you will find divider calculators on the internet, it's simple to use, you just need to know your input voltage and what you want output, example:
input voltage 2v =
0.750v output voltage
resistance 1 (signal) -10k
resistance 2 (grounded) 6k
Doesn't the 'Volume' pot at the input do this?
Or are you suggesting a voltage divider:
-before
-after
-instead of
the volume pot?
Question for Gregas:
When you notice the harshness in the sound at higher volumes, what's the position of the Volume control? 12 o'clock? 3 o'clock? 'wide open'?
Please help me to calculate that 750mV input limit; I'm confused.
The cathode on Gregas' preamp tube is at 2.6 V DC.
Shouldn't that allow a 2 V AC input signal without clipping?
That's an 'interesting' webpage.
I noticed that the capacitor 'tests' were all 'listening tests' in loudspeaker crossovers - different from the coupling cap application in this amp.
Also, the HumbleHiFi tester must have taken a lot of time (and money!) in testing, since he has 115+ different capacitors in his list and says he takes quite a bit of time for each one.
Not to say that capacitors may differ in their performance.......
With irony about the capacitors, everything is OK, those who have ears will hear the difference, the blind do not need glasses.
An example in the photo for you, so that you understand where the voltage comes from.
Yamaha CD-S2100 Output Level 2 +/- 0.3 V
Boyuu A9 Input Sensitivity: 750MV
if you feed amplifier 2v to the first stage (6N9PJ) of the amplifier, you get an overload, you get a bunch of distortion at the output of the amplifier.
The amplifier requires 750 mV, it requires a divider.
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I don't doubt what you have said and shown from the specs.
It's just that I don't understand how the 750mV 'sensitivity' number is calculated-or found by testing the amplifier.
The volume pot is a voltage divider - is the added divider with fixed resistors necessary?
The amplifier requires 750mV to reach full output. With a volume pot, you reduce to input voltage to the first tube, therefore controlling the power output. Why do you need a voltage divider?
jeff
You are mistaken, 750mV constant. Colleagues with good English will explain why you need to coordinate the signal from the source to the amplifier.
It is best to use for this matching transformer, less troublesome voltage divider.
"Matching transformers are designed to change the voltage level of electrical signals carrying useful information. They allow you to match the source of the signal with the load with minimal losses and minimal signal distortion."
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It depends where you tighten the set screw for volume
Off. Is that normally at 6pm?
Anyhow it starts to distort around 75 percent open .
The output level of your device (player, DAC, etc.), you can find out in the specifications of this device. Calculate it is not necessary.
Divider (resistors) is required. In some devices, the output signal can be up to 3v. C1 Mono D/A controller
It all depends on the output of your signal source. The volume control is only partially a divider, to a certain signal level.
It is a voltage divider all the way, from zero to maximum. It is how it works.
how it works I know))
It seems to me that you did not encounter devices with a 2-2.5 V output, it is simply impossible to listen at 30% volume. Breeze Audio DAC SU3 high level Audio decoder ESS9018 XMOS Asynchronous USB DAC
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Yes, you are correct about the position of the volume pot..
Most of the gear I have, 'Zero' is at about 7 o'clock and 'wide open' is at about 5 o'clock (clockwise rotation to increase).
That doesn't work for multi-turn pots or rotary digital encoders, I know!
When you get your hands on a scope and a few other bits of test gear, it will be interesting to look at the waveforms as the input voltage is increased, to see if you are getting clipping at higher input volumes.
Having 'efficient' speakers makes it easier when using relatively low-powered SE tube amplifiers. I didn't look up the specs on your speakers.
These are the speakers. I've got my volume knob set up pretty much like you've described. It sounds good at 12 noon then starts to get harsh and sometimes distort. Depending on the recording.
