Meter Calibration

[Michael F]

Although I never measured power and relative SPL levels when my 700B was in stock form, I do notice an increase in power following the Rev C upgrade. Wouldn't it be logical to re calibrate the meters to better display the new found power?

How do the meters correspond to maximum power output in stock form? It would seem the readings would be somewhat conservative now.

 

[laatsch55]

I will quote the "Calibration section of the manual...

 

[Michael F]

Which is my point precisely. With the new available power, a 0 VU reading would have to correspond to a 60+ volts, 14 volts above the reference voltage.
Even with stock values, would the needles not be bending at the clipping point?

 

[Gepetto]

Which is my point precisely. With the new available power, a 0 VU reading would have to correspond to a 60+ volts, 14 volts above the reference voltage.
Even with stock values, would the needles not be bending at the clipping point?

Not sure I understand the concern, the indication is the same as it always has been with the same absolute RMS voltage as a reference point. For example, do you want to change the -20dB setting to indicate 5Vrms instead of 4 at the 0dB mark?

 

[Gepetto]

Which is my point precisely. With the new available power, a 0 VU reading would have to correspond to a 60+ volts, 14 volts above the reference voltage.
Even with stock values, would the needles not be bending at the clipping point?

The stops on the meter needle are down by the pivot so the needles will not bend.

 

[laatsch55]

\And Mike, they are an approximation, and that's when they were new, and over thelast 40 years they have not gotten better.

 

[laatsch55]

If you can get that amp to clip on a set of speakers, let me know so I can write that one down.

 

[Gepetto]

Which is my point precisely. With the new available power, a 0 VU reading would have to correspond to a 60+ volts, 14 volts above the reference voltage.
Even with stock values, would the needles not be bending at the clipping point?

If you want to desensitize the meters more in the 0dB switch position then increase the value of the 22K resistor on the light board. The -20dB position will retain the original sensitivity as it is controlled by the 1.8K resistor.

 

[Michael F]

The stops on the meter needle are down by the pivot so the needles will not bend.

LOL, that was an attempt at humor

 

[laatsch55]

Such is non-face to face communication.

 

[Michael F]

If you can get that amp to clip on a set of speakers, let me know so I can write that one down.

Neither my neighbors or speakers would appreciate that! So far, 99.9% of my listening is done with the switch at the minus 20 position with the meters hovering below - 5 VU

 

[Michael F]

So what do the meters read at rated output or at clipping?

 

[laatsch55]

At 0db----265 watts into 8 ohms.

 

[laatsch55]

Never saw them clip with a set of speakers, however, when loaded up with my 2,000 watt dummy loads they are off the scale when that happens.

 

[jbeckva]

Never saw them clip with a set of speakers, however, when loaded up with my 2,000 watt dummy loads they are off the scale when that happens.

So you got some "big dummys"?

(signed, peanut gallery)

 

[laatsch55]

Yep, the Phase Linear Engineering Dept. load....

 

[Magic Smoke]

Thread bump..

My poor old Dixon meters were a bit munged up with right meter sticking about mid way, two years ago when amp donated to me. I opened up, gently cleaned movement of dust, added leds and all has been fine. Using a DC supply, I ran up both meters, thru meter board to 0db @ 12vdc indicated, then back. Again I bumped up a bit to +2 then stopped at -3, again both tracking smack on as meters put in parallel to supply. Note, check your diode direction for hookup.

Need to find cheap 8 ohm load resistors to do runup when Joe's board back in...

Old LINK for cleaning and such for Dixon meters for us new guys.

Mike

 

[Northwinds]

I have Dixon's in the Aerosmith 400, they are slightly smaller and look a little different then the Honeywell's