ModWright Headphone Amplifier - Here we go….

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modwright

ModWright Headphone Amplifier - Here we go….
« on: 11 Oct 2015, 06:37 pm »
OK, after watching from the sidelines for a long time, we have finally decided to enter the game, with Damon Coffman of Coffman Labs as circuit designer of this first all-tube offering!

3W+ into 32 ohms, proven capable of driving ALL of the most difficult loads, including The Abyss and HiFi Man headphones most recently at RMAF 2015.

I am working on the final chassis design and overall aesthetics, but here are the design constants:

(2)6922 driver tubes; (4)12B4 output tubes in PP, zero negative feedback.  SS voltage rectification.
Hand wound output transformers and phase splitting reactors! All Made In The USA!

Mini, 1/4" and XLR balanced outputs.

Target price ~$3K.

This will strictly be an amplifier, no built-in DAC.  We may also offer speaker outs for driving efficient desktop speakers.  I found that the prototype actually sounded quite nice driving my 97dB Daedalus speakers, to the limits of the amp's 3W power rating.  It couldn't ROCK my large show room, but at moderate levels, sounded incredible!  Certainly enough power for most desktop speakers.

We will be interested in a LIMITED number of BETA TESTERS!  IF interested, please let me know and get one our list!

Any feedback and input based on the above is welcome!

Thanks,

Dan

santacore

Re: ModWright Headphone Amplifier - Here we go….
« Reply #1 on: 12 Oct 2015, 04:47 am »
Good stuff!! I was very impressed by Damon's designs when I met him years ago at THE Show. I've been waiting to hear some of his newer designs.

Depending on when the tour happens, I would be interested. I have many top tier headphones to audition the amp with.

modwright

Re: ModWright Headphone Amplifier - Here we go….
« Reply #2 on: 12 Oct 2015, 03:37 pm »
Damon's previous design, the Prautes is exceptional!  This is as good or possibly even better.

How important is it for you guys to have binding posts for potential use with desktop speakers?

How about a preamp-out, to use as a preamp with a power amp?

How many inputs do most of you use for a HP amp?

Thanks!

Dan

Srajan Ebaen

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Re: ModWright Headphone Amplifier - Here we go….
« Reply #3 on: 12 Oct 2015, 07:01 pm »
Most desktop speakers tend to be small = very inefficient. Not sure how important speaker terminals would be on such a machine.

Double-tasking as a preamp... now that's a hole nutha proposition. I'd tick that box, twice even if there's enough real estate because, for the same reason, small speakers often want some subwoofer assist which goes below the desktop. For that, twinned outputs are nice to have. Same for general compact sub/sat systems in a studio or bedroom where the system goes on a lowboy, two small monitors atop against the wall, and one sub on the floor, perhaps with a TV in-between. Re: inputs, most I've seen have far too many line-level inputs. I'd think two RCA pairs would be sufficient so, ideally, two in, two out?

modwright

Re: ModWright Headphone Amplifier - Here we go….
« Reply #4 on: 12 Oct 2015, 07:42 pm »
Perfect!  Thanks Srajan, that makes sense.  I figure that most people have only a couple of sources and I wasn't sure about the desire for binding posts on a 3W amp.  The pre-outs make sense, and two sets is not a problem.

I am working on the aesthetics and overall enclosure concept design at the moment. I have some cool ideas and will share when I have a working model.

Take care,

Dan

santacore

Re: ModWright Headphone Amplifier - Here we go….
« Reply #5 on: 12 Oct 2015, 09:29 pm »
I'm with Srajan, 2 inputs is plenty for a headphone amp.

In my experience most purpose built headphone amps are just so-so at being preamps or integrated amps. Because of that, I personally would rather the circuit be kept simple and purpose built for headphones.  Consumers that want a all in one solution are typically on limited audio budgets. Therefore, a 3K headphone amp would typically not be something they are in the market for.

modwright

Re: ModWright Headphone Amplifier - Here we go….
« Reply #6 on: 12 Oct 2015, 10:43 pm »
Understood.  In this case, the input stage COULD be a standalone preamp.  I have to look at it some more, but it wold not represent any sonic penalty.

I hear you when you say that at this price, it will be more purpose-built, aiming at the serious headphone listener.  There are times and situations however, where I could see someone wanting to incorporate desktop speakers or something and for that reason, it would be attractive.

I agree that an 'all-in-one' solution is not what we are aiming at here.  I simply like to add as much functionality as I can to a design, WITHOUT compromising anything.

It is with this in mind, that I believe the power supply will also be external.

I am looking at  an overall footprint for the amp, that is about 8"W x 12"D x 3"H (5.5"H with tubes and transformers)External supply will be smaller and will only contain transformers, chokes and supply.  It could go on the floor or anywhere away from the amp.

I am thinking of exposed tubes with a removable 'cage' that will actually be an aesthetic feature, making the amp look great, while still allowing easy access to tubes for tube swapping.  No screws to remove!

I am getting excited about this release!

Thanks for your input!

Dan

santacore

Re: ModWright Headphone Amplifier - Here we go….
« Reply #7 on: 12 Oct 2015, 10:56 pm »
If there are no sonic compromises or headphone specific tuning, then I would say pre/speaker outputs could add value. Damon makes one heck of a great sounding preamp!!! In no way knocking your fantastic designs Dan. :thumb:

I like the idea of a smaller footprint amp along with an external power supply. Less shelf space is needed and it keeps the potential power supply noise far away. Win, win! No screw tube removal is a great idea.

modwright

Re: ModWright Headphone Amplifier - Here we go….
« Reply #8 on: 12 Oct 2015, 11:43 pm »
Thanks, it sounds great, will look great, and I am confident that it will be a successful product for us.

