Im looking to make some inline attenuators like the Rothwell's But i am unsure of what resistor values to use. I have some electronics experience but not so in depth to design this myself.
I am planning on using it between my preamp and poweramp because as it stands i have too much gain to use the two together. The Preamp is a Audire Diffet 2, im not sure of the output impedance of this unit but perhaps someone else knows?
The poweramp is a NAD C370 and im using it directly into the poweramp input (therefore bypassing preamp) the input impedance listed on NAD's site is 20k.
Im not sure how much attenuation i need but i think starting off with a -10db like the rothwell's would be a good place to start. If anyone would be willing to help me with this that would be great because id really rather build my own parts than spend the 60 bucks to buy the rothwell's I think it would also be good for others because i wasnt able to find much searching. I was only able to find one thread and i tried the schematic included but they didnt work well.
I am planning on using it between my preamp and poweramp because as it stands i have too much gain to use the two together. The Preamp is a Audire Diffet 2, im not sure of the output impedance of this unit but perhaps someone else knows?
The poweramp is a NAD C370 and im using it directly into the poweramp input (therefore bypassing preamp) the input impedance listed on NAD's site is 20k.
Im not sure how much attenuation i need but i think starting off with a -10db like the rothwell's would be a good place to start. If anyone would be willing to help me with this that would be great because id really rather build my own parts than spend the 60 bucks to buy the rothwell's I think it would also be good for others because i wasnt able to find much searching. I was only able to find one thread and i tried the schematic included but they didnt work well.
Hi,
fit the two resistors inside the RCA plug that goes onto the NAD poweramp input. No cable to help avoid the hf rolloff that would ensue due to capacitance between attenuator and input stage.
use a 10k in line and then choose a grounding resistor from the list.
Interconnect core to 10k to RCA centre pin.
and
RCA centre pin to grounding resistor to ground.
grounding resistor
4k7 => -9.9db these low atten give more risk of HF roll off
3k9=>-11db
3k0=> -12.7db
2k0=>-15.6db
1k5=>-17.7db
1k0=>-20.8db
750r=>-23db at this atten HF roll off almost zero @ 20kHz.
should be enough options to get you going.
BTW attenuation = 20 times [inv log (grnd res/10k+grnd res)]
This formula is not accurate because it does not account for the source impedance nor the poweramp input impedance but again it is close enough.
fit the two resistors inside the RCA plug that goes onto the NAD poweramp input. No cable to help avoid the hf rolloff that would ensue due to capacitance between attenuator and input stage.
use a 10k in line and then choose a grounding resistor from the list.
Interconnect core to 10k to RCA centre pin.
and
RCA centre pin to grounding resistor to ground.
grounding resistor
4k7 => -9.9db these low atten give more risk of HF roll off
3k9=>-11db
3k0=> -12.7db
2k0=>-15.6db
1k5=>-17.7db
1k0=>-20.8db
750r=>-23db at this atten HF roll off almost zero @ 20kHz.
should be enough options to get you going.
BTW attenuation = 20 times [inv log (grnd res/10k+grnd res)]
This formula is not accurate because it does not account for the source impedance nor the poweramp input impedance but again it is close enough.
Thanks for the response. I think i will try a couple different combinations first before i built the set to see which matches my needs the best. 😀
Did some a while back and gave 6dB reduction using the same value resistor for hot and ground.
http://www.diyaudio.com/forums/showthread.php?postid=547614#post547614
http://www.diyaudio.com/forums/showthread.php?postid=547614#post547614
Hi,
I have the very same question. A friend of mine, made me line-in attenuatrors on the high part of my tri-amped system with digital x-overs (Apogee Stage's 26inch ribbon works from 500Hz - 20KHz, driven by power part of vintage Luxman L-530 integrated amp).
Now, the level is adequate but unfortunately, the highs lost the magic and lot of that fine details that were present before.
Thank's a lot in advance for any suggestion.
Or have you lost a lot of euphonic distortion?
What values did you use in your attenuator? Too low and the crossover will struggle, too high and the power amp is being driven from a high impedance source. This can cause HF loss with capacitance and increased distortion with some input stage designs
What values did you use in your attenuator? Too low and the crossover will struggle, too high and the power amp is being driven from a high impedance source. This can cause HF loss with capacitance and increased distortion with some input stage designs
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Hi davidsrsb,
I don’t beleive that euphonic distortion lost now. The difference in high spectrum is really big. I am not sure about the values of the resistors but judging to new positions of analog output pots for highs, mids and lows, the atenuation is about 18dB. Now, all digital and analog outputs as well as analog inputs on my two x-overs, Electro Voice Dx34a, are set to zero (0) and the ballance of all 3 ranges are perfect. This setting give me the best sound from x-o and absolutely without any hum. In previous seting, the analog output pots for lows and mids were set to max i.e. +6dB and analog output pot for highs, was set to app minus 12dB. With this x-o setting, the hum was noticable at about 2 m in front of the speakers, and that was the reason why I attempted to attenuate the signal that goes to amp for high freq on another way.
My first reaction was that maybe the better quality resistors could improve the highs, but after a couple days of listening, it seems that I should remove them completely from interconnect cables, and try to find another solution.
Of course, the best solution should be to find another power amp with input sensitivity of 1V, sonicaly equal or even better than my present Luxman L-530, but this is not an easy task.
regards
I don’t beleive that euphonic distortion lost now. The difference in high spectrum is really big. I am not sure about the values of the resistors but judging to new positions of analog output pots for highs, mids and lows, the atenuation is about 18dB. Now, all digital and analog outputs as well as analog inputs on my two x-overs, Electro Voice Dx34a, are set to zero (0) and the ballance of all 3 ranges are perfect. This setting give me the best sound from x-o and absolutely without any hum. In previous seting, the analog output pots for lows and mids were set to max i.e. +6dB and analog output pot for highs, was set to app minus 12dB. With this x-o setting, the hum was noticable at about 2 m in front of the speakers, and that was the reason why I attempted to attenuate the signal that goes to amp for high freq on another way.
My first reaction was that maybe the better quality resistors could improve the highs, but after a couple days of listening, it seems that I should remove them completely from interconnect cables, and try to find another solution.
Of course, the best solution should be to find another power amp with input sensitivity of 1V, sonicaly equal or even better than my present Luxman L-530, but this is not an easy task.
regards
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