Intact Audio

Hi all,

I am planning to ask Dave for a pair of custom made AVC , it will be use just after my DAC , witch output 2.0 V rms , 112 ohm Z out , to drive my F6 amplifier with 10 k ohm Z in

am I wrong thinking that - 6 dB is my max reduction ?

I could have 14 step of 0.5 dB

what do you guys think ?


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Hey,

It is unclear what you mean by "6db is my max reduction". Do you want to be able to do some form of level matching and attenuate elsewhere?

dave

Hello Dave,

what I mean is , my dac output is 6dBv ( 2.0 v rms ), so I dont need more attenuation than 6 dBv

what would you suggests in my situation


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It is still unclear to me what you are trying to accomplish. 6dBv is 2V and 0dBv is 1V. That is not much of a range of attenuation.

dave

Hello Dave ,


You are right , I lost myself in calculation !!!

I need to attenuate my dac output from 2.0 v rms to say 0.5 v rms in the more step as possible

so I need 2 autoformers to do that job


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2V to 0.5V is only a 12dB range and will not be very effective for adjusting level.

are you looking to control overall system volume or match levels in a multi-amped situation?

dave

Hello Dave ,

I want to control de volume of the all system made by :

cd drive to Dac to amplifier

I thought the autoformer could be custom made in order to have 14 steps of nearly 1 dB , or 28 steps of less than 0.5 dB

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it can be but then you will not have a very practical range of attenuation.

dave

Hello Dave ,

what would you suggest to make the situation more "practical" ?

when I use the same system using the digital volume attenuation of my pc it works pretty well , it is still 12 dB


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if you have access to digital attenuation through your dac then you can monitor the levels through several types of music and come up with a workable rage. I find I routinely use about 30dB from quiet to loud listening sessions.

set the digital attenuation to -12dB and see it you ever feel the need to turn it down. It is conceivable that you could use a 12dB autoformer for the bulk of your critical listening and then rely on further digital attenuation for non-critical low level background music.

The thing that is unclear to me is if you plan on using only the autoformer for attenuation or a combo of both the autoformer and the digital volume control.

dave

Hello Dave,

the dac has no volume control I have it through the pc ( personal computer ) when I listen music with youtube or online radio

my concern is when I use my cd transport ( micromega cd 3.1 ) it output full digital level to the dac

what I want is having an autoformer attenuation after the dac , so i could control the volume while playing cd

and even when I listen through my pc i can set the digital level almost full and control the volume with the autoformer



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if you want all of your attenuation to be done with the autoformer you will need a 30dB range or more. What that range is becomes a function of your system gain.

dave

Hello Dave,

ok , what do you suggest as a custom autoformer , knowing what is it for , and knowing what are the various impedance involved

i wont ( ever ) have more than 2.0 v rms in , and my amp sensibility is 0.5 v rms

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The input sensitivity of the amp is the voltage input required to get to full power so you will need a minimum of 12dB attenuation to avoid clipping. Assuming the 30dB range I mentioned before, that makes the 42dB of attenuation of the $200 units at the edge and I suspect you will have "hair trigger" attenuation with only a few useable clicks. I would suggest the 2dB 28 position units wired to a 23-24 position switch using the taps with the most attenuation.

dave

Hello Dave,

I thought it was possible to wire an autoformer for my setup ( cost was not an issue ) , like having 24 steps ( or more ) to go from 2.0 v rms in to 0.5 v rms out , I was wrong

Thank you for your answers



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it is possible and I will gladly do it for you but as far as I can tell is it will serve no purpose and render your system unusable since anything above 0.5V will clip your amps so your loudest setting should be -12dB and you should go down from there.

dave

Hello Dave ,

my amp is an F6 from Nelson Pass , when I say sensibility is 0.5 v rms it means it is the minimum , it has 14 Db gain , it's maximum input sensibility is 2.83 v rms and then it start to clip , so with my 2.0 v rms dac output i wont make it clipping anyhow

here are the data for this amp : https://firstwatt.com/pdf/prod_f6_man.pdf

there is some misunderstanding , I think


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OK... so you can't clip it... the next question becomes how loud do you listen and what range do you need. the 0.57V input voltage gives 1W out so the question becomes how loud do you listen with respect to that?

dave

Hello Dave,

I normaly listen at less than 5 w , but it happens that I listen with the dac full scale , so 2.0 v rms into the amp

as said before my range is 0.5 v to 2.0 v rms

my speakers are 6.0 ohm

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Then tell me what the attenuation range and step size is and I'll wind them.

dave

Hello Dave ,

My range of attenuation is my range of tension , I have not need to attenuate voltage that I dont have , and I have no need to attenuate below my amplifier minimum sensibility

for the step the more the better , I suppose

fact is that I dont know what is possible or not , I just know what are my voltage and Z numbers , and you have them all

I look for an product as much as I look for suggestions and advice


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I have no need to attenuate below my amplifier sensibility

input sensitivity is the voltage input required to get to full power. If you have no need to go below that then you will be listening at full power all the time.

dave

Dave , please , you know what I am talking about , the minimum input sensibility as write in the Firstwatt document

these words are not from me , but from Nelson Pass


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Minimum input sensitivity is not a "thing". The firstwatt lists two different input sensitivities, one for full power (the accepted standard) and then one for 1W output which is not typical or traditional.

I have been going by the traditional definitions and use of an autoformer and it seems you are looking for something completely different. As I said above if you tell me what you want I will gladly wind it but I cannot proceed based on information I do not understand.

dave