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I’m afraid that’s a little misleading, Balanced Drive has 2 amps in series with the load, moving in opposite directions

By symmetry the (usually inaccessible) midpoint of the load doesn’t move and can logically considered to be grounded for figuring load currents, this makes it easy to see that the Load Impedance is Halved as seen by each amplifier in Balanced Drive

With 2 amps in series with the load there is 2x the amp output impedance – so you get 2x the influence of the Amplifier Output Impedance on the sound

The Voltage swing of each output amp side is halved for the same power and even order distortion products that are common to both amplifiers can cancel

Quote:
 Originally Posted by jcx I’m afraid that’s a little misleading, Balanced Drive has 2 amps in series with the load, moving in opposite directions By symmetry the (usually inaccessible) midpoint of the load doesn’t move and can logically considered to be grounded for figuring load currents, this makes it easy to see that the Load Impedance is Halved as seen by each amplifier in Balanced Drive With 2 amps in series with the load there is 2x the amp output impedance – so you get 2x the influence of the Amplifier Output Impedance on the sound The Voltage swing of each output amp side is halved for the same power and even order distortion products that are common to both amplifiers can cancel
Well in saying you are halving the impedence of the headphone, to me that implies a change in the ratio of current:voltage driving the headphones at a set output level. In a balanced amplifier, the way I understand it, that is not the case - each amplifier, in series, is driving the headphone with exactly the same output ratio, except that the numbers are halved for each for a given output level. Assuming my understanding is correct, the relevance to the original question is that indeed each module is outputing half the current in a balanced drive scheme, despite the fact that the impedence seen by the amplifier is halved. In a single ended drive scheme, a halving of impedence of the headphone would imply an increase in required current.

Hence, halving the impedence of the headphone, and halving the impedence as seen by the amplifier by implimenting a balanced drive scheme are two different things.

Am I on the right track? I admit I was wrong about the halving of output impedence.
I can't decide if I should upgrade from desktop 05...
Does the desktop 05 have bigger caps than the desktop 06? It looks that way in the pictures.
desktop 05

desktop 06

Also how much better is the 06 if you were to quantify it by percentage? 5%? 10%? Is it \$150 bucks better? Any further comments about desktop 05 and desktop 06 that might help me make up my mind would be greatly appreciated.
Quote:
 Originally Posted by YngwieJMalmsteen I can't decide if I should upgrade from desktop 05... Does the desktop 05 have bigger caps than the desktop 06? It looks that way in the pictures. Also how much better is the 06 if you were to quantify it by percentage? 5%? 10%? Is it \$150 bucks better? Any further comments about desktop 05 and desktop 06 that might help me make up my mind would be greatly appreciated.
Yes, the Desktop and Home '06 have smaller caps. HeadRoom, and my ears assure me that this does not have a negative sonic impact.

The difference between the Desktop '05 and '06 depends very much on your headphones, and your source. What headphones are you using, and what source? Though I could never tell you if it was worth it for you or not, I could be more helpful if I knew all the details. Also, have a look at my 'headphone comparison' with the impressions, which shows the differences in the level of the upgrade depending on the sensitivity and impedence of the headphones. Those comparisons were done with the Desktop '06 as reference.

Even without your system info, would it help for me to say that despite the fact that I enjoy rolling the modules from time to time just to remind myself of the different strengths and weaknesses, I can't seeing myself plugging in a Desktop '05 for quite a while...
My main headphones are DT 880, with HF-1 and HD 280 every now and again. My source is the overture dac, and sometimes an ipod photo w/pocketdock. This is the only amp I own, I usually run it off the brick and use it as my home source.

Quote:
 Originally Posted by TheSloth I can't seeing myself plugging in a Desktop '05 for quite a while...
Why would you plug in anything other than the max modules? Other than just for kicks or writing reviews...

### Sound Questions

I'm using a redwine modded ipod and K 701's, or ER 4P's, or UM-2's. What would you say is the difference in the desktop module for the micro in the 06 vs. the 05 module. I bought my micro in January. Has the slightly warm sound of the micro been maintained? Is the backround detail more articulated? Any of your impressions would be geatly appreciated.
Quote:
 Originally Posted by YngwieJMalmsteen My main headphones are DT 880, with HF-1 and HD 280 every now and again. My source is the overture dac, and sometimes an ipod photo w/pocketdock. This is the only amp I own, I usually run it off the brick and use it as my home source. Why would you plug in anything other than the max modules? Other than just for kicks or writing reviews...
Max Modules are a pain, and require a DPS. The Home Modules chew through the battery pack as if the batteries were free and grow on trees. The Desktop module is a great module for travelling and portable use. So I do have a use for a range of modules.