Monitor 7 v4 Specifications
Design - 3-driver, 2-1/2 way bass reflex, quasi- 3rd-order resistive port, floorstanding / tower
Crossover - 3rd-order electro - acoustic at 2.0kHz 2nd order electro - acoustic at 400Hz (lower bass driver)
Frequency Response - +/- 2dB from 47 Hz - 20 kHz
Low Frequency Extension - 33 Hz (DIN)
Sensitivity - 93 dB
Impedance - Compatible with 8 ohms
Maximum Input Power - 130 watts
Finish - Black Ash
Weight - 76 lbs. (34.5 kg)
Dimensions HxWxD - 40" x 7.625" x 15.375"
Monitor 7 v4 Specifications
Design - 3-driver, 2-1/2 way bass reflex, quasi- 3rd-order resistive port, floorstanding / tower
Crossover - 3rd-order electro - acoustic at 2.0kHz 2nd order electro - acoustic at 400Hz (lower bass driver)
Frequency Response - +/- 2dB from 47 Hz - 20 kHz
Low Frequency Extension - 33 Hz (DIN)
Sensitivity - 93 dB
Impedance - Compatible with 8 ohms
Maximum Input Power - 130 watts
Finish - Black Ash
Weight - 76 lbs. (34.5 kg)
Dimensions HxWxD - 40" x 7.625" x 15.375"
The Model A10 is not my amp (for some reason A10 schematics keep getting injected into this A9 thread discussion) - Mine is the Model A9 as per the schematics I uploaded in post #697. I think the A10 and A9 are different beasts are they not? Also mine has a PCB so it is not all P2P wiring as the schematics allude to which I think is why some of these discussions are confusing to me....
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All you're doing is attenuating the input signal, so that your volume control has a normal range. I understand now why you're doing this, but you make it sound like a mandatory modification, which it's not.
The A10 has 6N2P input tubes, and all tubes appear to be PCB mounted, but the basic topology is the same.
jeff
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With a different amplifier (with tone controls and 'loudness' bypassed or set 'flat') and the same music and same volume level (sound intensity from the speakers), do you find the same harshness problem?
Your speakers are sensitive enough that you should be able to get the music fairly loud (but undistorted) with the A9...how big is your listening space ?
(And how close your neighbours?
)The schematic would be the same whether the amp was built P2P, with eyelet/turret board, or with a PCB.
It's baffling at first but with more time spent comparing the schematic with 'the real thing' on your bench, you will get more familiar with it.
Printing out the schematics for the A9 and A10 and looking at them side-by-side will show you that they are very similar.
The caps that LongRoad is suggesting for possible replacement are the coupling caps (.22 or .33 uF) between the 'preamp' tubes and the power tubes. They pass the AC signal but block DC. Changes like that can sometimes make subtle differences in amps that are already working well.
With a different amplifier (with tone controls and 'loudness' bypassed or set 'flat') and the same music and same volume level (sound intensity from the speakers), do you find the same harshness problem?
Your speakers are sensitive enough that you should be able to get the music fairly loud (but undistorted) with the A9...how big is your listening space ?
(And how close your neighbours?
There's definitely a difference. My solid state amp sounds Warmer. I can crank it up and no distortion. I just compared the same song. On the boyuu the female singer started to sound garbled. I played it on my other amp with flat response. No distortion in the voice at the same volume level.
Well, definitely time for the scope, then...
You've checked all the wiring for errors, the hum is low, swapped out tubes, so you have eliminated quite a few possibilities.
Having a close look for bad solder joints ('cold solder joints') and touching up any that look suspect would be one thing I'd do. Clean up with flux remover or isopropyl alcohol if necessary then re-solder where warranted. A flux pen, good solder, and a hot iron...you probably already have those, so you could pass some time while waiting for that scope.. Common Soldering Problems | Adafruit Guide To Excellent Soldering | Adafruit Learning System
You've checked all the wiring for errors, the hum is low, swapped out tubes, so you have eliminated quite a few possibilities.
Having a close look for bad solder joints ('cold solder joints') and touching up any that look suspect would be one thing I'd do. Clean up with flux remover or isopropyl alcohol if necessary then re-solder where warranted. A flux pen, good solder, and a hot iron...you probably already have those, so you could pass some time while waiting for that scope.. Common Soldering Problems | Adafruit Guide To Excellent Soldering | Adafruit Learning System
You understood correctly. So the volume control works in full you need to lower the input signal to the specified value in the characteristics of the amplifier. As a voltage divider, you can use the volume adjustment potentiometer.
Using a calculator, you can consider the volume control as a resistor divider. As a result, we get the value of R101 and R201 see the scheme. Breeze Audio DAC SU3 high level Audio decoder ESS9018 XMOS Asynchronous USB DAC
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