27 replies to this topic

[Batty]

Just thinking about level matching here, I believe the standard output from a CD is 2 volts and the output from my NFB-2 is 2.5volts. Seeing as how my amp is a bit old school (1995) it's CD input would be matched to 2 volts. So here is the question, would it be a good thing to run attenuators and if so what value?

[GregWormald]

Good question--I want to hear the answer 'cause my pre is bit 'old school' as well.

If I can add to the question--Does such an attenuator affect the sound quality at all?

Greg

[lebowski]

I found no detrimental effect to sound quality using -10dB attenuators (Golden Jacks and Grave Science). Sound is more open and no longer edgy in higher frequencies.
Highly recommended.

[lebowski]

Forgot to add that you can order various values direct from Golden Jacks website. Has a brief description of most appropriate value attenuator for your application.

[pete_mac]

I found no detrimental effect to sound quality using -10dB attenuators (Golden Jacks and Grave Science). Sound is more open and no longer edgy in higher frequencies.
Highly recommended.

X 2

I've used Grave Science -10dB attenuated interconnects and also some DIY -10dB adapters for some time now and they do a great job. When used with vintage amps they give you more resolution with your volume knob too.

Absolutely essential IMHO.

[naggots]

I have a pair of Golden jacks that I don't use if anyone is interested. Didn't hear any issues when i needed them using Phono, don't have Phono now thus no longer needed. Cheap enough to try at $30 incl post as new incl docs.

[Zaphod Beeblebrox]

Just thinking about level matching here, I believe the standard output from a CD is 2 volts and the output from my NFB-2 is 2.5volts. Seeing as how my amp is a bit old school (1995) it's CD input would be matched to 2 volts. So here is the question, would it be a good thing to run attenuators and if so what value?

Should not be necessary. Unless you are operating the amp below (say) 10:00 o'clock on the the volume control. Only then should you worry about extra attenuation. The difference between 2 VRMS and 2.5 VRMS is insignificant.

[pete_mac]

Should not be necessary. Unless you are operating the amp below (say) 10:00 o'clock on the the volume control. Only then should you worry about extra attenuation. The difference between 2 VRMS and 2.5 VRMS is insignificant.

Fair call that... 2V vs 2.5V is less of an issue than 150mV vs 2.5V which is the situation that lebowski and I find ourselves in.

[Zaphod Beeblebrox]

Fair call that... 2V vs 2.5V is less of an issue than 150mV vs 2.5V which is the situation that lebowski and I find ourselves in.

The difference between 2 VRMS and 2.5 VRMS is hardly "less of an issue". It is a non-issue. As for your problem, then just solder up an appropriate attenuator, using regular resistors inside the amp. Paying outrageous amounts for external attenuators is not the approach I'd expect any technically qualified person to take.

[GFuNK]

Should not be necessary. Unless you are operating the amp below (say) 10:00 o'clock on the the volume control. Only then should you worry about extra attenuation. The difference between 2 VRMS and 2.5 VRMS is insignificant.

What about the issue of overloading on the input, especially with modern recordings using full range?

[Zaphod Beeblebrox]

What about the issue of overloading on the input, especially with modern recordings using full range?

That's what we have volume controls for.

[GFuNK]

That's what we have volume controls for.

Do you mean on the source? For those using an integrated amp that would mean possibly digital volume control if at all.

[Zaphod Beeblebrox]

Do you mean on the source? For those using an integrated amp that would mean possibly digital volume control if at all.

Doesn't matter where the volume control is, though it is more usual to have it on the preamp or the preamp section of an integrated amp. Either way, not using a volume control of some kind is an invitation to disaster.

[GFuNK]

Doesn't matter where the volume control is, though it is more usual to have it on the preamp or the preamp section of an integrated amp. Either way, not using a volume control of some kind is an invitation to disaster.

Let me use my Yammy amp as an example (rs700). It has a maximum input of 2.2 V, at which, the THD is quoted at 0.5%. It is for this reason that I had kingwa lower the nfb2 output to 2 V.

[pete_mac]

The difference between 2 VRMS and 2.5 VRMS is hardly "less of an issue". It is a non-issue. As for your problem, then just solder up an appropriate attenuator, using regular resistors inside the amp. Paying outrageous amounts for external attenuators is not the approach I'd expect any technically qualified person to take.

Our expectations are clearly different . The Grave Science cables are fantastic, both in normal and attenuated formats, so I have no qualms in spending a relatively amount on them and helping a local cable enthusiast to earn a crust.

I've got a few DIY attenuators which work great. I have contemplated modifying the -20dB attenuation switch on my amp to a -10dB cut instead... all in good time. Adding the attenuation directly onto the line level is pretty darn good idea though...

[Zaphod Beeblebrox]

Let me use my Yammy amp as an example (rs700). It has a maximum input of 2.2 V, at which, the THD is quoted at 0.5%. It is for this reason that I had kingwa lower the nfb2 output to 2 V.

Puke. I stand corrected. I had (possibly mistakenly) assumed that the amplifier (unstated model) did not use dodgy technology to perform switching functions. There's a good reason why decent preamps and amps use hard switches for all input switching functions. Not as convenient, but distortion is rarely a problem, even with quite silly input Voltages (< 50 VRMS).

