[00940]

the topology is very easy to trace from the pictures posted earlier. It's an opamp followed by a discrete ab buffer, made of bipolars, bd139/140 from what i can read. Something like figure 11c here : http://headwize.com/projects/showfil...=opamp_prj.htm

They use a simple 15V supply. Which explains the needs for coupling caps.

They use the cheapest electrolytic caps for input and output. The opamp is a glorious jrc206d (0.39$ at digikey).

The design is basic but honnest cheap stuff. Could probably be greatly improved by putting an opa2134 in there and changing the input/output caps.

 

[Gradino]

Quote:

Originally Posted by Gradino What is the difference between Project Head Box and Project Head Box SE??

But the difference between head box and head box se? (NO BETWEEN HEAD BOX AND MKII)

 

[leofahrer]

Quote:

Originally Posted by Gradino But the difference between head box and head box se?

http://audiotra.de/project/

I guess the head box is the predecessor of the head box SE (with two headphone jacks, black housing etc.), the head box MKII is a new, smaller amp with only one headphone jack...

Quote:

Originally Posted by 00940 The design is basic but honnest cheap stuff. Could probably be greatly improved by putting an opa2134 in there and changing the input/output caps.

Mmmh, sounds very interesting. Would that make it a really nice little amp or will it still be some kind of "mediocre"?? How much do those parts to change cost?

 

[Gradino]

Quote:

Originally Posted by leofahrer http://audiotra.de/project/ I guess the head box is the predecessor of the head box SE (with two headphone jacks, black housing etc.), the head box MKII is a new, smaller amp with only one headphone jack...

NO!

Today i have buy the "head box" but this is like head box se!!
http://audiotra.de/project/bilder/project_headboxse.jpg

I think that the difference is only in new name. The head box today is head box SE (this for new entry in catalog of MKII)

There is some people that can confirm this?

 

[00940]

Quote:

Originally Posted by leofahrer Mmmh, sounds very interesting. Would that make it a really nice little amp or will it still be some kind of "mediocre"?? How much do those parts to change cost?

I'd need to get my hands on one (or pictures of the downside of the pcb). I don't know if there is a rc filter in the biasing of the opamp, what are the running points of the ab buffer, if those ceramics are there for decoupling or bandwith limiting and so on. It could potentially be a nice little amp.

Total cost of the changes shouldn't exceed 15€ or so, at most.

 

[leofahrer]

Quote:

Originally Posted by Gradino I think that the difference is only in new name. The head box today is head box SE (this for new entry in catalog of MKII)

...that's exactly what I said - the head box is the predecessor of the headbox SE, which means the headbox SE is the new version (though I don't know what else besides the name they changed)...

Quote:

Originally Posted by 00940 Total cost of the changes shouldn't exceed 15€ or so, at most.

...well, that's not much, really. Why don't they use those other parts right from the beginning with the serial amp?

I guess that even a price of 115 Euro (worst case) would be cheap enough to get people to buy it, especially when it sounds quite nice...

I don't guess anybody has the possibility to make pictures of the downside of the pcb? Maybe the "tuned" hadbox MKII could turn out to be some kind of "budget reference"...

Leo

 

[Gradino]

I think that the head box se is very good amplifier for akg k 701.

I not agree whit people that have said that head box is not good.

This people probably haven't akg 701....

S.

 

[jplmk]

New Head Box (MKII) was apparently reviewed in the latest (Jan) What Hifi, and got 5 star rating. Dunno if it means anything (haven't yet seen the review), but atleast it got me interested.

I am getting a pair of MS-1's (being mailed), and as I will be running them with 5.1 amp and DVD (i.e. I don't think the headphone output is anything spectacular, and only the amp has it in the first place), I was thinking to hook them up to a headphone amp. I don't want to spent hundreds at this stage, so the new pro-ject with a ~100 € price tag sounds really good - Now I read that there could be an easy way to push it up a notch, by replacing the OPA with something better: 2134 was recommended, but as far as I know, I can only get my hands on to 2132 and 2227 (A and PA), of which the latter atleast seems to get good reviews (what do the letters A and PA stand for?).

Would changing the OPA require any other changes (not as far as I can see, as the voltage ratings etc. are on the same range) to work? I was thinking to solder a platform that I can then use to swap OPA's easily to find out the best option for this particular amp and the MS-1's.

