Doram Distortion Meter

saposoft · 2nd August 2011, 11:49 AM

Hi all
I've this Distortion Meter and I'm looking for info and/or manual for it .

Looks in good condition, battery test is OK , but Im not able to get anything out of , usually from the "RESIDUAL" output of a distortion analyzer there should be some kind of output related to input.
Please have a look into my blog entry for it

saposoft · 2nd August 2011, 12:36 PM

forgot the blog url ...

electronics_ranting

DF96 · 2nd August 2011, 02:17 PM

Doram was a retail trading name used for a while (in the 1980's?) by RS Components (formerly Radiospares), so try searching under that name.

cliffyk · 2nd August 2011, 06:29 PM

I am not 100% certain, however the controls look like those of an old military unit I played with many years back.

In operation you would first set the FREQUENCY control to the fundamental frequency of the test signal and then select an input scale as appropriate to your signal via the INPUT VOLTAGE control. Next, with the FUNCTION control set to the SET 100% function, use the SET 100% pot to obtain a 100% meter reading.

Now set the FUNCTION control to a desired %THD range, and in the last adjust the lower and upper (left and right) Coarse, Medium, and Fine controls to tweak the notch filter until the meter reading was at it's lowest.

At this point the meter indicates the THD, as the fundamental has been filtered out to the extent of the instrument's ability.

2nd August 2011, 11:49 AM	#1
saposoft diyAudio Member Join Date: Nov 2009	Doram Distortion Meter Hi all I've this Distortion Meter and I'm looking for info and/or manual for it . Looks in good condition, battery test is OK , but Im not able to get anything out of , usually from the "RESIDUAL" output of a distortion analyzer there should be some kind of output related to input. Please have a look into my blog entry for it

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2nd August 2011, 12:36 PM	#2
saposoft diyAudio Member Join Date: Nov 2009	forgot the blog url ... electronics_ranting

2nd August 2011, 02:17 PM	#3
DF96 diyAudio Member Join Date: May 2007	Doram was a retail trading name used for a while (in the 1980's?) by RS Components (formerly Radiospares), so try searching under that name.

2nd August 2011, 06:29 PM	#4
cliffyk diyAudio Member Join Date: Nov 2009	I am not 100% certain, however the controls look like those of an old military unit I played with many years back. In operation you would first set the FREQUENCY control to the fundamental frequency of the test signal and then select an input scale as appropriate to your signal via the INPUT VOLTAGE control. Next, with the FUNCTION control set to the SET 100% function, use the SET 100% pot to obtain a 100% meter reading. Now set the FUNCTION control to a desired %THD range, and in the last adjust the lower and upper (left and right) Coarse, Medium, and Fine controls to tweak the notch filter until the meter reading was at it's lowest. At this point the meter indicates the THD, as the fundamental has been filtered out to the extent of the instrument's ability.