This HMA-8500 MKII is another addition to my Hitachi amplifier family.
100 Watts * per channel, min RMS, at 8 ohms from 20 Hz to 20 KHz with no more than 0.005% total harmonic distortion (THD)
100 W/ch + 100 W/ch (8 ohms. 1 KHz T.H.D 0.005% SINUS DIN Rule) 120 W/ch + 120 W/ch (8 ohms, 20 Hz - 20 KHz, T.H.D 0.005)
130 W + 130 W (8 ohms 1kHz, T.H.D. 0.5% IEC)
150 W + 150 W (8 ohms 1kHz, Dynamic Power)
200 W (8 ohms, 1 kHz, T.H.D. 0.005, BTL connection)
Power bandwidth 5 Hz - 100 KHz (T.H.D 0.05% 1/2 Rated)
Frequency characteristics 0.5 Hz - 100 kHz (+0, -1 dB)
Harmonic distortion (8 ohms)(at rated output) Less than 0.008%
Harmonic distortion (8 ohms)(at 1/2 rated output) Less than 0.005%
Input sensitivity / Impedance 1V/47 k-ohms
Signal-to-noise ratio (IHF, A network, short circuited) 118dB
Damping factor (8 ohms) = 100 (i kHz)
* Measured pursuant to the Federal Trade Commission's Trade Regulation Rule on Power Output Claims for Amplifiers.
The information above is stated in the service manual.
This amp uses 4 x Hitachi 2SJ49 and 4 x Hitachi 2SK134 MOSFET's (2 of each per channel)
Internal circuitry is extremely similar to the HA-6 amp shown on my site and uses pretty much the same components in the power amps section bar the output MOSFET's.
MOSFET is an acronym for Metal Oxide Semiconductor Field Efect Transistor.
The HMA-8500 MKII also has an identical speaker delay connect and protection circuit using the HA12002 device.
Specification wise the HMA-8500 MKII and HA-6 are almost identical, both with 100 Watt output per channel and similar THD specks.
Obviously the massive difference is that this HMA-8500 MKII is a power amp only with MASSIVE VU meters on the front and needs a separate pre amp - the Hitachi HCA-8500 MKII.
Been looking for one of these units with matching pre amp for a long time, found the set on ebay and paid possibly over the odds for it but that's the chance you take with an auction.
When I got the units I stripped both power amp and pre amp down to check the guts out and as the photos show there were quite a few dry joints forming which I made worse just to show what they would look like when eventually the joints do fail, I ended up re soldering EVERYTHING and cleaning off the flux, took a long time but again worth it and I know it will not need looking at for quite a few years.