Input sensitivity

[Wansmith]

Hi there - i’d like to better understand input sensitivity of the tu8600 and tu8200 how how this impacts on sources of different output voltages, and also how it impacts considerations on using a separate preamp with gain

Just asking because i have a source component with a high output voltage (3.5V rms - abbas 2.2se dac)

My questions are what is the input sensitivity or tu8600 and tu8200 (the spacs say ‘rated input of ~340mV). Does this mean that this is the minimum rms source output voltage for the amp to operate at its rated power? What if the source rms is an order of magitude higher (ie 3.5V)? How does that impact on the amp’s operation?

Many thanks!

 

[rayma]

Right, you'd have to attenuate the input using the input level control by at least -20dB,
to avoid clipping the output.

Not necessarily bad, since input noise is reduced along with the signal. Also the amplifier's
level control is just after the RCA socket, so there is no input active circuitry to overload.

 

[Wansmith]

Thanks for the reply - makes sense. So essentially the only impact it has is the volume pot on the tu8600 will have less usable range?

 

[rayma]

Yes, but many are in the same boat with digital sources these days.

Much depends on your speakers. If they are not very efficient, you may use the level control
around the -20dB setting a lot, which often is around halfway up for a typical log volume pot.

 

[Winnie]

My DAC has an output of 6volts. Straight into the 8600R it gives me only two clicks of the volume pot. I use a (high quality) passive pre amp to attenuate the signal.

 

[Wansmith]

Thanks, thats very useful (my dac is 4V so i have a similar issue). Can I ask which passive pre you use?

 

[rayma]

You can just use a metal film resistor L-pad (1 series, 1 shunt) at the input.
The series resistor can be 10k, and adjust the shunt resistor for a suitable level (say 2k).

 

[paczeltf]

(...)

My questions are what is the input sensitivity or tu8600 and tu8200 (the spacs say ‘rated input of ~340mV). Does this mean that this is the minimum rms source output voltage for the amp to operate at its rated power?

Yes. Note though that Elekit specifies the power output with 10% distortion so you need even less for normal operations.

A lot of people are confused by rated power output vs. sensitivity. When you read that "my amp is rated for 10 Watts only but it sounds loud at 10 o'clock volume position", it is a typical example of that. There is an incorrect assumption here that it will sound even louder when turning up the volume, but in reality, the amp will start distorting at the same loudness level just at a different potmeter position.

 

[paczeltf]

You can just use a metal film resistor L-pad (1 series, 1 shunt) at the input.
The series resistor can be 10k, and adjust the shunt resistor for a suitable level (say 2k).

That is not necessarily a good idea, because the input impedance of the amp will drop from about 40 kOhms to 12 kOhms. Not all sources like that, check specs first.

 

[Winnie]

Thanks, thats very useful (my dac is 4V so i have a similar issue). Can I ask which passive pre you use?

Hi
I have a ladder type volume pot with bypass resistor. That's about as technical as I get

An interesting observation.

I can run my Decware Taboo (which seems a similar configuration with volume pot) with the pot flat out and then control the entire volume on the passive.

However with the Elekit I get a small amount of hiss in my sensitive speakers doing this. So I leave the Elekit volume at 50% where output is silent and control the volume via my passive.

Perhaps one of you clever people can explain this.

 

[bpdho]

That is not necessarily a good idea, because the input impedance of the amp will drop from about 40 kOhms to 12 kOhms. Not all sources like that, check specs first.

My current source for the TU-8200R is a Chord Qutest DAC with output impedance 0.4-0.9 ohm at 1 V (as measured by Stereophile). Will there be a problem if I use a 75 ohm T attenuator like the ones below?