AndrewT said:
Hi Andrew
So, formula is
... (R2 + Rs) * C2 = 0.75uS or 0.75uS/(R2 + Rs) = C2
If R2=1000R, Rs=50R then assuming 0.75uS is optimum
... 0.75uS / (1K000 + 0K050) = 714pF = C2 (~ 680pF)
Andrew, how does that look?
thanks
KL
KLe said:
Hi KLe,
Could I suggest you keep on open mind, try a few values, and let ur ears be the judge of what is optimum...
I'm just about to fireup my SKA up for the first time ( sorry Greg, various things, including moving to the USA, slowed me down ) so I havn't tried it on SkA yet but on other amps when I have tried this, my preference was no series resistor and no i/p capacitor...
...but this may be made possible in my set-up because my pre-amp is a TVC which rolls off sharply at about 100khz and also I generally solder my i/p leads to the PCB which means there is always some capacitance there which with some amps is necessary for stability.
mike
Hi Mikelm,
to omit the RF filter from an amp that has it specified is risking stability and may conflict with the designers set-up. In the GB, Ampguru specifically talks about the effective the input cap to ground has on the desired performance of his design.
Kle,
yes, experiment with the turn-over frequency, but don't omit it completely.
Try 0.5uS (very open) to 1.5uS (muffled).
to omit the RF filter from an amp that has it specified is risking stability and may conflict with the designers set-up. In the GB, Ampguru specifically talks about the effective the input cap to ground has on the desired performance of his design.
Kle,
yes, experiment with the turn-over frequency, but don't omit it completely.
Try 0.5uS (very open) to 1.5uS (muffled).
AndrewT,
Good guidelines for input filters - I will keep this on file for future refernce.
I am driving the SKA from a high value pot 20K so these settings work for me, although I must build myself a pre soon and eliminate this variable to the sonics.
Anyway, if nothing else it did expose my bad grounding scheme which was noticable once this very open sound was heard and fixed using Greg's grounding scheme.
John
Good guidelines for input filters - I will keep this on file for future refernce.
I am driving the SKA from a high value pot 20K so these settings work for me, although I must build myself a pre soon and eliminate this variable to the sonics.
Anyway, if nothing else it did expose my bad grounding scheme which was noticable once this very open sound was heard and fixed using Greg's grounding scheme.
John
KLe said:
Fantastic.
Even better when you call it Sec/Rad instead of uS if you find it mondane to toss RC numbers instead of just talking corner frequencies.
Excellent jaccojacco vermeulen said:
What would you recommend
... assuming the output impedance of your CDP is 50R, what cut off freq and sec/Rad would you recommend?
thanks
KL
Hi,
I hope you have noticed that the RF filter options all have turnover frequencies in the hundreds of kHz.
Using my usual decade divider to arrive at the frequency range (virtually) unaffected by the filter, one ends up in the tens of kHz.
Some will notice changes around 30kHz and most will notice changes above 10kHz. These just happen to be the 0.5uS and 1.5uS divided by that 10 that I use (at both the bass end and the treble end of the passband).
There is room to try RF filtering that falls outside the limits suggested. But using higher than 1.5uS would more than likely be to correct some other anomally and not strictly within the RF remit.
I hope you have noticed that the RF filter options all have turnover frequencies in the hundreds of kHz.
Using my usual decade divider to arrive at the frequency range (virtually) unaffected by the filter, one ends up in the tens of kHz.
Some will notice changes around 30kHz and most will notice changes above 10kHz. These just happen to be the 0.5uS and 1.5uS divided by that 10 that I use (at both the bass end and the treble end of the passband).
There is room to try RF filtering that falls outside the limits suggested. But using higher than 1.5uS would more than likely be to correct some other anomally and not strictly within the RF remit.
Hi Andrew
I noticed that jacco called your uS, sec/rad's. Is this correct?
What would you recommend
thanks
KL
Hi,
I use RC time constants as well as turn-over frequency when dealing with single pole filters, because it allows me to compare alternatives quickly (instantly) and calculate alternatives almost as quickly (particlarly useful when using combinations of E6 and E24 component values).
I had never dreamed of using Rads/Sec and certainly never thought of inverting that standard SHM descriptor when RC already does it for me and many others.
I use RC time constants as well as turn-over frequency when dealing with single pole filters, because it allows me to compare alternatives quickly (instantly) and calculate alternatives almost as quickly (particlarly useful when using combinations of E6 and E24 component values).
I had never dreamed of using Rads/Sec and certainly never thought of inverting that standard SHM descriptor when RC already does it for me and many others.
Thanks AndrewAndrewT said:
I think I will try this, then work higher(uS), if I don't like it.
Should be interesting 😀
Rads/Sec over and out 😎
thanks again
KL
wow
hi all
The day after i got my amp setup correctly
I had a few months from hell
dental surgury! and again 3 weeks later
the dentist also broke my scaplum (thought i was gonna die)
now i can actually hear the amp
The dentist drugs made me tripp balls every time i turned the amp on.
