Jim's Audio
Are you listening?
I tried to ask a question on your Ebay listing, but you have set up your Ebay seller account to not accept questions !
Can you supply two amp PCBs and two PSU PCBs? instead of 2+1
How much extra will the extra PCB cost?
Is the postage still correct for 2+2?
Are you listening?
I tried to ask a question on your Ebay listing, but you have set up your Ebay seller account to not accept questions !
Can you supply two amp PCBs and two PSU PCBs? instead of 2+1
How much extra will the extra PCB cost?
Is the postage still correct for 2+2?
from page 6
is this a typo?
125mA bias with 2pair output stage gives a total bias of 250mA.
The ClassA limit for push-pull is roughly twice the bias current, i.e. 500mApk
500mApk into 8r0 is equivalent to 1W into 8ohms.
Hi Andrew,
He does not really follow forums as he told me before, so I have sent him an email with the link to your question.
Ciao!
Do
Yes - you are right. The peak class A is in fact 1 W.
I however took the DC standing current level.
No,
the peak is Vpk²/R or Ipk²R
The proper power is Vpk²/R/2 or Vac²/R or Ipk²R/2 or Iac²R
for 500mApk which equals 353.55mAac sinewave the maximum ClassA power is 0.5²*8/2 = 1W
I would not state an instantaneous peak value, unless a specific component needed to never exceed such a value.
and this 1W of ClassA just happens to be -20dB relative to the maximum power of the amplifier.
Nice that we often listen at average levels of around -20db to -40dB relative to maximum power to avoid clipping on transients.
i.e. we often listen in the ClassA mode.
This is where Roender's amp with a maximum ClassA of ~5W (555mA bias giving ~-12dB rel. max Power) excels, we listen most of our time in ClassA.
Further, this may be why you found on listening tests that the amp when biased to greater than ClassAB optimal bias, sounded "better".
The extended range of ClassA avoided crossover distortion for more of the time.
the peak is Vpk²/R or Ipk²R
The proper power is Vpk²/R/2 or Vac²/R or Ipk²R/2 or Iac²R
for 500mApk which equals 353.55mAac sinewave the maximum ClassA power is 0.5²*8/2 = 1W
I would not state an instantaneous peak value, unless a specific component needed to never exceed such a value.
and this 1W of ClassA just happens to be -20dB relative to the maximum power of the amplifier.
Nice that we often listen at average levels of around -20db to -40dB relative to maximum power to avoid clipping on transients.
i.e. we often listen in the ClassA mode.
This is where Roender's amp with a maximum ClassA of ~5W (555mA bias giving ~-12dB rel. max Power) excels, we listen most of our time in ClassA.
Further, this may be why you found on listening tests that the amp when biased to greater than ClassAB optimal bias, sounded "better".
The extended range of ClassA avoided crossover distortion for more of the time.
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I'll try via Ebay again.
But it rejected all attempts to ask a question
I still can't get past the standard rejection message.
Just noticed that I am linked with Ebay.com
I'll try via Ebay.co.uk in case that is different.
Same result @ Ebay.co.uk and again after logging in to my .uk account.
weird.
But it rejected all attempts to ask a question
Seems very odd that a Seller does not accept questions and that the Seller claims
which has obviously been overridden by some Ebay setting.
I still can't get past the standard rejection message.
Just noticed that I am linked with Ebay.com
I'll try via Ebay.co.uk in case that is different.
Same result @ Ebay.co.uk and again after logging in to my .uk account.
weird.
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I can't even find the link for questions.
Another thing I just saw that I thought was interesting is on the V1.0 add he claims huge savings on the V1.0 boards but has the same price for V2.0.
Another thing I just saw that I thought was interesting is on the V1.0 add he claims huge savings on the V1.0 boards but has the same price for V2.0.
Shame to spoil this Thread with a supplier issue.
Can we remove these posts after we have found a way to contact Jims_audio and placed instructions here?
I have asked the Moderators to hold actioning deletion until we find a method of contacting Seller.
Can we remove these posts after we have found a way to contact Jims_audio and placed instructions here?
I have asked the Moderators to hold actioning deletion until we find a method of contacting Seller.
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Someone post a link to that Ebay page and I will take a look for you all. I am a fairly adept Ebay seller and can look and see if you are just missing the correct place to ask a question, often these things are rather confusing where they hide some features.
If you go down the page to where you see a number counter on the number of visitors to that page you will see where you can ask a question. At first there are a few stock questions that it will attempt to give you previous answers to questions but if you look carefully you will see the line for other questions. I hit that and instantly was able to post a question. I hope this helps those wanting to ask questions. The place to see the number counter and place for the questions is almost to the very bottom of the page and can take a few seconds to load after the initial page load.
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This message still comes up when I try to continue to ask other question.
He now knows there is a problem, yet has not turned on the "contact seller" function.
He has replied to a personal Email and has not come to this Forum to answer questions.
I could order 2+1, but there will be no method to change the order to 2+2.
Will there be a way to pay the extra $9.50 after "buy it now"?
It would be better if jims_audio opened the questions function.