Please HELP! (mods please move thread as needed)

[jokan]

I have an amplifier that can only accept 0.5mv/47kohm RCA input. Unfortunately I have no audio preamp that has such low level outputs.
Before I get suggestions of turning down the preamp, that doesn't cure the clipping/saturation problem no matter how low I turn the output voltage on the RCA output from my playback device.

The input stage is maxed at 0.5mv input. Think 20-30 years ago hi-fi.
Example, playing out of my Galaxy note 8's 3.5mm jack at full tilt doesn't cause audible clipping or over-saturation of the input stage.

I need your help in designing a converter to reduce the output voltage with minimal parts to reduce the voltage down to 0.5mv. Any higher and clipping occurs.
I like this little amplifier as it sounds great with a lower input signal voltage. Good enough that I see no reason to upgrade sideways to a device that takes a higher input voltage. It doesn't matter how low I set the amplifier given a 2v input. 1v and the distortion is reduced but present.
Go down to the headphone output from my phone and it's perfect.

If someone could take the time to draw up a schematic and list the parts needed for a 2 channel device that would serve as a adaptor to reduce the output from my DAC that would be great. I have zero intention of throwing out an amplifier from literally 2 years ago. It sound dynamic, clean and suitably matched to output voltage it is perfect. It isn't necessary to have adjustable gain control. My preamp will sort that out. The fewer the components used would be awesome. I dislike parasitic parts. This little amp is used on a literal desktop and will only be used for emergency use. I do not want to use cheap internal parts. No off the shelf converters. I am happy to assemble the converter, I suppose I need values and a simple schematic. I will source RCA input sockets and output sockets.

Thanks.

Yet another example that Gain control is NOT to be confused with volume control

 

[jokan]

I did find this simple, rudimentary potential solution, though i have zero idea on the overall fidelity of such a simple circuit.

From the looks of it, maybe there are two 1watt resistors, and 1 0.5 watt resistor. Though they could easily be 2, 1/2 watt resistors and 1 0.25 resistors that are used.

If anyone could share some light to what would happen to frequency response, tonal quality, that would be most helpful.

I love the little amp and want to be able to use it daily for youtube and TV for my second room.

Thanks ASR squad for any help. And MODS, please move the thread to the appropriate section as I couldn't find the correct spot!

 

[JayGilb]

RCA line level attenuators are available for purchase on-line if you are looking for a non-diy solution.

 

[sarumbear]

I have an amplifier that can only accept 0.5mv/47kohm RCA input. Unfortunately I have no audio preamp that has such low level outputs.
Before I get suggestions of turning down the preamp, that doesn't cure the clipping/saturation problem no matter how low I turn the output voltage on the RCA output from my playback device.

The input stage is maxed at 0.5mv input. Think 20-30 years ago hi-fi.
Example, playing out of my Galaxy note 8's 3.5mm jack at full tilt doesn't cause audible clipping or over-saturation of the input stage.

There seems to be a confusion here. If the HP output of a mobile phone can feed your amplifier without any issues the 0.5mV sensitivity is not correct. You get multiple Volts output level from a mobile phone in order to feed an HP.

You have not described what is that "amplifier". Is it a power only amplifier? You also said you have no preamp. Then what have you been listening in the last 203 decades that you have your amplifier?

 

[raindance]

Get a dual 10K pot, install at the input of the amp. Wiper goes into positive input on each channel.

If that doesn't fix it, you've got bigger issues.

 

[Vini darko]

These adjustable ones from stageline may be just the ticket (assuming you ment 0.5V not 0.5mV sensitivity). The -20db setting should work nicely.

 

[jokan]

These adjustable ones from stageline may be just the ticket (assuming you ment 0.5V not 0.5mV sensitivity). The -20db setting should work nicely.
View attachment 177941

@Vini darko you are correct, I missed that, I did mean 0.5mv.

Thanks for the help. I am not looking for a quick fix. I am looking for an audiophile grade, i'm even contemplating an audio transformer to reduce the 2V RCA level output from my RME DAC to a 0.5mv

The input stage can only accept a maximum of 0.5mv like in the olden days. Anything more and the sound is either audibly clipped or supersaturated and thus distorted.

Adjustable attenuators that are sold on the consumer level are cheap construction, and use unknown quality resistor, typically they are resistors that do work, but were never intended for audio use. I use VSR vishay's for most of my tube amplifiers and PRP in less audio sensitive parts. If that gives you any idea about what I think about resistors. Not only is the construction method important, but so is the casing that the resistor is enclosed in important for fidelity. Typically Carbon resistors like the ones sold by AMTRANS of Japan sound very poor in the upper and lower registers. Even Amtrans admits as much and they produce and sell them themselves.

Right now I'm thinking PRP, or Dale RN60-RN65's. If not I'll keep looking. I hate attenuators in general though I admit that they do work. It's more of a question of how high quality are they. All resistors are not created the same. If worst comes to worst I will pick up something like the devices that @Vini darko kindly suggested.

@sarumbear I think you might be looking too far into something that I didn't ask for help about. I know what I have, I know what the issue is. It's line output and line input voltage issues. A mobile via 3.5mm (my galaxy note 8, has tiny levels of output. Connect the same amplifier to my RME's 2V rca output and even with the gain cranked all the way down to best match the input maximum voltage, it's way too much input voltage causing audible clipping in the input stage of the amplifier. And YES I know what a gain control is unlike the people posting on the PA5 thread. I've been in the audio industry for long enough to know that gain control is not a volume knob, It's is used to match I/O gains to get the best possible matching of different equipment and to potentially lower noise floor as a side-effect. Thanks for your help but I think the others have given me extremely helpful, non-condescending advice.

