Yes I might have to go through it again, because the relay only clicks when it been on for 30mins

 

In this case, check Q705 and Q706. These are perhaps leaky until warm. These are 2SC1845 which are very common and inexpensive.

 

In this case, check Q705 and Q706. These are perhaps leaky until warm. These are 2SC1845 which are very common and inexpensive.

Thanks will do

 

Perhaps there are some more failed solder joints, it seems like you have found quite a few so far. And re-flowing solder joints with a decent soldering tool is much faster than even most analysis procedures. So that is my suggestion. Start in the area near the relay and re-melt the joints with just a bit more solder. Cheap and easy if it is the fix, and no harm done if it is not the fix. Provided you are reasonably good at soldering and the soldering tip is in good condition.

 

Perhaps there are some more failed solder joints, it seems like you have found quite a few so far. And re-flowing solder joints with a decent soldering tool is much faster than even most analysis procedures. So that is my suggestion. Start in the area near the relay and re-melt the joints with just a bit more solder. Cheap and easy if it is the fix, and no harm done if it is not the fix. Provided you are reasonably good at soldering and the soldering tip is in good condition.

thanks will do

 

OK, the very first thing to check is the switch that operates the relay that does the switch over. But if there is no relay then try switch cleaner, because it sounds like a switch problem.
AND, it also sounds like a rather useless feature, as I see it.

Pardon me for reviving an old thread but the direct drive does more than simply bypass the tone controls.

Signal to noise specifications are quoted at the amplifiers rated output.. but who listens to music at the rated output...particularly if that output is 110watts PC into 8 ohms.

What isn't apparent is that the signal to noise figure degrades linearly from its maximum at rated output as the volume is reduced so that by the time the volume is at 50% the signal to noise is now half what it is quoted in the specs.

That means a cd player who's signal to noise is around 100dB is being heard through an amplifier playing at 50dB signal to noise.. that is worse than a cassette without Dolby. Now admittedly the cd is a very lossless format but if signal to noise figures matter and cassette to cd difference suggests it does, then why should the signal to noise degrade so much at less than rated amp power?

Enter direct drive.

With direct drive, not only are the tone controls bypassed which increases the signal to noise ratio, but the connection is now via the unbalanced inputs and connect directly to a voltage gain amplifier then through a unity gain power amp.

This cause the noise to drop along with the signal as the volume control is lowered in a manner analogous to when Dolby lowers the volume of the frequency it is filtering..the noise there drops too.. causing the cassette to provide better signal to noise.

So.. the EDD isn't a gimmick but rather a rather sensible way to maintain the high signal to noise ratio of a quoted 106dB even when listening at half volume.

I'm unaware of any other amps that do this.

 

What sort of poor quality amplifier has a tone control section that increases the noise? On many integrated amplifiers the tone control section is entirely passive components, such that any addition to the noise level would be so little as to be very difficult to even detect, much less to hear.
And the reference to "unbalanced inputs" makes no sense in the context of recent technology, ( more recent that 1975).

The exception being if you are one of those who can hear the sound difference between having speakers connected with #16 lamp cord instead of connected with the "gold plated #12 Oxygen-free, copper" cables.

 

What sort of poor quality amplifier has a tone control section that increases the noise? On many integrated amplifiers the tone control section is entirely passive components, such that any addition to the noise level would be so little as to be very difficult to even detect, much less to hear.
And the reference to "unbalanced inputs" makes no sense in the context of recent technology, ( more recent that 1975).

The exception being if you are one of those who can hear the sound difference between having speakers connected with #16 lamp cord instead of connected with the "gold plated #12 Oxygen-free, copper" cables.

apologies for the late reply...

