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Duette Dual Headphone Amp

Printed From: Graham Slee at Hifi System Components
Category: Headphone Audio
Forum Name: Graham Slee Headphone Amps
Forum Description: Questions, answers and product information zone for Graham Slee Headphone Amplifiers
Printed Date: 08 Aug 2020 at 4:06pm
Software Version: Web Wiz Forums 12.01 -

Topic: Duette Dual Headphone Amp
Posted By: Graham Slee
Subject: Duette Dual Headphone Amp
Date Posted: 15 Jan 2008 at 12:51am
I'm told headphone amps with two output jacks sell much better than those with one - especially in the affordable sub £200 price band.
But what happens when the two sets of headphones are of different impedances? I mean, headphone users aren't known for buying two identical pairs on cost grounds alone? On the other hand I'm sure a lot of us have at least a couple of pairs of different headphones?
If one pair is low impedance and the other pair is high, then the relative sound pressure levels are going to be different. So much for the value added idea of kitting an amp with two headphone sockets.
I guess two amplifiers could be incorporated in one box? That would sort out the impedance difference. But then what if you wanted to play the music loud and your partner wanted to listen quiet? That suggests two volume controls, doesn't it?
And maybe you like Rock music while your partner likes Orchestral? So we now require two totally separate amps with separate inputs in the one box.
But then you decide you want to listen to the same music Wacko
But that means joining the sources - what a mess!
OK then, how about if it had a switch that selected separate inputs or commoned inputs? When switched to the common position the other pair of inputs could be used as a chain out. But then in an utopian world it would be great to have both inputs as chained pairs, but in a sub £200 unit that may be stretching it a bit.
So, without the utopian bit, do you think such an amp would appeal?
The cost of two amps would normally put such an amp beyond £200 GBP, but I've been developing a rather nice sounding discrete bi-polar stage and transistors can be obtained and implemented quite a bit cheaper. It's the hardware after all that is the major cost of any design.
Just wondering what to do with this design? How would you reason it out?

Not simple enough for Google-Bot to understand...

Posted By: sunhao
Date Posted: 23 Jan 2008 at 4:53am
I think as Graham mentioned, from a practical point of view, a headphone amp with two identical outputs is seldom used in its full potential, meaning, two headsets plugged and heard by two individuals at the same time.
Nevertheless some people do favor this design, probably out of a mentality that "more is better". Having a potential function (though seldom fulfilled) is, from a consumer perspective, a good thing. You see this mentality in lots of cases, for instance, many people here (in China) buy cell phones with a variety of functions, and most of them never learn to use even half of them! Still consumers like cell phones with more functions, a common phenomenon, even if they know clearly they will never figure out how to operate all the potential functions.  So having more functions, or more potential usage capabilities, is definitely a plus in the consumer psychology.  Other than that, I see no point of making headphone amps with two identical outputs.
But some headphone amps have two different outputs, one designed for high-impedance phones, the other for low-impedance phones. And this might be an interesting idea.

Posted By: EASY
Date Posted: 23 Jan 2008 at 6:47am
I enjoy sharing the same music with my gf a lot...but mostly during our travel...
I would also like to have 2 outputs on the amps...with our different tastes of headphones...for Orchestra...
but i guess we shall use the sound box  more...hehe...

que sara sara...whatever will be will be

Posted By: Sceptre
Date Posted: 08 Feb 2008 at 12:42pm
Hi Graham.

I often use a pair of headphones with my wife whilst watching a movie or listening to music on aircraft.
My current solution is to use the volume to set the high impedance headset then turn down the volume on the lower impedance unit (often Shure e4c) using the Shure provided inline adjuster.

My thoughts on your 'inclusive' dual head design are confused.  I could differentiate your offering to the young 'want to share this emotion with my love' but even teh iPod advert shows a young couple listening to one earpod each - Remember that Love is a drug!.

I would go with a single output and bundle a high quality Y splitter with a his and hers volume control.  Pink and Blue would sell well here so your vol doesn't get touched by accident.

Dual source dual out with ganging options are overkill.  Mobile listing is exactly that.  Siamese listeners (joined at the amp) will cause major issues (ear pain, broken cables, pedestrian accidents etc.)

Single market must be 95% of your market.
If a $50 unit were produced with a dual in dual out (think two boosteroos and an elastic band) capability, your market would be depleted.

Stick to the knitting, but allow it in kit form too!


Solo s/n 0806-13 Senn HD600

Posted By: Graham Slee
Date Posted: 09 Feb 2008 at 11:44pm
OK then, would there be any disadvantage anyone could perceive of in just making it a single output headphone amp - with just a single headphone jack?

(obviously it can't be called a Duette)

I am thinking now of replacing features with performance. Hiving off costs on the features to use better components in a low-compromise design. I'd like to make it no-compromise at all, but in the sub 200 pound (sub 400 dollars) price band, that's nigh-on impossible. However, it would be virtually no-compromise.

And with a bit of luck it'll be discrete. I must have tried about 4 or 5 discrete ideas since starting this thread - based on a bipolar transistor current-feedback design - with differing levels of performance. The one I seem to be settling on shares the same sort of SQ as the rest of the GSPaudio range.

Not simple enough for Google-Bot to understand...

Posted By: Charley Phogg
Date Posted: 11 Feb 2008 at 12:11am
I think what Sceptre said about a good Y adaptor is spot on. To me it would seem that if two people are listening to the amp at the same time that what SQ you would lose with the adaptor wouldn't be an issue, but would have no effect on it while listening solo ( no pun intended LOL ). Also allowing you to keep cost down from dual amps in one unit.

