Headphone Amp Build

[bcmatt]

if you are patient enough you can find nice secondhand Darkvoice for $100-150

I'm patient on this... Where do you typically find such things?

[bcmatt]

So, I feel like it would only be responsible at this point to take inventory of some random salvaged parts that I am pretty sure are all working. My wallet and the environment would appreciate some due diligence to see if something here would be appropriate for this... if I can test them somehow.

What I feel like might be most promising is maybe this:

Fleetwood power.jpg

Salvaged it from a (Fleetwood?) Radio cabinet that was going to the dump. This is the radio chassis that I also have:

Fleetwoodtop.jpg

There are a couple slips of paper with Chassis numbers and what-not that maybe can help me find a schematic.

I also saved some sort of DIY looking 18 watt style guitar amp in the most garbage combo cabinet ever seen. It was working, but even plugging into a real speaker cab, there was nothing impressive about the sound, so I began raiding it for parts. I still have the PT, OT and I think this choke was from it as well.

18watter1.jpg

18watter.jpg

I ought to test and document what I can about these transfomers anyways if I am ever to repurpose them.

Then there is this that I really cannot remember it's source:

Unknown Xformer.jpg

Maybe it is from the radio too, but I really doubt it would be completely puled out like this.

Anyways, any thoughts about any of this, or is it just frustrating garbage... too risky because some things cannot be measured like the power handling?

[bcmatt]

Ok, I just realized I have one more thing that might be way more relevant than anything else... and something I should really go over. It's an old Bogen MXM-A PA Mic Preamp/mixer:

20230817_081808.jpg

20230817_081823.jpg

I haven't even tested it, but perhaps I should test it out. Someone gave it to me and I've not molested it aside from grabbing a really nice 12ax7 or two out of it that is probably in my Express or Liverpool right now.

Bogen-MXM-A-Operating-Manual.pdf

[neskor]

I'm patient on this... Where do you typically find such things?

usually ebay or craiglist

[bcmatt]

With no OT you will need a lot of current pumping out of the output tubes you use for the build!

Maybe in terms of a 9 pin tube running a 12BH7 with its sections wired in parallel for each channel will do it.

Off the top of my head I think with such a set up you could get 5 watts with only some 250 volts on the plate.

For audio sake you would want a really good quality cap to decouple that plate voltage from your head phones!

I guess maybe it's this requirement of so much current with low voltage that maybe makes using my spare transformers unlikely... Or if some of them worked, it would take multiples and things are likely to be pretty heavy and unruly.

[bcmatt]

I'm patient on this... Where do you typically find such things?

usually ebay or craiglist

ok, I'll keep ,my eyes open. Just one Darkvoice I can find right now and it's $500 CDN

[neskor]

$160 in Ottawa
https://www.kijiji.ca/v-headphones/otta ... 1668649293

[bcmatt]

$160 in Ottawa
https://www.kijiji.ca/v-headphones/otta ... 1668649293

Haha! Yes! That is in Canada, but it's the other side of the country. I would totally jump on that, but he seems pretty strict about local pickup and cash only. That is encouraging that some decent prices exist though!

[bcmatt]

I'm still wrestling through this, and what I want to do. I found out a bit more information about another design... that would also need a specialty transformer that can handle the current of a 6080, but this one with a 12au7:

!2au7and6as7OTL.jpg

This is with some solidstate additions to bring a bit more clarity to the signal.

12au7+6080+SS.jpg

I see now that this is just a simple version of the darkvoice and the rest.

I think my main preference is that I would like to build something that has the option of driving my 250ohm headphones as well as my little desktop poweramp with some tubes in the circuit. I think I'd be fine with any...

[bcmatt]

The headphone amp idea is on hold. This spurred on a couple other higher priority projects.

I realized I don't use headphones at a desk for pleasure listening. I'd much rather listen through speakers and would much rather add some tube colour to those speaker setups I have.

I'm looking at this instead:
https://www.cascadetubes.com/the-12au7- ... or-preamp/

Skunkie designs has some tweaks based on her playing with a build of it:
https://www.youtube.com/playlist?list=P ... OvvaIx1swq

This, project I think I can swing at this point in my life while I am ordering some parts for my grandpa's old shortwave radio anyways.

[bcmatt]

So I finished this "Color Preamp" this evening. The last couple of RCA jacks arrived this morning so I finally had the rest of the pieces. The Ifi Zen Air phono stage also arrived this morning so I can now toggle between the record player and the pifi (I gave it two pairs of rca inputs with a simple toggle between them to select) I'll have to A/B compare the tube preamp in and out of the signal path to really see what characteristics it is changing in real time. I added the input gain levels for each channel so I can dial in the level of tube coloration as well as manually balance left and right.
My initial impressions without getting to turn it up too loud is that it does allow you to get a certain greasiness as you crank up the input levels as well as the general cliche terms of full, warm and round.
I'm not just doing this for the tube glue and filling up the shelf. I do want to see how it is really affecting the sound... so I will do a bunch of testing.

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