 

[luukas]

Five stars in Hifi... I've got to get a hold of that issue. I don't have too much faith in the headphone-related reviews they've had so far.

jplmk, I might have a Porta Corda II for sale soon (~two weeks) if you are interested. I think we could arrange an audition if you'd like, though I won't sell it before I get a new amp.

 

[PinkFloyd]

Quote:

Originally Posted by lini Yup, it's cheap - especially the components inside. And it sounds even cheaper.

How cheap does it sound? euros, sterling or dollars will do for the description

 

[lini]

Quote:

Originally Posted by PinkFloyd How cheap does it sound? euros, sterling or dollars will do for the description

To my ears, it sounded "worth 50 Euro max.". Thingy cost 200 Euro, though. Disappointment factor: huge. I'd say people should rather invest in a Go-Vibe than a HeadBox.

Greetings from Hannover!

Manfred / lini

 

[jplmk]

Quote:

Originally Posted by luukas Five stars in Hifi... I've got to get a hold of that issue. I don't have too much faith in the headphone-related reviews they've had so far.

Yup, can't be sure (haven't checked the mag myself, and dunno what they said about the others (if there were any in the review)), yet.

Quote:

Originally Posted by luukas jplmk, I might have a Porta Corda II for sale soon (~two weeks) if you are interested. I think we could arrange an audition if you'd like, though I won't sell it before I get a new amp.

Hmm, maybe

Need to think it over as soon as I get more info about the headbox (and the OPA mods). And getting the MS-1s will take two weeks or so anyway.

 

[jplmk]

Dough! The Feb issue of What Hifi has already ben launced, and couldn't find the Jan issue anywhere anymore. I surely would appreciate if someone having the mag available could post the details of the 5-star verdict for MKII to this thread. The Feb issue had the list of tested amps, SE had got 4 stars (commented as having generous connections, but lacking musical fidelity), can't remember when that was tested.

EDIT: MS-1s arrived today, so it didn't take 2 weeks, but was sent over during the weekend - that's fast.

 

[Dexon]

Quote:

Dough! The Feb issue of What Hifi has already ben launced, and couldn't find the Jan issue anywhere anymore. I surely would appreciate if someone having the mag available could post the details of the 5-star verdict for MKII to this thread. The Feb issue had the list of tested amps, SE had got 4 stars (commented as having generous connections, but lacking musical fidelity), can't remember when that was tested.

January 2004 Pro-ject vs X-canV3 , both get 4 stars. Just few lines of text.

 

[jplmk]

I eventually then went ahead, and bought the Head Box MKII, have had it now for roughly a week, during which I've done some extensive testing, and also started the modifications.

As someone earlier pointed out, the JRC op amp is a basic, and the amp could benefit from a better one - I got a OPA2227PA and OPA2132PA to compare, so after listening the amp for a day (which btw did sound good out of the box), I removed the original op amp, and attached a DIL8 socket on the board, and started vigorous (or that'a what I was prepared for) tests to see if any differences between the JRC and/or between the two OPAs would be heard.

I started first with 2227, and the change was not hard to notice - Compared to JRC to sound was noticeably crisper, and more accurate, throughout the range. I left the 2227 to burn in overnight (8+ hrs), and the next day swapped the 2132 on, and burned it in again overnight without listening it first. Then on third day, and started to compare these two, without knowing really which should be better.

Since I didn't have an amp in the beginning, I hooked the head box directly to my DVD player (CA DVD89) with a decent quality RCA. Immediately I noticed difference, 2227 being again more clear and accurate, natural with good soundstage. 2132 has stronger bass, but that makes the sound a bit inbalanced compared to 2227. One interesting thing I also noticed that 2132 seemed to get on my ears only after few minutes of listening, there's something on the sound that starts to numb your ears, so that you feel like removing the headphones for a second (umm, difficult to describe, but maybe you know the feeling

). I did quite a lot of swapping between the chips, tested various types of music and recordings (studio/live), and the results were pretty much the same, although especially live recordings made 2227 to stand out even more.

Long story short - I am really satisfied with the Head Box, and feel that it has a good price-quality ratio. I have not heard any other headphone amps, so that would be the next thing to do (just out of interest - need to hook up with the local meet(s)), especially on the same price range. Also it would be interesting to test a few other op amps (maybe the OPA627 if I can get it somewhere), and think about upgrading the caps as well, just out of curiosity (any suggestions?).