Q 1 -Q 4 emitter resistors
I must try to link them out before changing the amps to something else.
Thank you for the idee . 😉
I must try to link them out before changing the amps to something else.
Thank you for the idee . 😉
KLe said:
I can only report on this from other amps I have converted.
I never tried the SKA with the cap in the FB circuit - for me it's a must have to have DC coupling throughout.
The difference is significant - the sound is cleaner & clearer.
cheers
mike
mikelm said:
Agreed. D offset will wander with temperatur of the input pair(s), but this can be compensated to some extent if you can thermally couple them. In addition, some DC offset protect is a good idea. Definitely worth the hast though.
stueyh said:
yes R5-8
I left the resistors in place - just added a small solid copper wire to short them.
mike
Re: Q 1 -Q 4 emitter resistors
I am interested to hear you want to change amps - I wonder why ?
I have found that if you do to this amp the things you need to do to any amp to get the best from it . . . then it proves itself to be very good indeed.
I mean - quiet power supply, high quality components etc
What were you thinking to change to I wonder ?
cheers
mike
Erlend Sæterdal said:
I am interested to hear you want to change amps - I wonder why ?
I have found that if you do to this amp the things you need to do to any amp to get the best from it . . . then it proves itself to be very good indeed.
I mean - quiet power supply, high quality components etc
What were you thinking to change to I wonder ?
cheers
mike
Thanks Mike
I thought that DC coupling the feedback to ground would give significant improvement. Nice to have it confirmed.
🙂
addendum
I just noticed in spice that if you remove the emitter resistors of Q1 - 4 as I mentioned before that it affects the O/P stage bias current.
So if you try this mod you need to be aware that the bias current needs to be reset - in the way described in the instructions.
cheers
mike
I just noticed in spice that if you remove the emitter resistors of Q1 - 4 as I mentioned before that it affects the O/P stage bias current.
So if you try this mod you need to be aware that the bias current needs to be reset - in the way described in the instructions.
cheers
mike
Hi Mike,
I wonder if this bias current change would explain the change in sound?
On another mod altogether - I'm looking to make my SKA GB150 capable of accepting balanced inputs as I have a DIY preamp which outputs true balanced signals.
According to Greg, it's a simple mod to the front which I can probably make as an switchable option (perhaps?).
My thoughts about this made me wonder if the CCS tweak would still be effective or how would I find the new values for the synergy of this mod to be effective. One way is to run a simulation but I need to download simulation s/w, learn how to use it & possibly not trust it being a first time user.
So I got to thinking about doing the CCS off-board and playing with different CCS circuits/ running off batteries, etc. I seem to remember a SKA owner using his own CCS but can't find the post. Anybody here have more info?
I wonder if this bias current change would explain the change in sound?
On another mod altogether - I'm looking to make my SKA GB150 capable of accepting balanced inputs as I have a DIY preamp which outputs true balanced signals.
According to Greg, it's a simple mod to the front which I can probably make as an switchable option (perhaps?).
My thoughts about this made me wonder if the CCS tweak would still be effective or how would I find the new values for the synergy of this mod to be effective. One way is to run a simulation but I need to download simulation s/w, learn how to use it & possibly not trust it being a first time user.
So I got to thinking about doing the CCS off-board and playing with different CCS circuits/ running off batteries, etc. I seem to remember a SKA owner using his own CCS but can't find the post. Anybody here have more info?
jkeny said:
Don't think so
Since I did my mod I had bias current at different levels and the character of the sound has remained unchanged.
( All of my bias setting are quite high in my amp and my rails are at + / - 35V )
mike
I saw something...
When you put the BD to replace D5 D6. REMOVE d5 and d6 seems logical to me Vikash, in your picture they are still connected ... maybe ask Greg.
Also use a very small film of thermal paste on the BD to remove the air.
That would help with bias... I have the gb150d kit and bias is nearly spot on always, but fluctuates with room temperature.
When you put the BD to replace D5 D6. REMOVE d5 and d6 seems logical to me Vikash, in your picture they are still connected ... maybe ask Greg.
Also use a very small film of thermal paste on the BD to remove the air.
That would help with bias... I have the gb150d kit and bias is nearly spot on always, but fluctuates with room temperature.
SKA-Audio and Aussieamplifiers seem to build amplifier modules on more or less the same recipe.
Are these companies related, or competitors? Aussie Amplifiers seem to be located in Tasmania, but impossible to locate SKA-Audio. Could somebody please enlighten me on background of these companies 🙂
Are these companies related, or competitors? Aussie Amplifiers seem to be located in Tasmania, but impossible to locate SKA-Audio. Could somebody please enlighten me on background of these companies 🙂
Greg Ball resides up north, there should easily be a 1000 miles distance between him and Mr Holton, plus a 150 miles swim.
Mr SKA Ball is a Pro who turned kit DIY, Mr Holton more the other way round.
Anthony started out with high power PA orientated designs, Mr Ball has been the esoteric type from the start.
They're likely neither related nor competitors, but both in designing amps for quite some time now.
Mr SKA Ball is a Pro who turned kit DIY, Mr Holton more the other way round.
Anthony started out with high power PA orientated designs, Mr Ball has been the esoteric type from the start.
They're likely neither related nor competitors, but both in designing amps for quite some time now.
Price wise you can't do a mistake buying Greg’s amps. You can buy his complete kit and pay double the price to get a similar amp in the market. + You get excellent help. For me the skapre/optivol was the best component from Greg and the best value, I posted a picture of it in the solid state page.
A good ss preamp can be forgiving when plugged into tube power amp and save you quite a lot of money. For power amps my preference is tubes for many reasons, but I can live with the gb150d until I have enough money to get one tube that I really like.
A good ss preamp can be forgiving when plugged into tube power amp and save you quite a lot of money. For power amps my preference is tubes for many reasons, but I can live with the gb150d until I have enough money to get one tube that I really like.
Im thinking of building one of these amps, but i need ampere more than W. I heard I could get it to deliver more ampere with running less voltage, though it would be able to give less Watt. Anyone that can explain this more and if I need to configure it any other way too?
Tnx
Espen
Tnx
Espen
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