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May 24, 2017

Four Pairs of Headphones for Any Studio Setup

This guest post is brought to you by my friends at Headphone Ninja. Anyone following the blog knows I love headphones, and Jo-Ann and company have culminated four tried-and true classics to discuss.

Studio headphones fill the market today. However, many of them are either far too expensive or far too inaccurate when it comes to meeting the referencing demands of producers and audio engineers. While everyone would love to own a pair of the sleek Sennheiser HD800s or the beautiful Japanese cherry birch wood Fostex TH 900s, we don’t all have a Hans Zimmer’s budget.

In this post we explore four of the more preferred headphones available in 2017 that are well suited to the modern day studio.

Closed-back headphones

Audio-Technica ATH-M50X

Comfort is key when it comes to long studio sessions. The generously padded earcups and adjustable headband of the ATH-MX50 provides comfort, and while the headphones do clamp down reasonably hard, they do not physically strangle the life out of your temples. They are slightly heavy at 10-ounces, but this should not be a deciding factor for those looking to use these in a studio environment.

The ATH-M50X is fitted with large 45mm proprietary drivers that deliver exceptional clarity. Some individuals who have used these thought that the bass is slightly high, but the mid frequencies are fairly well represented. The higher frequencies also appear to be slightly bright, but not to the point of fatiguing the ear. The 90-degree swivelling earcup is great for single ear monitoring and the frequency response ranges from 15 - 20,000Hz.

Sony MDR7506

Introduced back in 1991, the Sony MD7506 has remained a firm favorite amongst many looking for high quality and reliable headphones. Their durability is as decent as a pair of plastic headphones can get, with the only real issue of deterioration being the earpads on the cups, but these are replaceable. At around 8-ounces, they are light enough to not burden the wearer much.

The MDR7506’s frequency response ranges from 10 - 20,000Hz. It has revealed a solid bass response in tests, albeit slightly bumped up in the 60 -100Hz range. Mids remain fairly flat while the low treble to the high treble frequencies are quite inconsistent; the sibilance range is slightly boosted and can be slightly piercing to the more sensitive ears. The soundstage is decent for a closed-back pair of cans. They have an 63-ohm rated impedance and their low leakage is also suitable for recording purposes.
The coiled 9.8-inch cord is more than enough for studio environments and it does come with a ¼ inch adaptor. The Sony MDR7506 gives many mid-range referencing cans a run for their money.

Open-back headphones

Sennheiser HD 650

The Sennheiser HD 650 are slightly pricier, but it seems important to add these cans for those who enjoy the spacier sounds that open-back circumaural headphones offer. The suede-like fabric is a nice touch on the large, encompassing cups that house the efficient neodymium magnets.

The slightly under-emphasized low bass frequencies with the minor boost on the high bass gives the headphones a more natural sounding low end. The mid range responses are pretty much flat throughout and the treble frequencies are consistent. Their impressive frequency response coupled with the spacious sound created by the deep drivers and open-back design makes these excellent for critical listening.

Needless to say, their isolation is pretty much non-existent, making these more suited to quieter environments. They are also less suitable for recording purposes, because they do leak quite a bit of additional noise, which in turn will bleed into your microphone. 

The Sennheiser HD 650 is an excellent referencing headphone and offer an awesome frequency response, though they are less suitable for recording purposes however.

Editors Note: The 650s can sound a little dull in the treble with the stock cable in some setups. A replacement featuring silver-clad copper can bring out the highs. Check with Zynsonix for additional details.


The AKG K712 PRO are another great choice for mixing and mastering purposes. The design is slightly bulky, but they are purposefully built for studios, so that is completely understandable. The memory foam earcups captures the shape of your head, but they are rather large. Sound wise, they deliver a spacious and accurate audio reproduction, but the sound is a bit warmer in the upper bass. Still, it is well controlled overall. The mids are represented accurately.

Sensitive ears may find the slightly boosted (and somewhat inconsistent) higher frequencies a tad overwhelming, as they can sound harsh. The frequency response ranges from 10 - 39,800Hz in its entirety and it has a low harmonic distortion.

As a whole, the AKG K712 PRO have a natural sound and are well suited to intensive referencing sessions. The open-back design means they are more suited for mixing and mastering in studios.

Wrap up

This is by no means a comprehensive guide to selecting studio headphones, but a look at some of the more popular headphones around at the moment for any type of studio. While they may mostly be mid-range headphones, they perform well within their specific categories and are well suited for studio use.

May 22, 2017

Millett NuHybrid Headphone Amp Using Korg NuTube

In Mid-March, the prolific DIYer Pete Millett introduced a new hybrid headphone amp called the NuHybrid using the Korg Nutube 6P1. The design is similar to the original Millett Hybrid, which spawned both the exceedingly popular Millett MAX and stripped-down Starving Student builds. The Starving Student was super-popular as it could be built for as little as $35, which is unheard of for an amp with two tubes.

To shake things up (Millett designs are rarely status quo), the old car radio tubes were eschewed for the new Korg Nutube. The Nutube is a low-power, directly-heated dual triode tube built using a process originally used for Vacuum Fluorescent Displays (VFDs) and emits a bluish-white glow when the tube is powered up. The Nutube has been popular with DIYers in Japan since it was released at the tail-end of 2016, but hasn't really caught on with DIYers elsewhere, at least yet. The cost of a Nutube is around $50, which may seem a little steep, but two noval signal tubes will set you back at least $30-35 these days, along with another $5 for sockets and the potential to have to replace them in a few years, which makes $50 not seem all that bad.

