TM
Portaphile
DIP SWITCH BANK 1: (Left in Picture)
4 – RIGHT CHANNEL GAIN:
ON = Low Gain (2.5) OFF = High Gain (7)
3 – GROUND CHANNEL BIASING:
ON = Class A Biasing ON (effect 1.1ma) OFF = Class A Biasing OFF
2 – WIDE BANDWIDTH – ALL BUFFERS (up to six total) – effect ~25ma w/6:
ON = Wide Bandwidth Mode ON OFF = Wide Bandwidth OFF
1 – RIGHT CHANNEL CLASS A BIASING:
ON = Class A Biasing ON (effect 1.1ma) OFF = Class A Biasing OFF
The Portable Audiophile
DIP SWITCH BANK 2: (Right in Picture)
4 – LEFT CHANNEL GAIN:
ON = Low Gain (2.5) OFF = High Gain (7)
3 – NO CONNECTION / NO FUNCTION
2 – POWER LED:
ON = Power LED ON OFF = Power LED OFF
1 – LEFT CHANNEL CLASS A BIASING:
ON = Class A Biasing ON (effect 1.1ma) OFF =
Class A biasing off.
What does it all do?
Gain Settings
The gain setting determines how much you amplifier amplifies. A high gain will amplify the input signal more than a lower setting. A common misbelief is that a higher gain is always best. Low impedance headphones do not require alot of gain to give a loud enough presentation. Setting the amplifier to a low gain will work best with low impedance headphones such as Grado's, Etymotics, Ultimate Ears and Shures, just to name a few. A higher gain is best for high impedance headphones, such as Senn's (i.e. HD600's, 650's, 580's), Berdynamics and AKG's, just to name a few. The switchable gain setting in this amplifier allows you to adjust the gain to whatever headphones you are using. This also gives you the flexibility to upgrade your headphones later on to either high impedance or low impedance without having to change amplifiers at that time.
Class A Biasing
Imagine that an amplifier works like a switch, whenever a signal is present, the amplifier will switch to the "on" state to amplify the signal. Biasing the amplifier to Class A will keep the amplifier in the "on" state all the time. The price of doing this is a small increase in power consumption. The benefit is that because of all that switching that will no longer be going on there will be a reduce of certain types of distortions and crosstalk that would normally occur. The effects are not night and day, but there are small noticeable improvements in the sound that are worth the effort. Keep in mind that each channel (a total of three) can have it's class A biasing turned on/off. You may want to play with switching between GND Class A Off:L&R Class A ON and GND Class A ON:L&R Class OFF and see which you prefer (as opposed to going all ON). You may be able squeeze a little extra time out of your batteries only using some of the Class A biasing.
Widebandwidth Mode
This little feature allows the buffers to work better, but there is huge increase in power consumption. Battery Life decreases by half. The improvement is much more noticeable than with the Class A biasing.
LED Power OFF
The small LED consumes a small amount of current. Turning this switch off cuts the power off going to the LED. By doing so, you get a small increase in battery life. The LED has no affect on sound quality, but who knows, the purest may just want this little sucker out of the circuit so here you go.
All of these switchable features are not in the signal path with the exception of the low gain setting. Keeping the amplifier in the high gain setting will keep all switches out of the signal path. In a purest approach I wanted all connections in the signal path to be soldered directly using short thick traces. Without mechanical connections in the signal path, the signal runs through direct conections. This is why I chose to keep the switchable functions based on power consumption that improve the performance of the internal components and not on changing the sound in any way such as with impedance switches and bass boosts, which if implemented as a switchable feature would require a mechanical connection in the signal path degrading the purity of the signal path. I do not recommend this type of feature and would not use this in one of my amplifiers. The Low Gain switch is the only one that I felt offered a real benefit and felt that a switch was necessary to make this convenient for the user. To implement this feature I found a way that even when the low gain setting is engaged a direct connection is still maintained without going through the switch. This allows the connection to remain as direct as possible while still offering switching abilities. Only half of each channel's signal goes through the switch, with half still going directly through a closed soldered connection using only Cardas solder. Small attention to details such as this is what makes the Portaphile Amplifiers so special.
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Portaphile Audiophile Headphone Amplfiiers All Rights Reserved 2007
