Why don't we try and figure something out together? The only thing I've come up with so far is a 6N1P and BUF634. I can't find much info on signal levels and such. Do you have any idea what the normal signal level from a passive bass pickup is? The gain of the 6N1P is 33, and from what I can figure out that seem to be roughly 15dB.
Hi!!!!
I dont know how much I can help to design a tube amp. What I can offer is some tube manuals/datasheets, my father used to build tubes stuff. But he dont know about hi-fi, only radio amps......
I Think that I have lot of 12ax7 tubes for the project.
I will use an active bass guitar so I need both inputs. I dont know how to design a preamp for bass, I dont know nothing about impedances of bass pickups.
If there is anything i can do, tell me. I also have some tube manuals, schematics, but they're like 30 years old.
thanks!!!!
I dont know how much I can help to design a tube amp. What I can offer is some tube manuals/datasheets, my father used to build tubes stuff. But he dont know about hi-fi, only radio amps......
I Think that I have lot of 12ax7 tubes for the project.
I will use an active bass guitar so I need both inputs. I dont know how to design a preamp for bass, I dont know nothing about impedances of bass pickups.
If there is anything i can do, tell me. I also have some tube manuals, schematics, but they're like 30 years old.
thanks!!!!
Just tell me what kind of features you want. Im going to buy my first bass guitar in the next 2 weeks. I have never played any kind of string instrument before, so you probably have a lot of things to teach me about what kind of effects and tone controllers would be nice to have. My first idea was to just build a small gain stage with a low mu (gain) tube and just a buffer but it looks like the signal might me a bit high to start with. I was aiming for just a bit over normal home stereo equipment line level but assuming closer to 2-300mV from the guitar Im afraid i will blow up the opamp or buffer on the output. I cant do any measurements before I get my bass.
You could try to build the one in the picture. It's a very simple schematic and sounds very good indeed, I recently built one myself. The original Alembic unit has two identical channels (which are modelled after Blackfaced Fender amps). I built a preamp with only one channel, and added "bass-shift" and "treble-shift" functions like present in the Mesa Boogie Bass400. I have built that preamp as well (a long time ago), and didn't like it much.
I did redesign the powersupply with DC heater supply, and B+ with a overkill amount of capacitance (had a bunch of caps lying around).
The preamp is easy to build and sounds super, I would say a fine candidate for a first project (if you treat the HT with the appropriate amount of caution).
I did redesign the powersupply with DC heater supply, and B+ with a overkill amount of capacitance (had a bunch of caps lying around).
The preamp is easy to build and sounds super, I would say a fine candidate for a first project (if you treat the HT with the appropriate amount of caution).
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Hello Mikael,
I am not much of an EE guy (rather ME) so I didn't measure anything, but this schematic is built by Alembic so I just considered it a finished design. I did hear someone say there is a mistake in the schematic somewhere.
But you are right, when using my (active) bass, the output is quite "hot", I am thinking of adding a 6db pad.
I am not much of an EE guy (rather ME) so I didn't measure anything, but this schematic is built by Alembic so I just considered it a finished design. I did hear someone say there is a mistake in the schematic somewhere.
But you are right, when using my (active) bass, the output is quite "hot", I am thinking of adding a 6db pad.
zafira1981 said:
sorry I dont know what you meanmy english is not good
Sorry, it was a humorous reference to the movie "spinal tap" :
http://www.spinaltapfan.com/atozed/TAP00160.HTM
Rigth now I'm copying the mesa boogie bass 400 circuit because it's not quite clear the image, and I'm not sure about all the values. Can someone with experience tell me the rigth values of the marked components?
i think:
1) 3.3M
2) no idea
3) 33K
what do you think?
Another question. The pots (volume, bass, treeble, etc) should be all logarithmyc?
thanks!!!
An externally hosted image should be here but it was not working when we last tested it.
i think:
1) 3.3M
2) no idea
3) 33K
what do you think?
Another question. The pots (volume, bass, treeble, etc) should be all logarithmyc?
thanks!!!
Hello Zafira,
I don't remember the pots I used but for the MESA preamp, but I remember I wired them backwards. I also think the mid had all of it's control in a very small rotational area, indicating I used a LOG pot instead of LIN?
I had a look at the paper version of the tube amp book which has the same schem, and 1 is indeed 3,3M and 3 is 33K.
Best regards and good luck with your project! Let us know how it's progressing!
Jarno.
I don't remember the pots I used but for the MESA preamp, but I remember I wired them backwards. I also think the mid had all of it's control in a very small rotational area, indicating I used a LOG pot instead of LIN?
I had a look at the paper version of the tube amp book which has the same schem, and 1 is indeed 3,3M and 3 is 33K.
Best regards and good luck with your project! Let us know how it's progressing!
Jarno.
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