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A Proper Vintage Power Amplifier |
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audiomik 
Old Croc 
Joined: 06 April 2010 Location: Bath, UK Status: Offline Points: 2956 |
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 Topic: A Proper Vintage Power AmplifierPosted: 11 March 2011 at 11:58pm |
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Spotted this link over on the Blue Room but think it deserves posting here as well!
1955 Valve Amplifier Like the idea of the sympathetic Light Show from the Mercury Arc Rectifiers and the 3 phase supply it needs  Mik |
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Warning! May contain Nuts
plus springs, washers, screws, etc, etc. |
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jbl_man
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Joined: 12 January 2005 Location: London. Status: Offline Points: 11308 |
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Posted: 12 March 2011 at 9:06am |
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Thats an interesting read Mik....love the bit at the bottom of the specs...weight..142kgs per channel!
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Be seeing you.
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audiomik
Old Croc
Joined: 06 April 2010 Location: Bath, UK Status: Offline Points: 2956 |
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Posted: 12 March 2011 at 1:32pm |
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well, it certainly makes the Amplifiers with conventional Power Supplies using transformers into 'light-weights'!
Not to mention that it's 56 years old and still running an internal pic of the EL6471:  but even better still a copy of the full service manual - mostly in Dutch Philips EL6471 Service Manual uses only 2 valves for the output stage anyone fancy building a couple of these then - 'monoblocks' were being discussed in other threads and this certainly fits the bill Mik Edited by audiomik - 12 March 2011 at 1:44pm |
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Nitz V1505
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Joined: 16 September 2009 Location: UXBRIDGE Status: Offline Points: 1719 |
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Posted: 12 March 2011 at 3:46pm |
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One of my dream amplifiers along side the GEC 1100w amp using V1505's. Also a big fan of multiple KT88 push pull parallel class B amp.
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LET THE BASS ROLL LIKE THUNDER
& THE TOPS LIKE LIGHTNING..... |
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audiomik
Old Croc
Joined: 06 April 2010 Location: Bath, UK Status: Offline Points: 2956 |
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Posted: 12 March 2011 at 9:39pm |
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Re: "Also a big fan of multiple KT88 push pull parallel class B amp."
just wondering how many KT88's would be needed, with all of the additional associated bias balancing, compared with a pair of QB3.5-750's running with an HT of 3.2kVolts or even something more modern in terms of decent high power Tetrodes rated at 1250 watts (or more) dissipation each? Datasheet for the QB3.5-750 output Valves used in this Amplifier at: QB3.5-750 ...........so the comparison can be done  Do like the overall simplicity of this EL6471 design, and the Mercury Arc rectifiers certainly have an 'visual interest factor' much greater than a bunch of silicon diodes! Reminds me of when I used to use surplus 813 Transmitter Valves; for building Amplifiers in the '60's Mik |
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Nitz V1505
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Joined: 16 September 2009 Location: UXBRIDGE Status: Offline Points: 1719 |
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Posted: 13 March 2011 at 1:32pm |
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You would need 10 pairs of KT88's ,preferably matched, to produce 1000watts. You could also use a single bias supply to simplify the circuit. The psu would have to provide atleast 575V at around 2.5A, newer versions of the Kt88 however can take up to 800V on the anode. This is a cheaper method of obtaining 1000watts because of the cost of more expensive valves. Edited by Nitz V1505 - 13 March 2011 at 1:41pm |
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LET THE BASS ROLL LIKE THUNDER
& THE TOPS LIKE LIGHTNING..... |
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jbl_man
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Joined: 12 January 2005 Location: London. Status: Offline Points: 11308 |
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Posted: 13 March 2011 at 1:43pm |
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To quote from the link posted by Mik "The EL6471 was designed for use in large stadiums and possibly concert halls and was never mass produced. Its final tubes are types QB3/750 beam tetrodes originally developed for transmitters. In good Philips Holland tradition, they are run “conservatively”. In the EL6471 product sheet Philips also mentions 2 kW, 10 kW and 20 kW versions of the amplifier (price on request)." The 20kw version must have been the size of a small shed? |
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Be seeing you.
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Nitz V1505
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Joined: 16 September 2009 Location: UXBRIDGE Status: Offline Points: 1719 |
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Posted: 13 March 2011 at 1:55pm |
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And probably designed for speech/PA in stadiums, 300-1000hz at a guess. Otherwise to produce real low frequencies I'd say the the o/p transformer would be the size of a shed!!!!!
Edited by Nitz V1505 - 13 March 2011 at 1:56pm |
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LET THE BASS ROLL LIKE THUNDER
& THE TOPS LIKE LIGHTNING..... |
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Muckerbarnes1
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Joined: 20 March 2010 Location: Stroud Status: Offline Points: 2637 |
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Posted: 13 March 2011 at 9:45pm |
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I love valves. Grew up with them. Still fix some valve amps. Got a couple of weird 35W ones here called Fantavox.
Never seen an EL6471 though.
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Billy Dawg.
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audiomik
Old Croc
Joined: 06 April 2010 Location: Bath, UK Status: Offline Points: 2956 |
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Posted: 13 March 2011 at 11:21pm |
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Ok, just when anyone thought that building a replica is off; up popped this site:
Royal Navy Type 182 Final Amplifier and Power Unit Quote: "For the High Voltage & High Energy experimenter, these units contain many useful parts. See photographs and descriptions of the components used in these units. Once stripped, these components may be re-used for a wide variety of applications" Do like the idea of deterring Torpedoes though - being quite a few miles from the sea  and for an HF Amplifier; unmodified it might never be 'beaten'!Think we already know manufacturers of suitable output Transformers, which looks like being the only main part 'missing' for quality full range Audio Some years ago I would have had a go at this sort of Project; but I just don't have the necessary space or facilities any more  Mik |
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Warning! May contain Nuts
plus springs, washers, screws, etc, etc. |
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Muckerbarnes1
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Posted: 14 March 2011 at 7:08am |
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Fortunately dettering torpedoes at the high ground here will not be any advantage either.
A great way to heat the workshop on a cold day. Proper audio visual display too.
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Billy Dawg.
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TONY.A.S.S.
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Joined: 21 February 2007 Location: United Kingdom Status: Offline Points: 6867 |
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Posted: 14 March 2011 at 4:15pm |
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These are not vintage, but they are very good sounding chinese valve amps, 80 watts per channel. As a lot of people will know, valves are still very popular in the Hi Fi business.
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