Measurements of TRV900 sound characteristics

Attenuator on mike input, using signal generator (1kHz), increasing input voltage until output one becomes distorted. Measured at different manually set mike gains (1 to 16) [in MENU]. Voltages are peak values.

Mic gain	Max. mic input [mV]	No of LEDs	Out voltage [V]	Gain
1	59	15	0.56	9.5
2	60	18	0.90	15
3	60	20	1.3	21.7
4	39	20	1.3	33.3
5	26	20	1.3	50
6	18	20	1.3	72.2
7	12	20	1.3	108
8	8.2	20	1.3	159
9	5.6	20	1.3	232
10	3.9	20	1.3	333
11	2.8	20	1.3	464
12	2.06	20	1.3	631
13	1.51	20	1.3	861
14	1.16	20	1.3	1121
15	0.95	20	1.3	1368
16	0.80	20	1.3	1625

In auto-gain mode, the gain depends on input signal. There are some measurements*:

mike input [mV]	Out voltage [mV]	Gain
0.5	400	800
0.7	560	800
1.0	800	800
1.2	910	758
1.5	960	640
2.0	1010	505
3.0	1030	343
4.0	1050	263
5.0	1060	212
10.0	1100	110

When signal is relatively weak, the AGC uses the largest gain, which is 800 (58dB). It approximately corresponds to the manual gain at level 13.

Frequency [kHz]	Input signal [mV]	Output signal [mV]	Gain [dB]
0.01	3.5	3	-1.3
0.02	6	30	14.0
0.05	8.5	130	23.7
0.1	9.5	195	26.2
0.2	10	220	26.8
0.5	10	220	26.8
1.0	10	220	26.8
2.0	10	215	26.6
5.0	10	205	26.2
10.0	10	180	25.1
15.0	10	145	23.2
20.0	10	125	21.9

Noise is approx. 2mV peak (at the output - measured with oscilloscope); 50Hz component is the most noticeable.

Flat from 50Hz to 20kHz; at 20Hz gain is –0.4dB, at 10Hz gain is –1.5dB. Noise is about 10/32000 (voltage), so about –70dB.

There were two resistors (1K) connected to the TRV900E mike input (between signal and GND). Manual gain setting has been used. Gain slider changed from value 1 to 16. The obtained average RMS (in dB) on the left (L) and on the right (R) channel were the following:

Mic gain	Noise L [dB]	Noise R [dB]
1	-62.3	-62.4
2	-62.7	-62.8
3	-62.5	-62.6
4	-62.6	-62.6
5	-62.8	-62.8
6	-62.5	-62.4
7	-62.5	-62.4
8	-61.6	-61.7
9	-60.5	-61.0
10	-59.0	-59.8
11	-56.7	-58.2
12	-55.2	-56.7
13	-52.9	-54.7
14	-51.9	-53.5
15	-50.7	-52.2
16	-50.2	-51.2

In auto-gain (AGC), the obtained average RMSs are -59.3dB for left and right channel.

However, noise characteristics over frequencies is much more interesting [pictures]. Namely, when using manual gain, there are some spikes existing at frequencies 50Hz, 100Hz, 150Hz, 200Hz, ... (note that I'm using PAL model), while in auto-gain (AGC), there is only one spike at 150Hz. Taking into account that signal amplification of the AGC is approximately the same to the manual one at level 13, it is clear that AGC gives much better signal/noise (S/N) ratio than when using manual gain (comparing RMS values, AGC gives about 4 to 6 dB better S/N ratio; compare also figures 'Mic gain 13' and 'Mic AGC'). Funny, isn't it? It seems that this low-frequency "contamination" comes from the manual-gain control (electronic volume M5222 and low-noise amp 4572) [picture]. I'll try to figure out why does it happen...

Noise is distincly weaker when using line in input (in VTR mode). The average RMSs are -78.0dB for left and -77.9dB for right channel. The frequency characteristic is given here. It is interesting that I've got a quite better result than John on VX2000.

How to build your own elastic suspension ("shockmount") and mike preamp with attenuator for AKG CK91 capsule? Read this.

SONY TRV900E mike characteristics