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Ramsa WP-9440

Stereo Power Amplifier (1989)

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Ramsa WP-9440

Specifications

Power output: 350 watts per channel into 8Ω (stereo), 700W into 16Ω (mono)

Frequency response: 20Hz to 20kHz

Total harmonic distortion: 0.05%

Damping factor: 100

Gain: 32.5 dB

Signal to noise ratio: 100dB

Speaker load impedance: 8Ω (minimum)

Dimensions: 480 x 149 x 486mm

Weight: 33.5kg

Finish: black

Year: 1989

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Comments

re: WP-9440

This is a really interesting design. It has 32 MT-200 17A 35Mhz output transistors. 16 per channel =2SA1295/2SC3264. the odd part is is that it is a 4npn and then 4pnp output section with predrivers... and then a second complete output section, complete with predrivers..run in parallel! two complete output sections, run in parallel. It's one of those things that is stated to be a no-no. Yet it works. Fairly high bias, blows hot air all the time, and very limited feedback.

The input section seriously hampers (totally kneecaps it!) the design and keeps it safe from pro level flubs and mistakes. It can be made into a single ended (input) high end audio amplifier by basically removing the entire op-amp based input board, and running a cap coupled input with some minimal pf level and resistance to ground. To use the input cards to make a passive input section. THEN it sounds great for high end audio. The amp is single ended (input) so loose the balanced input (opamp based), it's crap anyway.

What you get in return, is a 500w@0.05% 8 ohms/650w@0.1% 4 ohm/dual mono/fan cooled/high class a/b bias/low negative feedback ---audio amp. This thing will consume nearly 2200 watts when at full gallop. See images on the net for the japan spec unit, which is identical--those are the numbers listed. The euro and us spec units are de-rated, with regard to published numbers.

It is mostly, apparently (internet talk), regarding the output stage... a Technics 'audiophile' (SE-A3MKII) amp. In this case...doubled up into parallel output sections, with 50% more capacitance (120,000uf at 95V rails!) and beefier transformers. If it did not have the tunnel ram heatsink assembly, the air cooled heatsinks and frame would run the amplifier up to about 110lbs from it's approx 75lbs as a pro fan cooled amp.

All in all, an interesting and almost rare amplifier. I supplied the schematic after purchasing it, as I had just found a mint unused 9440 for almost nothing.... and maybe others will find this amp as interesting and worthy of modding out for the fun of it.

So yeah, high end audiophile design, which has been altered to be used as a pro amplifier. Ditch the pro crap mods....and make it back into something useful.

Mine was manufactured in yr 2000, so the design stuck around for quite a while.

If you feel you need to have the balanced inputs intact and want to use it as a pro studio amp, for monitoring, then the biggest change is from upgrading the power supply for the input boards ~and~ changing C116 and C516 (the two input boards) to 47uf or 100uf non polar (original is 22uf). The originals end up choking out the bass and bass transients. Just be careful with max power after that, as this limiting of the extreme bass registers is part of what keeps the amplifier stable under heavy constant pro 'live' loads. This needs to be done if you want full range bass as bass transients are totally MIA until this is done. Rail fusing may need an upgrade at this point. (from 3A to 4A or 5A) These sort of mods will invalidate the unit for pro install in commercial environments, and it would just be meant for fooling around at home at such point, where you can keep an eye on it.

re: WP-9440

Interesting. I wonder if it can be done with my 9220 and have you done the mods of making it a single ended hifi version? Please enlighten us some more with details, thanks !

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