Quote:
 Originally Posted by vorlon1 I'm using a redwine modded ipod and K 701's, or ER 4P's, or UM-2's. What would you say is the difference in the desktop module for the micro in the 06 vs. the 05 module. I bought my micro in January. Has the slightly warm sound of the micro been maintained? Is the backround detail more articulated? Any of your impressions would be geatly appreciated.
The iPod line out -> HeadRoom Desktop '06 -> K701 is a KILLER combination. I only received the Home and Max modules yesterday, so for the last month my bedside system has been exactly that and I don't know why but it sounds awesome. I could have used Home '05 Modules, which have nice class A biasing, but purely for the sonics alone, I chose the Desktop '06. I suppose there's that awful 'synergy' word, but in this case it's true. That really IS an upgrade worth having.

As for warmth, the main sonic signature of the amp is the opamp, in this case the OPA2134 which is a somewhat laid back opamp. The new output stage is simply transparent, and drives just about anything you throw at it. So, yes, the sound is still 'musical' but with increased definition throughout the spectrum, especially in the bass.

edit: just noticed you use ER4p's - take a look at my headphone comparison (post 22). You have the two headphones that gain the most benefit from this upgrade. The new modules made me rethink what an ER4p is capable of.
The thing is, there's really nothing I dislike about my current setup. I'm just being your typical weirdo head-fier, never satisfied with anything. I'd really like to hear a micro with the new module... maybe I'll just abuse headrooms return policy.
Quote:
 I could have used Home '05 Modules, which have nice class A biasing, but purely for the sonics alone, I chose the Desktop '06. I suppose there's that awful 'synergy' word, but in this case it's true. That really IS an upgrade worth having.
Thanks a lot for the information, because I like how it sounds now, and I would hate to upgrade and have it be "worse," but from your experience it sounds very worthwhile.
Added impressions of the '06 Home Module to post 22.
Quote:
 Originally Posted by TheSloth Added impressions of the '06 Home Module to post 22.

Thanks for the info. I managed to contact HR in time and have my desktop portable replacement changed from home 05 to home 06. Can't wait to hear it when I go to USA in May.
Well in your other thread I was pushing you for the date that you ordered for that reason, and am a little surprised actually that you didn't get an '06 module in the first place. Anyway, I'm glad you are getting the new Home module, which is a serious step up.

My DPS is 'on FedEx vehicle for delivery' so expect some more impressions later today. And just to clarify, I bought the DPS at full retail price - it was not a freebie from HeadRoom, though Jamey did offer me a BS1. I put my money where my mouth is on this one because I think the sound of the new modules is worth it. No shilling in this thread!

### Balanced operation; not quite right yet

Quote:
 Originally Posted by TheSloth Well in saying you are halving the impedence of the headphone, to me that implies a change in the ratio of current:voltage driving the headphones at a set output level. In a balanced amplifier, the way I understand it, that is not the case - each amplifier, in series, is driving the headphone with exactly the same output ratio, except that the numbers are halved for each for a given output level. Assuming my understanding is correct, the relevance to the original question is that indeed each module is outputing half the current in a balanced drive scheme, despite the fact that the impedence seen by the amplifier is halved. In a single ended drive scheme, a halving of impedence of the headphone would imply an increase in required current. Hence, halving the impedence of the headphone, and halving the impedence as seen by the amplifier by implimenting a balanced drive scheme are two different things. Am I on the right track? I admit I was wrong about the halving of output impedence.

At the same power P Balanced Drive amplfiers have to supply the full current I from both amplifiers at the same time

to compare we want the same power P into a given load R

P = I * V, I = V / R

To get a given P a single ended amp is putting out current I amperes and V volts

In a Balanced Drive amp there are 2 amplifiers , each putting out ½ V (+ and -) for a total drive voltage difference across the load of

½ V – (- ½ V) = V

with V volts across load R the current drawn is

V / R = I which is the same current the single ended amplifier has to supply

In Balanced Drive each amplifier has to still supply the full I even though they only swing ½ V each

Because the operating point of each amplifier side of the Balanced Drive has to supply the full I for only ½ V we say the load on each amplifier looks like the impedance (resistance) is lower by ½ = a 2x “heavier” load

Balanced drive doubles the possible voltage swing, but to achieve the potential 2x V the amplifiers on each side would have to supply 2x I
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