Quote:
Originally Posted by Patrick Turner
On Thursday, 6 November 2014 18:54:05 UTC+11, Donut wrote:
Hello!
My friend is working on his preamp and he shows me the circuit lately. The preamp named Grounded Grid and claimed that the circuit is GG as well.
However, some people called it a mu follower.....SO what is this?? GG or mu follower?
http://i2.photobucket.com/albums/y48...e/ggpreamp.jpg
I'm really curious!!
thx!
The circuit you refer us to is not a simple grounded grid gain stage.
On each channel there are 3 triodes. The single left triode is a cathode follower with high Z grid input. Its cathode is low Z output which drives the cathode input to bottom triode cathode of 2 series triodes which are arranged as SRPP pair. The output of the circuit is from top right triode cathode and after coupling cap there is an R divider from output to bottom triode grid of SRPP pair.
This divider is a NFB circuit where ß = 0.167. The advantage, if any, of this circuit is that phase of input is same as phase of output.
Unfortunately Transcendant Sound omit all the important info such as all the signal voltages and phases which leave inexperienced experimenters floundering because they cannot do basic diagnosis of such a very simple circuit.
I've tried this type of circuit and found no benefits other than phase not being inverted, but after realizing there is nobody in this world who can hear the difference of phase reversals, the ordinary µ-follower with 2 triodes aka bootstrapped follower is superior to the similar SRPP, and examples of what I mean are at http://www.turneraudio.com.au/preamplifiers.htm |
Here is confirmation of Patrick T's comment on our ability to hear phase. Copied from Fred E Terman's Electronic & Radio Engineering, 4th Edition.
A very good reference text for anyone involved in vacuum tube electronics. I got mine about 15 years ago used at a very good price.
Refer to
www.alibris.com for many books, both new & used.
Cheers to al, John L Stewart