wwood said:
Hi Bill,
Thanks, good post, this pretty much sums things up for me.
I am getting some pretty good ideas on correlation of sound to
this particular design and will post them when appropriate.
It should be basis for some good tech discussion. It may also
help other peoples future designs.
Is there any chance you can do the measurements with 4 ohms
at higher power? This will tell a lot more.
Cheers
Hi Terry,
I have a variety of other data but it is not coherent in that all is taken under varying conditions, kinda the wandering around one does during initial explorations. Unfortunately nothing significant at 4 ohms. Currently the amp is installed in my system for some listening and relaxing when I am not working on a major re-model job at home. When I get back to the bench I will be glad to do some 4 Ohm measurements, but it might be a bit. I look forward to the results of your studies and will get more data as soon as I am "allowed off the chain gang".
Bill
I have a variety of other data but it is not coherent in that all is taken under varying conditions, kinda the wandering around one does during initial explorations. Unfortunately nothing significant at 4 ohms. Currently the amp is installed in my system for some listening and relaxing when I am not working on a major re-model job at home. When I get back to the bench I will be glad to do some 4 Ohm measurements, but it might be a bit. I look forward to the results of your studies and will get more data as soon as I am "allowed off the chain gang".
Bill
I need help finding the right Transistors
Does someone know a good substitute for the BC556C and the BC546C ?
I just can't find any here in Germany.
Greg suggested to pick out ones that had a Hfe reading over 400 and use them in place of the C ones.
I could find allot of BC556B that were over 400 but none of the BC446B would be above 320. So I'm stuck.
I can't wait to get my SKA up and running.
To save some money I want to use just one tranny instead of going dual mono.
Did I understand it right that the SKA is not as sensitive to power-supply design than most other solid state Amps?
There haven't been allot of posts about the SKA the last few days. I am really eager to hear if the limits can be pushed by better components.
ShinOBIWAN have your Black Gates burned in yet?
Klaus
Does someone know a good substitute for the BC556C and the BC546C ?
I just can't find any here in Germany.
Greg suggested to pick out ones that had a Hfe reading over 400 and use them in place of the C ones.
I could find allot of BC556B that were over 400 but none of the BC446B would be above 320. So I'm stuck.
I can't wait to get my SKA up and running.
To save some money I want to use just one tranny instead of going dual mono.
Did I understand it right that the SKA is not as sensitive to power-supply design than most other solid state Amps?
There haven't been allot of posts about the SKA the last few days. I am really eager to hear if the limits can be pushed by better components.
ShinOBIWAN have your Black Gates burned in yet?
Klaus
ska chassis
Hi Shinobiwan, Haven't heard an update on your construction lately - hope things are progressing well. Have you received your hifi2000 chassis yet? After an initial response from Andrea he hasn't responded to any further requests for payment options. How did you conduct the transaction? I was hoping for paypal.
Other than that I've wired both ps's and am finishing the second amp board - will probably be done today. Sent pictures of progress to Greg - he caught one witless connection other than that the "visuals" at least are ok. Really looking forward to getting some ac into the thing.
Cheers,
Roman
Hi Shinobiwan, Haven't heard an update on your construction lately - hope things are progressing well. Have you received your hifi2000 chassis yet? After an initial response from Andrea he hasn't responded to any further requests for payment options. How did you conduct the transaction? I was hoping for paypal.
Other than that I've wired both ps's and am finishing the second amp board - will probably be done today. Sent pictures of progress to Greg - he caught one witless connection other than that the "visuals" at least are ok. Really looking forward to getting some ac into the thing.
Cheers,
Roman
Hi,
reading between the lines and adding 2+2 but not equal to 4, then here is my two pence (cents) worth.
Comparing a power amp to an opamp on steroids.
The PSRR is high at low frequency and falls badly towards high frequency. I suspect both power and Op fit this model.
SKA is reputed to have a much improved high frequency PSRR and I suspect that what Greg has achieved is an extended mid frequency PSRR that rolls off from a higher point. He may also have achieved closer matching between the +ve & -ve PSRR.
If that first assumption is correct then the bass PSRR may be the same between SKA and most other competent power amps.
On that basis you can listen to the music as Greg has said and not the PSU, but you still need a decent PSU to meet the bass requirement for sustained current delivery.