It was fun but im glad it has finally subsided
and i can really hear again
this is amazing amp
I was never a fan of pink floyd
now I absoulty love them
must finally have a system worthy of them
Also the new beatles albums are quite outstanding when played though this amp
I left my mom with it.
And when i walked back in she was playing air drums like a spastic monkey.
Quite funny to have my mom an old hippie say she dont rember the beatles ever sounding like that.(let it be naked)(and let it be aswell)
maybe trade her for a gb300?
greg if i had a daughter she would be yours!
Im sold i will never buy another amp
unless greg has designed it
hi all
The day after i got my amp setup correctly
I had a few months from hell
dental surgury! and again 3 weeks later
the dentist also broke my scaplum (thought i was gonna die)
now i can actually hear the amp
The dentist drugs made me tripp balls every time i turned the amp on.
It was fun but im glad it has finally subsided
and i can really hear again
this is amazing amp
I was never a fan of pink floyd
now I absoulty love them
must finally have a system worthy of them
Also the new beatles albums are quite outstanding when played though this amp
I left my mom with it.
And when i walked back in she was playing air drums like a spastic monkey.
Quite funny to have my mom an old hippie say she dont rember the beatles ever sounding like that.(let it be naked)(and let it be aswell)
maybe trade her for a gb300?
greg if i had a daughter she would be yours!
Im sold i will never buy another amp
unless greg has designed it
Hi all,
i also finished SKA GB150 amp.
I had some troubles, but because i didnt follow correctly instructions from Greg.
Now i can really enjoy listening.
It is really amazing sounding amp; very clean, natural, good control bass, big soundstage, but it is not oversized.
I using single CLCLC +-45V power supply, but i think would be much better with double PSU.
Bias on 10R (checking on fuses sockets) resistors is 1.5V;
C9=47uF on feedback i change with wire and this make also big improvement (before i tried double antiparallel 22uF BG NX HiQ capacitors), but should be check thermal and DC offset stability (change from 1.2V to 1.5V on 10R (on fuses sockets).
Now is connected with passive pre = 10k Alps pot.
I already order SKApre from Greg.
regards, Bostjan
i also finished SKA GB150 amp.
I had some troubles, but because i didnt follow correctly instructions from Greg.
Now i can really enjoy listening.
It is really amazing sounding amp; very clean, natural, good control bass, big soundstage, but it is not oversized.
I using single CLCLC +-45V power supply, but i think would be much better with double PSU.
Bias on 10R (checking on fuses sockets) resistors is 1.5V;
C9=47uF on feedback i change with wire and this make also big improvement (before i tried double antiparallel 22uF BG NX HiQ capacitors), but should be check thermal and DC offset stability (change from 1.2V to 1.5V on 10R (on fuses sockets).
Now is connected with passive pre = 10k Alps pot.
I already order SKApre from Greg.
regards, Bostjan
Re: wow
Thanks m0rb0, that's excellent 😎
Thanks Bostjan, that's excellent, also 😎
Question ... removing C9 makes the amp DC coupled ... could you describe the big improvement in more detail 🙂
thanks
KL
m0rb0 said:
Thanks m0rb0, that's excellent 😎
a333bt said:
Thanks Bostjan, that's excellent, also 😎
Question ... removing C9 makes the amp DC coupled ... could you describe the big improvement in more detail 🙂
thanks
KL
Hi KL,
yes, music is more detailed, more transparency, more clean sound.
Before i was using Hiraga Monstre, which has no cap in signal path, and i was missing that.
try it.
regards, Bostjan
yes, music is more detailed, more transparency, more clean sound.
Before i was using Hiraga Monstre, which has no cap in signal path, and i was missing that.
try it.
regards, Bostjan
Hi Bostjana333bt said:
Yes, I will have a talk to Greg about, especially after your experience 😎
thanks
KL
a333bt said:
Hi Bostjan
Just wondering if you would mind telling me a little bit about the Hiraga Monstre
thanks
KL
Hi KL,
i had Hiraga Monstre 8W amplifier, because i didnt need much power for my high efficiency speakers. Here is no need for signal capacitors, which i dont like.
I didnt have direct comparison with SKA amp.
Monstre is very good sounding, musical, transparent and also good bass control. It very stable, simple and very pleasant.
With regulators i got better and more natural sound. Without them was too warm. It is very depend on PSU. It need only +-12V supply.
SKA is another class, maybe is not so musical, but very clear and honest in positive way.
Still waiting for SKApre.
Maybe can someone share experiences with SKApre?
regards, Bostjan
i had Hiraga Monstre 8W amplifier, because i didnt need much power for my high efficiency speakers. Here is no need for signal capacitors, which i dont like.
I didnt have direct comparison with SKA amp.
Monstre is very good sounding, musical, transparent and also good bass control. It very stable, simple and very pleasant.
With regulators i got better and more natural sound. Without them was too warm. It is very depend on PSU. It need only +-12V supply.
SKA is another class, maybe is not so musical, but very clear and honest in positive way.
Still waiting for SKApre.
Maybe can someone share experiences with SKApre?
regards, Bostjan
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