The Mitronic PA100 2SJ50/2SK135 ready for test.

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With some delay because of repair of several Luxman amplifiers a.m., the Mitronic PA100 is ready for the complete measuring test.

The first data from the Mitronic PA100 at only +-30Vdc and 50mA pr. output device:

https://picasaweb.google.com/vbkolse...96040978440882

MITRONIC PA100 and the first measurement data:

The plus / minus 30 Vdc and 50 mA for each output transistor revealed the following data:

At 100kHz / 1 Watt output power was the PA100 amplifier - 0.1 dB down.
At 250kHz / 1 Watt output power was the PA100 amplifier - 1.0 dB down.
There could not be measured higher in frequency as the built-in RC circuits 10R / 47N in the amplifier limited the measurement.

By only + - 30Vdc and an output power of 1 Watt, and from 20 Hz to 20 kHz on the HP distortion analyzer, the overall distortion was below 0.02%.
Quite good of the design from 1982.

At full voltage of about +-60Vdc will the amplifier undoubtedly provide other measurement data.

https://picasaweb.google.com/vbkolse...97038376433890


MITRONIC PA100.
All transistors measured after Hfe, amplification:

Right channel: 2SA970 BL Hfe: 296, 296, 295
BF760 Hfe: 116
BF757 Hfe: 120/120
Hitachi 2SJ50: 1,151V, 1,141V.
Hitachi 2SK135: 0.943V , 0,939V.
Right channel DC offset: <0.507 mV DC

The incredibly low DC offset is a result of the measured transistors.
https://picasaweb.google.com/vbkolse...97619801908146

MITRONIC PA100.
All transistors measured after Hfe, amplification:

Left channel: 2SA970 BL Hfe: 301, 302, 299
BF760 Hfe: 117
BF757 Hfe: 121/116
Hitachi 2SJ50: 1,341 V, 1,340 V
Hitachi 2SK135: 1,044 V, 1,040 V
Left channel DC offset: <4,502 mV DC

The incredibly low DC offset is a result of the measured transistors. The left channel DC offset however, is approx. 4mV higher than the Right channel, but still very low.

Overall view of the Mitronic PA100:

https://picasaweb.google.com/vbkolsen/MitronicPA100#

This MITRONIC PA100 amplifier circuit seems to work nicely. It is difficult to spot any shortcomings in the first measurement tests , I would say :)......but more to come.....

http://www.tubeamp.hobbysider.dk
 
I have looked for that circuit erlier. After the final test, I would like to have the gerber files.

Regards Gudmund

The MITRONIC PA100 must be assembled in a cabinet with power supply before it is possible to get the final data .
I do not have a + - 60Volt supply available which have limitation of amperes built in . Construction may take some time :)

Regards Kim
 
No problem...the good stuff comes to the one who are waiting.

Gudmund


Gudmund,.... before you take action to make a layout of the circuit there is a single component that can be better. C3 and C4 on the schematic are two polarized capacitors from Nippon Chemicon .... instead of these two polarized capacitors use a single bipolar Nichicon "Muse" 100uF / 50V ( the green ones).
Nichicon "Muse" capacitors should have better audio signal characteristics.

rgds. Kim
 
No problem...the good stuff comes to the one who are waiting.

Gudmund

Now when the amplifier PA100 is in place in terms of voltages and bias current, we will try to use better resistors even though the selected 1% types and Philips PR resistors are not of poor quality.
SHINKOH tantalum to £ 2.80 for 0.5 Watt and £ 5.50 for 1Watt is not cheap, but if there are other resistor types such as TAKMAN carbon film non-inductive, non-magnetic, 2% to £ 0.55 for 0.5 watt and 1Watt for £ 1.00 .... so there is an obvious opportunity to experiment :)

PR9372 metal films, Amtrans carbon film,Audio Note,Shinkoh,Charcroft,Takman,Arcol,Mills,Takman,Holco,Allen Bradley,duelund resistor,Kiwame carbon film,M-resist supreme resistors
 

Gudmund

Member
2010-02-27 7:13 pm
Now when the amplifier PA100 is in place in terms of voltages and bias current, we will try to use better resistors even though the selected 1% types and Philips PR resistors are not of poor quality.
SHINKOH tantalum to £ 2.80 for 0.5 Watt and £ 5.50 for 1Watt is not cheap, but if there are other resistor types such as TAKMAN carbon film non-inductive, non-magnetic, 2% to £ 0.55 for 0.5 watt and 1Watt for £ 1.00 .... so there is an obvious opportunity to experiment :)

Kim, I must admit that experiments with resistors will only be actual for me when both mosfet outputs channels plays here :)

Regards
Gudmund
 

Gudmund

Member
2010-02-27 7:13 pm
Mosfet PCB ready

Now when the amplifier PA100 is in place in terms of voltages and bias current, we will try to use better resistors even though the selected 1% types and Philips PR resistors are not of poor quality.
SHINKOH tantalum to £ 2.80 for 0.5 Watt and £ 5.50 for 1Watt is not cheap, but if there are other resistor types such as TAKMAN carbon film non-inductive, non-magnetic, 2% to £ 0.55 for 0.5 watt and 1Watt for £ 1.00 .... so there is an obvious opportunity to experiment :)

PR9372 metal films, Amtrans carbon film,Audio Note,Shinkoh,Charcroft,Takman,Arcol,Mills,Takman,Holco,Allen Bradley,duelund resistor,Kiwame carbon film,M-resist supreme resistors

I have found your Hi-Fi website at "Google Sites":
https://sites.google.com/site/httpstubeamp/

If you read this, the Mitronic PA100 is ready for further listening tests. The amplifier is very stable with the matched Hitachi SJ50/2SK135, stays under a few mV DC on the output terminals, and the first sound impression is very promising. :)
 
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