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Bose 1800 Dual Slave Amp

Test Report on: Bose 1800 Dual Slave Amp
Date: Aug. 1975. £550 ex VAT.

The Bose 1800 is a very high power dual channel slave amplifier capable of giving an output of 400 watts RMS per channel into four ohms or 250 watts per channel into eight ohms. The basic unit is 19 inch rack mounting but the manufacturers can provide, as an optional extra, a transit case with removable front and back, in which the amplifier may be transported and operated. When mounted in this case, the amplifier is suitable for use on stage. As with most slave amplifiers, the only controls provided are a gain control for each channel and an on /off switch. A pilot light is fitted and a high temperature indicator illuminates that if the thermal cut out operates due to the amplifier overheating.

A novel feature is an output peak level indicator which consists of a set of light emitting diodes for each channel. These successively light as the power level is increased, so at very low power they are all out and as the power is increased more of them light until they are all on. Two lights at the top of each column indicate when the amplifier is being overdriven.

Input jack sockets and output terminals, which will also take 4mm plugs, are on the back panel.


The construction is very solid, making the total weight approx. 80lbs. Both the sides of the case and a large proportion of the back panel are finned heat sinks for efficient cooling. An enormous mains transformer and two very large electrolytics fill the centre of the case and there are printed circuit boards on each side of the electrolytic.

The construction of each amplifier board is quite complicated because all the amplifier components, including the output transistors, are mounted on the board. An intermediate heat sink transfers the heat from the output transistor to the main heat sink and all the electrical connections go to the boards via plugs and sockets. The result is that a complete amplifier can be removed and replaced in less than five minutes.

The quality of components and workmanship is good and the wiring tidy and well secured.

The mains cable is of the retained type and has the wrong colour coding for use in Europe. It also has a moulded-on American mains plug which is also unsuitable for use in this country.

The amplifier comes complete with input leads, L.S. connectors and an instruction book.

Parameter Results Test conditions Comments
Power O.P. (one chan only) 595 W.r.M.S. Into 4 ohms at onset of clipping Very good - spec.
365 W.r.M.S. into 8 ohms @ 1 KHz 400w into 4 ohms and 250w into 8 ohms

Distortion (total harmonic) 0.07% @ 400w into 4 ohms @ 1 KHz Very good
0.635% @ 100w into 4 ohms @ 1 KHz
0.06% @ 4w into 4 ohms @ 1 KHz

Output Short circuit test OK 2 minutes short circuit
Thermal cut out operated after 1 min. 40 sec.
Open circuit output test OK
Capacitive load test 10% overshort of square wave 4 ohms and 2uF load OK

Sensitivity 1.49 V.r.M.S. for 250 watts into 8 ohms Not sensitive enough for some European pre amps.
1.33 V.r.M.S. for 400 watts into 4 ohms This level is + 4dBm

Output level indication Worked at correct levels Very good, imaginative and useful.

Frequency response -1dB at 16KHz Good - No detectable bass roll off at 10Hz
-3dB at 32KHz

Noise —98dB Below clipping (400w into 4 ohms)
broad band measurement
Very good

Thermal cut out Ok Good - Self-resetting


A very good quality product with an excellent performance that well exceeds the manufacturers claims. With a total power output capability of 800 watts with both channels operating, a price of £550 excluding V.A.T. is not expensive, viewed on the old pound per watt basis.

We contacted the manufacturers about the American colour coded mains lead supplied (common to most imported American equipment) and we were advised that this is going to be changed to the European standard in the future.

Previous Article in this issue

Davoli Tempest 50T

Next article in this issue

Gretsch 7670 Country Gentleman

International Musician & Recording World - Copyright: Cover Publications Ltd, Northern & Shell Ltd.


International Musician - Sep 1975

Donated & scanned by: Mike Gorman


Gear in this article:

Amplifier > Bose > 1800

Review by Bruce Gibbs

Previous article in this issue:

> Davoli Tempest 50T

Next article in this issue:

> Gretsch 7670 Country Gentlem...

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