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Old 12th July 2012, 03:22 PM   #1
b3nny11 is offline b3nny11  Yugoslavia
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Question ECC85, EL84 tube amp please help.

hi to all,
i'm new here. i have few tubes myself and i want to make a tube amp but i can't fid the right schematik so i would be thankfull if someone could help. i scavanged 2 el84 tubes from old broken radios and whit them main transformator and the output transformators. i alsso have 1 6l6gc, ECC85, 3x EM08 and more frome old tv's a friend gave me. i would be realy happy if someone would help. thanx. the problem is mostly with the output transformator. it has 3 connections primary from the tube and 2 for a 4ohm speaker marked max power for 4 watts.
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Old 12th July 2012, 04:42 PM   #2
DF96 is offline DF96  England
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You can use the ECC85 in any ECC81 circuit, just by wiring the heater correctly. However, ECC85 is getting rare and expensive so a replacement is likely to cost more than ECC81.
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Old 12th July 2012, 05:20 PM   #3
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I've no shortage of ECC85. There also must be a chnese sub, the Dared/Fat Boy/HCT hybrid amp uses them as pre-amp tubes.

Somewhere there is a site with a series of ECC85/EL84 amps. They are PP but might give some clues if you want to go stereo SE amp.

Thread: Wim's DC EL84 amp

updated URL to site EL84 DC coupled tube amp

If as DF96 says, it can drop into an ECC81 circuit, search out RH84.

dave
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Old 12th July 2012, 07:45 PM   #4
b3nny11 is offline b3nny11  Yugoslavia
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well yes it's pretty expensive the ecc85. 22 Euro for 1 tube. but some schematics would be helpfull... i have no luck finding anything... as said the most problem are the output transformers. most schematics have only 2/2 ends mine have 3/2 ends
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Old 12th July 2012, 09:10 PM   #5
b3nny11 is offline b3nny11  Yugoslavia
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hehehehe lool well thanx for everything and trying to help me...

i jus brew up a low voltage amp out of those two el84 using only one i think that on's wor of ther's bed sound quality and just 2.4 plate current as shown on foto...

i just took some aligatorclips power supply... the gird current is shown on foto, the voltage driving the tube is ~25volts it's perfectly for my headphones.
i have that feeling that somethings is bad but it's working... pretty good sound tough! if i done something wrong just say so...

OMG! i can't upload the immage!
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Old 12th July 2012, 09:42 PM   #6
oshifis is offline oshifis  Hungary
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Don't use ECC85 for audio (unless you want to experiment). The are UHF variable transconductance (= nonlinear) triodes. They are designed so that the AGC circuit adjusts their gain by varying the grid voltage. They will distort the audio signal. Better alternative is the ECC88 (lower gain) or ECC83 (higher gain). You can use also ECC81, ECC82, and you can find circuits also with ECF86, etc.
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Old 12th July 2012, 10:06 PM   #7
DF96 is offline DF96  England
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The ECC85 data sheet does not mention AGC. Example circuits for VHF front-ends using ECC85 usually omit AGC. The mutual characteristics for the ECC85 and ECC81 look very similar. The 85 really is an 81 with internal screen and different heater. Neither triode is particularly linear, but OK for small signals and possibly balanced circuits like LTP. ECC83 or 88 will be more linear in appropriate circuits.
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Old 14th July 2012, 10:55 PM   #8
b3nny11 is offline b3nny11  Yugoslavia
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ok i have a good schematic... but.... it's not good... as i connected the power tube as shown both way's i got red plated tubes... luky they're working...

the ecc 85 is pretty good as a preamp tube.

the first foto is the lov voltage amp... the big trafo is just for the fillaments...
later i expanded to stereo the sound was excelent...

the second should be the schematic with wich i got red plated tubes...
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Old 15th July 2012, 12:21 AM   #9
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That schematic shows a cathode resistor suitable to be shared by two output tubes. For one tube try twice as many Ohms.

All good fortune,
Chris
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Old 19th July 2012, 10:27 AM   #10
b3nny11 is offline b3nny11  Yugoslavia
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Default SUCCES!

so... after muh searching i finaly found 1 schematic that maybe good.
well let's hope that it is good...
just need to get all the parts.

i also scavanged some tubes aswell! many probably unusable but what can be done abut it.
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