Hi,
yesterday i had a short conversation with my teacher, i was asking questions related to exam. Beside things directly related to it (digital control), we also talked about distortion and overload characteristics of preamps.
He was very interested in my modification to 47 preamp output stage where i wanted to get different harmonic distortion spread/sound, so i used ECC99 tube and tried various amounts of local feedback.
I got interested in this modification by reading EMI paper about 47 preamp, it says that the output stage produces more 3rd than 2nd harmonic distortion etc. There was also post from Winstion O'Boogie where he is confirming this claim:
http://www.groupdiy.com/index.php?topic=7292.80
and a little more here:
http://www.groupdiy.com/index.php?topic=17847.20
Instead of "normal" exam i will probably present my modification to the output stage, measurements of distortion spread before and after, and also write a little about overload/distortion characteristics of IC, pentode and triode amplifier.
The only reading i could find about this is "Tubes vs Transistors: Is there an audible difference?" by Russel O. Hamm:
http://www.dwfearn.com/tubes_vs_transistors.html
It is interesting that the article in fig.6 shows more 3rd than 2nd distortion for pentode, while EMI says their EF86 input stage has more 2nd than 3rd. Well, R.Hamm wrote that different circuits show different characteristics which is understandable.
My plan now is to build simple IC preamp, 47 type with two output stages and measure what i can. I hope i get a chance to use university's laboratory because i don't have distortion analyzer and other lab gear. I'm all excited about it and this is for sure more interesting than digital control, at least for me ;D
As i'm going to write few pages about this thematic, i would like to find more information if possible.
Can anyone please point me to further reading about this things?
And did anyone measure distortion spread of standard EF86 input stage used by Mullard, Quad, EMI and many others?
I would also like to hear any comments about what i'm going to do.
I hope i get a chance to use university's laboratory to measure this things myself. I'm all excited about it and this is for sure more interesting than digital control, at least for me ;D
Miha
yesterday i had a short conversation with my teacher, i was asking questions related to exam. Beside things directly related to it (digital control), we also talked about distortion and overload characteristics of preamps.
He was very interested in my modification to 47 preamp output stage where i wanted to get different harmonic distortion spread/sound, so i used ECC99 tube and tried various amounts of local feedback.
I got interested in this modification by reading EMI paper about 47 preamp, it says that the output stage produces more 3rd than 2nd harmonic distortion etc. There was also post from Winstion O'Boogie where he is confirming this claim:
http://www.groupdiy.com/index.php?topic=7292.80
and a little more here:
http://www.groupdiy.com/index.php?topic=17847.20
Instead of "normal" exam i will probably present my modification to the output stage, measurements of distortion spread before and after, and also write a little about overload/distortion characteristics of IC, pentode and triode amplifier.
The only reading i could find about this is "Tubes vs Transistors: Is there an audible difference?" by Russel O. Hamm:
http://www.dwfearn.com/tubes_vs_transistors.html
It is interesting that the article in fig.6 shows more 3rd than 2nd distortion for pentode, while EMI says their EF86 input stage has more 2nd than 3rd. Well, R.Hamm wrote that different circuits show different characteristics which is understandable.
My plan now is to build simple IC preamp, 47 type with two output stages and measure what i can. I hope i get a chance to use university's laboratory because i don't have distortion analyzer and other lab gear. I'm all excited about it and this is for sure more interesting than digital control, at least for me ;D
As i'm going to write few pages about this thematic, i would like to find more information if possible.
Can anyone please point me to further reading about this things?
And did anyone measure distortion spread of standard EF86 input stage used by Mullard, Quad, EMI and many others?
I would also like to hear any comments about what i'm going to do.
I hope i get a chance to use university's laboratory to measure this things myself. I'm all excited about it and this is for sure more interesting than digital control, at least for me ;D
Miha