Phillips 830A speaker type variation

[chipp1968]

Well my I pod, actually a creative model, runs on my Murphy A8 with very good results indeed. Of course it may not work on all radios so well. I have never heard anyone else warn about damaging the amp on a radio doing such a thing.
I would expect a restored item whether it be a radio TV or car to perform near to its original intended limits of the original design, allowances being made for some age related deteriorations that cant be rectified easily.

[geofy]

Hi Chipps
With digital systems some caution has to be excised when connecting to a high powered directly coupled amplifier, like those in a good hi-fi system. Especially if the optical output of a dvd player is used as it can drive the amp output to nearly DC causing the speakers to make large excursions with attendant risk of damage. I don't expect there is to much risk in connecting an ipod, as the frequency response and power output of the radio will be limited, though they do have the ability to give a much higher transient response than an analogue player.
I agree that with changing components it is possible to bring a set back to near or even better than its original spec because of the quality of new components compared with the original. But at what stage does the original radio stop being original. If every component is replaced then it is no longer the set you started out with. How about a picture of the Murphy A8 I have not seen one of these. Murphy are among the all time great British sets.

Geof

[Herald1360]

I really can't see HOW you could possibly damage a valve amplifier (gram input of radio) by connecting modern digital equipment to it. The greater dynamic range is irrelevant- all that means is the quietest bits will disappear under the noise floor of the amplifier. The volume control can be set to control the peak input level to what sounds acceptable. If you do overdrive the input, well valves are pretty tolerant and the resulting distortion won't sound as bad as a hard clipping solid state amp anyway.

The impedance mismatch is not significant- the iPod (or whatever) output will be capable of driving a relatively low impedance (around 10K or less) and will simply be loaded less by the 500K or so of the old gram input. If there's any frequency compensation on the gram input, that will modify the sound somewhat, but HiFi it ain't!

Chris

[chipp1968]

As requested a Pic of the Murphy. The stand isn't an original one, I constructed it from a small picture of one. I couldn't get access to one at the time. Fortunately its not too far off the real thing to worry. The amp works really well as I have said, the tuner part needs some work.

[geofy]

Hi Chipp
That is a great looking radio. You have very good woodworking skills by the looks of the stand. Thanks for the picy.

Chris I do agree that valves will tolerant overload of the input, in this respect they are better than transistors, the point I was trying to make (and wishing I hadn't!) is that a modern digital system especially if it has an optical audio output as good DVD's such as JVC and Panasonic have, it is possible for them to output high levels as low as 2Hz which if sent through a directly coupled amplifier could seriously overdrive a loudspeaker, not my words, it is in the user manual, though arguably a high end speaker system may have a limiting or cut-out devices.

Geof

[petervk2mlg]

There was an older thread (now closed) on this subject.
I can confirm that the UK model of this set had a dynamic speaker, whereas the Continental model used a magnetic or reed type speaker of the type used in the circular "frying pan" Philips speakers.
I have both variants here and the differences are confirmed by the relevant circuit diagrams.
Peter

[stevehertz]

Originally Posted by geofy

.... One 'problem' when using a digital source in any vintage amplifiers is the digital source has a much wider dynamic range and could potentially damage components that where never intended to reproduce this type of signal.

I'm also into valve guitar amps and I can tell you that they are much better able to respond to large dynamic ranges than comparable SS stuff. I don't see why the same shouldn't be the case with the audio section of a vintage radio. I mean, there may be a problem with distortion on high peaks (just keep the volume and input level down to suit), and the set's speaker not being able to handle the 'volume' or frequency range, but other than that, damage to components (plural)? I very much doubt it.