I took my Yamaha RX570 in and had it looked over by a service tech. He said that the Bass,treble and Balance controls were not working. He attached the receiver to a set off quality speakers and it sounded pretty good. Can anyone tell me what would it take to get these individual function controls to work?
The RX570 included (on the front panel and with a LED indicator to let the user know when the feature was engaged [which is, when you think of the claimed operation of the feature, a complete oxymoronic contradiction]) what was termed a "Pure Direct" switch.
If the tech had engaged the switch and told you the controls were non-functional in all cases, the tech is an idiot. If the tech had not engaged the feature but the controls were non-functional, then you need the switch repaired ... assuming, that is, you wish to use this fairly BS feature.
Pure Direct was a feature found on most of Yamaha's consumer level receiver/integrated amplifier and pre amp models in the early to mid 1990's. Engaging the switch bypassed most of the pre amp controls of the receiver and (more or less) sent the audio signal directly to the power amplifier after passing it first through the buffered volume control.
(A receiver consists of three discrete components enclosed into one chassis; a tuner/radio, a pre amp and a power amplifier.)
A "pre amp" is also known as a "control amplifier" since that is where the vast majority of your operational controls exist for selecting which input to use along with any tone controls or other filters included in this section of the receiver's circuitry.
Volume and channel balance controls also exist within the pre amp. If the control amp lacks a phono pre amplifier circuit, it may also be called a "line stage" or "line amp" yet it may still rather loosely be described as a "pre amp" since most line stages do include a few dB of signal gain. Therefore, you can think of a "pre amp" as the circuitry which affects the signal in some way other than merely adding "watts" to the output. That is the job of the power amplifier which steps up the signal in gain by adding both Voltage and Amperage which there by makes the signal more appropriate for driving a real world loudspeaker.
Controls for the tuner/radio are split between the tuner and the pre amp depending on what the switch or knob actually controls.
Speaker selection switches exist outside of the pre amp and are connected to the power amplifier outputs just prior to the speaker connectors (though most receivers also include some buffer circuits and some protection devices in this area).
When the Pure direct switch in engaged on your receiver, the audio signal bypasses the tone controls and is sent (more or less) directly from the input jacks to the volume control and from there on to the power amplifier.
The marketing "logic" behind this feature was a supposedly more direct signal path without the intervening controls/circuits which can cause some audible distortions when there are multiple switches/controls/circuits for the signal to pass through. It was Yamaha's attempt at portraying their products as more capable of "high end audio equipment" performance which, at the consumer audio level, generally eschews more circuitry than is absolutely necessary. At the same time, Yamaha wished to be seen as being more user friendly and familiar to the average "consumer level" receiver buyer.
In the end, the feature and the equipment really did not approach high end consumer audio grade performance and the inclusion of this feature did very little in the way of making the signal any cleaner or the music any better. But it did give know nothing salespeople one more button to point to on the display shelves.
As I've said several times recently while discussing receivers, they sell the sizzle and not the steak.
So, if the "tech" had engaged the switch (the LED should light at that point), then there would be no tone controls in the audio signal path. No tone controls in the audio signal path means you can twiddle the tone controls all you want but you won't hear anything change with your twiddling.
If this "tech" doesn't comprehend what the controls on your receiver control, I don't think I'd trust him to work on my equipment. This is the sort of fool who would spend hours hunting down a non-existent "problem" of "non-functional" tone controls and then either try to repair what isn't broken or tell you the receiver should be replaced due to issues he cannot locate and cannot repair ... because they are not broken.
Believe me when I say I have worked with techs this dumb. Usually, they will break out the soldering iron and begin to hardwire what isn't meant to be permanently connected inside the component. You can guess what happens when they hardwire something that isn't meant to be hardwired. It's seldom pretty because they haven't looked at the schematic or they would have seen what they shouldn't be hardwiring in the first place. A tech who doesn't refer to a schematic is like a doctor who hasn't bothered to actually consult his PDR.
Admittedly, mass market receivers have included a lot of gobbledegook, BS geegaw and totally worthless (non-)features over the years. And no one can be expected to know everything about every component. Particularly if the component was sold while the tech was still p00ping in his diaper.
