Eros + 3.6mv into amp which needs 2V

[Artemandr]

Please give me an advise about phono (Eros) and amplifier matching (Is Eros perfect phono for me?). I have tried to find answer on the forum by couldn't.
How much voltage from the phono i need to make my amp really happy?
I have a Decware se84ckc SET amplifier (inpuit impedance 100K) which needs 2 volts signal to reach full output - it is an amplifier which is power amp with passive volume control (no gain).
But with my 3.6mv MM cartridge i will have only 1.2V out from the Eros if i am correct. 50db gain=20*LOG10(1.2v/3.6mv*1000)

Is it sufficient amount of gain/voltage? Does it means that i will have just a 40% less in volume or it affects also fullness and dynamics of the sound?
Or it is much better to have a phonostage which will give me almost 2volts?
Thanks!

 

[Paul Birkeland]

Your calculations are correct (nicely done), you'll end up with about 1.14V out of the Eros.

This is a difficult question to answer in some ways.  A triode strapped EL84 is usually biased with around 10V on the cathode.  That means that we want the tube ahead of the EL84 to be able to delver 20V peak-to-peak.  The 6N1P will take 1V and make 33V when setup as an ideal voltage amplifier.  Even with less than ideal loading, the amplification factor of the 6N1P remains pretty high.  20V P-P is 7V RMS.  With the 6N1P reasonably well loaded, that would mean an input sensitivity of 200mV is a bit more realistic.

This all seemed very odd until I noticed a pair of trim pots inside SE84CKC.  If you turn these up a bit, your amp will become more sensitive ad there will be no gain issue.

 

[Artemandr]

Thank a lot for such detailed description. Unfortunately my technical level is much lower than yours so i am just cannot understand what you mean by "input sensitivity of 200mV is a bit more realistic". And there are no trim pots inside my amplifier (you've found wrong picture - i think this is a preamp because i don't see output transformers inside the chassis). Output tube by default is SV83 (not El84).

 

[Paul Birkeland]

Ah, that's what I get for using google images.

There's some extra gain to be had in that circuit, it has likely been optimized to not be overly sensitive when paired with high level sources.  You might want to contact the manufacturer to see about modifications to change the input sensitivity to 1V RMS.

 

[fullheadofnothing]

Have you determined that you actually need 2V for your desired listening level? I.e. with your current speakers and your current source component (presumably one with an output of 2V or larger), are you running out of room on your volume control?

 

[Paul Joppa]

This is a case of accidentally comparing apples and oranges.

Phono cartridges and preamps are specified at 5cm/sec groove velocity at 1000Hz. This is typical of "0 vu" signals - the maximum signal voltage averaged over a few hundred milliseconds. Peak instantaneous signal voltages are about 5 times greater (14dB) for typical well-recorded vinyl recordings. This 14dB difference is usually called "headroom." Digital systems and power amplifiers are usually specified at clipping, i.e. peak instantaneous signal voltage.

So your 1.2v nominal output from Eros is actually 6v peak.

Like everything, the reality is still more complicated. Low-power SETs which typically have no feedback can be run into moderate clipping without it being objectionable, which is not true of amps with large amounts of negative feedback. My rough rule of thumb is you can go about 6dB (twice the voltage) before the clipping becomes a problem. 0.8v nominal into your amp will produce up to 6dB of clipping on peaks, while Eros produces 1.2v nominal (and 6v peak.

Having said that, it is worth noting that there is a wide variation among records, so all the above numbers are necessarily approximate.

 

[Artemandr]

"Have you determined that you actually need 2V for your desired listening level?"
My CD player has nominal 2.3Vrms output (Arcam CD23T) so setting the amp volume to the 80-85% (just cut off this additional 0.3V) on some records i reach audible clipping margin and the music near this margin sounds really good.

So what is your advice, Paul - should i try the Eros? Do i need the phono whith higher gain or even Eros can be on the high side?
Unfortunately i can't try it before buy because i live in Europe and i am not sure whether it will be possible to sell 230v unit whithout big loss if it will not fit in my system.