RSD (Recording Studio Design) ( renamed: Studiomaster) 800B vs Phase Linear 400

[oldphaser]

I was going through all my filing cabinets filled with catalogs, sales brochures and manuals and found an old Studiomaster catalog with a RSD 800B amplifier in it and remembered seeing some verbiage on the internet about it.

The following text was obtained from Studiomaster's web site: http://www.studiomaster.us/about.html

"Studiomaster started in 1976 as RSD (Recording Studio Design) and one of the first British companies to build high powered sound reinforcement amplifiers with studio quality specifications.

The RSD 800B, was a robust amplifier with 800 watts per channel - England's answer to the USA's Phase Linear 400, and Australia's Jands J300S. RSD was unable to keep up with demand for their 800B, as it became the amp of choice for all the great British and Euro bands of the 70s and 80s, including Pink Floyd."

COMMENT: Studiomaster's web site states the RSD800B was 800 watts per channel. Their catalog lists it at 225 watts per channel into 8 ohms at 1 KHz. I wonder what it was at 20KHz? The THD specs are all also listed at 1KHz.. No mention of 20Hz to 20KHz anywhere.

Here is another web site with some schematics and comparisons:
http://www.angelfire.com/sd/paulkemble/sound2.html



I would like Joe's and Nick's thoughts about the amplifier and comparisons.

Ed

 

[oldphaser]

I saw an old thread from 2012 on this subject and am going through it now.

I just added a hyperlink from the old thread to this thread.

Ed

 

[oldphaser]

I just found this on the web. I haven't had a chance to follow up on the hyperlinks yet.

RSD was set up by Phil Dudderidge, Paul Dobson and Graham Blyth, building custom PA systems for the likes of Roy Wood's Wizzard, Mungo Jerry and Steve Harley & Cockney Rebel amongst others, with custom-built mixing consoles derived from a Bill Kelsey original design. Phil & Graham went on to create Soundcraft and Phil is now Executive chairman of Focusrite plc but before all this he toured with Led Zeppelin, worked as sound guy for Implosion at the Roundhouse in London and also worked for Hiwatt. There are a couple of articles about him here:
http://www.mixonline.com/news/profiles/phil-dudderidge-qa/366249
http://www.mixonline.com/news/profi...ion-uk-technology-us-live-sound-market/374211

 

[WOPL Sniffer]

Looks like all they sell now is Chines Junk.

 

[THD+N]

It appears the 800b is a direct copy of the PL400. I wasn’t aware of this amp until now. I’m surprised the 800b uses 2N3773’s for outputs. The power supply is 150 volts according to the schematic, but the 3773’s are only rated at 140VDC. Not a good selection for reliability and operating at maximum output.

Even if the 800b power supply had good regulation, I would question the reliability based on 6 output devices. The Adcom 555 has similar output power specs, but used 8 output devices.

Since it is a direct copy of the PL400, I would anticipate very similar, if not identical, specifications for noise and distortion.

 

[oldphaser]

Studiomaster 800C Amplifier

In the same "Recording Studio Design & Studiomaster" catalog that has the RSD 800B Power Amplifier in it is the Studiomaster 800C Power Amplifier. The specs appear to be the same. Albeit the Studiomaster 800C doesn't have any VU meters.

Ed

 

[THD+N]

I just noticed some notes on the 800b schematic at the bottom edge...
Output Power @ 1kHz, prior to clipping, <0.25%:
120W, 16 Ohm
220W, 8 Ohm
340W, 4 Ohm
480W, 2 Ohm

It appears the notes on the schematic are valid, but the other specs from the sales brochure, etc are typically marketing numbers.

 

[oldphaser]

Studiomaster 800B/800C Power Amplifier Review (Modern Recording February 1982)

Studiomaster 800B/800C Power Amplifier Review (see pages 76-77)

https://www.americanradiohistory.com/Archive-Modern-Recording/80s/Modern-Recording-1981-02.pdf