Frequently Asked Questions
Do you offer customization?
Yes, gain can be customized upon request to match your headphones, although this is generally unnecessary. To request free gain customization, mention your headphones during checkout with PayPal. Customized orders may delay shipment by 1 business day.
The following cannot be customized by JDS Labs:
• Input Jack
• Output Jack
• DC Jack
• Bass Boost Toggle Switch
Different jack requirements (such as RCA or 1/4" stereo jacks) can be fulfilled using appropriate adapter cables.
What other tins/enclosures are available?
The cMoyBB PCB is designed only to accommodate rectangular mint tins. Other enclosure types are not possible.
Alternative mint tins are very rarely available. The tins pictured at right might be in stock. Contact me prior to ordering for more details.
Can the bass boost toggle switch be replaced with a knob?
This modification is only available to do-it-yourselfers, as described in the Assembly Guide. JDS Labs does not stock the required potentiometer for the modification.
Will the cMoyBB work well with my headphones?
With nearly 2000 owners worldwide, the cMoyBB has received positive reviews from owners of practically every brand and most models of headphones on the market. Chances are, someone has tried the cMoyBB with your headphones and enjoyed it.
However, I do not own every set of headphones in the world and therefore cannot provide you with an honest opinion. I personally use Sennheiser HD-280 Pros, Grado SR-60s, Beyerdynamic DT-880s, and a variety of earbuds. The cMoyBB sounds great with them all.
The cMoyBB is fully capable of driving headphones of all impedances. High impedance headsets such as Sennheiser HD-650's (300 ohms), Beyerdynamics DT-770's and DT-880's (250 ohm editions), etc. are easily driven by the cMoyBB; an 18-24V power adapter can help to achieve dangerously loud volume levels with such models. Moderate and low impedance headphones such as AKG K-701's, Grado SR-60/80/125/225/325's, Ultimate Ears Super.Fi and Triple.Fi's, and Shure IEM's are also commonly paired with the cMoyBB.
Please browse through the cMoyBB's extensive Customer Reviews and you will likely find comments specific to your headphones.
What kind of cable do I need?
The cMoyBB uses standard 3.5mm (1/8") stereo input and output jacks. You will need a male-to-male 3.5mm interconnect cable (also known as a mini-to-mini cable) to connect your audio player to the amplifier.
I have no specific brand recommendations. Instead, I offer the following advice:
Choose a heavily shielded cable. Look for terms such as "shielded," "noise-rejecting," or "braided." These cables use an additional grounding wire and and/or shielding sheath to avert a small amount of electromagnetic interference. Additionally, every cheap interconnect cable I have used has worn out in under a month, causing static, popping sounds, or a broken signal when the cable is wiggled. Invest in a rugged cable!
*I occasionally stock interconnect cables. Contact me for details.*
What is the expected battery run-time for the cMoyBB?
Battery life depends on volume, headphone impedance, and of course battery type. A typical 9V alkaline battery should last approximately 25-30 hours under heavy usage. Other battery types are also safe to use (NiCd, NiMH, Li-Ion, etc.), but be aware that the cMoyBB does not provide charging capabilities.
A 9.6V NiMH battery and external charger are worthwhile investments if the amplifier is to be used portably.
What is the benefit of higher voltage?
Voltage supplied to an operational amplifier sets the upper and lower signal boundaries for the opamp's output. When asked to produce output beyond these maximum voltage boundaries, the opamp chip clips the signal and you will hear distortion. Therefore, a higher voltage supply allows the opamp to produce higher volumes.
There is practically no benefit to increasing supply voltage unless you desire even louder playback (such as with especially inefficient and/or high impedance headphones). A 9V battery is more than adequate for reaching dangerously loud volumes with most headphones, but if you find volume lacking, try an 18V power adapter or two 9V batteries wired in series.
All opamps are limited to "swinging" within a fixed distance from the voltage supply rails. Rail-to-rail opamps are able to drive signals much stronger before clipping. Thus, a rail-to-rail opamp is another way to achieve higher volumes, without resorting to higher voltage.
Why can't a cMoy be powered from a vehicle's 12V accessory outlet (or hardwired to the +12V supply)?
The power adapter warning mentioned in the instructions sheet applies to every cMoy, not just the cMoyBB.
Most vehicular audio systems use an audio ground which is directly connected to the vehicle's negative battery terminal. Let’s call this ground “V-“, and the vehicle's positive battery terminal "V+".
The negative DC power input of the cMoy is not connected to its audio ground. Instead, the cMoy's audio ground is electrically biased halfway between the battery/DC input voltage. Let's call the cMoy's positive and negative voltage supply connections "Vp" and "Vn", respectively. In other words, a cMoy power circuit creates its own "virtual ground" equal to 0.5*Vp.
When you wire a vehicle’s +12V supply to a cMoy, you are connecting the vehicle's V+ supply to the cMoy's Vp, and V- to Vn. This immediately presents no problems. Plug in a set of headphones and an iPod and your music will sound great. However, as soon as you plug the cMoy into your vehicle's auxiliary radio input, you are effectively shorting “Vn“ to the “virtual ground”. This instantly fries the cMoy’s power circuitry (the cMoyBB v2.02's optional "D2" diode can sometimes prevent this damage).
Thus, if you wish to use a cMoy with a car/truck/motorcycle’s auxiliary radio input, you must use a 9V battery to avoid shorting out the “virtual ground.” The other option is to power the cMoy from the motorcycle’s battery and only use headphones and an external audio player, such as an iPod.
How do you change the operational amplifier chip?
The chip sits in a socket from which it can be removed. If you do not own an IC extraction tool, use any thin, flat tool to pry the chip from its socket. A flathead screwdriver works well; needle nose pliers can also be used.
What other opamps do you recommend?
The stock OPA2227 opamp is an excellent chip. If you wish to experiment, several alternative chips are recommended in the Bill of Materials page. Because opinions vary from person to person, it is best for you to perform your own research and audition several chips. These discussions may help:
• Head-Fi: Best sounding opamp...
• Tangentsoft: Notes on Audio Op-Amps
Most dual-opamp chips available in the standard DIP-8 package will work. It is important to choose an opamp with an acceptable minimum supply voltage. The cMoyBB supplies +/- 4.5V when running on a fresh battery. Therefore, an opamp with a minimum supply voltage of +/- 5V would be unacceptable. This limitation can be overcome by using a higher voltage power adapter.
SOIC-8 (surface mount) or pairs of single-opamp chips can be used in conjunction with an appropriate BrownDog™ adapter. Again, it is important to research such chips prior to purchase.
Has my order shipped?
Check your e-mail, or login to PayPal and click on the transaction. See the Policies and Shipping pages for further information.
Do you ship internationally?
JDS Labs ships worldwide. Please see the Shipping Rates page for complete details.
Many questions may also be answered in the Instructions guide.
