[Grinnell]

I just got a Cornet II off AA.  Tungsol 12ax7/RCA Cleartop 12au7/sovetek 5AR4.

My system is a primaluna PL2 with De Capos.

My first thought was what a hum.  But it turns out that i had the volume on the PL2 set too high (for the cornet)  It was a 9 o'clock which is great for the Bottlehead Seduction (w/C4S upgrade) but way too loud for the Cornet II.  I had to turn it down to 8-7 o'clock position basically no hum and loud enough.

Now my question is the Seduction puts out about 40db of gain and the Cornet 44db.  Not much difference on paper but a big difference through my amp.

Not a problem i like the cornet much more than the Wright WPP200c ( too colored, tubey)

But i wanted to get some thoughts on this.

thanks

karl

[GRD]

Karl,

I'm assuming you're asking about hum.  The Cornet has a bit more gain than your other phono stage but that shouldn't be an issue.  The Cornet is a pretty quiet phono stage so I would check the usual suspects.  Short the inputs and see if the hum disappears (hum coming from the input - ie. turntable/leads), see if moving the C2 around reduces the hum, etc.  Also, I had a 12AX7 tubes that hummed - one of the Tungsol re-issues. 

This should be a start. 

Grant

[Grinnell]

Thanks for the reply.  Its not the hum that is quiet when the volume level with the cornet is equivilant to the volume setting with the Seduction.  Its the difference in the volume settings with the 2 phono stages to get the same volume out of the speakers that has me wondering.

The Cornet seems to be putting out out a lot more sound than just 4db more than the Seduction.

I do like the sound I'm getting its btw the Seduction and the Wright which I think will go up for sale soon.  Just didn't find what i wanted with that.

[Brinkman]

What are you wondering?

If you know the output of your cartridge (in mV) you can multiply that by 100 (voltage gain of 40dB) or by 158.5 (voltage gain of 44dB) to calculate the theoretical output of your respective pre-amps.

As you can see, the Cornet has about 1.6 times the gain than the Seduction. Since apparent increases in loudness are best measured logarithmically, this translates to a difference of 4dB.

Without knowing the gain and input sensitivity of your Primaluna (and the nature of the volume pot/attenuator), and the apparent beginning & end points of your volume knob (and the number of demarcations on it), it's difficult to prescribe how these gain changes should manifest visually.

[Grinnell]

Thanks, my math skills are a bit limited.  I didn't realize that 4db translates to 1.6X more gain, I expected it to be less of an increase.

No problem just a bit of a surprise in difference.

[poty]

To be simple:
For voltage:
G_(dB)=20 * log₁₀(V_1(V)/V_0(V))
V_1(V)/V_0(V) = 10^(G_(dB)/20)

where
G_(dB) - gain in dB
V_1(V)/V_0(V) - relation of voltage on the output to voltage in the input.

The above formula is good in assumtion that the voltages are measured on the equal resistance.

[Brinkman]

Poty,

Would the following formula be correct for determining the output (in V) for a known Vin and Gain (in dBs)?:

V_1(V) = (10^(G_(dB)/20))*V_0(V)

Ben

[poty]

Basically answering - yes.
BUT, you should remember:input resistance and output load must be near equal to achieve accuracy of the formula as soon as dB is originally power value. For example, the formula is wrong for power amplifiers, because the output voltage can be less, than input (but on less resistance load) with positive gain nevertheless.