If you have this circuit wired up on a chassis , it might be a good idea to take off all passive parts and solder on new ones as might be suggested by one of us on the forum.
What dc supply do you have ( volts)
What is the signal level of your source. ( CD player about 1 to 2 volts)
How much do you need at the output ( 2 volts ? ) Does it go to a power amp or a headphone amp ?
Is there a long interconnect cable ( in meters!) between the pre-amp and the power amp?
What dc supply do you have ( volts)
What is the signal level of your source. ( CD player about 1 to 2 volts)
How much do you need at the output ( 2 volts ? ) Does it go to a power amp or a headphone amp ?
Is there a long interconnect cable ( in meters!) between the pre-amp and the power amp?
If it's the way you drew it, then, yes, it's haphazard. This would have trouble swinging as much as 1 volt without severe distortion. Define what you want the preamp to do (gain, output impedance, max output voltage, noise) and it can be redesigned to work considerably better.
yes it does distort easily and it hums
i want it to run into my st70 so i can listen to some nice music (notice how im keeping my cool) i just want to listen to some nice music is all. i thought this thing would do now it turns out ... etc.
if you could guide a blind m
i read that diodes drop the voltage by 30% i think that would be too much what about two parallel diodes, one pair for each leg. 1n4007s?
It wouldn't surprise me, he designs by ear. Still, the schematic makes little sense so I understand the disbelief expressed here.
how about my disbelief after waiting 6 weeks for delivery now you scholarly gentlemen are asserting that the design is haphazard and "odd". and then someone says i can run the cd player right into the amp ... well .... i didnt even get tubes with the kit etc yikes.
can i use 1n4007 diodes to drop the heater current?
"where is the regulatory agency? "
We are, it's a bad design.
TUBE RECTIFIED STEREO PRE-AMPLIFIER KIT
I like the chassis so you could change the schematic and enjoy a decent preamp. Gain is going to be a problem, the ST70 has a high input sensitivity.
We are, it's a bad design.
TUBE RECTIFIED STEREO PRE-AMPLIFIER KIT
I like the chassis so you could change the schematic and enjoy a decent preamp. Gain is going to be a problem, the ST70 has a high input sensitivity.
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An externally hosted image should be here but it was not working when we last tested it.
I can't read the values but the topology is the same as the schematic chopchip posted.
Hello,
Too much gain is going around especially with CD players. A passive preamp can suck the life out of the music. I have been enjoying an Aikido Cathode Follower buffer with pleasant results. A B1 buffer also works well.
The specification sheets say 6.3 volts +- for the heaters. 7 volts is above the recommended + 10%. 6 volts would be better.
You might try rolling in a 6CG7 or 12AU7 to reduce the gain. They pin the same as your
6N1P’s.
DT
All just for fun!
Too much gain is going around especially with CD players. A passive preamp can suck the life out of the music. I have been enjoying an Aikido Cathode Follower buffer with pleasant results. A B1 buffer also works well.
The specification sheets say 6.3 volts +- for the heaters. 7 volts is above the recommended + 10%. 6 volts would be better.
You might try rolling in a 6CG7 or 12AU7 to reduce the gain. They pin the same as your
6N1P’s.
DT
All just for fun!
i just built a litte input/output box with a volume control in the middle and im running the cd player into the amp. sounds reasonable, i guess this is as good as it can get assuming that a preamp will just alter the sound. now i can use my expensive patch cords becuause they improve the sound
so the st70 has low input sensitivity eh? i guess that would make gain a problem. well at least i have a nice transformer and chassis. maybe ill develop enough understanding by default to do some designing
so the st70 has low input sensitivity eh? i guess that would make gain a problem. well at least i have a nice transformer and chassis. maybe ill develop enough understanding by default to do some designing
yeah that is the frightfull image of my horrible travels through the land of deceit in search of sonic bliss. ill just start practicing my plasitic recorder more with earplugs in to improve the sound quality
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Yes, but note that you cannot use them for the entire heater supply (of 4 tubes) due to their maximum rating which would be exceeded.
In general diodes don't drop 30% of voltage across them, they drop 0.65V (or more - depending on current) per PN junction.
If you intend to keep the weird arrangement of paralleled 6N1P tubes for a combined total of four tubes you are going to need 4 duiodes (in case of DC supply) or 8 (in case of AC supply).
First determine whether your heater supply is AC or DC. Use voltmeter set to DC range to do that. If you get stable reading, reverse the leads and measure again. You should get same stable reading but with opposite sign (if it was -7V before, it should be 7V after reversing the leads). If you get odd readings that are close to 0V and/or jumping up and down all the time, switch your meter to AC range and measure again to confirm that you've got AC heater supply.
yeah, it is ac and i think that is why the thing is a humbug. the supply voltage comes directly from the secondary at well over 7 volts. the designer advises to install series resistors to bring down this voltage but he didnt include them in the basic design and does not supply them. i figured that 1 ohm 2 watt resistors would the job. the filaments pull 300 ma each. ill just have to find some probably order them via ebay.
i would like to see a better design for these components i looked aikado but will have to look further.
thanks a lot!
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