In other words do not skimp on the PSU and you will get the benefit of high frequency PSRR.
reading between the lines and adding 2+2 but not equal to 4, then here is my two pence (cents) worth.
Comparing a power amp to an opamp on steroids.
The PSRR is high at low frequency and falls badly towards high frequency. I suspect both power and Op fit this model.
SKA is reputed to have a much improved high frequency PSRR and I suspect that what Greg has achieved is an extended mid frequency PSRR that rolls off from a higher point. He may also have achieved closer matching between the +ve & -ve PSRR.
If that first assumption is correct then the bass PSRR may be the same between SKA and most other competent power amps.
On that basis you can listen to the music as Greg has said and not the PSU, but you still need a decent PSU to meet the bass requirement for sustained current delivery.
In other words do not skimp on the PSU and you will get the benefit of high frequency PSRR.
Re: ska chassis
The cases arrived safely and as promised. They really do look superb in the flesh. I've owned a Bryston an amp in the past and these really remind me of those. Big thick brushed alu face plate and large black anodised heatsink down the flanks of the case. The chunky handles are superbly machined and I would feel very confident actually using them to lift and carry the amp, so they're not just cosmetic although they do look rather nice.
I haven't done anything other than unpack each to take a look. I'm concentrating on getting a rather substantial speaker project finished. Eventually the amps will be assembled and will power these 3-way actives.
Andrea doesn't accept paypal. I had to make a big leap of faith and deposited the money directly into his account. When you hear from him ask him to give you payment details. He was fairly speedy in replying to my emails but maybe he's busy?
You can get them from another source in Italy for a little more expense and they accept credit cards, if your feeling nervous, so you'll be covered. I can't remember what it was called now though, I've checked my bookmarks but I cleared a load out about a week ago and I think that one went along with the other's that didn't look of any use.
rez said:
The cases arrived safely and as promised. They really do look superb in the flesh. I've owned a Bryston an amp in the past and these really remind me of those. Big thick brushed alu face plate and large black anodised heatsink down the flanks of the case. The chunky handles are superbly machined and I would feel very confident actually using them to lift and carry the amp, so they're not just cosmetic although they do look rather nice.
I haven't done anything other than unpack each to take a look. I'm concentrating on getting a rather substantial speaker project finished. Eventually the amps will be assembled and will power these 3-way actives.
Andrea doesn't accept paypal. I had to make a big leap of faith and deposited the money directly into his account. When you hear from him ask him to give you payment details. He was fairly speedy in replying to my emails but maybe he's busy?
You can get them from another source in Italy for a little more expense and they accept credit cards, if your feeling nervous, so you'll be covered. I can't remember what it was called now though, I've checked my bookmarks but I cleared a load out about a week ago and I think that one went along with the other's that didn't look of any use.
belden
I found the following website if anyone is interested in using Belden's 89259 cable for ska. Spent a long time searching local suppliers with no luck. 89259 can be ordered online by the foot from ram - url below. I ordered some today so will post again when I get it to let you know about how this turned out.
http://www.ramelectronics.net/index.html
rez
I found the following website if anyone is interested in using Belden's 89259 cable for ska. Spent a long time searching local suppliers with no luck. 89259 can be ordered online by the foot from ram - url below. I ordered some today so will post again when I get it to let you know about how this turned out.
http://www.ramelectronics.net/index.html
rez
Re: Re: ska chassis
Perhaps you mean : http://www.audiokit.it/ENG/Frames/Introduction1.htm
ShinOBIWAN said:
Perhaps you mean : http://www.audiokit.it/ENG/Frames/Introduction1.htm
Need a little help with grounding
I've finally finished the construction of my GB150D, everything seems to be great except a noise that comes from both channels when there is no signal. I'll try to describe it to you; It's loud, I'm able to hear it even from 3 meters away. It sounds like a buzz or more like the sound of boiling water but thinner. I think it's a grounding problem and I'm going to apply a new grounding schema. Please look carefully to the attachment files and tell me which is correct/best. The Light green lines are the earth,
grey is the ground to chassis and dark green is the chassis ground circuit. If you have another suggestion to make, please do. The mains power voltage in Greece is 220V/50HZ. I use two trafos of 33-0-33 at 200VA and two psus of 40.000ìF, one for each channel.
Thanasis.
