Prototype of New OTL Headphone Amp

Wolf Ear Audio · « **on:** 6 May 2016, 09:49 pm »

Thought I would show off the new prototype of my OTL headphone amp.

I'm just finishing up the 3D CAD so I can get the chassis going, but I wanted to collect a couple of your thoughts on this first.
It uses a 6P15P-EV in SET cathode follower mode to power the headphones and is meant for high impedance headphones such as the Sennheiser and Beyerdynamic models. It is also a no feedback single ended design and uses only film caps all round for the entire amp.
I am currently using the 6N6P as the driver tube. It is very neutral and handles everything with ease. I have also used the 6SN7 tube for the driver stage and really like both of them, as they both do duty as driver very easily. The 6N6P is much more affordable, but has almost no tube rolling options whereas the 6SN7 has tons of options available but costs a bit more.
So I want to get your opinions on which driver tube you prefer and then commit to that one for production.

ZLS · « **Reply #1 on:** 6 May 2016, 10:26 pm »

If you use the 6SN7, can a 12AS7 be rolled in?
It is much more reasonably priced.

Wolf Ear Audio · « **Reply #2 on:** 6 May 2016, 11:56 pm »

Quote from: ZLS on 6 May 2016, 10:26 pm

If you use the 6SN7, can a 12AS7 be rolled in?
It is much more reasonably priced.

Did you mean 12SN7? It could be wired either way with no circuit changes, but it would only be usable with the type it is wired for. It would only take a single 6SN7 though, so the cost would not be too great

Canada Rob · « **Reply #3 on:** 10 May 2016, 05:34 pm »

9 pin tubes are generally very affordable so I would go with: 1) what sounds best. 2) greatest amount of tube rolling options. When a person is at this level for a headphone amp, I personally think penny pinching on 9 pin tubes is really a moot point.

My 2 cents (Canadian funds) worth.

Wolf Ear Audio · « **Reply #4 on:** 10 May 2016, 06:07 pm »

Quote from: Canada Rob on 10 May 2016, 05:34 pm

9 pin tubes are generally very affordable so I would go with: 1) what sounds best. 2) greatest amount of tube rolling options. When a person is at this level for a headphone amp, I personally think penny pinching on 9 pin tubes is really a moot point.

My 2 cents (Canadian funds) worth.

As always, I like your approach.
Both the 6SN7 and 6N6P are very linear tubes with similar gain, but I decided on the 6SN7 for the driver tube and submitted my chassis design this morning for production.
I will be shipping this amp stock with (2) 6P15P-EV (EL84 rollable) for the output stage and (1) 6N8S (Russian equivalent 6SN7. Rollable with all 6SN7 types) for the driver tube.

santacore · « **Reply #5 on:** 10 May 2016, 06:11 pm »

Good call on choosing the 6SN7 as the driver. Not only is this a great sounding tube, but I think the general public really loves to tube roll no matter the cost. Will this amp have a single output impedance? If so, what?

Wolf Ear Audio · « **Reply #6 on:** 10 May 2016, 06:26 pm »

Quote from: santacore on 10 May 2016, 06:11 pm

Good call on choosing the 6SN7 as the driver. Not only is this a great sounding tube, but I think the general public really loves to tube roll no matter the cost. Will this amp have a single output impedance? If so, what?

Yes, measured output impedance is about 70 ohms. This is an OTL no feedback design, so this is about as low as it will go with a single linear output tube. It's very good for different high impedance headphones out there. I personally have a Beyer T1 I use with this, though I wish to someday try it with the Audeze LCD-4 (which has an impedance of 200 ohms)

Wolf Ear Audio · « **Reply #7 on:** 4 Jun 2016, 09:52 pm »

Chassis are complete and going out for anodizing Monday and laser etching right after that. Hoping to get everything ready within 2-3 weeks!

Here's a sneak peak at the chassis layout:

Note: This is my personal chassis (painted hammertone bronze). The production chassis are being anodized black.

Wolf Ear Audio · « **Reply #8 on:** 21 Jun 2016, 04:14 pm »

Not exactly an OTL, but here's a my personal transformer coupled headphone amp:

It's compatible with 6L6, EL34, KT88, etc. for the output stage and 6SN7 for the input stage.

Their chassis, along with the OTLs' chassis are done being anodized today and will be getting their silk screening done within the week. New products pages and announcement by end of next week (fingers crossed!).

santacore · « **Reply #9 on:** 22 Jun 2016, 05:01 am »

That looks like a great amp! I've always been partial to transformer coupled amps.

Quote from: Wolf Ear Audio on 21 Jun 2016, 04:14 pm

Not exactly an OTL, but here's a my personal transformer coupled headphone amp:

It's compatible with 6L6, EL34, KT88, etc. for the output stage and 6SN7 for the input stage.

Their chassis, along with the OTLs' chassis are done being anodized today and will be getting their silk screening done within the week. New products pages and announcement by end of next week (fingers crossed!).

