Hi all:
Like the title says, it works!!! My first tube build. It is my interpretation of Thorsten's now-classic 2-tube ultra-simple MM phono stage. And, I did it
- right from laying out and etching the PCB to debugging the final cct.
Here's some photos...
This is the PCB under test
Ahhhh, the satisfaction. It doesn't hum, it doesn't buss or crackle - in fact it is dead silent until I feed it some signal. Then, it makes all of the right noises and so far they sound pretty right.
As always, comments welcome
Jess
Like the title says, it works!!! My first tube build. It is my interpretation of Thorsten's now-classic 2-tube ultra-simple MM phono stage. And, I did it
- right from laying out and etching the PCB to debugging the final cct. Here's some photos...
An externally hosted image should be here but it was not working when we last tested it.
This is the PCB under test
Ahhhh, the satisfaction. It doesn't hum, it doesn't buss or crackle - in fact it is dead silent until I feed it some signal. Then, it makes all of the right noises and so far they sound pretty right.
As always, comments welcome
Jess
More photos
An externally hosted image should be here but it was not working when we last tested it.
And, with the lid on...
Please excuse the clumsy work on the case top - I had an idea of a different type of tube guard - it didn't work out
Soon it will get polished and look pretty
Jess
An externally hosted image should be here but it was not working when we last tested it.
Please excuse the clumsy work on the case top - I had an idea of a different type of tube guard - it didn't work out
Soon it will get polished and look pretty
Jess
Thank you all for the kind words
Yeah, I was really amazed. Once I got it running and ready to hear, at first I thought that it wasn't working. I had to turn the volume almost to the max before I heard that faint rushing sound that tubes make. It really is quiet.
Next steps will be adding CCS to the plate supply of the 6DJ8 and a better PS, maybe FET regulated. And, of course, some work on the cabinetry
Jess
Yeah, I was really amazed. Once I got it running and ready to hear, at first I thought that it wasn't working. I had to turn the volume almost to the max before I heard that faint rushing sound that tubes make. It really is quiet.
Next steps will be adding CCS to the plate supply of the 6DJ8 and a better PS, maybe FET regulated. And, of course, some work on the cabinetry
Jess
The thread where I found Thorsten's phono schematic is here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=28957
(it's about 2/3 of the way down the page.)
As for parts - well.....
As said, I laid out and etched the PCB myself (hence the unjustified pride ) I used ExpressPCB software and the toner transfer method. If anyone wants the artwork, I could post it, but I don't think it is anything special.
As may be seen, I cut 7/8" holes for the tube sockets in the PCB material and brought the various traces up to the sockets, with very short wire jumpers to bring the signals and voltages from the PCB to the tube socket pins. (I will try to take a photo of the underside of the board, but that will be next week).
Parts are carefully matched, but probably not the best 'audiophile' choices. Most of the Rs are salvaged from an old Grundig radio. The caps are all new, but parts I have had hanging around for years, except for the 2.2uf output caps (a gift from a buddy-thanks Jerry).
I won't get into the PS now, 'cause I am feeding it with suitable power from another tube device. When I build a dedicated PS for this phono stage, I will post it.
Jess
http://www.diyaudio.com/forums/showthread.php?s=&threadid=28957
(it's about 2/3 of the way down the page.)
As for parts - well.....
As said, I laid out and etched the PCB myself (hence the unjustified pride
) I used ExpressPCB software and the toner transfer method. If anyone wants the artwork, I could post it, but I don't think it is anything special.As may be seen, I cut 7/8" holes for the tube sockets in the PCB material and brought the various traces up to the sockets, with very short wire jumpers to bring the signals and voltages from the PCB to the tube socket pins. (I will try to take a photo of the underside of the board, but that will be next week).
Parts are carefully matched, but probably not the best 'audiophile' choices. Most of the Rs are salvaged from an old Grundig radio. The caps are all new, but parts I have had hanging around for years, except for the 2.2uf output caps (a gift from a buddy-thanks Jerry).
I won't get into the PS now, 'cause I am feeding it with suitable power from another tube device. When I build a dedicated PS for this phono stage, I will post it.
Jess
Hear the silence..
Congrats Jess:
Doesn't feel great when theory becomes reality right in front of you??
All that research & head scratching has now paid off....with your magnificent phono stage whispering at you.....
Now that you have er' all up & running & dialed in...take you time designing an enclosure/cabinet.....something well deserving of your prized creation.
_____________________________________Rick............
Congrats Jess:
Doesn't feel great when theory becomes reality right in front of you??
All that research & head scratching has now paid off....with your magnificent phono stage whispering at you.....
Now that you have er' all up & running & dialed in...take you time designing an enclosure/cabinet.....something well deserving of your prized creation.
_____________________________________Rick............
Yep, it sure does!!!
Well - I was listening last night and it seems too bright in the highs (and a little muddy in the bass). I think that the 1nF cap I used in the RIAA eq stage is not doing a good job. I will replace it asap. The 2 10nF between the gain stages I am fairly sure of as they measure within .25% of each other and about 1% from spec.
As for the muddy lows (not bad, just noticable, as I have a Velodyne LDU 12 subwoofer which can do really good bass), I am less sure what may be causing this. I will have to scratch my head some on this.
Indeed.
I prefer the appearance of wood (plus I can work it not too badly) but a phono stage needs good EFI protection, so may buy a suitable case.Jess
nice work!
i did a similar scratch built phono stage last year. used almost all spare parts that i had around. maybe a $50 project. i'll have to post a schematic.
basically, its 2 6eu7's (sections both paralleled) loaded by CCS diodes with a passive EQ in the middle. i wanted a ~2Vrms output from it, so i needed about 55dB of gain. the great thing about the CCS loading is that i could use back to back filament transformers for a 150V power supply. plenty enough headroom and linear too. it does want to pickup noise from the psu, but otherwise it can be very quiet. not bad for a back-of-an-envelope design.
guess i should check the riaa accuracy sometime. sounds good though.
enjoy!
i did a similar scratch built phono stage last year. used almost all spare parts that i had around. maybe a $50 project. i'll have to post a schematic.
basically, its 2 6eu7's (sections both paralleled) loaded by CCS diodes with a passive EQ in the middle. i wanted a ~2Vrms output from it, so i needed about 55dB of gain. the great thing about the CCS loading is that i could use back to back filament transformers for a 150V power supply. plenty enough headroom and linear too. it does want to pickup noise from the psu, but otherwise it can be very quiet. not bad for a back-of-an-envelope design.
guess i should check the riaa accuracy sometime. sounds good though.
enjoy!
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