dBm to dBV true RMS - Space Echo Cal

[ruffrecords]

On page 2 of the RE201 service manual, they list the nominal level of the mic input as -50dBm and 2.4mV, into an input impedance of 900 ohms. This is close (2.4mV into 900 ohms is -52dBm), but the other values given in the table are quite wrong - unless Roland is using dBm here to mean what we'd now call dBu. Then all the numbers make sense; -50dBu is 2.4mV and -24dBu is 44mV, as stated.

View attachment 104404

In days of yore it was common to use dBm (600) to express voltages at any impedance. -50dBm(600) is 2.45mV. 44mV is actually -24.9dBm(600).

Cheers

Ian

 

[Tubetec]

What would be amazing would be if we could embed the Tonmiesters toolbox on the Groudiy page with a pop up menu to select the calc you want ,without even leaving the page .

Its hard to image that someone would complain about a resource dedicated to teaching people and understanding the concepts ,then try and have it pulled down .
In any case we can live with the German language version , that no problem at all .
How can someone try and claim ownership over a mathmatical formula thats been put into a spreadsheet anyway ?

I might take the opportunity to email Alexander and ask for his permission to use the calculators for educational purposes on GDIY .

 

[user 133392]

I would be more than happy to host a US mirror of the site if you could pass that on to Alexander. I use the site very frequently.

The English language version seems to be running now.

FWIW The US Copyright Code permits educational Fair Use. Hosting it in a different country might be advantageous.

 

[Analog Pitstop]

Assuming the usual 50Ohm modern standard devices: dBm's will NOT reflect 1:1 with dBu's.
As was told previously by many, using dBm for voltage is essentially wrong. Zero practical and educational value - in my opinion: how many have today a 600Ohm spectrum analyzer?
Besides, there are formula using power as parameter, and formula using voltage as parameter. A few people worked hard to derive those formula and laws of nature in an unchanged form that is usable to us even today.

It reminds me of a funny booth on High End Münich, seriously attempting to sell magic electrical tapes for loudspeakers cables - and yes of course - made of top secret materials. It proudly had even a "theory" supported by a "Doctor" and measurements made some "technician guru ears". I said, that all this tells nothing to me, because I have seen many frauds with doctor titles in their pockets and many technician guru's which actually did not knew much at all (compared to their peers, not to the people on the street). They did not have even above average ears