Wolf Ear Audio · « **Reply #10 on:** 22 Jul 2016, 04:20 pm »

Thought I would update as it has been awhile.
I ran into a few bumps in the road which I delayed the product launch. We will no longer be anodizing our chassis, as this has so far proved far more troublesome than it is worth. Our new chassis will all be powder coated and there is a very awesome local business that does fantastic work.
The new powder coating also wasn't very friendly when it came to getting silk screened, so I had to figure out a different way to add the labels, logo, etc. Everything is now getting etched on polished steel plates which will be mounted on the chassis. Our manufacturer for the plates says they'll be ready early August, so we hope that is correct.
We will also be doing a limited run of certain finishes of the new amp that look just great, so I'll be happy to show off some photos soon if anyone is interested.

If anyone has any questions, please feel free to ask and I will respond as quick as I can.

Guy 13 · « **Reply #11 on:** 22 Jul 2016, 05:32 pm »

I'm always interested in anything - everything
Made in CANADA !

Guy 13

orientalexpress · « **Reply #12 on:** 22 Jul 2016, 06:33 pm »

I love a simple design and look .

Wolf Ear Audio · « **Reply #13 on:** 22 Jul 2016, 06:44 pm »

Quote from: orientalexpress on 22 Jul 2016, 06:33 pm

I love a simple design and look .

Thanks! The picture above is only my own personal amp (that I spray painted... and not very well lol).
The professionally powder coated ones look much better and they are fairly large. Quite a bit bigger than the Kitoki, as it has more large chokes, etc.
The transformer coupled one weighs in at about 25lbs, the OTL a bit less (I'll release full specs when I have pictures of the chassis with plates).

Armaegis · « **Reply #14 on:** 18 Aug 2016, 05:09 am »

As a certified headphone nut (I used to have monoblocks for my Hifiman HE-6 for goodness sake!), this is intriguing to me.

I've added you to my list of Canadian manufacturers over at headfi... http://www.head-fi.org/t/548624/listing-canadian-companies-retailers

Do you have any more information available yet? Need any reviewers? I have both owned and reviewed a lot of headphone gear, as you can see from my profile here: http://www.head-fi.org/u/136355/Armaegis
I have also built the Bottlehead Crack about three times now, which is perhaps one of the most well known OTL headphone amps out there.

Wolf Ear Audio · « **Reply #15 on:** 19 Aug 2016, 07:08 pm »

Quote from: Armaegis on 18 Aug 2016, 05:09 am

As a certified headphone nut (I used to have monoblocks for my Hifiman HE-6 for goodness sake!), this is intriguing to me.

I've added you to my list of Canadian manufacturers over at headfi... http://www.head-fi.org/t/548624/listing-canadian-companies-retailers

Do you have any more information available yet? Need any reviewers? I have both owned and reviewed a lot of headphone gear, as you can see from my profile here: http://www.head-fi.org/u/136355/Armaegis
I have also built the Bottlehead Crack about three times now, which is perhaps one of the most well known OTL headphone amps out there.

Good timing on your question. After yet a couple more delays, I finally have all my parts in this week and am currently building stock units.
I am aiming to do my product announcement for Monday or Tuesday for the transformer coupled headphone amp and the OTL *should* be ready soon after (can't rush perfection and I want this to be perfect).

smk · « **Reply #16 on:** 19 Aug 2016, 08:54 pm »

Powder coated chassis probably as durable & may be less expensive than anodizing. Although ultimately may be more expensive with plates, logos, etc. Any price estimate/dimensions?

Wolf Ear Audio · « **Reply #17 on:** 23 Aug 2016, 05:00 pm »

I will be posting a release topic shortly

mr haney · « **Reply #18 on:** 21 Sep 2016, 03:19 pm »

Can you give a ball park figure on price for the OTL headphone amp. I try to not even read about products over the
$1200 to $1500 mark. Why read about equipment I will not spend that much money on. I really wish you had a transformer output tube amp in the $1200 to 1500 range ! Thanks

Wolf Ear Audio · « **Reply #19 on:** 22 Sep 2016, 04:28 pm »

Quote from: mr haney on 21 Sep 2016, 03:19 pm

Can you give a ball park figure on price for the OTL headphone amp. I try to not even read about products over the
$1200 to $1500 mark. Why read about equipment I will not spend that much money on. I really wish you had a transformer output tube amp in the $1200 to 1500 range ! Thanks

I'll try to get the full release done by next week, but expect the price to be around 2000-2400CAD (1500-1850USD). Size and appearance will be quite similar to Makoyi, but uses different tubes. I'm really excited about this one, as I love OTL designs and this one is by far my favorite headphone amp I have designed. It's like they say, the best transformer is no transformer (but it is very difficult to design an OTL for low impedance loads).
I can also custom make you something if you are interested (and we can make a lower price model with electrolytic caps, etc.). PM or e-mail if interested.