 But then you would still have the issue of different impedence 'phones. I think the splitter with separate volume  controls sounds good. Where would you lose the least amount of SQ, with a splitter like that, or dual jacks with dual gain switches ( if even possible )? But then your back at added cost.

  I see it as two different markets. The young kids, like my daughter sitting in the back seat of the car with her friend and they share the headphones, which they wouldn't care about sound. Or the dating couple, or married couple without kids that does alot of traveling and if that was their thing, cost wouldn't be an issue.

 Would a line out that they could feed into another amp be feasible?. That way they'd have to buy two Wink.

Posted By: sunhao
Date Posted: 11 Feb 2008 at 7:18am
I really wish to see Graham produce a headphone amp that is even better than Solo.  In its price band I believe Solo is unbeatable when driving Sennheiser's and AKG's.

Posted By: Sceptre
Date Posted: 12 Feb 2008 at 1:08am
Graham, I didn't mean to quash the Duette name but did feel that it was a dead end (commercially).  I'm not a fan of me too marketing but if it were in such demand then why have Apple resisted a two output device?  It is a differentiator but this is a mass market take up.  Kids will spend more money on their Hello Kitty iPod add on rather than SQ issues.

I think there is a bigger market in the custom 'wallet' that accepts a mobile source (Nano etc) and seamlessly access the data and adds an excellent DAC and amp of solo capability without the need for extra wires and elastic bands.  By making a Nano the sixe and shape of an iPhone with the required DAC, amp and cells t make a Solo on the move.  That would be hot.

2 models with the same external appearance - 1 Med Q with no DAC and a 'thumping' amp to beef up the sound for kids.  The other a top of the line unit with DAC, GSP magic amp (with high efficiency) and a 1/8 and 1/4 inch jack (one at a time though) so either can be used.

Names - iFi is TM'd by Klipsch.  iQ is some Piano tutor system.  You must check out the most absurd ipod accesory though (  iPhoney - not an iPhone but looks like one - you'll get a lot of media attention for free. (currently a software package though

I like this product though.  The market you want are the iPhone and Touch users (not Nano).  Make the cradle take the iPhone and make call it the GSP iFiAmp.  42GB Touch with a £350 DAC amp addon.  World market looking for a neat solution for a market of growing discerning iPod users that now want to go upmarket.  Give them something neat (I mean without interconnect wires) that they can drive their Grado SR60's with.

I'm sure you have amp designs at hand.  Just get the 'capsule' or 'module' to hold the iTouch right and you are well on your way.

Beats the two boostaroo and elastic band idea I think.



PS - boost visits to this forum by allowing posters to be notified of updates to topics that they have commented on - people like it!

Posted By: Kasper
Date Posted: 22 Feb 2009 at 1:07pm
Dual output jacks certainly appeals to me. I had already made up my mind, that my next amp is going to feature this, since shared experiences are the best IMHO. How great is it not to sit and listen to albums together in marvellous detail and presence!

Also its extremely useful when deciding on your next headphone for A/B tests.

If dual volume controls isnt going to increase the cost, I am all for it. Otherwise its no problem with just one volume control, not at all a deal breaker for me.

I do think the "duette" would appeal, even the utopian version, that have both inputs as chained pairs and makes the cost go above £200.

Posted By: Sceptre
Date Posted: 23 Feb 2009 at 12:54am
May I suggest two Novo Kits and an elastic band?

If you require portability I suggest a 30m extension cable.

Seriously, on sharing things with friends, I have found that 'timing' is often the core of the experience.
So why not have two very separate systems and try and sync the two playbacks together.


Sceptre - Chairman of the single out amp campaign.

Mac-Apogee Duet- Solo SRG PSU1
240GB iMod - ALO PV-Cap -Voyager, D10, LISA III
Cyrus DVD 7+Q
JH|13 Pro,D7000, Ed 9, RS-1, HD600 (APS v3), ATH ESW10, Pro750, HFI 780, IE8, SA6 HD25-11, e4c.

Posted By: mrarroyo
Date Posted: 23 Feb 2009 at 2:36am

Graham, how about the easy and cheap way of using a resistor to provide the low/hi impedance jacks? Thus if two headphones of different impedance are use the low impedance one would have large resistor in series to reduce the volume. I am not technical so do not laugh to hard at my idea.


Posted By: Kasper
Date Posted: 23 Feb 2009 at 5:40pm
Originally posted by Sceptre Sceptre wrote:

May I suggest two Novo Kits and an elastic band?

If you require portability I suggest a 30m extension cable.

Seriously, on sharing things with friends, I have found that 'timing' is often the core of the experience.
So why not have two very separate systems and try and sync the two playbacks together.


Sceptre - Chairman of the single out amp campaign.

Timing is important I agree, and so much easier on an amp with dual output jacks!
This way two people can share one great source on one great set of ICs. Think of the cost of what you suggesting here.

I have no plans for adding another source (CDP) for a long time (I am aware that you can get splitters.. but those will tarnish the SQ). Spending that money on heaps of music, is a much more enjoyable investment for me, besides I need a real good DAC one day too. And I would never consider buying two of the same amps either!

Two output jacks is the natural thing to offer, when you already have a product line featuring only one. I cant wait to see this happen.

Posted By: Jitter
Date Posted: 24 Feb 2009 at 6:05pm

Portable DAC with amp to connect my iPod to.......

.... but have to get the bits out of the iPod first.  Many have tried Cry

...... and that's my opinion, take or leave it

Posted By: mrarroyo
Date Posted: 25 Feb 2009 at 1:49am
Get an iRiver H120/H140 and an iBasso D10 w/ an small optical cable!


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