Vintage Quad 33 Preamp & 303 Power Amp - Service & Bench Testing

Comments · 156

• NO

  @NovaluxStereophonic · 1 year ago · pinned

  Thanks to a keen eyed viewer I was able to identify a math error in my distortion analyzer. The scope screen reads 19.5Vrms and 19.1Vmrs at clipping into 8 ohms which equates to approx. 45W per channel both channels driven which matches the specification of the original Quad 303 amplifier.

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• BO

  @bobfrankish8883 · 1 year ago

  Hi from the UK Ben! I'm a 73 year old audio engineer so was brought up on these, it's great to see them again. I used to work for a company in the UK called Stereosound Productions, we also made domestic audio equipment. We used those Callins capacitors, they were made in Ireland and were rubbish, many were faulty from new. Because they are sealed and can't vent they used to explode dramatically! Quad also made a mono-block amplifier called the 50E. It used the same case as the 303 but had an output transformer so could match any load right up to 100 volt line without power loss. It's true that the 303 just didn't have the punch and dynamics of the 405, but in its' time it was still a nice sounding amplifier.

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• ZA

  @Zalgol · 1 year ago

  Thank you for producing such a clear and informative video of the Quad 303 and 33. Your descriptions were clear, &nbsp;and accurately related to the images. (unlike some others). I was particularly pleased to see the recalibration process for the power amp. <br>QUAD audio &nbsp;was the &nbsp;brain child of Peter Walker He was the inspirational designer of the early &nbsp;“Quad” equipment, &nbsp;and he devised the 303 circuitry which incorporated &quot;symmetrical triples&quot; output stage which produced low distortion, and high reliability. <br>His designs were conservatively rated, and as such many continue to survive and work more than 60 years after their introduction. <br>The things that tend to fail are the components due to age, rather than the design or use. Unfortunately some original semiconductors are now obsolete and virtually impossible to obtain, &nbsp;but there are some good modern work arounds which can keep these venerable products functioning for many more years.

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• DE

  @derekheeps8012 · 1 year ago

  The Bulgin power connector is not some &apos;weird&apos; or proprietary thing ! Bulgin power connectors were widely used up to the 1960s and beyond , only being replaced by the 10A IEC power connectors when they started to come out around the 1970s . Even now , Bulgin connectors are still quite widely used .

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• FA

  @favorit601 · 3 months ago (edited)

  The power amp is still a beast in sound quality. The way to PLAY MUSIC. Forget what you learned from 50 years of marketing of other companies.<br>And to be honest: Wasn’t it a pleasure to get this amp done. How serviceable.

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• RO

  @ronniepirtlejr2606 · 3 months ago (edited)

  As a &nbsp;electronics hobbyist &amp; not having a whole lot of hands-on experience. I would feel l comfortable working on this. This is a beautiful amplifier without all the BS.👍

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• ED

  @edherdman9973 · 4 months ago

  On top of everything else, these units have a beautiful industrial design, and a bit cheerful too. &quot;Nothing new under the sun&quot; but it&apos;s new to me.

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• LA

  @LawsonsStudio · 2 months ago

  A timely video for me. I&apos;m being sent two 303 power amps next week. I&apos;ve just finished a Quad 405 and was amazed how well designed it was for the tech. 12 screws and it was in bits.

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• DU

  @DurokSubaka · 3 months ago (edited)

  I knew that Lafayette Four channel decoder I still have in the basement would become fashionable again

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• SU

  @sureshlala6462 · 1 month ago

  This is very nicely documented, thank you for spending the time showing the testing and commentary.

• JO

  @johnbirchall7077 · 9 months ago

  Excellent. The Quad gear, especially that made during the lifetime of Peter Walker, are &quot;cultural icons&quot; for many British enthusiasts, were heavily used by BBC who were pioneers in audio engineering, and bring up a lot of memories for older guys. The marketing for the company&apos;s recent 33/303 homage claims that one of the original 33 is in MoMA, New York.

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• EC

  @ECStrat · 4 months ago

  Good ole discrete circuitry is what makes them sound so good. Love my Quad33

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