15-06-19
13:05:35
回覆 (300): 6C33 SE Test Report
 
 
its filament requirement is 6.3V x 6A  
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If that is the case, then it's better to do away with any tube socket. The best way IMHO is to have the contact pins directly welded.  
 
2A3, it's your turn to show your brilliant feat!  
 
 
limage
15-06-19
12:20:27
回覆 (299): 6C33 SE Test Report
some even suspect the heat causes a short life.  
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That's true for certain, whatever tube we are talking about. 6C33 belongs to the group of worst offenders as its filament requirement is 6.3V x 6A if memory serves. See, just the filament is already outputing 37.8 watt of heat close to that of a 40 watt light bulb. And we haven't talk about the anode current yet.
Derek2A3
15-06-19
12:01:28
回覆 (298): 6C33 SE Test Report
 
 
Have heard stories saying that the 6C33 runs real hot and some even suspect the heat causes a short life. Any idea about this issue?  
 
limage
15-06-19
11:09:07
回覆 (296): 6C33 SE Test Report
6C33 users have voiced out that the tube doesn't last very long.  
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True when the poor tubes are used in OTL machines and being pushed to deliver lots of current. In case of SE with output trans, I bet they should last much longer, anyway, you'll see.
Derek2A3
15-06-19
11:07:16
回覆 (297): 6C33 SE Test Report
Circuit board on the bottom left is the rectifier and caps for driver stage @ roughly 370Vdc. The middle bottom circuit board contains power supply for negative grid voltage and DC supply for driver stage. The 6C33 uses AC 6.3V.  
 
Sorry la, no v-cap, no Mcap and no fancy oil tank! Just Germany made F&T, Wima and Hovland. I am not picky at all when it comes to caps and resistors. Just a mix of Dale, RMA carbon and Japanese and RS resistors. For output and power transformer, I kind of pay the greatest attentions.  
 
Just ordinary Pi filter for the separate B+ for the 6C33 and driver circuits. The 6C33 B+ use silicon diodes and then a GZ37 as a slow start before the first cap and choke.  
 
Fixed bias allow adjustment from 50ma to 220ma max for the 6C33.  
 
The amp is young and I don't have a clear description for its sound yet but seems to have the potential to become a top SE amongst others I have.  
 
No more SE amps for the near future. Next is a LCR phono with separate shunt regulated tube power supply and all Tango MC, LCR and pre-line output cows. Total 16 tubes plus Nixie tubes for the volume indicator!  
 
Good night!  
 
bobui
15-06-18
23:19:16
回覆 (296): 6C33 SE Test Report
Final look of my 6C33 SE. I have changed the input tube to E88CC. The upper tube of the mu follower remains to be 12GN7.  
 
I have six new 6C33. Only one pair is very well matched. The second pair is ok matched with about 8% deviation in current. The last two are total rubbish. Go to display and become white mouse for further project.  
 
I was told that finding matched pair 6C33 require a fair amount of luck! Time to stock up!  
 
bobui
15-06-18
22:49:09
回覆 (295): 6C33 SE Test Report
Here is how my zero feedback PX25SE amp look like at 20Khz.
bobui
15-06-18
16:36:57
回覆 (294): 6C33 SE Test Report
Here is how my zero feedback SE amp look like at 20Khz. You can see that the square wave is distorted to looking like the Alps more than a square! Both the 6C33SE and the PX25SE have zero overall feedback.  
 
Show u more pictures of the final finished 6C33 later tonight.  
 
Additional notes:  
1. Man 6C33 users have voiced out that the tube doesn't last very long. Since, I have not been a long user for this tube. Not much I can share other than some logical steps as follower.  
a. For fully burn in tube. Take extra heat up time on the faliment before applying B+  
b. For tue new from the box. Heat the falliment for half an hour or more before gradually apply B+ start with very low ma and take steps to allow the ma raise to desire level.  
c. Clean all the pins regularly to avoid bad contacts. Especially the grid and cathode to minimize negative a fall in the negative grid.  
 
overall sound: At first switch on last night with only half the desire current, already sound way better than my PX25 SE amp. More subjective reports coming after fully run in.
bobui
15-06-18
16:33:49
回覆 (293): 6C33 SE Test Report
The 6C33 project is completed. Here is a test report.. Below is 20Khz square wave taken out from the output terminal of the 6C33 amp. Not bad when compare with my PX25 and SV811-3 SE amps. In fact, the shape shows much better frequency response than nearly all my SE tube amps. Much come from the lower winding ratio or the output.  
 
