[preproman]

   
I'm aware both FirstWatt and Pass Lab amps are created by Mr. Nelson Pass, but if you're saying this, then is Pass Labs a superior brand?

 
 
Yes, I'm going by an interview I saw with Nelson Pass as he describe the difference between Pass Lab and First Watt.  Plus the Pass Lab amps are not offered to the DIY community AFAIK.  

 

[Steve Eddy]

Yes, I'm going by an interview I saw with Nelson Pass as he describe the difference between Pass Lab and First Watt.  Plus the Pass Lab amps are not offered to the DIY community AFAIK.  

Oh no, Nelson doesn't mind selling Pass Labs amps to DIYers at all.

But yeah, the First Watt stuff is more an exercise in simplicity, as well as an avenue to explore more unusual designs that wouldn't quite fit the mold of the broader high end market. The Pass Labs designs are generally more complex and the casework much more refined and consequently more expensive.

And in my opinion, Nelson is the elder statesman of audio and I can't really think of anyone who has contributed more to the DIY community.

se

 

[ALRAINBOW]

Good morning Steve
Would you be so kind to weigh in on resister loading useing headphones on speaker amps

Thanks
Al D

 

[Steve Eddy]

Sure. Is there any particular aspect you'd like me to address?

se

 

[ALRAINBOW]

Yes there is . Some of use speaker amps for headphone amps , as I am sure you are aware of., now I do to , and some amps it has no affect in the sound , others it is really a needed. And some it lowers the noise floor. This happens even with op amps for headphones. Why and what rules generally should be followed doing this. This is a somewhat debated topic with many including me weighing in. As I can follow schematics well and have a basic understanding of bios with transistors and tubes . But I do lack in a real principle that causes this . And a method besides listing to have some kind of conformity in this...

Any thoughts sorry it took me so long to post back going all over the city just got back to office..

Al D

 

[Steve Eddy]

Ok, finally have more than a few minutes to bang out a reply.

When using speaker amps to drive headphones, unless the amp has rather low rated power into loudspeaker loads, you often have to deal with excess gain, i.e. a speaker amp will typically have a lot more gain than is required to drive a typical headphone to sufficient levels. This means you'll have a lot less useable range on the volume control.

So basically, short of reducing the gain of the amplifier, you need to attenuate the amp's output. The simplest way is with a single resistor in series with the amp's output. This forms a voltage divider consisting of the series resistor and the headphone's impedance. A secondary effect of this is to increase the output impedance of the amp by the amount of resistance of the resistor. This doesn't present a problem for orthos which have a flat, virtually purely resistive impedance, but can be problematic with dynamic headphones which don't.

This can be addressed by adding a second resistor that's in parallel with the headphones. And in that case, the source impedance seen by the headphones is the parallel combination of the series resistor and the resistor across the headphone (technically the amp's inherent output impedance of the amp is added to the series resistor, but the series resistor will typically be much higher than that so it can often be ignored).

As for noise, the voltage divider will attenuate everything, noise and music, because of course a resistor can't tell the difference between the two. So any quiescent noise produced by the amplifier won't be quite so loud which is of benefit for headphones with high sensitivity.

This help?

se

 

[ohhgourami]

Ok, finally have more than a few minutes to bang out a reply.

When using speaker amps to drive headphones, unless the amp has rather low rated power into loudspeaker loads, you often have to deal with excess gain, i.e. a speaker amp will typically have a lot more gain than is required to drive a typical headphone to sufficient levels. This means you'll have a lot less useable range on the volume control.

So basically, short of reducing the gain of the amplifier, you need to attenuate the amp's output. The simplest way is with a single resistor in series with the amp's output. This forms a voltage divider consisting of the series resistor and the headphone's impedance. A secondary effect of this is to increase the output impedance of the amp by the amount of resistance of the resistor. This doesn't present a problem for orthos which have a flat, virtually purely resistive impedance, but can be problematic with dynamic headphones which don't.

This can be addressed by adding a second resistor that's in parallel with the headphones. And in that case, the source impedance seen by the headphones is the parallel combination of the series resistor and the resistor across the headphone (technically the amp's inherent output impedance of the amp is added to the series resistor, but the series resistor will typically be much higher than that so it can often be ignored).

