Primary impedance for el 34

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wiz
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Primary impedance for el 34

Post by wiz »

Hi all,

I want to upgrade the O/T in my Laney GH-50 and wondering what you guys think the ideal value tor the primary Z is for el34, 6ca7, kt77 tubes is?

I'm considering MM with 4400 ohm, also waiting to hear back from laney about the stock trannies value. According to the schemo it runs about 402v at the transformer (dunno if that helps).

Thanks in advance. Wiz.
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ToneMerc
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Re: Primary impedance for el 34

Post by ToneMerc »

I don't know what's ideal, but I don't think you can go wrong around 3200-3400 for a pair.
tubeswell
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Re: Primary impedance for el 34

Post by tubeswell »

1k7 to 5k range with something like 2k5 to 3k2 being more 'optimal'
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jelle
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Re: Primary impedance for el 34

Post by jelle »

It depends on your expectations...



Do you expect tight lows and a lot of marshall 50w 70's gain or are you looking for AC/DC lead gain which is more dependant on KT66 powertube distortion? They do sound different.

:?: :?:

If you go with KT77, EL34's I'd go with 3.5K/4K @ 400V B+. Just IMHO. :D
wiz
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Re: Primary impedance for el 34

Post by wiz »

hey thx all, im using a muff for fuzz so whatever compliments that i guess, but i do prefer the sound of el34's rather than 5881/6l6's. I know tone is such a subjective thing but trying to find as many opinions before i go ahead and replace the o/t.
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VacuumVoodoo
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Re: Primary impedance for el 34

Post by VacuumVoodoo »

jelle wrote: If you go with KT77, EL34's I'd go with 3.5K/4K @ 400V B+. Just IMHO. :D
I second this.
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JamesHealey
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Re: Primary impedance for el 34

Post by JamesHealey »

5.2k load those puppies up good and get a wide frequency range and lots of drive-compression
wiz
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Re: Primary impedance for el 34

Post by wiz »

Hey all, just heard back from Laney and was told the dc resistance O/T primary is 102 ohms.
Cliff Schecht
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Re: Primary impedance for el 34

Post by Cliff Schecht »

Unless you are testing the original OT for continuity that number is pretty useless..
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Kagliostro
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Re: Primary impedance for el 34

Post by Kagliostro »

Not able to explain better

The choice of the OT depends on the type of tubes, on the plate voltage and on the number of tubes you use for your PP

as to establish a correct OT for one tube you must look to the curves of the tube in the datasheet looking to match the voltage (B+) of your PT

it isn't a simply thing, so many peoples look to an existing amp with near same features and plagiarize the OT impedance

Kagliostro
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jon
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Re: Primary impedance for el 34

Post by jon »

I've heard of EL34's running up to 8K. I think 5K is just about right though
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VacuumVoodoo
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Re: Primary impedance for el 34

Post by VacuumVoodoo »

Even as high as 11k for one pair.
B+=800V
Usg=400V
Pout=100W
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Ian444
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Re: Primary impedance for el 34

Post by Ian444 »

Funny you should mention 11k, I pulled some trannies from a Chinese EL34 PP stereo amp and they were 11k, I sort of gave up on ever using them in anything, they are about the size for 80W and the B+ in that amp was around 460V. I wondered how it ever worked :)
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VacuumVoodoo
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Re: Primary impedance for el 34

Post by VacuumVoodoo »

EL34 strapped for triode operation, cathode self-bias, no bypass cap on cathode resistor. Raa 10k and 15W output at <1% distortion. Hi-Fi amp therefore big OT, probably spec'd down to below 20Hz.
See Mullard data sheet page 3:
http://www.mif.pg.gda.pl/homepages/fran ... e/EL34.pdf
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Roe
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Re: Primary impedance for el 34

Post by Roe »

for a pair of el34s at 400v, 3k5 like a 784-139 is perfect
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