That fact, however, does not excuse a tech who cannot, or does not, look at the circuit schematic for technical information regarding a product they have never seen before.
Nor does it excuse a tech who does not realize they really do not know what they are doing and misses completely the fact they have been outwitted by a 20 year old, base line Yamaha receiver.
Avoid this shop at all costs ... though, with this level of skill and obviously lacking in any sort of depth of curiosity, it's doubtful that tech would be there when you went back in a few weeks. Only the permanently damaged equipment he has touched will remain.
Thanks for your response. So if I understand you correctly, I should be able to press in on the Pure Direct button and once again have full use of the Bass, Treble and Balance functions.
By the way, the tech did not tell me that I needed a new receiver but said that using it as it was rather than replace it seemed like the thing to do.
Again, many thanks for your time and willingness to share your knowledge with others.
First, keep in mind you have a roughly twenty-plus year old receiver. The 570 was not at the top of Yamaha's equipment line and was built - as most all mass market receivers are built - to compete on a product/feature/watts vs dollar cost comparison with other lines.
This will mean not the best, most costly parts were employed in the design of this receiver. Rather, the most cost effective parts - from the manufacturer's stand point - were selected.
Manufacturers must consider their warranty repair costs to be a considerable chunk of their investment in any product. Audio companies have literally gone out of business when they failed to secure sufficient backlogs of parts or the finances to secure the parts when required.
Yamaha is on no way about to go out of business due to parts supply but their concern is that most parts used in their products are going to make it through the warranty period without issue. After that, you are on your own.
Yamaha no longer supports this receiver with replacement parts. If for some reason the switch has failed, then you may not be able to easily by pass its function.
Switches themself are somewhat generic (though their physical attachments in a circuit are not) and there may be a tech who would be willing to rig another switch in its place if you insisted and were prepared to pay.
Most techs are hesitant to do such repairs on "vintage" receivers though due to the chances they can become tied down to a product that may have multiple failures waiting to occur due to the age of the product.
I would guess most techs would advise you to simply use the receiver "as is" or buy new and have a product with some warranty.
Going in and hardwiring past the switch should be possible but probably more costly (and not necessarily pretty) than most users could justify for the addition of these somewhat less than useful features. Bass and treble controls are very gross (meaning very broad and not highly refined) in their actions and often do more harm to a signal than can be justified by their presence. This is one reason the high end of consumer audio tends to ignore their inclusion into a circuit.
Balance controls are mere potentiometers of a sort and mostly unnecessary if the system and the listening space have been properly set up. Unless you sit and focus on the music to the exclusion of all else, most systems will produce an adequately "balanced" output between the left/right channels.
That said, yes, there is an LED which indicates the "pure direct" switch has been engaged. At that point, the signal is diverted around the tone controls and they would have no direct influence on the audio signal.
Since even LED's of this vintage are fairly reliable, if the LED is not powered up, the switch is (probably) not active. At that point you should have tone controls.
Switches of the mechanical type used in this receiver are not as long lived nor are they as reliable as the LED however. A simple visual confirmation would tell you whether the switch is in (engaged) or out (not engaged).
Assuming the switch is still functioning in some manner, this is all you would need to re-establish tone controls for this receiver.
"So if I understand you correctly, I should be able to press in on the Pure Direct button and once again have full use of the Bass, Treble and Balance functions."
You have it backwards. The tone controls are "in circuit" until you press the switch "in". At that point, the LED should light up. That's your indication the pure direct feature is active and the signal has been routed past the tone controls.
There is an extremely small chance that, even after twenty years time, both the bass and treble controls and the balance control would all become non-functional individually. Thay are all grouped together with the pure direct feature however. The odds are in your favor that you only need to use the switch to get them back in circuit.
Have you read the owner's manual for this component? If you never had or no longer own the manual, it is available on line.
As I have taken more interest in my audio equipment, I am having more questions. I find myself going back over your response to my original questions, and I am finding the answers to these additional questions addressed in your original response. Thanks again for sharing your knowledge and expertise.