Perhaps an eloquent writer will review the product for us... 8)

Thanks,

Dan

talk2me

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Re: ModWright Headphone Amplifier - Here we go….
« Reply #9 on: 14 Oct 2015, 05:32 pm »
Why not put the headphone amp in the Elyse?  :thumb:

modwright

Re: ModWright Headphone Amplifier - Here we go….
« Reply #10 on: 14 Oct 2015, 11:29 pm »
There is not enough room in the Elyse for this circuit.  There are six tubes and two output transformers in this amp, plus two phase splitting inductors.  The way that I would add a headphone amp to the Elyse, if I were to do that, would be a discrete SS impedance matching buffer circuit.  In that case, I am not sure how much power it could provide, but likely NOT 3W+ into 32 ohms, pure Class A.  This is a dedicated headphone amp.

Dan

modwright

Re: ModWright Headphone Amplifier - Here we go….
« Reply #11 on: 15 Oct 2015, 12:59 am »
OK guys, feature checklist:

Inputs (2) RCA
Preouts (2) RCA

Headphone Outs:
(1) IEM stereo mini jack (padded down for higher efficiency IEMs)
(1) 1/4" stereo jack.
(1) 4P XLR stereo out.

Power supply: External box to be on floor or anyplace away from headphone amp.

Amplifier dims: Preliminary design = 8"Wx12"Dx3"H (not counting output transformers and tubes).
Power Supply dims: Preliminary design = 8"W x 10"Dx3"H.

Phase switch?
Hi/Low Gain switch?

Other features?

Thanks!

Dan

talk2me

  • Jr. Member
  • Posts: 172
Re: ModWright Headphone Amplifier - Here we go….
« Reply #12 on: 15 Oct 2015, 06:32 am »
There is not enough room in the Elyse for this circuit.  There are six tubes and two output transformers in this amp, plus two phase splitting inductors.  The way that I would add a headphone amp to the Elyse, if I were to do that, would be a discrete SS impedance matching buffer circuit.  In that case, I am not sure how much power it could provide, but likely NOT 3W+ into 32 ohms, pure Class A.  This is a dedicated headphone amp.

Dan

Gotcha, makes sense.

Srajan Ebaen

  • Industry Participant
  • Posts: 255
Re: ModWright Headphone Amplifier - Here we go….
« Reply #13 on: 15 Oct 2015, 09:23 am »
From the sound of it, it'll be push/pull so presumably have low output impedance. Then an impedance selector may be unnecessary. A hi/lo gain switch would be useful given your gain however. Padding down the 3.5mm jack standard is smart. Adding a hi/lo to the other two ports will help out the higher-eff full-size phones.

modwright

Re: ModWright Headphone Amplifier - Here we go….
« Reply #14 on: 15 Oct 2015, 10:36 pm »
Hi Srajan, yes, it is P-P and transformer coupled.  It can actually work easily even into an 8 ohm load, so yes, quite a low output impedance.

The pad for the IEM/mini jack is a given. I think a hi/low gain switch would also allow for more flexibility.

Thanks for the feedback,

Dan W.

modwright

Re: ModWright Headphone Amplifier - Here we go….
« Reply #15 on: 11 Nov 2015, 04:03 pm »
Heading into the home stretch on this design!

First of all, it was taken to RMAF 2015 and auditioned with The Abyss headphones and HiFiMan HE1000's.  In short, it handled the difficult load of the Abyss headphones well!  It also sounded fantastic to Arnie Nudell's ears with the HE1000's, listening to a master recording he brought that was phenomenal.

Features:

(2) pair RCA inputs.
(2) pair RCA preouts.
IEM stereo Headphone out, padded to allow proper power to IEMs.
.25" stereo Headphone out.
4-Pin XLR balanced Headphone out.

(Unit can operate with both .25" and 4-pin XLR outs operating at the same time.  IEM input is switched and may only operate by itself)

Two Box design:
External power supply for lowest possible noise floor.
Supply and headphone amp to be: 8"Wx12"Dx4"H
5-Pin XLR umbilical - 4ft.

Two box and slim form factor allow flexibility of placement on desk or in rack.

Tube complement:
(2) 6922/6DJ8/7308
(4) NOS 12B4's.


Transformers:
Interstage and output transformers all hand-wound from Electraprint.

Fit and finish is being decided, but enclosures will feature custom color powder-coat finish.  Looking at either nickel plated or powder coated transformer end bells to match chassis color.

Exposed tubes for easy tube rolling.  Transformers will be horizontal mount with top end bells exposed.

Top quality parts will be used throughout, including NOS Russian Mil-Spec silver contact selector switches, MWI and NOS oil caps, NOS tubes and carbon film resistors.

I am excited about this….more soon!

Thanks,

Dan Wright


modwright

Re: ModWright Headphone Amplifier - Here we go….
« Reply #16 on: 16 Mar 2016, 02:22 pm »
I am re-directing this thread to a new thread: 'Introducing 'Tryst''.

The design is complete and Tryst will make its debut at SoCal CanJam 2016 in Costa Mesa.

Thanks for all of your input and support!

Dan