Wanting to build a tube amp

[PintoDave]

I'm wanting to build a nice tube amp to complement some of my headphone use, I'm interested in this "warm tube sound" I hear comes with the territory. I have a CMOY in an enclosure for use at my desk, powered off dual 9v batteries. It works well, but I feel there is something I'm missing...
 
I've been searching the forums for awhile and can't seem to find anything really contributing to what I want to do.
 
Cost wise, let's start with something cheaper and work our way up.
 
I don't want any hybrid stuff.
 
Would prefer building the amp without a kit, rather doing it from scratch. I have done electronic projects like this in the past and find them very entertaining.
 
I've looked at Headwize.com and am having trouble figuring out the difference from all of the amps listed, however did find the SE OTL page and found in intriguing.
 
Tube tech is new to me, reading schematics on wiring up the proper pins is a bit confusing right now. If I can find a site that explains it more I'm sure I'll catch on to it quickly, I'm a quick learner when it comes to technical things. Keep in mind I find no time in projects wasted. I have started many a projects and half way through them stop because it's either impossible to complete or I loose interest. Either way I have gained experience and knowledge from it. I don't think I'll stop half way through this, it may just take some time on my budget, which is fine by me.
 
So, what recomendations are there for a first time tube amp builder that's non hybrid but can introduce me to a good "warm tube sound" I'm wanting to experiance?

 

[nikongod]

My advice would be:
 
Build a hybrid. 
Preferably one that runs the tubes under relatively low voltages. 24-48V is common. I would lean towards this for reasons of both safety, and your description of the sound you seek. 
 
Seriously. 

 

[PintoDave]

Safety as in personal safety or equipment safety, or both? I have built and repaired high voltage circuits in the past, I'm not as worried, but how about my equipment?
 
I was looking at the Bottlehead Crack OTL tube amp kit, and was thinking of something like that, but built from scratch if possible.
 
Do you have something like this in mind?
 
http://headwize.com/?page_id=759

 

[kchapdaily]

keep in mind that building an all tube amp pretty much limits you to high impedance headphones

 

[nikongod]

I cant open the link I mean, I can click it, and it tries to go somewhere, and it dies. 
 
Anyways, the Bottlehead Crack is basically the same thing as the VanWarde OTL. There are some part differences, but if you dropped 2 unlabeled schematics on a desk there is only one difference - the VanWarde OTL uses a resistor (and cap?) on the cathode of the gain tube, where the CRACK uses a red LED. The argument for the LED is that it measures better and costs less.
 
You *could* build all tubes for low impedance headphones - if you used output transformers, but output transformers drive the prices up. 
 
For safety - I meant primarily building safety. Safety for headphones is about the same, and kind of low. OTL amps have a nasty habit of sending VERY high voltage spikes through the headphones when you turn on and off. The solution is easy - you just unplug your headphones before you do something but its worth note. 
 
Hybrids also drive low impedance headphones easily. Without switching to a transformer coupled design OTL amps "kinda sorta" drive low impedance headphones, but kinda sorta don't. 

 

[PintoDave]

I see. The link is to a SOHA amp on headwize utilizing a 12au7/ecc82 tube and opa2134 or similar opamp, per channel. Stating it is very capable of driving 16 to 300 impedance cans easilly. After 20 minutes of power on it sounds its best, but is ready to go after about 30 seconds.

There is a lot of info there and a plethora of schematics posted along with parts lists and interchangeable cross referances. Seems get straight forward and simple with all of the supplied information.

My dad has his bachelor's in ee and studied a lot of tube circuits in college and said he would love to partner up on the project if I found something doable and would meet my expectations.

Any input on the SOHA here?

Also doing some research on the millet.

 

[vixr]

I've never built the P2P SOHA, but I did build the PCB version of the SOHA that was for sale around here a few years ago...It easily drives my HD-600 and HD-555 Senns. I dont have any low impedence phones. The SOHA had a much brighter sound than the Milletts I've built, almost to the point of being crashy and tinny...The 12AU7 MHSS I built on a homebrew PCB sounds pretty damn good.

 

[nikongod]

I was thinking more along the lines of a MHSS for a simple hybrid - the layout is really very close to a tube amp with the super-simple output stage, but either way  

 

[kchapdaily]

+1 for mhss. great amp, nice and cheap too. good first project especially since your dads an ee

 

[AudioCats]

what kind of phones are you using? If the phone impedance is high enough, a Bijou might be a good option.

 

[PintoDave]

Using low impedance cans. 32 - 64. I agree the hybrids would be a better choose from what I have been reading the past few days.

 

[PintoDave]

So, for now, I have a split between the two (will probably do the other some time down the road), which do you guys (gals to?) recommend first?
 
The Simple Tube/Opamp Hybrid Amp (SOHA)
http://headwize.com/?page_id=759
 
Or
 
The Starving Student Millet Hybrid
http://www.diyforums.org/SSMH/SSMHoverview.php
 
Both look doable, not to expensive, and small enough that I can get a good size piece of exotic hardwood to use as an enclosure and have it look decent and not take up to much space (keeping the mrs. happy!)

 

[kchapdaily]

ive loved my starving student. cant say anything about that amp from headwize but you wont be dissapointed with a ssmh

 

[MisterX]

http://www.tubecad.com/2008/01/blog0132.htm
 
Is another option for a low voltage toob amp.

 

[nikongod]

Quote:

http://www.tubecad.com/2008/01/blog0132.htm
 
Is another option for a low voltage toob amp.

 
A friend lent me a 24V akido, with DN2540 output stage (95% sure it was DN2540) and it was pretty sweet.