2. amps-preamps
  3. 1357675217

Preamp - 18 dB Gain too low?

Being a newbie to audio stuff, I'd like to hear your opinion whether should I replace my preamp. To get to a reasonable loud volume, my preamp has to be at around 1PM to 2PM position for most of CD and music DVD. Should I get another preamp with higher gain? If so how much more? Why don't the manufacturers make higher gain? Probably some sonic compromise with high gain active preamp?

Any suggestions are welcomed.

Preamp: Conrad Johnson PV-10AL, gain 18 dB.
Amp: Shuguang S845MK (tube amp 848)
Speakers: Tekton Lore (Sensitivity 98 dB)
Room: 25 x 17 x 8'
nguyen787

Showing 7 responses by nguyen787

nguyen787 OP
52 posts
 
My CJ preamp is inverted phase. I made a mistake but corrected. Frankly I could not tell the different between correct and incorrect phase. No volume gain or loss after correcting phase. Good call Montytx.
nguyen787 OP
52 posts
 
Thank you all. Sound like I have been worried out of nothing.

Initially I hooked up the amps with a passive preamp Lightspeed Attenuator and the volume was low, dialing around 2:00 to 4:00 to have reasonable sound. Figured that active preamp would help, swapped out to CJ and it did. The volume knob is now at 1:00 to 2:00

The amp sensitivity is 4V. Is it low or high? I have no idea what 4 Volts really mean in term of sonic amplification.
nguyen787 OP
52 posts
 
The source is Oppo BDP 103.

The amp spec is confusing because the website and the manual state two different spec:

Grant Fidelity website
Output power: 25w
Response: 10Hz to 30KHz
SNR: ≥85dB
THD: ≤1.0%
Input sensitivity: ≤1.0V
Output impedance: 4Ω, 8Ω
Tubes: Standard Shuguang 845B×1, 300B-98 x 1, 6SN7GT ×1 per amp

Manual:
Input impedance: 100kohm
Input Power Voltage: 4.0V
Output Power：28W
Output impedance: 4、8Ω
Frequency Response: 10Hz-30KHz
THD: less than 1.5%
S/N Ratio：85dB
Power supply：AC 115V 60Hz
Power consumption: 170w per channel

Not sure what to believe.
nguyen787 OP
52 posts
 
Hi Dave,
Thank for sharing the detail of your measurement. I swapped the active preamp CJ 18 dB gain with a passive Lightspeed Attenuator, and I found that most of CDs, I have to push the volume knob to 3 - 5 PM (MAX == 5 PM) to obtain the desirable volume. The low sensitivity amp, 4 V, seems to be an issue. Bought this amp without understanding the input sensitivity spec...

What is attenuation voltage ratio and what does it tell us?
nguyen787 OP
52 posts
 
Being ignorant how you calculate 22 dB more gain with Rogue Apollo? Any websites or references are appreciated.
nguyen787 OP
52 posts
 
I looked into their spec for preamp S200MK and also found a mismatch between in the manual and Grant Fidelity website.

Manual:
Output Voltage: more than 3V, maximum 10V
Output impedance: less than 10k ohm
nguyen787 OP
52 posts
 
Checked and corrected Oppo setting per suggestions, do not see any different on sound level. Volume --> fixed at 100%.

George raised an interesting concern - main voltage. The amp power outlet plug written "115 V, 50/60 Hz" seems OK for US AC electricity. I am wondering Shuguang started out design as for 230 V and made shortcut to convert to 115 V for North America market, compromised the amp voltage? I really don't know, just speculating. I did send my question to Grant Fidelity about the spect mismatch, but have not heard back from them yet.
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