I use a mu follower driver circuit for its low output impedance. The 6C33 does have a fairly large input capacitance that create a charging and discharging action for the driver stage.  
 
bobui
15-06-18
16:18:34
回覆 (292): 6C33 SE
Thanks for your kind words. More pictures of the internal completed 6C33 and test results coming plus the LCR phono preamp and some fairly large power blocks.  
 
bobui
15-06-08
09:31:38
回覆 (291): 6C33 SE
 
Very nice looking and compact mono-block !
Cadiver
15-06-07
00:19:32
回覆 (291): Do you still remember?
The second Monday of June was the Queen's birthday public holiday in HK prior to 1997.  
 
bobui
15-06-06
19:41:40
回覆 (290): 6C33 SE
Here is a preview of my current project. 6C33 single ended. I first hooked up a 6C33 on a test bench some six to seven years ago. It was crystal clear and powerful sound with nothing more than a weak power supply and inadequate drive.  
 
Spec:  
1. 230V HT @ 200ma for the 6C33  
 
2. E283cc (identical construction as the ECC803s) but different pin out and 12GN7 in mu follower driver circuit  
 
3. Fixed bias  
 
4. Separate B+ for driver and output valve  
 
5. Roughly 15Watts  
 
6. Tango 600ohms primary output transformer.  
 
LCR RIAA phono coming next!  
 
bobui
15-06-02
12:14:18
回覆 (289): long wait for the beauty!
2nd switch is an industrial grade spring loaded  
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A friend came over to my den last Sunday afternoon. He was so delighted with my tea and Waitrose Tea Biscuits.  
 
I told him tea bags are PG. To make good tea, you must use a Tea pot. For two persons tea. Need to throw in not two tea bags but three!!???lor!  
 
One tea bag for you, one tea bag for me and one for the pot!  
 
 
 
 
bobui
15-06-02
12:00:31
回覆 (288): long wait for the beauty!
 
 
What's more: the 2nd switch is an industrial grade spring loaded switch with triple contact pairs of 30A rating (parallel wired) to ensure uninhibited current flow at all times.  
 
limage
15-06-01
15:58:20
回覆 (287): long wait for the beauty!
limage way of handling the matter though clumsy, is in fact pretty clever have to say. Just allow the contacts of the first switch to arc and tarnish, the 2nd one being in parallel would be of the same potential on both sides, so shouldn't create any sparks what so ever when toggled either on or off. Thus, a low resistance can be maintained in the primary for ages.
Derek2A3
15-06-01
15:22:24
回覆 (286): long wait for the beauty!
Believe me, you'll be horrified!  
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I believe u!  
 
If the two switches do not touch down at the exact moment. Let say even just 3/10 of a second away. Which of the two switches induce greater damage from the spark?  
 
The one that touch down first or the one came in after? My answer goes to the one came in after. Not the one that touch down first.  
 
bobui
15-06-01
12:34:54
回覆 (285): long wait for the beauty!
 
 
Unless you have a parallel bar connected between them  
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Yes, you are right, the 2 switches are connected by wire.  
 
You may not know the extent of damages caused by arching unless you have the switch dissembled. Believe me, you'll be horrified!  
 
 
limage
15-06-01
12:18:08
回覆 (284): long wait for the beauty!
How do you manage the two switches activate (touch down) at the same second? Unless you have a parallel bar connected between them, right? if not, you basically are only using only one, you know what I mean!  
 
For high power amp such as my upcoming 3 pairs Svetlana 811, I would use this below. Pull to activate and push down to disconnect. The contact pins are much larger than a standard toggle switch and some versions can with stand as much as 100A!  
 
bobui
15-06-01
12:10:52
回覆 (283): long wait for the beauty!
 
 
Any idea how these switches are constructed — platinum contacts in oil bath?  
 
I've been searching in vain for the ultimate on-off switch for the Premier One over the last 30 years. The major problem with high powered amps is the tremendous power surge upon turn-on, which results in serious arc no matter what method has been used to have the spark suppressed. Overtime, the switch turns shit and the amp lacks the final kick of menacing power!  
 
To address this problem, I use a stupid but reliable method: dual switch in parallel. The only drawback is the sequence I have to strictly follow when turning on and off the amp. Yes, I would still have the need to service the 1st switch in a year or two, but the second switch would remain flawless for years on end.  
 
limage
15-06-01
11:58:29
回覆 (282): long wait for the beauty!
bobui
15-06-01
11:45:58
回覆 (281): long wait for the beauty!
for firing nuclear missiles in Hollywood movies. Are you sure they are radiation free?  
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Armed ---- Launch  
 
The USA equivalent of Crompton is made by GE which is also bullet proof but with a lesser extravagant military look and Japan equivalent is by Yokogawa. I have a Yokogawa, fancy attaching it to your amp, Cadiver?  
 
