I own a couple of Hypex 400 OEM amplifier boards.
I read some of the Hypex white-papers and many topics here on diyaudio, but I've not understood clearly if I can drive the Hypex 400 OEM using unbuffered input (1K8 impedance) with my Technics SU-9070 preamplifier (600 ohm rated output impedance).
I'd like to add a potentiometer according to "Configuration B":
So I would have, using 0.33K series resistors:
amp Zin = 1.8K
vol pot = 50K
effective parallel resistance = 1.73K
source see 0.33K+0.33K+1.73K = 2.39K, when set to maximum volume.
gain = 1.73K/2.39K= 0.72 = -2.8dB
When set to minimum volume, the input impedance is 0.66K (0.33K + 0.33K). Could that impedance be driven by the preamplifier?
Theoretically I would say "no". I wrote 'theoretically' because doing some measurements with my DMM seems that the preamplifier output impedance is much lower than 600 ohm... but I have to perform more extensive tests about.
Have some of you experienced succesfully an Hypex amplifier driven by a solid state preamplifier - using unbuffered input on the Hypex?
*Note: I wonder if it's possible to bypass the buffer to get the best possible sound quality.
Another question is, with a gain of 2.8dB I would lost half of the Hypex power on the way (since there is a doubling in power every 3dB), that's right?
Thanks for your help 🙂
I read some of the Hypex white-papers and many topics here on diyaudio, but I've not understood clearly if I can drive the Hypex 400 OEM using unbuffered input (1K8 impedance) with my Technics SU-9070 preamplifier (600 ohm rated output impedance).
I'd like to add a potentiometer according to "Configuration B":
An externally hosted image should be here but it was not working when we last tested it.
So I would have, using 0.33K series resistors:
amp Zin = 1.8K
vol pot = 50K
effective parallel resistance = 1.73K
source see 0.33K+0.33K+1.73K = 2.39K, when set to maximum volume.
gain = 1.73K/2.39K= 0.72 = -2.8dB
When set to minimum volume, the input impedance is 0.66K (0.33K + 0.33K). Could that impedance be driven by the preamplifier?
Theoretically I would say "no". I wrote 'theoretically' because doing some measurements with my DMM seems that the preamplifier output impedance is much lower than 600 ohm... but I have to perform more extensive tests about.
Have some of you experienced succesfully an Hypex amplifier driven by a solid state preamplifier - using unbuffered input on the Hypex?
*Note: I wonder if it's possible to bypass the buffer to get the best possible sound quality.
Another question is, with a gain of 2.8dB I would lost half of the Hypex power on the way (since there is a doubling in power every 3dB), that's right?
Thanks for your help 🙂
I use UcD400 OEM unbuffered driven by LM4562 OP-amp DAC output stage. It has 60 ohm output impedance and max 2V output voltage. It drives UCD with ease. Input sensitivity of UCD400OEM is 9V so I have a little power from it but the sound and speaker control is simply incredible. I have never heard such sound from any amplifier before. It is better than any linear amplifier which I know. It is clean and transparent, smooth and fluid, with absolutely no sonic signature and with incredible 3D soundstage and incredible bass. Noise level is so low that in order to hear it you need to put tweeter inside of your ear. This is reference class amplifier but you need to drive it unbuffered from strong source.
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