Please recommend me a TUBE DIY headamp to build.

OTL isn't the best idea to drive low impedance headphones in general, but if you really want to build it i'd start looking at one of headphone amps at tubecad.com. They have an awesome documentation where choice of tubes is explained so it would be easy to mod the amp to suit your needs.

m.

ps. here you go: http://tubecad.com/Product_PDFs/Octal_Stereo_Rev_C.pdf

Are you open to Hybrids?  The SOHAII is a nice amp..

I've read that the Cavalli CTH (Compact Tube Hybrid) Amplifier performs well with the grados.  The approximate build cost should be around $200 or less, and there's a group buy of the PCB here:

http://www.head-fi.org/forum/thread/536098/group-buy-for-cth-compact-tube-hybrid-pcb

It might be the last run in a long time, so hurry~

Cavalli Bijou

The reason I chose to bug Alex to do another run of the CTH was because I knew that you could throw a variety of phones at it and have it perform up to snuff. Another reason was the flexibility in what tubes could be used. The tubes in this amp really shape the sound and there are ton of choices. Finally, it's not too expensive to build... ~$200 with a few tubes.

If you want to use an OTL amp for Grados then the Cavalli Audio Bijou is probably your best bet due to its variable NFB.

You should also check out the Bottlehead Crack, there are a few tweaks mentioned in their Forums to improve its use with low impedance phones and it does use the 12AU7 as one of its tubes.

What is your budget?

Modify a Transcendent Sound OTL, preferably the Single ended one since it's the lowest powered one. Its impedance is apparently 1 ohm.

Otherwise the Aikidos or the Bijou are probably the best bets. There's also a few OTL projects here: http://gilmore2.chem.northwestern.edu/projects/index.htm , but you're own your own out there.

I don't know about you, but I do not describe hybrids as "OTL" (though they do lack output transformers). If you do, then your choices are much wider open.

Quote:

Originally Posted by hi-fiber 

 

mr. forte they dont disclose the bottlehead crack schematic? i wanna see it.

I heard somewhere that this is to prevent theft of their designs? I'm not really sure. It's fairly irrelevent though since grados just don't sound that good out of a crack. They are really meant for high impedence cans. In all honesty I prefer the sound of my sr-80's plugged into a little dot 1+ than into my crack.

Quote:

Originally Posted by hi-fiber 

please note that i will BUILD this amplifier for minimal expense... thats also the main reason why i wanna go OTL

 

If that's your main concern, that changes things! I would then recommend the Pete Millett Jonokuchi, which you can find here: http://www.pmillett.com/Jonokuchi.htm . The total cost apparently is $200 + enclosure. It's transformer-coupled, but frankly, any OTL design out there will either be 1) low impedance, 2) cheap or 3)neither.

It should be noted that, since it's been published on the 31st of January, nobody has listened to it yet.

Quote:

Originally Posted by hi-fiber 

I shall check on each of your suggestions and make a list of tubes that is needed then i will consult the local tube store.

You can always order online.

Quote:

Originally Posted by hi-fiber 

mr. forte they dont disclose the bottlehead crack schematic? i wanna see it.

You won't find the schematics: Bottlehead is a business that sells kits. Since it's all point to point anyway, how many would be willing to buy the kits if they had the schematics for free? You can, however, see some pictures of the insides on their website.

One more thing: shipping costs can be killer if you don't live in the States, especially with multiple sources (I am in Canada, and even here it can be pretty bad).

If that's the case, kits can help reduce these costs. I would check the Bijou OTL kit or the EHHA Rev. A Hybrid kit at Glass Jar Audio, the Millett Hybrid MiniMax kit at Beezar or the Bottlehead S.E.X. at Bottlehead. I know there is only one pure tube OTL in that list, but for Grados, I would really recommend either Hybrid or Transformer-coupled.