Hello fellow diyers...got me vintage tube jap preamp circa 1967 on the way and was just doing some research on it and nothing much about it...this pre will be my modify unit...I have a AI modulus 2c and I don't want to mess with it yet...this one is all point to point and no ic at all so can be easily upgraded/modified...my question is what tube brand/model should I try?...label says ecc82/83...it takes 4 tubes total...two for phono likely...here a link to the unit I purchased. Thanks in advance for any advice you can give I love you guys. Noriyuki Kawano Tube Preamp with Phono Stage Luxman Transformer Perfect Sound | eBay
thanks eli...just purchased a couple new sovtek and used rca 5963 on line...5963 must be the american equivalent to the ecc82?...any particular reason for this choice...I should invest in a tube tester one day as i may end up with alot of tubes I will want to sell
The 60 bucks invested doesn't seem like much to me for tweaking a preamp and would pay more for better tubes if there was a chance that they would be better and I don't even know what's already in it...however at the relatively inexpensive tweak I am in...I have spent far more messing about with $500 phono cartridges... how you think this pre will compare to AI 2c with used bugle boys for phono and new EH 6922 for line
okay...what do you suggest Enzo and what is an active load with a mu output...I am an electrician but I don't know much when it comes to electronics...sorry but please elaborate
The ECL82/6BM8 is a small signal triode and a power pentode inside a single envelope. The type is used in power amps of modest wattage.
The ECC82/12AU7 is a symmetrical twin triode.
The "crowd" really needs to see a schematic, before rational tweak recommendations can be made.
If the Japanese preamp uses 1N4nnn rectifier diodes, replacement with UF4007s is 100% safe and should yield a small performance improvement.
The ECC82/12AU7 is a symmetrical twin triode.
The "crowd" really needs to see a schematic, before rational tweak recommendations can be made.
If the Japanese preamp uses 1N4nnn rectifier diodes, replacement with UF4007s is 100% safe and should yield a small performance improvement.
looking at the pics from the link above the diodes that I see are tophat shaped soldered directly to tranny and one side has ball shaped diodes if thats what they are?..so this unit not using UF4007s...I think
I use dn2540 depletion mosfet as active loads, just needs two resistors and your off, led to bias on the cathode. Low mu small Idh Triodes are not that common but 6sn7 was popular and much more linear though you'd need an octal socket. I use 4p1l but you'd ideally need a more complicated power supply for that.
Noticed this item on that page:
"...Amplier [sic] was manufactured for Japan so its AC electric volt is 100-110V 50/60Hz, you need step down transformer if you want to use it in 220V area."
You're in Calgary AB Canada; power there is same as here in the US, no? 117VAC nominal, perhaps as high as 125VAC. You would need a Variac, a bucking transformer, or a power-transformer replacement.
Take care,
—
J. E. Knox "The Victor Freak"
Definitely do something to reduce the line voltage to 100V if this is designed for Japanese mains voltage as opposed to US/CA mains voltages which nominally are 20% higher. (120V) Japanese specified transformers often fail quickly on our mains voltage, and if the transformer does not everything else will be overstressed. Check that there is not a 115 - 117 tap on the power transformer, if not you need to reduce the voltage.
Look up bucking transformer configuration at get yourself a 15 or 18V transformer of 25VA or so..
This unit might be rare/collectible - I'd hesitate to suggest anything beyond tube rolling here without knowing better, and Eli's suggestion for tubes seems quite reasonable.
Look up bucking transformer configuration at get yourself a 15 or 18V transformer of 25VA or so..
This unit might be rare/collectible - I'd hesitate to suggest anything beyond tube rolling here without knowing better, and Eli's suggestion for tubes seems quite reasonable.
Use a small inexpensive transformer to buck the line voltage to 100V, a resistor will work, but will dissipate appreciable power as well as substantially raise the supply impedance at the power transformer primary. (Depending on the supply design the high supply impedance might also affect the performance of the pre-amplifier.) Since it is a pre-amp the current draw is likely not to vary much with signal level, in the case of a power amplifier this would be a pretty bad idea.
A small toroid or EI rated at 50VA and 20V should suffice. Suitable transformers are made by Antec and many others.
A small toroid or EI rated at 50VA and 20V should suffice. Suitable transformers are made by Antec and many others.
looks like it runs on 100-110v you will need to get a step down transformer or modify the power supply to run on 120-130 as that is whats coming out of our walls today. With 20 extra volts on the primary your secondary will be much higher than it was ment to run and may even red-plate.
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I don't see the logic..how can a resistor be any worse than the bucking tranny when it comes to primary impedance...yes the resistor dissipates power but the pre get its voltage/current from the rather large filter/reservoir caps
Because the resistor adds significant series resistance, the transformer just transforms the already rather low source impedance of the mains, and only very slightly increases the source impedance.
The voltage regulation in the face of varying loads will be much better due to the much lower source impedance which may be less critical since this is not a power amp. I am not sure what the effect of the altered peak to average ratio on the AC input will be on your B+, because as the rectifiers start to conduct the charging current will cause an increasing drop across that resistor and the voltage at the peak will drop slightly more than it normally would. Might not even matter, all I can say is I never use resistors for this application assuming that the designer expected relatively stiff mains voltage at the input of his power transformer.
The voltage regulation in the face of varying loads will be much better due to the much lower source impedance which may be less critical since this is not a power amp. I am not sure what the effect of the altered peak to average ratio on the AC input will be on your B+, because as the rectifiers start to conduct the charging current will cause an increasing drop across that resistor and the voltage at the peak will drop slightly more than it normally would. Might not even matter, all I can say is I never use resistors for this application assuming that the designer expected relatively stiff mains voltage at the input of his power transformer.
I just got home today and unpacked this pre and took the covers off...surprise I didn't think that each tube could be a stereo tube??...after staring at the bottom wiring for a bit I could see that both phono channels entered one tube first...the picture in the link will also show this...two coax type cables from phono definitely go first to one tube??
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