(9 Reviews)
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5 stars are for placemarker. It would help to know ( and help Allt. sell) details such as: are tubes included [ALL ELECTRONICS: Yes, the tubes are included - you get everything in the main picture] ? The big one, is this line preamp or phono ? Ad seems to indicate phono, but then why have a volume pot - that would be on line preamp or amp, not phono. Also would be nice to have some specs [ALL ELECT: Unfortunately, we don't have any more specs at this time]. If this is a phono/mic preamp is there a way to switch from phono to mic compensation ?
This little preamp seems to work well, but there is no documentation with it, there's nothing to tell you what tubes are needed to drive it or anything else about it. The tubes are unmarked and I had to use Google translate to figure out which was the input and which was the output because all the markings are in Chinese characters. So, five stars for price and one star for documentation makes it three stars overall.
First examination of valve markings provides the numbers 6J19 OR 6J1. A search on the Web provides a data sheet for 6J1. It's in Chinese, but fortunately, the Chinese use Arabic numbers.
If you are familiar with valve data sheets, you know what parameters are probably provided:
1) Filament volts- 6,3
2)Valve layout- Pentode .
3) Design center or Max anode volts- 120
4)Design center or Max screen volts- 120
5) Anode current- 7,35mA.
6) Screen current- 3,2mA.
7) Transconductance- 5,1mA/volt.
8) Anode resistance- 12-25Kohm.
It looks like it's a sharp cutoff, low voltage pentode.
I hope that this helps.
LS-
Just got this today. Haven't tried it out. The circuit card looks good. The tubes look pretty rough, pins bent and corrosion on one tube's pins. Also no markings to indicate what type of tube. I assumed this would use 12AX7 tubes which are common in pre-amps, and I have in my parts bin. But these look smaller. Can someone tell if 12AX7 tubes will work? I'll update the review after firing it up.
If you look at the center photo above, showing the inputs, outputs, and power input; the signal input is on the left furthest from the power input. The audio output is closest to the power input. Hope this helps. I also bought the case and labeled these, but I agree that we shouldn't need to search for this type of information after purchasing the product.
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