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Speaker amps for headphones - Page 132

post #1966 of 3116
One of my companies jobs is home theatre and whole house. Nowadays it s different
But about ten years ago I used L PADS they had a transformer inside
It was used to keep the load the same to the amp as you lowered the volume.
They fit in a reg light box where. Switch or outlet would go
post #1967 of 3116

Sounds more like an autoformer than an L-pad...

post #1968 of 3116
I just seen one in radio shack . It was rated at 80 watts . What it does is keep the same load on the amp as you adjust the volume on the speaker and it was a stereo one too one knob and it should do what we want perfectly. I got. A phone call and for got to buy it.
post #1969 of 3116
Quote:
Originally Posted by ALRAINBOW View Post

That is what I really want to use . So I can vary the two resisters and listen for changes other than volume . Does someone have alink to some l pads I can try. But l pads have two coils inside usage for volume control without opening the load to speakers . Can you elaborate on the concept please.

 



L-Pads are often wirewound resistors, so they look like coils.
I would guess they have more inductance than your average resistor.
post #1970 of 3116
Quote:
Originally Posted by Chris J View Post
 
Quote:
Originally Posted by ALRAINBOW View Post

That is what I really want to use . So I can vary the two resisters and listen for changes other than volume . Does someone have alink to some l pads I can try. But l pads have two coils inside usage for volume control without opening the load to speakers . Can you elaborate on the concept please.

 



L-Pads are often wirewound resistors, so they look like coils.
I would guess they have more inductance than your average resistor.

I thought wirewound resistors had less inductance? All the non-inductive resistors used in my headphone interface were the non-inductive wirewound type. Although I do I know that air core inductors are simply coiled wires so it is something of a conundrum.


Edited by robrob - 12/19/13 at 11:48am
post #1971 of 3116
I am not saying to add ind either but when someone here mentioned
L pads it's the only one I know
post #1972 of 3116

I would not be very concerned about inductance since speaker amps have to drive large inductive loads. The wire resistors inductance is a small faction of the inductance found in speaker crossovers. We do not need to fuss over this.

post #1973 of 3116
Quote:
Originally Posted by robrob View Post

I thought wirewound resistors had less inductance? All the non-inductive resistors used in my headphone interface were the non-inductive wirewound type. Although I do I know that air core inductors are simply coiled wires so it is something of a conundrum.

They have more inductance than other resistors
They are really designed for high power applications.
I really doubt the designers of L-Pads were thinking about us when they design them, I.e. I don't think high quality audio is their top priority!
OTOH, you often see them used as trim pots in loudspeakers with treble and midrange trims.
post #1974 of 3116
First of not all wire wound resisters are the same. As the ones with more space between them will have no inductance.
As for lands yes not intended for us. And they are a transformer as i said . The purpose of it is to keep the same load on the amp and allow for controlling the volume they are rated as well about 80 watts for a good one . And you can smoke them too . Lol I have. As I amusing the resister network you people were so kind to design , I have an issue.

I have an amp solid state rated at about 100 watts at 8 ohms . And using the HE6 headphones .

So I have a 8 ohm and 2 ohm in series with tap in the middle of them. As shown in this thread . Well the attenuation was fine but the 8 got hot , too hot. They are 10 wire wound in ceramic . So after this I just left the two resisters connected to the speaker terminal and connected the headphones directly to the speakers terminals so they all are in parallel .

The sound level seems to be the same and all is well . So does someone here know what I did that was wrong ?
post #1975 of 3116
Quote:
Originally Posted by ALRAINBOW View Post

I have an amp solid state rated at about 100 watts at 8 ohms . And using the HE6 headphones .

So I have a 8 ohm and 2 ohm in series with tap in the middle of them. As shown in this thread . Well the attenuation was fine but the 8 got hot , too hot. They are 10 wire wound in ceramic . So after this I just left the two resisters connected to the speaker terminal and connected the headphones directly to the speakers terminals so they all are in parallel .

The sound level seems to be the same and all is well . So does someone here know what I did that was wrong ?

Headphone_Resistor_Network_Preferred.jpg

Is this the attenuation circuit you used? Was R2 8ohms and R3 2ohms?

post #1976 of 3116
Yes it is .
post #1977 of 3116
Quote:
Originally Posted by ALRAINBOW View Post

Yes it is .

Then you should have had about 14 dB of attenuation....  Wouldn't sound the same at all as connected directly across the amp output.

 

Now if you had the 8 ohm across the amp and the 2 ohm in series with the headphones, I could see the 8 ohm getting hot and the output to the headphone would only be 0.3 dB down with 50 ohm cans.


Edited by potterma - 12/19/13 at 7:00pm
post #1978 of 3116
The way I have the dac and amp connected is that there is a volume control on the dac as well as the amp. AS such I am not able to be certain that there was not change in volume .

But it did sound fine both ways , but my question was why did the 8 ohm resister get so hot. When connected to headphone. Now When just placed across the output of the amp and the headphones conect red direct to the output as well . The resisters are fine. Does anybody have any thoughts on this . 10'watt resisters.
post #1979 of 3116
Quote:
Originally Posted by ALRAINBOW View Post

The way I have the dac and amp connected is that there is a volume control on the dac as well as the amp. AS such I am not able to be certain that there was not change in volume .

But it did sound fine both ways , but my question was why did the 8 ohm resister get so hot. When connected to headphone. Now When just placed across the output of the amp and the headphones conect red direct to the output as well . The resisters are fine. Does anybody have any thoughts on this . 10'watt resisters.

The 8 ohm is going to drop ~4X as much power as the 2 ohm no matter what  you do with the headphones.  Since we don't know if the volume setting was changed between the two configs, I'd guess the volume got turned down.  A more careful experiment is required to clear up the confusion.

post #1980 of 3116
What is there to be confused about . I followed what was given , it's not the volume I care about it's why was the resister overloaded. It's a ten watt resister. The way the circuit is destined the power for the headphone and the total power goes through that resister but regardless how odd I achieve excess of 10 watts . Now that the headphone is out of the circuit it's fine ice cold . So the headphones were using some serious power .
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