Almost forgot something important. The tube is a GE 5814a and although a well regarded tube, I have not really compared this to the other 12au7 on hand. With a tube change, so does the sound.
Looking at the build guide, the 4s does roll off the last octave about 1 db and the output impedance is around 70K ohms. So when you are using this to drive a SS amp with a typical input impedance of say 20K, that disparity may raise the distortion levels and/or drop the top octaves even more. It's a good intro to building tube gear, since it's such a simple a circuit. But I don't think it was ever meant to be an audiophile linestage.
I don't have enough EE sense' to know how all this electrical stuff works and why it does what it does but I didn't quite follow the instructions on the 4s build. You guys held my hand the whole way. Things like the volume pot moving to the input, resistor and cap changes, and trying to optimize the unit for only the 12au7 surely had some affect on performance. Did these changes help or hurt performance ... meh, I got no idea, just happy to get it working without being electrocuted. One biggie that did help was up-sizing the output cap from the oem .47uf to 2uf. That one change made a huge difference in the bass cutoff (<I learned how to calculate this along with load lines:). And for those who believe a cap is a cap is a cap, well, rolling caps in this output does make a difference in the sound.
The designer mentions this preamp is to show how different tubes sound, don't recall 'audiophile' being mentioned, so, I suspect your hunches are correct on all counts, i.e.; this is an inaccurate distortion generating machine.
It also helped me to learn a tiny little bit of why those electrons do what they do, and this is something that has held my interest since childhood. I find things of the electrical kind fascinating. (on bucket list: giant 6' singing Tesla coil ... or is that a lodge coil?)
Now if I could just get this darn Borbely pre figured out I'd have something to compare.
The audiophile term is also regarded as one that will praise a crap speaker that cost $25k because of how it strokes their ego overer a sound signature that they truly enjoy or is accurate. How many of us would call ourselves an audiophile?
We need to come up with another name for that type of person - maybe a Stereophile?
I built this same linestage as a gift for a friend of mine years ago. He still uses it with his CD player and says it takes the edge off those harsh sounding discs mastered in the 80s. If you want higher performance, you have the basic parts already there and could likely morph this into a number of other designs. You understand the basics now and resistors, coupling caps & tube sockets are pretty cheap!
Already have too many half baked projects, so I really need to get this Borbely tube/hybrid pre up and running before moving onto the next project. Your 6dj8 pre looks interesting, or something using the 12au7 since I have a small stockpile of those.
On a whim, quietly unhooked boy's Schitt modi dac and took it, and my laptop, out to the trailer to sample some Spotify tune'eg. Spotify on laptop w/highest quality setting>all windows enhancements off>usb to Schitt dac>into the same 4s pre, and the Sadies.
Considerably better than using the analog out from the old iphone3s.
It was pretty easy to pick out Phil Collin's backup singer entering the mix. The bottom end sounded and felt better. Biggest thing was the soundstage. It was more natural, and, caution audiophile term, more 'there'. I assume the Aune will still have better focus and detail vs the 4s, but the improvement in the how the performance was portrayed, was a definite step up.
Comments
Almost forgot something important. The tube is a GE 5814a and although a well regarded tube, I have not really compared this to the other 12au7 on hand. With a tube change, so does the sound.
Looking at the build guide, the 4s does roll off the last octave about 1 db and the output impedance is around 70K ohms. So when you are using this to drive a SS amp with a typical input impedance of say 20K, that disparity may raise the distortion levels and/or drop the top octaves even more. It's a good intro to building tube gear, since it's such a simple a circuit. But I don't think it was ever meant to be an audiophile linestage.
I don't have enough EE sense' to know how all this electrical stuff works and why it does what it does but I didn't quite follow the instructions on the 4s build. You guys held my hand the whole way. Things like the volume pot moving to the input, resistor and cap changes, and trying to optimize the unit for only the 12au7 surely had some affect on performance. Did these changes help or hurt performance ... meh, I got no idea, just happy to get it working without being electrocuted. One biggie that did help was up-sizing the output cap from the oem .47uf to 2uf. That one change made a huge difference in the bass cutoff (<I learned how to calculate this along with load lines:). And for those who believe a cap is a cap is a cap, well, rolling caps in this output does make a difference in the sound.
The designer mentions this preamp is to show how different tubes sound, don't recall 'audiophile' being mentioned, so, I suspect your hunches are correct on all counts, i.e.; this is an inaccurate distortion generating machine.
It also helped me to learn a tiny little bit of why those electrons do what they do, and this is something that has held my interest since childhood. I find things of the electrical kind fascinating. (on bucket list: giant 6' singing Tesla coil ... or is that a lodge coil?)
Now if I could just get this darn Borbely pre figured out I'd have something to compare.
The audiophile term is also regarded as one that will praise a crap speaker that cost $25k because of how it strokes their ego overer a sound signature that they truly enjoy or is accurate. How many of us would call ourselves an audiophile?
We need to come up with another name for that type of person - maybe a Stereophile?
I built this same linestage as a gift for a friend of mine years ago. He still uses it with his CD player and says it takes the edge off those harsh sounding discs mastered in the 80s. If you want higher performance, you have the basic parts already there and could likely morph this into a number of other designs. You understand the basics now and resistors, coupling caps & tube sockets are pretty cheap!
Already have too many half baked projects, so I really need to get this Borbely tube/hybrid pre up and running before moving onto the next project. Your 6dj8 pre looks interesting, or something using the 12au7 since I have a small stockpile of those.
Hope you guys had a good time at Indy.
On a whim, quietly unhooked boy's Schitt modi dac and took it, and my laptop, out to the trailer to sample some Spotify tune'eg. Spotify on laptop w/highest quality setting>all windows enhancements off>usb to Schitt dac>into the same 4s pre, and the Sadies.
Considerably better than using the analog out from the old iphone3s.
It was pretty easy to pick out Phil Collin's backup singer entering the mix. The bottom end sounded and felt better. Biggest thing was the soundstage. It was more natural, and, caution audiophile term, more 'there'. I assume the Aune will still have better focus and detail vs the 4s, but the improvement in the how the performance was portrayed, was a definite step up.