[scompton]

I have an NAD 3155 and it has too much gain for me. I rarely use more than the first 30 degrees of pot and for most of my headphones, just the first 15 degrees. It's really hard to make fine adjustments.

It has a preout and main in and I assume I can make a cable with resistors to go between them to reduce the gain. What I don't know is do I just put resistors in series or do I need a network? Also is there a way to determine the resistor values other than trial and error?

In case it matters, the pre out impedance is 800 ohms and the main impedance is 22k ohms.

 

[rocker]

I've seen these in some audio mags - seem to be well thought of - I know you can get them on Audiogon
Attenuators

 

[scompton]

I'd rather make some. Those cost 39 pounds and I doubt that they're anything but resistors in a pretty case. Also if I bought those I'd still have to make a cable. The RCA jacks I want to connect are less than an inch apart.

 

[rocker]

Do whatever...just pointing them out.BTW, you actually plug your existing cable into the attenuators.

 

[olblueyez]

Yeah, its just a couple of Bi-RCA jacks with resistors.

 

[scompton]

Quote:

Originally Posted by rocker /img/forum/go_quote.gif Do whatever...just pointing them out.BTW, you actually plug your existing cable into the attenuators.

I didn't mean to put down your suggestion. It just doesn't work for what I need.

The jacks are currently connected by jumpers. I have another amp that needs jumpers, so making a cable to reduce the gain actually will serve 2 purposes.

 

[Duggeh]

These in-line RCA attenuators will destroy the sound. Ruin the treble and upper mids in particular. The reason that expensive ones exist is because they're made with unobtanium super transparent resistors I assume.

 

[NelsonVandal]

You need two resistors per channel, one in series and one to ground after that, and Ohm's law. You could also use a potentiometer. I guess something like 10k would do depending on your preamps output impedance and poweramps input impedance.

 

[NelsonVandal]

Quote:

Originally Posted by Duggeh /img/forum/go_quote.gif These in-line RCA attenuators will destroy the sound. Ruin the treble and upper mids in particular. The reason that expensive ones exist is because they're made with unobtanium super transparent resistors I assume.

The only reason this unobtanium super transparent attenuators sound better is the psychological effect spending a lot of money has, or they have some built in flaw that make them sound different, not better.

If in-line RCA attenuators destroy the sound like you say, it's only because too low (or maybe, but not likely, too high) values have been choosen, or there are some unnessecary capacitors in them. The volume pot in your amp is an attenuator. After the pot, there's almost always resistors in sereies and parallel. At the preamps output there's also almost always a resistor. There's no reason to believe that two cheap medium quality resistors are going to destroy the sound. IMO opamps, transistors, capacitors and grounding topology is what really make the amp sound like this or that, not resistors, connectors or cables and such.

 

[Duggeh]

This isn't something I believe, its something I've experienced when I owned such products and in all settings in which I tried them they were detrimental to the sound and not in a subtle way. None had capacitors in them, what would be the point unless you wanted to create a notch filter? And you'd need far larger caps than would fit into an RCA barrel for that.

 

[olblueyez]

Quote:

Originally Posted by Duggeh /img/forum/go_quote.gif This isn't something I believe, its something I've experienced when I owned such products and in all settings in which I tried them they were detrimental to the sound and not in a subtle way. None had capacitors in them, what would be the point unless you wanted to create a notch filter? And you'd need far larger caps than would fit into an RCA barrel for that.

Never read about anyone having a different experience than what Duggeh describes. Its always the same story, they destroy sound quality.

 

[12Bass]

Quote:

Originally Posted by scompton /img/forum/go_quote.gif I have an NAD 3155 and it has too much gain for me. I rarely use more than the first 30 degrees of pot and for most of my headphones, just the first 15 degrees. It's really hard to make fine adjustments. It has a preout and main in and I assume I can make a cable with resistors to go between them to reduce the gain. What I don't know is do I just put resistors in series or do I need a network? Also is there a way to determine the resistor values other than trial and error?

Ummmm...

I have an NAD 3150. How about using the Low Level button which is designed expressly to give more usable range to the volume control?

 

[NelsonVandal]

Quote:

Originally Posted by Duggeh /img/forum/go_quote.gif This isn't something I believe, its something I've experienced when I owned such products and in all settings in which I tried them they were detrimental to the sound and not in a subtle way. None had capacitors in them, what would be the point unless you wanted to create a notch filter? And you'd need far larger caps than would fit into an RCA barrel for that.

I can understand why attenuators is detrimental for the sound since they change the output impedance from low to high. This is why passive preamps sound like they do. I just can't understand why an expensive fancy looking attanuator would do it any different.

Scompton, since you know the impedances, you could use a single resistor in series. Since the output impedance of your preamp is highish, the impedance matching will be suboptimal using a passive attenuator, and threre's a risk that you'll get a degraded sound just like Duggeh and olblueyez says. But what the heck. This ain't rocket science or expensive parts we're talking about so go ahead and try it.

If you're a dedicated DIY'er, you could build your own cheap preamp and probably beat the built in one by a mile.

 

[mrfloopy]

I've got a pair of Rothwell in-line attenuators on the input to my NAD C352 (I've only got one source connected to it, and I didn't want to put the attenuators between the pre-out and main-in) and they don't do anything bad to the sound to my ears. I did get them off eBay so they were a good price.

I also use Goldenjacks -10dB attenuators between my DAC and Little Dot MK V, and they don't do anything bad to the sound to my ears, and they're cheaper than the Rothwells brand new.

I've also got Goldenjacks -20dB attenuators I have used between a DAC and my MK V, and they didn't do anything bad to the sound to my ears.

Harrison Labs are probably the third well-known in-line attenuator manufacturer, and might be cheaper depending on where you are, although I haven't tried their product.

 

[Beefy]

Quote:

Originally Posted by Duggeh /img/forum/go_quote.gif This isn't something I believe, its something I've experienced when I owned such products and in all settings in which I tried them they were detrimental to the sound and not in a subtle way. None had capacitors in them, what would be the point unless you wanted to create a notch filter? And you'd need far larger caps than would fit into an RCA barrel for that.

Quote:

Originally Posted by olblueyez /img/forum/go_quote.gif Never read about anyone having a different experience than what Duggeh describes. Its always the same story, they destroy sound quality.

I've had very different experiences to what you both suggest with 'Goldenjacks' attenuators. I have three sets of the -6dB model, and they cause no degradation in sound quality whatsoever. They are voltage dividers (which is exactly what a volume pot is anyway) with one resistor in series with the source and one resistor to ground. They reduce the voltage seen by the input stage of the amp, while keeping the impedance seen by the source constant.

But for a quick DIY solution, you can easily juts put a resistor in series with the input and there is no reason why you would degrade sound quality. Just match the value of your current impedance: eg, if it is currently 50kohm, put 50kohm in series (try and keep total impedance under 100kohm though). This is a very common suggestion for the high gain Starving Student (recommended by either Uncle Erik or dsavitsk, I can't remember).

EDIT: Oh, and AMB has recommended a voltage divider setup for changing the 'gain' on the B22 here. There is *no* problem with input attenuation if it is done properly.