The Korg NuTube

One of the nice things about the design is you don't have to feed it plenty of amps. The whole thing runs off of a 24V power supply, so it is much safer than a typical tube-based build. A pair of OPA551 op-amps to drive the headphones, but others can be rolled in for a different sound signature. Pete has made the design so it can be built cheaply (~$120) and placed in a Serpac plastic case. Much like Pete I don't like status quo, so I'll be building a case from scratch for my NuHybrid amp. I wanted to make the amp look like an old tabletop radio, so a wood frame would be needed.

A quick trip to Home Depot yielded a 6ft long by 3.5" wide piece of maple.

A little bit of routing and a few 45 degree cuts on a miter saw and we have a frame. Note the inside of the frame is rabbeted so the front and rear plate can sit flush. The 5/8" pieces in the middle are for screws to hold the plates in place. This is a photo after an initial coat of Minwax Pecan colored stain and seal combo. Yes I know it's sacrilege for anyone who works with wood regularly, but it's quite and easy.

Frame to hold PCB inside

As wood doesn't protect from errant EMI/RFI, I've added some copper shielding tape which will be electrically connected to the front and rear aluminum plates to get 100% coverage.

Copper EMI/RFI Tape for shielding

The board is quick and easy to populate and should take even the most OCD solder slinger less than 3 hours. Below is an image of the PCB. The checkered areas indicate where double-sided tape is applied to the board to hold the NuTube in place.

NuHybrid unpopulated PCB

Below you'll see my PCB about 90% populated. I changed a couple of the parts in the BOM. The BOM calls for Wima polyester, but you can switch them out with Polypropylene for about $2.50 more and they fit without issue. I also went with Elna Silmics in the power supply. The Silmics sport a 7.5mm lead spacing versus 5 on the Nichicons, so they have to be pressed into place otherwise they'd stand crooked. They also encroach a bit on other areas of the PCB, so the Wimas needed to be mounted on the bottom. I also went with Takman carbon film resistors in most areas. The 1/4 watt variety are only 36 or so cents a pop at Sonic Craft, so it won't break the bank to use them.

Note the large-and-in-charge Silmics in the power supply section  

I picked up two aluminum plates 1/8" thick for the front and back. I usually get them pre-cut from eBay but will also use a miter saw with a metal blade if the size I need isn't available. The back of the unit needs holes for four RCAs and 24v DC. Although I doubt the unit gets very hot due to the low power requirements, I drilled a hole pattern at the top for heat to escape, as with wood it will trap it in otherwise. The aluminum is spritzed with Hammertone paint in a copper finish.

1/8" thick aluminum plate with holes for RCA, DC

Attaching the unit to the front panel are the 1/4" inlet nut and the TKD potentiometer nut. I went with the nicer TKD potentiometer as suggested by Pete. $40 is a bit painful but I'm tired of using Alps Blue Velvets for every build. The front LED, switch and coupling capacitors (Russian Silver Mica) are connected with fly leads (22ga. silver clad teflon solid core wire I had left over from a Bottlehead build). The wiring to the RCAs is Cardas 24ga. stranded in teflon. Note the space between the two mica caps in order to reach the adjustment pots. The RCAs are Switchcraft units I had on hand. The switch is much higher rated than it needs to be, but I have tons of surplus switches and like the big old school ones. If you're looking for low cost and high quality, check out Apex Jr.

Attaching the panels gives the nearly finished product...

Vent holes probably not needed, but look nice

The last touches were an engraved front plate and changing the pilot light to a funkier looking one.

All done and sounds great!

Please remember that building/modifying circuits can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a build or modification posted above and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard. 

May 19, 2017

Help out Dave from Planet 10 HiFi

Dave over at Planet 10 HiFi has been instrumental in pushing the envelope for single driver speaker designs, including the much lauded Fonken and MiniOnken designs and the amazing Frugal horn which can be built with Mark Audio or Fostex drivers.

He also developed and patented the EnABL process which dampens and improves drivers (an interesting read if you have time). He's also developed many speaker cabinet designs, hosted a number of group buys, and has been a cornerstone of the DIY community.

Dave currently needs our help. Last year Dave's wife, Ruth, found him laying on the bathroom floor, ghostly pale and staring wide-eyed. Ruth immediately called an ambulance and Dave was taken to Vic General where an emergency CT Scan and speedy blood work prompted another ambulance to rush him to Royal Jubilee for emergency surgery less than an hour after leaving their home. It turned out that an abdominal aortic aneurysm had burst (one of multiple previously undetected aneurysms), his chest was full of blood and infection was raging through his upper body. Two gifted surgeons spent over 10 hours working valiantly to save his life. Dave survived the surgery to replace his entire aorta, top to bottom, and was kept in an induced-coma for almost a week to allow the body to begin to heal. The surgeon said Dave had incredible tenacity to make it through the surgery. 

Fortunately, Dave just got back at home last month and has been slowly recovering, but as you can imagine there are many expenses associated with medical difficulties of this magnitude and being out of work for so long. 

I encourage you to join in the GoFundMe to help out Dave and Ruth as they traverse this challenging time in their lives, especially if you value the great things Dave has done for the DIY community. You can also see the latest updates at DIYAudio