• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

yaoin

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#101
salas said:


Just maybe, there is some polarity inversion somewhere, even in the internal wiring of Yaqin itself, typical for unexplainable lack of bass, due to acoustic cancellation of opposite polarity woofer movement. Just reverse the polarity of the wires in only one speaker input, and listen if bass comes up stronger. Very easy check, just to be sure. If not fruitful, then borrow a preamp and drive the Harman's main in RCAs. See if it (most probably) skips that worn out input selector. The Yaqin just has power (main) in RCAs at its front. These are not outputs, that is why you can't drive the Harman from there.
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Okay that one I haven't thought of so I'm going to try.

I were into that to get a preamp to the harman and lift out the power amp section as it's very easy because it's totaly separeted from other parts of the receiver and than let a friend of mine build a wooden nice cabinet to it and move over the thing, and only use it as a power amp.

About the Yaqin, it should have a power to drive my loadspeakers as the harman is only 75 watts but it's transistor and not even a mosfet, at least that's what I believe.
But special it is that's for sure!

But those front RCS (learning the tech 🙂) in the yaqins front are by the manual "external pre input jack" says (input 0.6V) left and right and packed mode when (input 0.25V) is selected.

What is this and what they mean by that? I took a cable from harmans pre out and pu in there but no sound come out at all. Does this work or meybe the output of the harman not good for the Yaqin.
 
#102
They are just extra front inputs, with sensitivity selection. Actually they change the sensitivity by lifting the SRPP input stage cathode bypass cap giving it some local degenerating feedback. This means that the 0.6V position will sound different tonally too. Inputs you drive from outputs. If you got a wire from Harman's pre out and it did not drive the Yaqin, it means no signal. Maybe you must engage some switch on the Harman, or it is defective there too.
 
#104
Lowrider said:
Maybe your player has a variable output, meaning an output with volume control, you can connect it direct to those front inputs in the Yaquin...

You should not need to dismantle the HK to use it as an amplifier, doesnt it have amplifier direct inputs ?
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Yes its have one but I thought it would be nicer in the wooden cabinet as there is the fm/am radio and the preamp with the selector why shoul I have those left? this is a receiver with sparate radio preamp and the pewer amp in one agly box. 🙂
 
#105
salas said:
They are just extra front inputs, with sensitivity selection. Actually they change the sensitivity by lifting the SRPP input stage cathode bypass cap giving it some local degenerating feedback. This means that the 0.6V position will sound different tonally too. Inputs you drive from outputs. If you got a wire from Harman's pre out and it did not drive the Yaqin, it means no signal. Maybe you must engage some switch on the Harman, or it is defective there too.
Click to expand...

It's just getting whorst and whorst isn't it? 🙂
 
#106
Lowrider said:
The first stage is different, you have a pentode I have a double triode aikido, second stage is identical, except for the tubes, if I could I would combine your first stage and my second stage...

Have you tried triode mode, if your speakers are sensitive enough, you might like, and then you can also try no NFB... :angel:

I am going to be burned for the last statement... :hot:
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I haven't tried to tinker with triode mode yet as I'm still working to get my preamp to sound right. It is almost 50 years old so I'm having a hard time finding spare parts.

As for removing NFB that is one thing I hope to try, but I am not sure that the result will be pleasing as the amp is pretty dependend on it.

Actually the EF86 pentode is triode strapped to reduce the gain 😀
 
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