Headphone amp with tube PS

[dsavitsk]

Thanks for the new onslaught of info. I was hoping that you, dsavitsk, would jump in here.

I'd be careful what you wish for. I'm really just a the poser here.

Anyhow, the Mapletree uses those hammond transformers at 2400:32, and while scaling up a transformer like that often rolls off the bass, the word on the street is that the bass is still quite good. I am guessing that a few extra ohms is okay, or that putting a resistor in parallel with your phones to bring the load down to 25 or so would also be okay. However, how they will respond in a parafeed design is unknown.

So, the basic schematic I am tinkering with there is like http://www.nutshellhifi.com/library/Pix-C.gif except using LEDs to do the biasing, and placing the cap between B+ and the transformer, rather than between the ground and the transformer (you could do it like in the schematic, but this seemed like a safer option.)

The Specos are used by a certain kit manufacturer. I think they are used as autoformers and that the secondaries are ignored. If they work that way, then using them in a design like the espressivo amp may be an option.

I have not so much as breadboarded either of these yet, so I have no idea if they will work, let alone sound good. But, what I like is that they can be built very cheaply, but by upgrading the transformers and the one cap, they could conceivably turnin to good performers.

As I said before, I do think that looking into a transformer coupled Aikido is a good option. I've not heard an Aikido, but everyone here seems to like the circuit a lot. If those Hammonds work at the impedance you need, then it shrinks the coupling cap quite a bit too so you might be able to get rid of the electrolytic. The Mapletree schematics are on page 4 of this: http://hollowstate.netfirms.com/mapletreebranches1.pdf and will give you some ideas how to accomplish this.

-d

 

[Phergus_25]

Well, there it goes.
I just picked up my phones and started up my HP rig for the first time in a few days and I'm SOOO happy with it.
I think I am going to read up on design and at some point make another amp, maby in a month or two, but for now Im set.
I think when I do make one Im going to make an Aikido with normal OTL and then read up on how to incorperate the transformers.
I still plan to order the PCB in a few days just so that I will have some thing to read up on and its alot easier for me to visualize when I have something in hand.
Im sure Ill be back in a month or so, depends on how much extra cash I have laying around.
-greg
PS- thanks again guys.

 

[dsavitsk]

I babbled a bit about this project in this thread, so I thought I'd post an update. It is basically an Espressivo with lots of cheap parts.

Sound is quite good, bass could be better, but for a $4 output transformer it's not bad at all ...

An externally hosted image should be here but it was not working when we last tested it.

Lots of details at: http://www.ecp.cc/less-pressivo.html