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Ask Bob.. Taking questions for the Bob Carver morning meetings.


Ar9Jim
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Dear Carver fans,

I'm in meetings with Bob several times per week, and can take a few minutes to ask questions and report back to you in this thread. Bob has opinions on most topics that are viewed through his physics perspective. 

 

Here's a question to start that I asked Bob.

Bob, will a high end power cord improve an amplifiers performance over the cable supplied in the box? Answer - No, it will not. Some market improvements with no scientific basis for such claims. 

 

Feel free to ask Bob questions. Please keep them short and direct.  I'll report the answers to your questions back to this thread a couple times per week after the meeting.

 

Hope this is fun and educational. Enjoy !  Ask Bob!

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Jim,

 

Cool idea.  Two questions have been bugging me ever since I started playing around with Sunfire amplifiers.

 

1.  Bias Adjustment. Where should you set the bias adjustment on Sunfire amplifiers?

2.  Offset Adjustment.  Where should the Tracking Down Converter offset adjustment be set?

 

Perhaps these questions are too detailed.  Perhaps they vary depending on which amplifier you are talking about.  

 

At the moment, I'm working on a Sunfire Cinema Grand Signature 400 x 7.  I've set the bias on all seven channels at 1mv.  Offset at + and - 7 volts.  Seems to work well, but I worry.  I pretty much pulled these number out of thin air.

 

Any suggestions would help.

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Another question I have asked Bob and his reply. Bob being a physicist, designs products for the given application of reproducing music through loudspeakers. 

 

Question- Bob how are you able to offer an amplifier like the Crimson 275 that only weighs 19 lbs and uses what seem to be undersize output transformers during resistive load test, yet it sounds fantastic, makes lots of power and owners love them? What gives? 

 

Answer- I've been known for designing high performance, lighter weight amplifiers that more people could afford. The smaller output transformers work very well with this high voltage design. They don't experience saturation when playing music into the dynamic loads of loudspeakers.  This reduces weight and cost, without sacrificing the musical performance.  

Edited by Ar9Jim
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3 minutes ago, wrf said:

Jim,

 

Cool idea.  Two questions have been bugging me ever since I started playing around with Sunfire amplifiers.

 

1.  Bias Adjustment. Where should you set the bias adjustment on Sunfire amplifiers?

2.  Offset Adjustment.  Where should the Tracking Down Converter offset adjustment be set?

 

Perhaps these questions are too detailed.  Perhaps they vary depending on which amplifier you are talking about.  

 

At the moment, I'm working on a Sunfire Cinema Grand Signature 400 x 7.  I've set the bias on all seven channels at 1mv.  Offset at + and - 7 volts.  Seems to work well, but I worry.  I pretty much pulled these number out of thin air.

 

Any suggestions would help.

You got it Wayne. Meeting in the am..

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Another Sunfire question.  One I've asked before and only guessed at the answer.

 

My understanding of the Tracking Down Converter in a multichannel Sunfire amp is that the inputs from all channels are combined.  This composite signal is then used to throttle the rail voltage to all channels.  My question revolves around idle and partially loaded channels in the amp.  Given that the throttled rail voltage represents the needs of all channels combined, doesn't this cause problems when one channel is heavily loaded and others are only partially loaded?  Perhaps this isn't an issue with musical loads, but it this something you need to be careful of when bench testing a multi channel amp?

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Question: would a modern designed, advanced material, long format, wide frequency-response ribbon idea still be a viable contender vs the line source ribbon array? 

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I'm still trying to wrap my brain around the idea of using a feedback loop to interact with the speakers/room. I actually get the concept from the view that the speakers can be microphones for the amp. What does the amp do with this information? Is it related to the whole spectrum of signal or just the bass? Thanks.

 

  I talked with an audio engineer friend of mine about this. His version of understanding is that it would sort of like DSP (but not DSP) with a calibrated mic. Well, I get that, but the drivers in the speakers aren't calibrated to the amp in any way, right? So, there is another avenue to use them still I suppose, and this is my curiosity.

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On 11/13/2022 at 6:56 AM, wrf said:

Jim,

 

Cool idea.  Two questions have been bugging me ever since I started playing around with Sunfire amplifiers.

 

1.  Bias Adjustment. Where should you set the bias adjustment on Sunfire amplifiers?

2.  Offset Adjustment.  Where should the Tracking Down Converter offset adjustment be set?

 

Perhaps these questions are too detailed.  Perhaps they vary depending on which amplifier you are talking about.  

 

At the moment, I'm working on a Sunfire Cinema Grand Signature 400 x 7.  I've set the bias on all seven channels at 1mv.  Offset at + and - 7 volts.  Seems to work well, but I worry.  I pretty much pulled these number out of thin air.

 

Any suggestions would help.

Hi Wayne,

The numbers that come to mind are 80-120ma for bias and 12 volts for downconverter offset. Neither adjustment will do harm and the amp will actually function at the extremes of their adjustment range. 

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On 11/13/2022 at 7:40 AM, wrf said:

Another Sunfire question.  One I've asked before and only guessed at the answer.

 

My understanding of the Tracking Down Converter in a multichannel Sunfire amp is that the inputs from all channels are combined.  This composite signal is then used to throttle the rail voltage to all channels.  My question revolves around idle and partially loaded channels in the amp.  Given that the throttled rail voltage represents the needs of all channels combined, doesn't this cause problems when one channel is heavily loaded and others are only partially loaded?  Perhaps this isn't an issue with musical loads, but it this something you need to be careful of when bench testing a multi channel amp?

Its actually the highest voltage that drives the downconverter but not the combined sum. 

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On 11/13/2022 at 9:37 AM, cuda said:

Is there any plans to bring back Bobs Latest Amazing Line Source speaker? Or are they a money looser for the company?

The ALS will likely be back in 2-3 years. Right now the new preamp and amplifiers are at the top of the schedule. Bob 

 

I'll be in Snohomish in the near future and will take inventory of aluminum extrusions and plan from there. Jim

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On 11/14/2022 at 8:52 AM, PMAT said:

Question: would a modern designed, advanced material, long format, wide frequency-response ribbon idea still be a viable contender vs the line source ribbon array? 

Hi Paul, Yes it would. A properly designed long ribbon can perform excellent. 

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On 11/14/2022 at 7:45 PM, 4krow said:

I'm still trying to wrap my brain around the idea of using a feedback loop to interact with the speakers/room. I actually get the concept from the view that the speakers can be microphones for the amp. What does the amp do with this information? Is it related to the whole spectrum of signal or just the bass? Thanks.

 

  I talked with an audio engineer friend of mine about this. His version of understanding is that it would sort of like DSP (but not DSP) with a calibrated mic. Well, I get that, but the drivers in the speakers aren't calibrated to the amp in any way, right? So, there is another avenue to use them still I suppose, and this is my curiosity.

Hi Ken,

1st question- Its the full spectrum. Every sound wave produces a signal that is used by the amp.. 

 

2nd question- I'll ask Bob to explain more about this. He has an interesting voltage feedback and separate current feedback loops. The back EMF from the speakers feeds back to the driver stage of the amp.. I've heard it work, moving from large rooms to hotel rooms at shows. The soundstage details of scale seem to be less effected by room size and shape. Thats a real trick in an average size hotel room, to get the room size to disappear when you close your eyes, and get the sensation of changing physical locations. It works.

 

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