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ADCOM GFA-535 II
Power Amplifier (1990s)
© 2011 KenRockwell.com. All rights reserved.

Intro   Specs   Performance   Measurements   Compared   Usage   Recommendations

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ADCOM GFA-535 II Power Amplifier

ADCOM GFA-535 II Power Amplifier (about $250 used). enlarge. This free website's biggest source of support is when you use these links, especially this link directly to the ADCOM GFA-535 II Power Amplifier at eBay (see How to Win at eBay), when you get anything, regardless of the country in which you live. Thanks! Ken.

 

ADCOM GFA-535 II Power Amplifier

Rear, ADCOM GFA-535 II Power Amplifier. enlarge.

 

December 2011   ADCOM Reviews   Audio Reviews   All Reviews

 

Adcom CGA-545 II Review

Right now, all I have is this lab report. Audition is still to come.

 

 

AP118:

4 x 6,800 µF 63V

6' polarized plug

extruded front not a heat sink

4A 250V internal fuses

30W idle warm power consumption.

 

1994: 0.04% $375

 

GFA-535L added two level control trims above the IOC lights

535: crappy rear connectors, 2 swotchale sets of speakers

Whicte versions

 

Gain

Measured at 1 kHz, 1 Watt output into an 8 Ω load:

Sample
Left
Right
AP118
27.143 dB
27.154 dB
AP230
27.129 dB
27.145 dB

This calculates out to 22.74x gain.

124 mV in is 1W out into 8 Ω.

1.24 V is 100 W out into 8 Ω.

 

 

 

Frequency Response

AP230 sample:

ADCOM GFA-535 II

ADCOM GFA-535 II (AP230) Frequency Response to 20 kHz, ±5 dB scale.

 

ADCOM GFA-535 II

ADCOM GFA-535 II (AP230) Frequency Response to 20 kHz, ±1 dB scale.

 

ADCOM GFA-535 II

ADCOM GFA-535 II (AP230) Frequency Response to 20 kHz, ±0.2 dB scale.

 

ADCOM GFA-535 II

ADCOM GFA-535 II (AP230) Frequency Response to 110 kHz, ±5 dB scale.

 

ADCOM GFA-535 II

ADCOM GFA-535 II (AP230) infrasonic Frequency Response. (-60 dB scale).

 

AP118 sample:

ADCOM GFA-535 II

ADCOM GFA-535 II (AP118) Frequency Response to 20 kHz, ±5 dB scale.

 

ADCOM GFA-535 II

ADCOM GFA-535 II (AP118) Frequency Response to 20 kHz, ±1 dB scale.

 

ADCOM GFA-535 II

ADCOM GFA-535 II (AP118) Frequency Response to 20 kHz, ±0.2 dB scale.

 

ADCOM GFA-535 II

ADCOM GFA-535 II (AP118) Frequency Response to 110 kHz, ±5 dB scale.

 

ADCOM GFA-535 II

ADCOM GFA-535 II (AP530) infrasonic Frequency Response. (-40dB scale.)

 

Noise

AP230 sample:

Adcom

Adcom GFA-535 II (AP230) Output noise spectrum.

 

A-weighted noise (AP230):

 
Left
Right
Input fed from 5 Ω source impedance
-92.4 dBV
-92.4 dBV
No input connection
-72.3 dBV
-75.1 dBV

 

Unweighted noise (AP230):

 
Left
Right
Input fed from 5 Ω source impedance
-86.3 dBV
-85.3 dBV
No input connection
-61.6 dBV
-71.0 dBV

 

AP118 sample:

Adcom GFA-535 II (AP118) Output noise spectrum. Roll mouse over to compare to AP230 sample.

 

A-weighted noise (AP118):

 
Left
Right
Input fed from 5 Ω source impedance
-92.4 dBV
-92.4 dBV
No input connection
-56.7dBV
-58.9 dBV

 

Unweighted noise (AP118):

 
Left
Right
Input fed from 5 Ω source impedance
-83.7 dBV
-85.5 dBV
No input connection
-48.7 dBV
-57 dBV

 

 

DC offset (AP230 sample)

Measured into 8 Ω:

 
Left
Right
Input fed from 5 Ω source impedance
±75 µV
+100-300 µV
No input connection
±75 µV
+150 µV

 

 

Damping Factors and Output Impedances

AP230:

Output Impedances

Left
Right
50 Hz
56 mΩ
13 mΩ
1 kHz
57 mΩ
14 mΩ
20 kHz
69 mΩ
20 mΩ

 

Damping Factors at 8Ω

Left
Right
50 Hz
143
615
1 kHz
140
571
20 kHz
116
394

 

Method and raw data

Voltage drop when applying an 8 Ω load:

Left
Right
50 Hz
-0.0606 dB
-0.0142 dB
1 kHz
-0.0612 dB
-0.0147 dB
20 kHz
-0.0750 dB
-0.0220 dB

R source = (R load/attenuation ratio) - R load.'

 

AP118:

Method and raw data

Voltage drop when applying an 8 Ω load:

Left
Right
50 Hz
-0.0099 dB
-0.0092 dB
1 kHz
-0.0093 dB
-0.0094 dB
20 kHz
-0.0154 dB
-0.0150 dB

R source = (R load/attenuation ratio) - R load.

