So, I built a 12AU7 preamp based on this design:
DIY 12AU7 Tube preamp
I modified it to use a 260v power supply, so R17 is more like 20k and R19 is more like 12k. It's okay, but I'm not super thrilled. The 12AU7 is probably not a great choice of tubes (I already had them though). I feel like this preamp is limiting the dynamic range, and even with a pretty substantial attenuator (don't remember the exact details), it's got a gain of 10, which is still way too much if you're coming off a DAC or your typical CD player.
The other problem you run into is that noise becomes way more difficult to eliminate with that kind of gain.
For some reason you see a lot of 12AX7 designs, and I suspect it's just because it's such a popular tube for guitar amps, and some of that spills over into the HiFi arena.
I've been playing with the idea of building something more like this, which by the way is NOT a finished design by any means (so I don't suggest building it), and there are several things I don't like about it. But just a little food for thought.
Edit: I forgot to mention that the 600:600 transformer was just because I wanted to play with a balanced output. I have some suitable Jensen transformers, so I wanted to give it a try.
DIY 12AU7 Tube preamp
I modified it to use a 260v power supply, so R17 is more like 20k and R19 is more like 12k. It's okay, but I'm not super thrilled. The 12AU7 is probably not a great choice of tubes (I already had them though). I feel like this preamp is limiting the dynamic range, and even with a pretty substantial attenuator (don't remember the exact details), it's got a gain of 10, which is still way too much if you're coming off a DAC or your typical CD player.
The other problem you run into is that noise becomes way more difficult to eliminate with that kind of gain.
For some reason you see a lot of 12AX7 designs, and I suspect it's just because it's such a popular tube for guitar amps, and some of that spills over into the HiFi arena.
I've been playing with the idea of building something more like this, which by the way is NOT a finished design by any means (so I don't suggest building it), and there are several things I don't like about it. But just a little food for thought.
Edit: I forgot to mention that the 600:600 transformer was just because I wanted to play with a balanced output. I have some suitable Jensen transformers, so I wanted to give it a try.
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Agreed. I was given exactly this advice when I built my preamp, didn't listen to it (because hey, lotsa folks build 12AX7 and 12AU7 preamps with plenty of gain, right?), and now I'm getting ready to build a buffer stage to replace my 3-month old preamp build.
Here, I hate 6n1p, 6n6p and so on. Over smooth with no excitement, lot of distortion.
You can get a hundred times better sounding NOS tube in the 6sn7 or 12sn7 , then there are 'secret' tubes which trounce the 6sn7, look at bartola valves website.
Aikido, Aikido, Aikido, this can be used in any system with a great fidelity, easy implementation and acceptable input noise without fuss.
I would use a stock Aikido with stock parts in a 100K$ system, it is that good.
You can get a hundred times better sounding NOS tube in the 6sn7 or 12sn7 , then there are 'secret' tubes which trounce the 6sn7, look at bartola valves website.
Aikido, Aikido, Aikido, this can be used in any system with a great fidelity, easy implementation and acceptable input noise without fuss.
I would use a stock Aikido with stock parts in a 100K$ system, it is that good.
Easy implementation is a good thing for me, not having built an amp before.
That's a strong endorsement for the Aikido, I'll have to look more closely at that design.
What are the pros and cons of a point to point build vs buying an Aikido PCB?
As far as tubes, I suppose a lot of it depends on what I can find at a decent price, being in England might restrict what I can find that isn't going to cost more than I would like to spend. This is why I asked about Russian tubes, they are readily available and affordable.
If i do go for the Aikido, what tubes do folks recommend for that design?
That's a strong endorsement for the Aikido, I'll have to look more closely at that design.
What are the pros and cons of a point to point build vs buying an Aikido PCB?
As far as tubes, I suppose a lot of it depends on what I can find at a decent price, being in England might restrict what I can find that isn't going to cost more than I would like to spend. This is why I asked about Russian tubes, they are readily available and affordable.
If i do go for the Aikido, what tubes do folks recommend for that design?
I built a point to point aikido.
I choosed 6sn7 with matched sections and implemented a B follower input stage, the input noise is the biggest problem, however the rest is history!
The draw back of the B follower is more odd harmonics and a big reduction of even order.
It is very easy to built. With a ez81 tube rectiver you are in business.
It is so unfortunate for this that I use integrated amplifiers...
Compaired to hifi solid state pre-amp without feedback, the aikido stands its grounds firmly and assure a constant pure musical sound ( with a little added warmth )
I choosed 6sn7 with matched sections and implemented a B follower input stage, the input noise is the biggest problem, however the rest is history!
The draw back of the B follower is more odd harmonics and a big reduction of even order.
It is very easy to built. With a ez81 tube rectiver you are in business.
It is so unfortunate for this that I use integrated amplifiers...
Compaired to hifi solid state pre-amp without feedback, the aikido stands its grounds firmly and assure a constant pure musical sound ( with a little added warmth )
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