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DIY amp for k702's?

post #1 of 16
Thread Starter 

Hey Everyone,

 

About two months ago, I received my AKG k702's, and have been very happy with them sofar (except for that nasty headband :) ). They're the first step in getting more into my passion for headphones. For the last 10 year I've been listening through my AKG k271's, which, for the last three years, were driven by a Oatley Electronic k272 portable (tube) amp. For my home set-up, I'm looking for an affordable DIY that would suit the k702's. Is there any particular amp you guys can recommend? Even though the k272 amp is only a tube amp in part, I do appreciate its "tubieness". I mainly listen to electronic music, and find that the "digital", or sometimes a bit cold, sound this music has to it would benefit from a tube amp. 

 

I look forward to hearing from you!

 

Gijs

post #2 of 16

I'd recommend M³. If you ever feel the music is "bass-light", the M³ can be built with an adjustable bass-boost.

post #3 of 16
Thread Starter 

Thanks for your suggestion!

 

Initially, I considered getting the Bottlehead Crack, but Doc B informed me that this amp would not be best suited for the (low impedance) k702's (at 62Ohms). He suggested the S.E.X. instead. 

 

Also, I took a look at the Torpedo. 

 

I've just gone through the AMB website, and think that the M3 would certainly make an interesting project. In terms of cost, how much should I expect to spend?

As for skills required: I did build the Oatley k272, a portable hybrid tube amp. This was mainly a matter of stuffing a PCB, hooking up the in- and out sockets and making sure grounding was in order. Am I correct in thinking that the M3 would be more demanding to build than that? 

post #4 of 16

How much money do you have to spend on this?

post #5 of 16

2 different views, looks more trouble

65pFOd
Edited by ITALIAN9 - 8/28/13 at 8:01am
post #6 of 16
Thread Starter 

All in all, I'm thinking of spending something between usd 250 and 300.

post #7 of 16
Thread Starter 

I've done some more reading on the M3, and the more I read, the more interested I get... Would it be possible to build one on my plm 250/300 usd budget? And do I have to go for the S11 power source straight away as well? Or could I start off with a simpler one and get the S11 later, as an extra upgrade?
 

post #8 of 16

For just parts and board? Sure (my last BOM for M³ and σ11 was $225 more or less), but the chassis is a couple hundred dollars more. The more you want the chassis to be customized (silk-screen, cutouts, hole-punched, anodized, etc.) the higher the cost. I would say $700 to be safe.

post #9 of 16

I do not have a Torpedo, but I do have a SSMH with 19J6 tubes and a K271.  Based on the tone of the 19J6/6J6, I think you would enjoy the Torpedo.

 

Which opamp do you plan to use for the M^3?

 

For the M^3 you can stuff it into a Hammond case (cheaper).  You can also use a more basic voltage regulation circuit and upgrade to the S11 later.  A basic circuit based on a 3-pin regulator is fine.  You can use a "Tread" type regulator.  You can look at that circuit in the LM317 datasheet.  If you build around 24V you can also use the LM7824.

 

You can definitely go on the cheap, but it will take some planning and foresight to have an upgrade path.

post #10 of 16

The torpedo is a good option and I think you might want to consider the millett hybrid minimax as well.  

 

About the M^3 I think that if you do your own chassis work and don't want something extremely extravegant than you should be able to stay within budget.  Another option is to omit the O22 power supply and opt for a walwart if you really want to keep costs down.  That way you can always upgrade later as well but with the walwart it won't sound nearly as good as with the O22.  A good power supply makes a big difference.  

post #11 of 16
Thread Starter 

So far, I've done a lot of reading on both the Torpedo and the M3, and both appeal to me, but in different ways. The Torpedo comes as a complete kit, so there's no need to source parts yourself, and rolling tubes should be fun. The M3 on the other hand would make for the better learning experience and, as far as I've read, allows for a bit more "customizing"... I'll do some reading on the Millet as well, and end up rolling a dice in order to make a decision...

 

I did read in the Torpedo Build thread that TomB wasn't sure the Torpedo would be a good match for the AKG k701's (which have the same impedance as my k702's (http://www.head-fi.org/t/570317/dsavitsk-beezar-torpedo-build-thread/45#post_7889081) Does anyone have any thoughts on this?


Edited by Gijs - 9/1/13 at 11:21am
post #12 of 16
Quote:
Originally Posted by Gijs View Post

So far, I've done a lot of reading on both the Torpedo and the M3, and both appeal to me, but in different ways. The Torpedo comes as a complete kit, so there's no need to source parts yourself, and rolling tubes should be fun. The M3 on the other hand would make for the better learning experience and, as far as I've read, allows for a bit more "customizing"... I'll do some reading on the Millet as well, and end up rolling a dice in order to make a decision...

 

I did read in the Torpedo Build thread that TomB wasn't sure the Torpedo would be a good match for the AKG k701's (which have the same impedance as my k702's (http://www.head-fi.org/t/570317/dsavitsk-beezar-torpedo-build-thread/45#post_7889081) Does anyone have any thoughts on this?

If you really want to learn than definately go for something where you just don't blindly put parts in a PCB.  I mean I built the Minimax and learned a lot but would have learned a lot more if I had built something like a point to point cmoy or starving student or even an M^3 or beta 22. 

 

I read what TomB wrote and it says at the bottom that the minimax or starving student might be a better match.  Fred_fred is acctually selling starving student PCB's right now which is a rarity so that is an option or you can go with the minimax.  

post #13 of 16

Just an FYI, but I believe I stated later on in the Torpedo thread that some of the recent changes we incorporated changed my mind on the K701.  I've owned a pair for many years and have listened repeatedly to it with a Torpedo.  It does fine.  The bass may not be as tight as with a MiniMAX or MOSFET-MAX, but then the midrange and soundstage is much better on the Torpedo.  So, I think it's a perfectly suitable amp for the K701, depending on what you're looking for.wink.gif  Of course, YMMV ...

post #14 of 16
Thread Starter 

Tom, apologies! I just re-read part of the Torpedo build thread, including your most recent comments on match between the Torpedo and the k701's. I should like an amp to be able to give the k702's a nicely controlled and tight bass. The music that I listen to is rather bass-heavy and dont't want to run the risk of lower frequencies sounding muddled. Is this something a Torpedo might be able to counter by, for instance, the right choice of tubes or output caps? 

post #15 of 16
Quote:
Originally Posted by Gijs View Post
 

Tom, apologies! I just re-read part of the Torpedo build thread, including your most recent comments on match between the Torpedo and the k701's. I should like an amp to be able to give the k702's a nicely controlled and tight bass. The music that I listen to is rather bass-heavy and dont't want to run the risk of lower frequencies sounding muddled. Is this something a Torpedo might be able to counter by, for instance, the right choice of tubes or output caps?

It's possible.  I guess with what I was stating up there, though, is the Torpedo's soundstage exploits the advantage of a K701/2, rather than really compensating for its weaknesses.  This includes a really glorious midrange as well.  Bass is never muddled, but it's probably not going to give you the slam and impact that a solid-state or hybrid might.  You won't get as much of the other things, though.

 

It's hard to say whether you would like or dislike it with the information at hand ... I just wanted to correct the basic premise where I originally stated that the K70x didn't do so well - that has changed, IMHO.

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