Is it possible to passthrough the input to the Sapphire to another pair of RCA for connecting an additional amp after the Sapphire? (I basically have 2 headphone amps and would like to switch between the two with minimal fuss).
Is it as simple as adding another pair of RCA and just wiring directly to the input connectors?
Is it as simple as adding another pair of RCA and just wiring directly to the input connectors?
Hello Richard,
With the Sapphire 4 configured at 150ma bias & closed loop, I am thinking about pushing the unit to drive my HiFiMan HE-400i. The headphone is a gain hog with your gain calculator recommending a gain of 31 (HE-400i spec'ed at 94 db spl/v, and 35 ohms).
There's a note on your .xls to keep the gain < 30. Would I damage the circuit if I went beyond, say gain of 35? I have the output transistors well heat sinked & fan cooled.
Thanks, Henry
With the Sapphire 4 configured at 150ma bias & closed loop, I am thinking about pushing the unit to drive my HiFiMan HE-400i. The headphone is a gain hog with your gain calculator recommending a gain of 31 (HE-400i spec'ed at 94 db spl/v, and 35 ohms).
There's a note on your .xls to keep the gain < 30. Would I damage the circuit if I went beyond, say gain of 35? I have the output transistors well heat sinked & fan cooled.
Thanks, Henry
I am using Sapphire V4 with gain set at 15db with Yamaha HP1 modded (sensitivity- 94db), HE-500 (89db), Fostex T50rp mk3 modded (90db).. I only go upto 9pm pot position with HE500 with DAC output of 2.43V . So having higher gain may not be needed for HE400i, unless the source you are using has much lower voltage output.
The 35 ohms on the HE-400i means 94 dB/V is 80 dB/mW. They are a pig to drive, no question, pretty much the most demanding cans out there for both current and voltage.
A gain of 30 V/V should be fine however, and the Sapphire circuit biased to 150 mA is more than capable of handling the power requirements.
A gain of 30 V/V should be fine however, and the Sapphire circuit biased to 150 mA is more than capable of handling the power requirements.
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Sapphire 4.2a
I'm moving the custom 4.1-LL version to the primary development path.
The new board is 4.2a, incorporates the larger capacitors of the LL version, and adds a couple of layout adjustments.
The circuit is unchanged.
Gerber files attached.
I'm moving the custom 4.1-LL version to the primary development path.
The new board is 4.2a, incorporates the larger capacitors of the LL version, and adds a couple of layout adjustments.
The circuit is unchanged.
Gerber files attached.
Attachments
I've had the Sapphire 4.1 for quite a while now and while I like it alot, when listenting through my HD650 the sound feels much flatter and less dynamic than compared to my AMB CK2III.
Both amps have TKD 2CP2500 pots.
I have Mundorf supremes in the Sapphire, could that be the cause, or maybe its the gain?
It is currently set to 12dB, but based on the Gain calculator, the HD650 at 300ohms and 97db/mW (or 103db/1V) the gain should be 22-23. Does that make sense?
Both amps have TKD 2CP2500 pots.
I have Mundorf supremes in the Sapphire, could that be the cause, or maybe its the gain?
It is currently set to 12dB, but based on the Gain calculator, the HD650 at 300ohms and 97db/mW (or 103db/1V) the gain should be 22-23. Does that make sense?
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I found some 499R resistors and swapped those in (config is single gain, open loop), which brings gain to 21db.
Initial impressions are that things are much more "lively"
