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Old 26th February 2008, 10:17 AM   #1
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Default The end of the 300b Dream?

Hi
After having been set (pardon the pun) on building 300b monoblocs and buying the iron, I am left wondering wether i should go ahead given the dramas with valve life and quality.
I have a chinese version and bluntly speaking whould love 15 watts or so so I had thought of a parallel version.
Single tube alternatives?
845.. scary volts inside and am not willing to risk it.
6c33c Maybee provided I could get some reliable ones and good sockets and 8 amp heater supplys....
kr tubes.. expensive, dont sound like a 300b and future supplys questionable...
So have i missed anything? What have others done for 15 watts and above of set pleasure?
regards
Nick
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Old 26th February 2008, 10:27 AM   #2
Zen Mod is offline Zen Mod  Serbia
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Default Re: The end of the 300b Dream?

Quote:
Originally posted by duderduderini
Hi
After having been set (pardon the pun) on building 300b monoblocs and buying the iron, I am left wondering wether i should go ahead given the dramas with valve life and quality.
I have a chinese version and bluntly speaking whould love 15 watts or so so I had thought of a parallel version.
Single tube alternatives?
845.. scary volts inside and am not willing to risk it.
6c33c Maybee provided I could get some reliable ones and good sockets and 8 amp heater supplys....
kr tubes.. expensive, dont sound like a 300b and future supplys questionable...
So have i missed anything? What have others done for 15 watts and above of set pleasure?
regards
Nick
well - if you have doubts ......... maybe you aren't nutz enough?


in that case - go for any of craziest Pass amps .......

or - find less demanding spks, and use some less expensive tubes for output ones ............ buy enough of them for rest of life
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Old 26th February 2008, 10:33 AM   #3
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Default No Honest I am nuts

I have to be nuts... Im into tubes!!!!
So 6c33c or 300b?
Nick
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Old 26th February 2008, 10:53 AM   #4
Zen Mod is offline Zen Mod  Serbia
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Default Re: No Honest I am nuts

Quote:
Originally posted by duderduderini
I have to be nuts... Im into tubes!!!!
So 6c33c or 300b?
Nick

you already have iron for 300B ........ so ......

just find a way to buy few pairs of decent ones ( find russian mistress , or something similar ) ........
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Old 26th February 2008, 02:38 PM   #5
arnoldc is offline arnoldc  Philippines
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I was in the same dilemma as you- 6C33C-B vs. 300B x 2 to drive a commercial speaker (LSA1) that I really like.

I have embarked on a project to build a pair of PP 300B. Then I heard a LAMM driving them, so I thought of building the 6C33C-B circuit of Borberly Audio, but then I can't get the tubes, so I'm back with the PP 300B....

I'm nuts, maybe I should build them both.
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Old 26th February 2008, 04:03 PM   #6
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Quote:
Originally posted by arnoldc
..........

I'm nuts, maybe I should build them both.

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Old 26th February 2008, 04:34 PM   #7
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Default Re: The end of the 300b Dream?

Quote:
Originally posted by duderduderini
Hi
After having been set (pardon the pun) on building 300b monoblocs and buying the iron, I am left wondering wether i should go ahead given the dramas with valve life and quality.
You've come this far, go for it. Quality may have been an issue in the past, but it's been improving lately.

Quote:
Single tube alternatives?
Unforch, there really aren't any. The original 300B came out the same year that the 807 did. That was the end of the triode era, and there is a definite lack of AF power triodes (though RF triodes were rather common, but as "zero bias" tubes for the most part: Class A2 required, and the usual pentode problems: high rp's, higher h3 and above) in the same class as the 300B.

Quote:
What have others done for 15 watts and above of set pleasure?
regards
Nick
What I'm doing is working on a design for an 845 based SET. The big volts don't bother me, the OPT iron is available (from Lundahl, not cheap, but it's available) and PSs can be made easily from "control xfmrs". Other than that, perhaps trioded 813s (still big volts required) or perhaps some big HD pents can be trioded.

I was originally considering a SET based on the 812: moderate voltages, Class A2, decent output. However, Jack at Electraprint couldn't promise that the necessary 8K4 : 8R OPT wouldn't be good enough for anything other than a gee-tah amp. (Kudos to Jack for being honest about this, and not ripping me off ) SET gee-tah amps aren't of any use to me, and not exactly a practical proposition for a player. So I dropped that design if favour of the 845.
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Old 26th February 2008, 04:48 PM   #8
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The RCA type 1623 is the poor mans 300B if you can find any.

Victor
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Old 26th February 2008, 08:52 PM   #9
Jeb-D. is offline Jeb-D.  United States
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If you already bought the iron for 300b you should stick it out.

For future SE builds, I would recommend the 6c33c. I've gotten 15Wrms out of one. The 6c33c horror stories come from people using them in designs that have multiples in parallel and/or in circuits that require precise balance.

Cathode bias SE - you can just pop one in and from time to time clean the pins and sockets. That's it!

Fixed bias SE - pop it in, bias it (be sure to design it so the pot doesn't have a lot of range), let it heat up for 30min then adjust the bias again. Then use the amp regularly for a few days to a week, then re-bias it. After that point you really shouldn't have to mess with it for a long time. Just every few months clean the pins and sockets and re-check the bias if you want to be carefull. I ran my fixed bias 6c33c SE for a year without problems (I didn't clean the pins, sockets or have to re-bias it). It is now parted out to donate parts to a better 6c33c design i'm building.

The 6c33c sounds excellent and has a very unique tone. It's Probably my favorite tube.
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Old 26th February 2008, 10:21 PM   #10
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Default Where does one procure a decent 6c33c?

Hi Jeb
Do you have a reliable source of these tubes?
How would you describe the sound of them.. I dont mind smooth sounding tubes with good bass at all
regards
Nick
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