[LuzArt]

That's what we have volume controls for.

What about the issue of overloading on the input, especially with modern recordings using full range?

For the benefit of those who haven't used attenuators on an input and are wondering what they can offer, I have to highlight a really important point.

A volume control simply increases the level of the voltage from the preamp stage. If the preamp is being overloaded by a hot signal from a DAC or CD player (as GFuNK has suggested) ie 2V into an amp rated at 150mV input sensitivity, then the volume control won't do anything to change this, it will only change the level POST preamp stage.

Attenuators are for reducing the voltage BEFORE the preamp's input, hence not overloading the preamp stage, hence avoiding unpleasent reproduction from hot sources.

Therefore, suggesting "that's what we have volume controls for" isn't quite helpful.

[Nada]

Does anyone know how to work out impedance issues for attenuators on balanced XLR inputs inot a power amp?

Id like to make 15dB balanced attenuators but dont want to mess with impedance matching.

I used to know a site that had five circuit designs for DIY attenuators. Anyone got links for circuit designs that have the impedance issues addresses?

[Zaphod Beeblebrox]

Therefore, suggesting "that's what we have volume controls for" isn't quite helpful.

Depends. With almost all old style amps and current generation high end preamps, the input signal is routed directly to the volume pot, via mechanical switching systems. Therefore, no overload will occur, unless nonsensically high Voltages are applied. Sometimes a buffer will be employed, but good designers will ensure that around 10VRMS signals can be dealt with, without problems. With many mid-fi products, solid state switching is employed. These switches most definitely suffer distortion problems with elevated input Voltages.

It all depends on the switching system and where the volume control pot is placed.

Certainly, when using Euro style input systems (DIN standard) then attenuators are a good idea, due to the large mis-match between modern digital sources and the preamps used.

[Nada]

found it - fantastic online calculator for resister values and impedance too: http://www.giangrand...tenuators.shtml


anyone know how I wire this "O" pad circuit:


to the XLR pins inside the XLR male-female adaptor below?





Pin Function

1 Chassis ground (cable shield)

2 Positive polarity terminal for balanced audio circuits (aka "hot")

3 Negative polarity terminal for balanced circuits (aka "cold")^[11]

Edited by Nada, 09 May 2012 - 10:30 AM.

[naggots]

The difference between 2 VRMS and 2.5 VRMS is hardly "less of an issue". It is a non-issue. As for your problem, then just solder up an appropriate attenuator, using regular resistors inside the amp. Paying outrageous amounts for external attenuators is not the approach I'd expect any technically qualified person to take.

Except it's reversible and won't void warranties.... And if 1 source output is full vol at 10am where others are 3 pm...... Save speaker issues when switching.

Edited by naggots, 09 May 2012 - 12:38 PM.

[emesbee]

Hmm, attenuation is something that had never occurred to me. Looks like a whole new world of potential tweaking opening up. (I must remember to check the specs on my DAC and amplifier (c1999) tonight).

[Batty]

Just found that Line level input sensitivity on my Copland is 130mV and phono is 3mV.

At least I got the phono right for the DL-103 and 10:1 SUT

It would seem I would benefit from attenuators on the output of my DAC.

[Art Vandelay]

Depends. With almost all old style amps and current generation high end preamps, the input signal is routed directly to the volume pot, via mechanical switching systems. Therefore, no overload will occur, unless nonsensically high Voltages are applied.

I think it was a Musical Fidelity preamp (A3cr?) I opened up and took a look at. It employed a voltage gain block and a buffer, with a motorized pot in the middle. It exhibited a large amount of (leading edge) overshoot when driven with a > 1kHz square wave at amplitude > 1V pp. I had to redesign a nested feedback loop to cure the problem.

I suspect there are many preamps around these days that employ a similar topology, and if the voltage stage gain is set to >5 and the rail volts are <15 there could well be trouble.

Of course any competent design will have no such problems but competent design is not always synonymous with ‘audiophile’ products.

[GregWormald]

An intensive Google session has revealed that while some people love their attenuators (usually between pre and power) a reasonable proportion of those who have installed them between source and pre state that they 'dull' the sound, and have removed them.

Since my issue was not critical, but only preferring a match in volume control settings between sources, I think I'll give it a miss.

Thanks for the help, all.

How are you going on this, Batty?

Greg

[lebowski]

An intensive Google session has revealed that while some people love their attenuators (usually between pre and power) a reasonable proportion of those who have installed them between source and pre state that they 'dull' the sound, and have removed them.

Since my issue was not critical, but only preferring a match in volume control settings between sources, I think I'll give it a miss.

Thanks for the help, all.

How are you going on this, Batty?

Greg

some like the edge and perceive this as more detail however, a hot signal needs to be dealt with.

Edited by Lebowski, 09 May 2012 - 07:09 PM.

[LuzArt]

Greg, my experience with Goldenjacks has been excellent, because I chose an appropriate level of attenuation for the amp input sensitivity. By contrast when I used the att's on Proac's Leben, there was no benefit. Turns out the Leben's in sens. was higher and didnt require att'ing. Horses for courses then.

Edited by LuzArt, 09 May 2012 - 09:47 PM.

[Batty]

Not really had the time to look into this much, I'd like to try before buy too.