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Author Topic: Hiraga mc preamp cartridge load impedance  (Read 3176 times)
Tropentarn
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« on: June 01, 2013, 09:19:09 AM »

Hello boys,

Hopefully I can find help here. I built the Hiraga MC preamp, great improvement over the musical fidelity xlp. But... The gain is too much. What can I do now? Im thinking about adding a 100ohm resistor to the imput. Any idea about this? Do I have to consider the existing impedance from the components? Thanks in advance for help
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Janos
Tropentarn
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« Reply #1 on: June 01, 2013, 09:20:39 AM »

Schematic

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Janos
rfgumby
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« Reply #2 on: June 01, 2013, 02:44:30 PM »

Yes you'll have to consider the existing impedance.   Is it distorted, or just too loud for your other equipment?   The best idea would be to attenuate or pad it after the preamp, if you load it between the cart and phono pre, you'll alter the tonal characteristics.
« Last Edit: June 02, 2013, 01:36:58 AM by rfgumby » Logged

Scott

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You don't need a weather man to know which way the wind blows    -Bob Dylan
soundlistening
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« Reply #3 on: June 01, 2013, 02:46:07 PM »

Resistors at input may upset cartridge load as in parallel with.
What is the cartridge?
I would use a t.pad at output, so 47k/47k with desired attenuation (http://www.nu9n.com/tpad-calculator.html)
This is obviously if your phono stage is 47k.?
Tim
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Tropentarn
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« Reply #4 on: June 01, 2013, 03:59:57 PM »

The cartridge is the denon 103 and the phonostage is the musical fidelity xlp. There is no distortion, the volume is to loud. Any person have an idea what is the impedance of the hiraga?
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Janos
carawu
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« Reply #5 on: June 21, 2013, 08:23:25 PM »

Well,

as far as my memory works well: this is a current type step-up.
No load required.
But please set the offset to zero. Else your cartridge could fry.
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Regards, Carsten
odermatt
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« Reply #6 on: June 22, 2013, 07:35:04 AM »

This is the case carawu.

And I told it many many times the audiophile things are great simple things and their marketing concept was at that time that you have to use only semiconductors from a dedicated company to get sonic healing.
Here it might be the case as 737 has lowest rbb compared to 560 , but I might remember that Aschenbrenner sold kits for le Monstre in the late 80:s for a hell of a lot of money with semicond not only Tosh rather than what was available
I think this is a kind of current mirror or so The original thing was sold in a small box , but the article show a huge P supply and if you built this and do not have safety precautions for firing it up you will also french frie your cartridge By the way I built about 20 of this MC things like leach, l'audiophile, and many others. and so on and so on.
Impedance?  there are a lot of articles in elector eg on how this work but as CW says not very important here but if the circuit works just gibe it a try....


BR

Peter
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Tropentarn
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« Reply #7 on: June 25, 2013, 07:04:33 AM »

Ok boys,

Things sorted. Gain reduce with resistors at the input. Load impedance with resistors at the output. Magic! Waiting to compare it in about two weeks time with a wester electric/jensen step up transformer.

Thanks boys
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Janos
Albertfifties
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« Reply #8 on: March 12, 2021, 01:45:12 PM »

Please, Ihave the PrePre by Hiraga. the 2SB373 version (P-transistors). The gain is (in LTSpice simulation) 36 dB, in practice I have to have the volume potmeter at about 8 'o-clock, so fairly turned down.
That with my SPU that has a n output of around 200 microvolt. . .

how did you do this?
  • Quote
    Gain reduce with resistors at the input

Is it say 50 ohms parallel to the input/cartridge? I do not expect that a divider at the input is used. That would damp the signal too much.

I do not like a divider at the output of the Hiraga PrePre. Say after the capacitor, 47k to the input of the RIAA filter section. It creates noise there, high ohmic resistances .


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Albertfifties
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« Reply #9 on: March 12, 2021, 01:57:58 PM »

Ah,
\solved it - you drew them in the picture above.
In parallel.
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Albertfifties
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« Reply #10 on: October 09, 2021, 09:21:02 PM »

I tested it, and the effect is not what I expected soundwise, but cant describe how. wink
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aboos
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« Reply #11 on: October 09, 2021, 09:39:20 PM »

The Hiraga prepre is a current input amplifier with a very low input impedance (a few ohms only). Therefore, putting resistors in parallel to the input does not work! For reducing the gain, the 2.2 KOhm collector resistance must be reduced! However, at the same time you need to reduce the 4.7k as well and set the input offset voltage again to 0 Volts!
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Andreas
Albertfifties
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« Reply #12 on: October 10, 2021, 04:49:58 PM »

Quite agree.
Might have to change the DC too? To keep the same operating current from the design?
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