All amps lower their signal to noise ratio when the signal path is lengthened, whether you can hear it or you can't, because all electronics generates noise, it may not be detectable because amplifiers like this 1992 vx800 are so well designed, but in the post 1982 digital music era, an older amplifier like this, can benefit from improved s/n ratio especially when previous amplifiers circa 1970s and 80s would have been setup for tape players of the 60s with an appalling 50dB s/n then tape decks that raised to 65 with dolby B in 1969 and then to 77dB with Dolby C in 1979 and then 85dB in 1989 with Dolby S. CD arrived in 1982-3 and had ~100dB s/n.
Now the unbalanced inputs are straight RCA inputs just like the phone, tape, tuner and aux of any amp but with one important difference... The unbalanced inputs go straight to a voltage gain amplifier(not an attenuator) which in turn goes to a unity gain power amplifier. This construction instead of using an attenuator meant that as the volume is lowered from full, not only does the signal reduce down to listening levels as you'd expect, but so to does the noise of the amplifier along with it, regardless of how low it is to start with. It is not just a bypass of the tone controls as that is achieved with the tone bypass switch beside the balance knob, take a look at its facia.

Now the Extended direct drive also allows for the balanced inputs to be used. These are the Canon connection cables of which you may be aware reduce common mode noise in a connecting cable by simply sending two identical signals but out of phase by 180deg along the cable and subtracting them in the amp end to get the intended signal without induced noise on long cable runs.

Now, as it takes more circuitry to reduce this induced cable noise on the balanced inputs, the s/n of the balanced is 3dB lower than the unbalanced inputs of which I referred, so that if the cable run is less than 10 m or so, the unbalanced is the way to go.. but whatever you think of induced noise in connecting analogue components, this amplifier allows not only for 106dB s/n but also a signal path construction that maintains that 106 at even low listening levels, when you're more likely to use the amplifier instead of absolutely full blast when many amps are at their best s/n.

CD players of the time were sporting s/n ratios of over 100dB so it made sense to have the amplifiers keep up. Direct drive was the answer at the time because you didn't need to put the amp at full blast to get the rated s/n even if it did match the 100+dB of the digital source.

So unbalanced is relevant to the conversation because that allows for a higher s/n over balanced as long as the connecting pathway between the components is not more than 10 m or so.

My point is that the EDD isn't just a bypass of the tone controls.

It's clearly meant for listening to content at levels less than full blast and with the high s/n ratio of digital content.

by the way, the twin behemoth transformers in this amp are using OFC windings and as the power supply induces noise to the other components, that's probably a good thing.

I take your point that many of these changes aren't audible to the average listener, but the change in sound qualit from tape deck to CD does illustrate the fact that maintaining high s/n has advantages for sound clarity and for reference series CD players with a s/n of 111dB you don't really want to pair it with an amp that loses its s/n ratio as the volume is turned down because all that quality of a damned good source is being diluted down.

 

Not only would the differences be inaudible to the listener, they are mostly only detectable with good test equipment. While that is vitally important to a few folks, in a blind test who can detect the difference between the 100dB S/N ration and the 60 dB S/N ratio??? Is it really important to hear the violinists's fingers on the strings??
And with what sort of program material does it matter???

 

Not only would the differences be inaudible to the listener, they are mostly only detectable with good test equipment. While that is vitally important to a few folks, in a blind test who can detect the difference between the 100dB S/N ration and the 60 dB S/N ratio??? Is it really important to hear the violinists's fingers on the strings??
And with what sort of program material does it matter???

It's a personal preference but I'll remind you that each 3dB is a doubling in sound so too a doubling in noisebif it's a measure of a/n. So there's quite a big difference between 106 and 60dB. It's the difference between a CD and a tape deck without even Dolby. Play both and you'll get the idea how background hiss can ruin the dynamic range andmpact the silent pauses in some tracks.

Thanks for your input. I trust you understand now how a 46 dB difference is significant when every 3dB is a doubling of sound.

 

I happen to own one of those very elaborate preamplifier/tone control systems. It is the middle of a 3 section Sony system. Tuner, preamp/control package/ power amp. And the preamp package does sometimes suffer from dropout as well. The effort to solve the problem would be very great as the system has a large number of PC boards and a vast nest of interconnection cables. More complex than most systems that I have seen.
My experience with the system has been that in the "bypass" mode the sound does is not quite right for the listening area. And my choice of music does not have segments where a noise level 60 dB down below the program would be a big deal.