[Amebix]

Hi, I just wonder a little about how self biased amps work.

All I know (I believe) is that they need the current/power from loudspeaker amps (?) to drive them.

My parents have this Stax headset and amp combo that has not been used for some years. Some the reason I wonder is in case that I (hypthetically) would get a chance to use them on another system than their loudspeaker system. But I'd be corious anyway.

Could someone explain me the basics of this - how much power (Watts) the stax amps needs to drive it, and what alternative sources that can drive them? (does it have to be a full size loudspeaker system, made for regular full sized speakers?)
(I don't own any loudspeaker system atm)

The amp is a SRD-7-SB-mk2.

 

[krmathis]

Yes, you need a speaker amplifier to drive the SRD-7SB MK2. But the good news is that almost any speaker amplifier can be used, as long as it puts out ~3-4 watts or more in 8 ohm.

The SRD-7SB MK2 is what we call a transformer, as it just transform the signal. Not amplify it.
You find amplifiers (energizers) out there though, all the SRM-xx units. Which hook up directly to the source, and hence eliminating the speaker amplifier step.

SRD-7SB MK2: Source (CD player or like) -> Speaker amplifier -> SRD-7SB MK2 -> Headphone
SRM-xx: Source (CD player or like) -> SRM-xx -> Headphone

Self Bias (SB) mean that it tap the bias supply for the headphone from the audio signal fed it from the speaker amplifier. While non-SB units plug into the mains (wall plug) for power to the bias supply.

A bit clearer now?

 

[Amebix]

Yes, especially wondered about the watts, thanks a lot!

Apart from that, is the speaker amp and source crucial to the sound quality the headphones will deliver, or will it be (close to) an equally big jump in sound quality from lower range headphones (ie grado sr125) no matter what amp is used?

 

[krmathis]

The sound signature (and quality) of the source and speaker amplifier will shine through. So their quality certainly make a difference.

You have not mention which headphone your parents have paired up with the SRD-7SB MK2. But if its a Lambda, then you are in for a surprise. Pretty much regardless of source and amplifier that one would be a clear step up from ie a Grado SR125.

So about time you convince your parents into allowing you to hook it all up.

 

[spritzer]

THe SB system simply take some of the audio signal (i.e. voltage) off the secondary off one of the built in transformers, feeds it though a second transformer to step it up some more and feeds it into the bias supply. That has a voltage limiter on the input so the bias can never exceed 580v/230v. Simple yet effective.

Stax are very revealing and any one of them will benefit from a better signal chain.

 

[Amebix]

Ok. My idea was something among the lines of "maybe I can get an uber headphone setup by only spending 200$ and get a speaker system with the deal" (or the other way around)

The headphones are Gamma-pros.

 

[Simon Painter]

Have just stumbled on this old thread, which is completely relevant to me, having recently bought a pair of the first series Lambdas. I'm trying to decide which Stax head unit to look for, to go with the Lambdas - a self biasing option seems like a good idea 'cos I've got a beefy integrated with two sets of speaker binding posts, one pair of which I could usefully use to feed the SB head unit - I'm thinking too that the SB option will likely be less expensive than a full Stax 'phone amplifier but am worried that there might be quality compromises... any comments, anyone?

 

[Simon Painter]

Can anyone link me to a photo of the inside of an SRD-6 / sb? (I have the circuit diagram, already...)