Something like this below-
bobui
15-06-01
11:45:11
回覆 (280): long wait for the beauty!
Those toggle switches remind me of the ones used for firing nuclear missiles in Hollywood movies. Are you sure they are radiation free?
Derek2A3
15-06-01
09:27:49
回覆 (279): long wait for the beauty!
Looks very cool, want them !!
Cadiver
15-06-01
01:18:29
回覆 (278): long wait for the beauty!
After many years of search and investigate, I finally got these below. Crompton Parkinson DC volts meters and military toggle switches.  
 
Both for my ultimate preamp/phono projects that comes with valve shunt regulated power supply and LCR RIAA.  
 
The Cromptons are true Industrial/military grade bullet proof! What a beauty!
bobui
15-05-31
22:41:42
回覆 (277): Black Magic
drink it and see if you would turn green and become incredible hulk?  
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Let me be the white mouse and try out a bottle first. "I don't go to hell, who would ar!"
bobui
15-05-19
08:37:31
回覆 (276): Black Magic
Who told you they are wine? It is already written on bottle that these are black magic solutions, drink it and see if you would turn green and become incredible hulk?
Derek2A3
15-05-18
17:51:22
回覆 (275): Black Magic
A translator flew in all the way from Aus and he is going to dinner with my family today. He brought over a bottle of this wine below. Have zero idea about this wine and in fact, I have accumulate two bottles now of unidentical vintage.  
 
Any idea? I was told some vintages only produced as little as 50 cases! Tell me about it please! I am new to red wine ar!  
 
bobui
15-05-17
19:16:53
回覆 (274): "So, if I call you, dont make a fuss"
A friend of roughly 15 years my junior just called to tell me how surprisingly pleased he is with his newly acquired Diana K Wallflower LP. LP, OK! Especially fond of the song "I'm not in love". He went on nonstop telling me how magical he feels about she on this particular song which I have no dispute at all but the thing is, he doesn't seems to realize Diana K isn't the original singer of this song.  
 
I quickly went through the album and it really didn't mention it was written and first sung by 10CC. However, it did say the song is by Eric Stewards lor which for today younger generation may have easily mistaken that Diana is the original singer for a song written by someone else which is very common is Jazz.  
 
I care and I make a fuss lor!  
 
 
 
bobui
15-05-12
23:53:47
回覆 (273): Vortexion
Abandon work this afternoon and came home early to put some finishing hours to bring life back the below cows!  
 
Vortexion is a bloody old brand from the United King of doom. These below you see were actually taken out from two mono blocks of Vortexion amplifiers named Wembledon. They were made in the late 50s and targeted only to recording studios and PA use. These cows were so old ages that all the external wires were rotten to almost like dust the minute I put my hands on them.  
 
Took them apart and went deep into the output end of the enamel copper wire to solder new external wires.  
 
Rub and sand before a primer and a coat of Hammer spray. Total over eight solid hours of hard labour.  
 
One the left are two power transformers, output in the middle and chokes> All good now for a pair of mono blocks. The output is 6.6K PP and for 35Watts at 20Hz.  
 
Anyone got an good old valves I can borrow?  
 
 
 
bobui
15-05-12
22:21:32
回覆 (272): "What more could you ask for!"
Try this my friends. My all time best Beethoven Sonata No.29, Adagio  
 
Wait till you get to around 9:20 onwards, its bloody breathtaking. To me, this is the most wonderful piece of piano solo work. "What more could you ask for!"  
 
 
bobui
15-05-08
15:19:10
回覆 (271): Happy man! Finally!
 
>>Time to reserve all you pocket money for your children piano lessons!  
 
We tried last year. When he sat down in a group keyboard class, we sat behind him, he turn around and look at us frequently, when teacher said use your 2nd finger hit the middle key, he started to cry ! That's it for the class ...  
 
Last week, we ask again if he wants to play piano, he said yes but he also said don't want to go to class. So I don't know what to do now. It's not until you experience some of these details, it is not easy to appreciate seeing other young kids playing musical instruments and liking it ...  
 
I might send him to a drum class instead ... what the hack !
Cadiver
15-05-02
10:59:23
回覆 (270): Happy man! Finally!
Nevertheless, it's live from home setting, so it still sound better than reproduced music.  
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My CEO plays for the church on a weekly basis (Sunday service) and practice a few sessions every week. Other than her usual Baroque - Handel, Bach, Purcell or Scarlatti, she sometimes treat me with short pieces of Beethoven or Chopin. My highlight of the week lor! And I have a life long entry ticket for free!  
 
Time to reserve all you pocket money for your children piano lessons!
bobui
15-04-29
23:35:33
回覆 (269): Happy man! Finally!
 
OK, I will look for run.  
 
The D and the A (#1, #4) are also my all time favorite of chop-pin.  
I use to have access to friends who play piano and I always ask him to play them, unfortunately, he & she was never able to play them continuously the entire thing. Nevertheless, it's live from home setting, so it still sound better than reproduced music.
Cadiver
15-04-29
22:39:19
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