• 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.

Musical Fidelity X10D schematic

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#21
X10D Mods

Hello Tube_Dude !

Not shure to have understood :
For a gain of 6, the resistor change from 1.5k to 22k : OK
So the ratio for resistors is 15 (not 5)

Now for the // cap : change the original 220pF (on attached scheme) for a smaller one with a ratio of 15 ? No ?
220 pf / 15 = 15pF

So sorry for my ignorance !
R.C.
 

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#22
Re: X10D Mods

Ciu said:
Hello Tube_Dude !

Not shure to have understood :
For a gain of 6, the resistor change from 1.5k to 22k : OK
So the ratio for resistors is 15 (not 5)
Click to expand...


Hi Ciu

Sorry for the delay I have been to busy... 🙁


The gain is given by the formula I give in my previous post.

Imagine (all the people..... 🙂 ) that you change the 1k5 resistor for a 1 Ohm resistor , we have:

1+ (1/ 4k7 ) that give

1+ (0,0002 ) or a gain of ~ 1

Now if you change the 1k5 for a 4k7

we have

1+(4k7/4k7 ) that give a gain of 1 +(1)= 2

Remark, that we have passed from a feedback rsistor value of 1 to 4.700 (4.700 times greater ) and the gain of the stage only have become the double .

Then for a gain of 6 the value of 22 k is absolutely correct.

I hope to be clear now... 🙂


Regards


PS: In your last schematic the 4k7 resistor become 8k2 , so for a gain of 6 the 1k5 resistor must become ~41k or a more normal value of 39 K
 
#23
X10D Mods

Hello Tube_Dude


For a gain of 6 you must change the 1.5 K resistor for 22 k. As the resistor is 5 times greater , the // capacitor must be ~ 5 times smaller for the same time constant

That was the beginning of my trouble ! 22k /1.5k = 5 ?

In my study case, for a gain of 6, the resistor changes from 1.5k to 39 k, OK !

And the value of the cap, how to calculate, where do you find the ratio ? Any recommanded technology for the cap ? Voltage (>= 30v ?)

Many thanks for your patience !
R.C.
 
#30
XD10

Hi RC,

I have a clone XD10. I am interested to know the ouutcome of your mods if you dont mine sharing. I have change all the supply cap with panasonic FC 2200uF/35V, change the diode with ultra fast soft recovery and bypass the diode with 0.1uF caps. All the transistors in the power supply removed/bypass. I also upgraded all the caps in the circuit. Did u manage to inxrease the gain?
Thanks
NikS
 
#31
Re: XD10

niksh said:
Hi RC,

I have a clone XD10. I am interested to know the ouutcome of your mods if you dont mine sharing. I have change all the supply cap with panasonic FC 2200uF/35V, change the diode with ultra fast soft recovery and bypass the diode with 0.1uF caps. All the transistors in the power supply removed/bypass. I also upgraded all the caps in the circuit. Did u manage to inxrease the gain?
Thanks
NikS
Click to expand...


I know this thread is a little old, but.......!?

I'm running mundorf supreme 4.7uf on the output, but there are a couple of 0.22uf cap in the audio path. What would be a good upgrade here? I don't want to change the gain just improve the quality of the components.

I have already ordered Panasonic FC's for the supply section and I'm also waiting for hexfreds to replace the diodes.

What other upgrades should I consider?

Thanks Ian
 
#33
This is the diagram of the clone sold on ebay!

If you are building, use decent diodes and Panasonic FC 1000uF caps on the supplys and also choose something nice like Mundorf coupling caps on the output. These are the parts fitted if you upgrade the X10D. Also its worth getting cryo treated valves as they tend to be less microphonic.
 

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