I've finally finished the construction of my GB150D, everything seems to be great except a noise that comes from both channels when there is no signal. I'll try to describe it to you; It's loud, I'm able to hear it even from 3 meters away. It sounds like a buzz or more like the sound of boiling water but thinner. I think it's a grounding problem and I'm going to apply a new grounding schema. Please look carefully to the attachment files and tell me which is correct/best. The Light green lines are the earth,
grey is the ground to chassis and dark green is the chassis ground circuit. If you have another suggestion to make, please do. The mains power voltage in Greece is 220V/50HZ. I use two trafos of 33-0-33 at 200VA and two psus of 40.000ìF, one for each channel.
Thanasis.
Attachments
Hi Msamkl,
I would do neither.
You have kept the mains safety earth separate - very good.
Keep the power ground separate. Connect all the big power returns to this ground. Include the speaker returns, Zobel ground, decoupling ground.
Keep the transformer centre tap away from the power ground, take it straight to the PSU common by the shortest, straightest route - even move some components to achieve this.
Then connect the centre tap to power ground.
Make a signal ground for each amplifier, connect the RCA ground wire, PCB input ground and PCB feedback to each of these. No decoupling connected here. Check all four grounds are insulated from each other. They could for convenience be very close or widely separated if that suits your layout better.
Now the options.
You have three types of grounds;- Mains, power , signal,
Mains and power direct together with a link wire and resistor to signal ground.
or power and signal direct together with a link wire and mains via a resistor (10r) as your diagram.
or all three direct together.
or an option I have not tried, resistor connections between all three grounds.
Experiment with where you put that resistor. By keeping all three ground separate you can experiment with very few changes.
I would do neither.
You have kept the mains safety earth separate - very good.
Keep the power ground separate. Connect all the big power returns to this ground. Include the speaker returns, Zobel ground, decoupling ground.
Keep the transformer centre tap away from the power ground, take it straight to the PSU common by the shortest, straightest route - even move some components to achieve this.
Then connect the centre tap to power ground.
Make a signal ground for each amplifier, connect the RCA ground wire, PCB input ground and PCB feedback to each of these. No decoupling connected here. Check all four grounds are insulated from each other. They could for convenience be very close or widely separated if that suits your layout better.
Now the options.
You have three types of grounds;- Mains, power , signal,
Mains and power direct together with a link wire and resistor to signal ground.
or power and signal direct together with a link wire and mains via a resistor (10r) as your diagram.
or all three direct together.
or an option I have not tried, resistor connections between all three grounds.
Experiment with where you put that resistor. By keeping all three ground separate you can experiment with very few changes.
Terry, this grounding is wrong : you must not lead input ground by common wire with output ground into PS, but by two separated wires. You must imagine, that output ground have not " zero " resistance and by continuous current from load is " modulated " input ground = positive feedback = instability.
Thank you both for your suggestions...
Andrew, can you please make a drawing with your suggestion because my English is too poor to figure out what you suggest?
Terry, have you also constructed the GB150? If so, did you apply this grounding schema that you suggest? You have connected the input jacks earths to the chassis ground. What circuit did you put between them? Is it the same that Greg suggests (1 resistor 2,7 ohm and two anti-parallel diodes) or just a resistor?
I've tried both of my drawings but none had solved the problem. I even tried a third one that appears to make some improvement. The noise is reduced but not enough. When I disconnect the mains power ground from the chassis and connect only the star's earth to the chassis, then the noise disappears completely. When I only disconnect the star's earth from the chassis, then the noise is reduced so much that I have to get my ear close to the speaker to hear it.
Can you figure out what is happening here? What is producing the noise?
Thanasis.
Andrew, can you please make a drawing with your suggestion because my English is too poor to figure out what you suggest?
Terry, have you also constructed the GB150? If so, did you apply this grounding schema that you suggest? You have connected the input jacks earths to the chassis ground. What circuit did you put between them? Is it the same that Greg suggests (1 resistor 2,7 ohm and two anti-parallel diodes) or just a resistor?
I've tried both of my drawings but none had solved the problem. I even tried a third one that appears to make some improvement. The noise is reduced but not enough. When I disconnect the mains power ground from the chassis and connect only the star's earth to the chassis, then the noise disappears completely. When I only disconnect the star's earth from the chassis, then the noise is reduced so much that I have to get my ear close to the speaker to hear it.
Can you figure out what is happening here? What is producing the noise?
Thanasis.
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