Thanks guys for the speedy replies. I think I know what direction to take to rectify this over-saturation/clipping issue. I'm sure I can fix it now.
Now I have to decide on which resistors to purchase as in brand. I have that cheat sheet from another user who ran into the exact same issue of clipping/over saturation and I took his little diagram as an example. This thread for me is over. I have the answers I was looking for.

Much obliged and grateful for your help.

 

[jokan]

There seems to be a confusion here. If the HP output of a mobile phone can feed your amplifier without any issues the 0.5mV sensitivity is not correct. You get multiple Volts output level from a mobile phone in order to feed an HP.

You have not described what is that "amplifier". Is it a power only amplifier? You also said you have no preamp. Then what have you been listening in the last 203 decades that you have your amplifier?

The power amplifier in use is of zero consequence. The input can only accept 0.5mv max. The make/model of the amplifier is completely not the issue.

 

[Jimbob54]

@Vini darko you are correct, I missed that, I did mean 0.5mv.

Thanks for the help. I am not looking for a quick fix. I am looking for an audiophile grade, i'm even contemplating an audio transformer to reduce the 2V RCA level output from my RME DAC to a 0.5mv

The input stage can only accept a maximum of 0.5mv like in the olden days. Anything more and the sound is either audibly clipped or supersaturated and thus distorted.

Adjustable attenuators that are sold on the consumer level are cheap construction, and use unknown quality resistor, typically they are resistors that do work, but were never intended for audio use. I use VSR vishay's for most of my tube amplifiers and PRP in less audio sensitive parts. If that gives you any idea about what I think about resistors. Not only is the construction method important, but so is the casing that the resistor is enclosed in important for fidelity. Typically Carbon resistors like the ones sold by AMTRANS of Japan sound very poor in the upper and lower registers. Even Amtrans admits as much and they produce and sell them themselves.

Right now I'm thinking PRP, or Dale RN60-RN65's. If not I'll keep looking. I hate attenuators in general though I admit that they do work. It's more of a question of how high quality are they. All resistors are not created the same. If worst comes to worst I will pick up something like the devices that @Vini darko kindly suggested.

@sarumbear I think you might be looking too far into something that I didn't ask for help about. I know what I have, I know what the issue is. It's line output and line input voltage issues. A mobile via 3.5mm (my galaxy note 8, has tiny levels of output. Connect the same amplifier to my RME's 2V rca output and even with the gain cranked all the way down to best match the input maximum voltage, it's way too much input voltage causing audible clipping in the input stage of the amplifier. And YES I know what a gain control is unlike the people posting on the PA5 thread. I've been in the audio industry for long enough to know that gain control is not a volume knob, It's is used to match I/O gains to get the best possible matching of different equipment and to potentially lower noise floor as a side-effect. Thanks for your help but I think the others have given me extremely helpful, non-condescending advice.

Thanks guys for the speedy replies. I think I know what direction to take to rectify this over-saturation/clipping issue. I'm sure I can fix it now.
Now I have to decide on which resistors to purchase as in brand. I have that cheat sheet from another user who ran into the exact same issue of clipping/over saturation and I took his little diagram as an example. This thread for me is over. I have the answers I was looking for.

Much obliged and grateful for your help.

You're confusing everyone even more. Accepting a correction to 0.5v then still saying 0.5mv. Which is it?

 

[zermak]

If you have a RME DAC why don't you simply use it as preamp and never exceed -17dBFS on the volume (if using RCA outs)?

 

[jokan]

There is zero confusion, except for your part. I clearly corrected myself

 

[BDWoody]

The power amplifier in use is of zero consequence. The input can only accept 0.5mv max. The make/model of the amplifier is completely not the issue.

.5mv is roughly what you get from a Turntable cartridge.

 

[jokan]

.5mv is roughly what you get from a Turntable cartridge.

I am well aware.

 

[Deleted member 21219]

The power amplifier in use is of zero consequence. The input can only accept 0.5mv max. The make/model of the amplifier is completely not the issue.

Humor us. It won't kill you. Please tell us the make and model of the amp, and if you could, tell us the designation (name) of the RCA input on this amp.

 

[Jimbob54]

Some phones can output the full 2v, some 1 v, some less. Not fractions of mv at the upper end of their slider.

The pixel 4a was rated here as "very low" at 0.3v. So, no, your assertion that the note 8 outputs fractions of mv at full bore is highly unlikely. https://www.audiosciencereview.com/...oogle-pixel-4a-smartphone-audio-review.16251/

 

[jokan]

Some phones can output the full 2v, some 1 v, some less. Not fractions of mv at the upper end of their slider.

The pixel 4a was rated here as "very low" at 0.3v. So, no, your assertion that the note 8 outputs fractions of mv at full bore is highly unlikely. https://www.audiosciencereview.com/...oogle-pixel-4a-smartphone-audio-review.16251/

I already stated I have a galaxy note 8.
it's connected via 3.5-RCA adaptor.

 

[jokan]

Humor us. It won't kill you. Please tell us the make and model of the amp, and if you could, tell us the designation (name) of the RCA input on this amp.

No. I will not make this into an endless thread. I've already asked the mods to lock the thread so THIS doesn't happen. I have my answer that the first few responders were helpful in providing. The rest of the responses are just dragging things on unnecessarily.