 

Maximum Output at 1 kHz into 8 Ω load

89W at 121.3 V AC power input at 0.1% THD (1.1700V RMS input).

94W at 121.2 V AC power input at 1% THD (1.2150V RMS input).

Overload lights start to turn on at 1% THD, 50% on at 2% THD, and 100% on at 2.8% THD.

 

10 ms burst of 1 kHz (10 cycles) at 1 per second: 46V Pk = 32.5V RMS = 132W Pk at 122.1V AC power input. Burst Input level: 1.400 V RMS.

 

THD

ADCOM GFA-535 II

ADCOM GFA-535 II THD at 1 Watt.

 

ADCOM GFA-535 II

ADCOM GFA-535 II THD at 1 kHz.

 

SMPTE IMD (AP230 shown, AP118 similar)

ADCOM GFA-535 II SMPTE Intermodultion Distortion

SMPTE (60Hz+7kHz @ 4:1) Intermodualtion Distotrion vs. input voltage.

 

 

19+20 kHz DFD ((AP230 shown, AP118 similar, per DIN IEC 268-3 or 118)

ADCOM GFA-535 II

ADCOM GFA-535 II DFD at 1 watt RMS.

 

ADCOM GFA-535 II

ADCOM GFA-535 II DFD at 25 watts RMS.

 

ADCOM GFA-535 II

ADCOM GFA-535 II DFD at 50 watts RMS.

 

Driving a pair of B&W Matrix 805 (AP230 shown, AP118 similar)

ADCOM GFA-535 II

ADCOM GFA-535 II (AP230) Frequency Response driving B&W Matrix 805, ±0.2 dB scale.

ADCOM GFA-535 II

ADCOM GFA-535 II (AP118) Frequency Response driving B&W Matrix 805, ±0.2 dB scale.

 

ADCOM GFA-535 II

ADCOM GFA-535 II THD at 100 mW driving B&W Matrix 805. Note expanded scale down to 0.0002% THD.

 

Introduction         top

Intro   Specs   Performance   Measurements   Compared   Usage   Recommendations

adorama

 
B&H Photo - Video - Pro Audio

Ritz Camera

I use Adorama, Amazon, Ritz, B&H, Calumet, J&R and ScanCafe. I can't vouch for ads below.

The

 

Rated Specifications         top

Intro   Specs   Performance   Measurements   Compared   Usage   Recommendations

±

Ω

µ

¼

½

¾

Input

3 VR

 

Output

8 VRMS

3 VRMS or more into 2 kΩ.

 

Frequency Response

20 - 20,000 Hz ±1dB.

 

Distortion

Less than 0.25%.

 

Internal Components

8 integrated circuits ("ICs").

28 transistors.

91 diodes.

 

Power

6-foot rubberized cord.

Unpolarized plug.

120 VAC.

50-60 Hz.

25 watts.

1/4 amp AGC fuse.

 

Size

9.5 x 5 x 11.8 inches, WHD, without wood case.

 

Weight

6 pounds (2.7 kg).

 

Warranty

Three years, parts and labor.

 

Price

$375, 1994.

 

Performance         top

Intro   Specs   Performance   Measurements   Compared   Usage   Recommendations

 

Overall

This cra

 

Measurements         top

Intro   Specs   Performance   Measurements   Compared   Usage   Recommendations

 

I used a state-of-the-art Rohde &Schwarz UPL for these measurements.

The traces are color coded for the Left Channel and the Right Channel.

 

Processors Bypassed

Phase Linear 1000 Autocorrelator frequency response

Gain vs frequency, Phase Linear 1000, processing bypassed, 200mV sine wave input. (measurement: Rohde & Schwarz UPL.)

I didn't separate the traces for clarity; there really is an 0.2 dB imbalance.

 

 

 

 

Compared         top

Intro   Specs   Performance   Measurements   Compared   Usage   Recommendations

Dynamic Range versus Data Compression

Dynamic range compression is when the differences between loud and soft are reduced. After dynamic rang

 

Usage         top

Intro   Specs   Performance   Measurements   Compared   Usage   Recommendations

ADCOM GFA-535 II Power Amplifier

Rear, ADCOM GFA-535 II Power Amplifier. enlarge.

See also the ADCOM GFA-535 II Owner's Manual.

 

 

Recommendations         top

Intro   Specs   Performance   Measurements   Compared   Usage   Recommendations

Hey, for $150 or so, the

 

If you've found this report helpful, this free website's biggest source of support is when you use these links, especially this link directly to the ADCOM GFA-535 II Power Amplifier at eBay (see How to Win at eBay), when you get anything, regardless of the country in which you live. Thanks! Ken.

 

More Information

ADCOM GFA-535 II Owner's Manual.

ADCOM GFA-535 II Service Manaual.

Stereophile (535)

http://passdiy.com/

http://www.linearaudio.nl/interviews/np.pdf

http://www.diyaudio.com/forums/solid-state/5280-adcom-555ii-nelson-pass.html

 

 

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Mr. & Mrs. Ken Rockwell, Ryan and Katie.

 

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