Thank you guys, I will compare to the F5 manual. I will build it stock of course first and then afterwards think about changing it if needs be......
Fran
Fran
MEGA-amp said:
I've been using A75 for over 14 years now and this amp also does not feature current limiting circuitry (besides having 24 output devices per channel). During that time I only had to replace one single device due to accidentally shorting the output.
With F5, changing one of the devices would be a piece of cake, not like A75 here: http://www.diyaudio.com/forums/attachment.php?s=&postid=52955&stamp=1029963266
There are certain gains in sound quality and if you feel little adventurous I would suggest to try the amp with out it.
bluemartini said:
Yes, presently it is PC as a source, the main reason is that with PC I'm using different DAC, whith higher output that allows me to properly drive the F5.
The output from a DAC used with Shigaclone is too low. Besides, I got seriously interested in PC as a source and I like to continue my research. There was discussion in other thread on that subject: http://www.diyaudio.com/forums/showthread.php?postid=1689863#post1689863
Of course I'm still using CD transport in my main system. PC is still not exactly up to a task, but coming very close 😉
What bias current are you running the beast at? Higher current gives less distortion in this topology. 
You can still keep the thermistor while running a high bias current - perhaps you need to change the values however...
You can still keep the thermistor while running a high bias current - perhaps you need to change the values however...
Does removal of the current limiting circuitry cause much extra power draw? The heatsinks I'll be using ran a little warm with Zen V4s mounted (100W/ch to dissipate).
-j
-j
I didn't notice much difference in stability with thermistors and I compared two channels side by side: one with one without thermistors. I don't have a proper chassis, it's open concept so thermistors don't get affected by heat much.
I have the bias set to according to manual (600mV voltage drop). What I plan to do is to have the amp running over few days, set all the adjustement and then replace trimmers with fixed resistors.
Did anybody experimented with gain? Whould be a problem adding 5dB or so?
I have the bias set to according to manual (600mV voltage drop). What I plan to do is to have the amp running over few days, set all the adjustement and then replace trimmers with fixed resistors.
Did anybody experimented with gain? Whould be a problem adding 5dB or so?
So by my calculation you would need to remove:
Q5, Q6
TH1, TH2
R15-22 inclusive
No links needed or traces to be cut.
Seems it would be easy enough to try out later.
I take it you need to do the same startup procedure. Would there be anything else to watch out for when doing this for the first time?
Peters boards are so good I don't see a big problem removing components later.
(here I am asking this question and I haven't even built the thing yet, however, while I have your attention I reckon its timely to ask!)
Fran
Q5, Q6
TH1, TH2
R15-22 inclusive
No links needed or traces to be cut.
Seems it would be easy enough to try out later.
I take it you need to do the same startup procedure. Would there be anything else to watch out for when doing this for the first time?
Peters boards are so good I don't see a big problem removing components later.
(here I am asking this question and I haven't even built the thing yet, however, while I have your attention I reckon its timely to ask!)
Fran
Make absolutely certain that P1/P2 are set to minimum, check with meter. And of course that nothing is shorted before powering up.
You _do have to readjust bias so that the current draw was the same as before. Use the same procedure as you did the first time.
-j
-j
> Did anybody experimented with gain? Whould be a problem adding 5dB or so?
Yes, but IMHO it does nothing to improve the richness of sound, which is already not its strongest point.
As posted here ages ago, my preferred configuration is Toshiba 2SK1530 / 2SJ201, balanced, 2A bias, 0R22 source resistors. I like Toshibas better than Fairchilds, but I am known to be biased.
Patrick
Yes, but IMHO it does nothing to improve the richness of sound, which is already not its strongest point.
As posted here ages ago, my preferred configuration is Toshiba 2SK1530 / 2SJ201, balanced, 2A bias, 0R22 source resistors. I like Toshibas better than Fairchilds, but I am known to be biased.
Patrick
And how IR Mosfets compare as that's what I'm using now.
The main reason for gain increase is that I wouldn't like to go with an active line stage, and I'm mosty OK as it is, but having slight margin with some discs would be nice.
The main reason for gain increase is that I wouldn't like to go with an active line stage, and I'm mosty OK as it is, but having slight margin with some discs would be nice.
EUVL said:
Did you mean to say otherwise or are you actually estimating the sound not to be as dense and rich as you like?
Samuel Jayaraj said:
Isn't this subjective? I mean there are a lot of different factors that change the sound. From the output transistors to the wiring used or the power supply components. Even the source or the CD's played. Kind of a balancing act with the other components in your system.
Sort of like the same way when they do remastering. They use different equipment, preamps etc. for each project to tweak the sound and make it sound most natural.
Nelson likes the Fairchild parts because he thought they sounded better. I'll go with his judgement first before I start experimenting.
The subjectiveness and construction variants are well understood by me; but I assume that Patrick is well seasoned and would have come to his conclusions, listening to relatively the same setup as other amplifiers in his possession, to which he is comparing the F5 and so it would be great for Patrick to chime in.
"The output from a DAC used with Shigaclone is too low. Besides, I got seriously interested in PC as a source and I like to continue my research. There was discussion in other thread on that subject: http://www.diyaudio.com/forums/showthread.php?postid=1689863#post1689863"
Thanks, I have been running a Linux setup in the thread from Soundcheck via usb and been very happy. I will certainly read the thread you have above.
Thanks, I have been running a Linux setup in the thread from Soundcheck via usb and been very happy. I will certainly read the thread you have above.
Firstly answer to Peter, I have not tried IRF Mosfets for the F5, so I have to pass on this one. It is difficult to describe the difference btw Toshibas and Fairchilds. The bandwidth for both device types are similar, but the Toshibas just sound more natural.
I tried to increase gain to 20dB as this is what I have for my reference amps. I did mention earlier in one of my posts in this thread that the particular configuration of my balanced F5 was a touch on the bright side. Increasing the gain made it sound even thinner. But then I cannot speak for Nelson's version as published. I guess either you have to wait for his comments, or just try for yourself.
I increased gain by increasing the feedback resistor. This has probably the least consequence.
Patrick
I tried to increase gain to 20dB as this is what I have for my reference amps. I did mention earlier in one of my posts in this thread that the particular configuration of my balanced F5 was a touch on the bright side. Increasing the gain made it sound even thinner. But then I cannot speak for Nelson's version as published. I guess either you have to wait for his comments, or just try for yourself.
I increased gain by increasing the feedback resistor. This has probably the least consequence.
Patrick