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Old 14th December 2010, 01:27 PM   #21
aldovan is offline aldovan  Brazil
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Default Output transformer

Quote:
Originally Posted by SemperFi View Post
Man I just love small and cheap amps now Which OT are you using? I am mightily impressed with the XSE series from Edcor, tho not with pentodes. (triodes drives them wonderfully)
My friend

The output transformer Is made in a transformer factory here in Brazil. I make the calculus and the industry build for me.
But I will get a Edcor GXSE10 for a comparation...

Aldovan
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Old 16th November 2012, 09:21 PM   #22
Karsan is offline Karsan  Spain
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Hi, where did you get the grid curves for triode operation of the 6j9p?
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Old 16th November 2012, 10:32 PM   #23
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Quote:
Originally Posted by Karsan View Post
Hi, where did you get the grid curves for triode operation of the 6j9p?
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Old 16th November 2012, 10:38 PM   #24
Karsan is offline Karsan  Spain
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Ok thanks!
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Old 17th November 2012, 01:05 AM   #25
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Super cheap...?

1. Change E180F to 6AU6, there's boatloads of these around and the price is good. More abstract choices abound, especially oddball triode-pentodes. Nothing wrong with letting one half of such a device go unused, if you only need one. And hey, you could add a "tube roll" switch (at moderate price increase) to change between the triode and pentode in the envelope!
2. Replace LED with resistor. LEDs cost money.
3. Don't parallel caps: besides being a useless procedure, they waste space. Additionally, don't use name-brand capacitors; end-users know the sellers simply pump up prices artificially on components that have no audible effect whatsoever. I haven't seen many capacitors any cheaper than Cornell-Dubilier DME series, plus, they're really, really compact. Absolutely perfect for coupling use.
4. 6W6 is an oddball choice, but makes a reasonable triode. Prices may vary. 6V6 would be more common, and is in current production [I think..??], but price varies accordingly with market. YMMV. Rolling options include... pretty much any comparable pentode, certainly the 6Y6 mentioned, but also 6K6, 6F6 (a bit lower gain), higher voltage variants like 12L6, and even miniature variants thereof, like 50C5, etc.
5. The output transformer isn't specified, but do make sure to grudgingly spend a couple bucks there, you won't regret it.
6. Dump the series choke, it's expensive dead weight. Yeah it makes things quieter, but the thread title is "Super cheap amplifier" after all!! All right, you probably do want the choke in there, but only grudgingly.
7. We've already got silicon diodes, dump the damper. Also, less filter capacitance could be used, at expense of ripple levels.

Tim
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Old 17th November 2012, 03:02 AM   #26
AJT is offline AJT  Philippines
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Quote:
Originally Posted by aldovan View Post
Why spend money on expensive chinese tubes ?
With 6W6GT you have a better sound quality than the Chinese tubes for only a feaw dollars!!! The plates of the 6W6GT are balck and well sized, as were the valves in the U.S. end of the 50s. Nowadays we do not manufacture more valves with this quality. What is sold today is a beautiful product, but not as durable.
My Shuguang 300B are stored !
I'll make a lamp with them ...
i tend to agree...i use 12W6/12EN6 in guitar pp amps and is preferred over the EL84, i don't know why, but some guitarist like them...

i suspect that in a hi-fi amp, they will sound good....
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Old 17th November 2012, 03:12 PM   #27
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Use two parallel interstage caps /1 uF and 330 nF/ with different structure is not good idea. It decrease quality of sound in M and H freeq., because small AC current across different media. Please, check with only one of both caps and listen carefully.
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Old 18th November 2012, 05:54 PM   #28
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I would like to see it with a 6Au6 or 6Sj7. A cathode resistor instead of an Led. Loose the choke, keep the damper tube and I don't think it will make it sound tubey but I like the slower warm up. Use a cheap Hammond 125 transformer and loose the paralleled caps. I have some 6W6's in my tube caddy to try.
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Old 18th November 2012, 07:11 PM   #29
jane is offline jane  Norway
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I think I would have decoubled the 6W6 cathode resistor(s)..
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Old 18th November 2012, 08:27 PM   #30
aldovan is offline aldovan  Brazil
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Default If you want more cheap, go to silicon amplifier

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Originally Posted by Original Burnedfingers View Post
I would like to see it with a 6Au6 or 6Sj7. A cathode resistor instead of an Led. Loose the choke, keep the damper tube and I don't think it will make it sound tubey but I like the slower warm up. Use a cheap Hammond 125 transformer and loose the paralleled caps. I have some 6W6's in my tube caddy to try.
The russian 6J9P cost U$1 for me. The 6AU6 and 6SJ7 have poor sound.
A led cost cents...if I remove the damper, the choke and the others components, the quality down a lot. Them is best use no power transformer and connect direct to 127V using tubes with 50V FILAMENT.
The hammond 125 is very bad in frequency response...
My friend, you probabily is a silicon amplifier user...
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