As for noise, the voltage divider will attenuate everything, noise and music, because of course a resistor can't tell the difference between the two. So any quiescent noise produced by the amplifier won't be quite so loud which is of benefit for headphones with high sensitivity.

This help?

se

Wow great reply!

 

[songmic]

Ok, finally have more than a few minutes to bang out a reply.

When using speaker amps to drive headphones, unless the amp has rather low rated power into loudspeaker loads, you often have to deal with excess gain, i.e. a speaker amp will typically have a lot more gain than is required to drive a typical headphone to sufficient levels. This means you'll have a lot less useable range on the volume control.

So basically, short of reducing the gain of the amplifier, you need to attenuate the amp's output. The simplest way is with a single resistor in series with the amp's output. This forms a voltage divider consisting of the series resistor and the headphone's impedance. A secondary effect of this is to increase the output impedance of the amp by the amount of resistance of the resistor. This doesn't present a problem for orthos which have a flat, virtually purely resistive impedance, but can be problematic with dynamic headphones which don't.

This can be addressed by adding a second resistor that's in parallel with the headphones. And in that case, the source impedance seen by the headphones is the parallel combination of the series resistor and the resistor across the headphone (technically the amp's inherent output impedance of the amp is added to the series resistor, but the series resistor will typically be much higher than that so it can often be ignored).

As for noise, the voltage divider will attenuate everything, noise and music, because of course a resistor can't tell the difference between the two. So any quiescent noise produced by the amplifier won't be quite so loud which is of benefit for headphones with high sensitivity.

This help?

se

 
Sorry to butt in on your conversation, but does my HE-Adapter serve as the resistor? Or is it merely an adapter that simply relays speaker output signal into 4-pin XLR without altering anything?

 

[ohhgourami]

   
Sorry to butt in on your conversation, but does my HE-Adapter serve as the resistor? Or is it merely an adapter that simply relays speaker output signal into 4-pin XLR without altering anything?

Yes, there are resistors that are in series and parallel. I still think simple wirewound resistors are better as there are many reports of coloration/degradation with the HE-Adapter.

 

[songmic]

Yes, there are resistors that are in series and parallel. I still think simple wirewound resistors are better as there are many reports of coloration/degradation with the HE-Adapter.

 
Uh-oh, really? I invested around $300 on speaker cables, $150 on HE-Adapter and $400 on aftermarket 4-pin XLR cable... too late to turn back now. 

 

[ohhgourami]

   
Uh-oh, really? I invested around $300 on speaker cables, $150 on HE-Adapter and $400 on aftermarket 4-pin XLR cable... too late to turn back now. 

Terminate the speaker cables with a 4-pin XLR. Sell the HE-Adapter and buy some resistors for $10.

 

[ALRAINBOW]

Steve , thanks for replying. I have several more questions.

If the first resister is to be in series to reduce the overall out voltage and allow to increase our volume pot. Does this effect factor damping factor.
Second question. I am assuming the resister in parallel with the headphones is to match the nominal imp of that particular headphone.
Third question . Would it be better to have the resister as like 8 ohms. And resister in series from there to antenna the the output voltage and the final resister in parallel with headphone matching the headphone . At the speaker terminal the amp would see a nominal load of 8 ohms .

Does this make sense .
Ex.. Hd800 300 ohm, he 6 50 ohm.

Last with high imp headphones like a hd 800

Al D

 

[NZtechfreak]

Thank you for that post Steve, wonderful. There is a sentiment that suggests a person doesn't truly understand something unless they can explain it simply, or stated differently, in a form that is accessible to the person receiving the explanation in a way that facilitates their understanding - your post is a wonderful example of that.
 
As a doctor, which is to say fundamentally a scientist, and also a musician, I really appreciate the fine line between appreciating sound science, while also realising that it has limits where it intersects with something subjective like music, and for me your commentary is the perfect marriage of those two sometimes difficult bedfellows.
 
My thanks sir.

 

[drez]

Anyone tried a Job 225?  For some reason I'm keen to jump on that hype train...

 

[brunk]

  Anyone tried a Job 225?  For some reason I'm keen to jump on that hype train...

Haven't tried it, but if you can find it for it's last street price of $799 or under, I say go for it!