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Old 3rd April 2010, 04:10 AM   #51
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then your 2 x 60 V, 5 A transformer will do just fine.
this part I needed. as per ur diagram I am going to assemble one. i want to know how much ampeare needed for smooth running. thankyou tom sir for spenting ur valuable time for me.................

manu
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Old 3rd April 2010, 10:12 AM   #52
AndrewT is offline AndrewT  Scotland
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the general rule is that the transformer VA be roughly between the maximum output power and twice the maximum output power.
A 60+60Vac 5Aac transformer, i.e. 600VA, will successfully power between 300W and 600W of total maximum output power.

But this is not a work/not work rule.
The transformer will be able to power amplifiers outside the 300 to 600W range
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regards Andrew T.
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Old 6th April 2010, 06:34 PM   #53
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Default Musical Fidelity Titan bias

I think that Musical Fidelity are using a very simple solution. Looking at the picture of the Titan amp there is on pot per row of transistors. (the lower row can not bee seen in the picture) The amp consists of two amps i bridge configuration per channel. This bias solution will give the advantage of low cross over distortion as each row of transistors, 5 in each row, will be adjusted separatly. I think the pot is just connected to V+ (V- lower row) and the diodes in the 5 transistors in series and then to ground. Comments?
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Old 28th May 2010, 03:38 AM   #54
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Default Join the party

Just got ten pairs of STD03N/03P. Excited to get start!
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Old 29th May 2010, 08:01 PM   #55
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Hi Pansons,

I am very curious how you will like them.

Subjectively and personally speaking, I prefer the STD mid-highs over the termaltrak's. For me in combination with the LME49810, the STD's sound faster, deeper and more alive (very analytical and detailed). On the contrary, I like the bass tightness and control better with the termaltrak's or the BPA300 chip designs. Of course it is all about implementation, But this are my observations with the same kind of implementation for all devices.

The STD03's are not easy devices and kind of limited in application.
I suggest if you work with the LME49810 as driver you make two variable bias adjusting points. One for the bias pins on the LME49810 (900 ohm fixed with 300 ohm variable in series) and a second variable one of 200 ohm between the diode string. The resistor value for the bias pins of the LME49810 is around 1K to obtain the 2.5mA pre bias current. But slight variations in this resistor make the whole bias to rise or slow significant till a degree that there can be danger or under bias. Therefor you want to fine adjust this value. Please trust me on this, I've bin there done it, and blow them twice A good note is, that a STD03 blows friendly and softly, and often break inside the die even before the fuse blows. So no spectacles

Good luck! And I look very forward to your measurements and listening impressions.

With kind regards,
Bas
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Old 31st May 2010, 03:53 AM   #56
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Quote:
Originally Posted by Sebastiaan View Post
Hi Pansons,
The STD03's are not easy devices and kind of limited in application.
Hi Bas,

Thank you very much for your valuable advices.

I initially will use 49811 with one pair 03N/03P. Referring to your schematic shown in post 3 of the thread, you put caps C11 and C12 across the base pins. Did you put them there in concept design stage? Or trail and error? I find that without cap my test unit will oscillate when loaded by just a small cap, 270 pF//8 Ohm. The waveform is shown below. I did not encounter such problem with ThermalTrak. Is it because of the super high current gain of 03N/P?

The test unit and its THD+N vs freq for 18W/50W into 8 Ohm are shown below.

Panson
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File Type: jpg oscillate with cap load.JPG (139.5 KB, 721 views)
File Type: jpg Test Unit.JPG (94.1 KB, 689 views)
File Type: jpg THD+N vs freq.JPG (84.4 KB, 670 views)
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Old 31st May 2010, 12:21 PM   #57
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Quote:
Originally Posted by panson_hk View Post
Hi Bas,

Thank you very much for your valuable advices.

I initially will use 49811 with one pair 03N/03P. Referring to your schematic shown in post 3 of the thread, you put caps C11 and C12 across the base pins. Did you put them there in concept design stage? Or trail and error? I find that without cap my test unit will oscillate when loaded by just a small cap, 270 pF//8 Ohm. The waveform is shown below. I did not encounter such problem with ThermalTrak. Is it because of the super high current gain of 03N/P?

The test unit and its THD+N vs freq for 18W/50W into 8 Ohm are shown below.

Panson
Dear Panson,

If I understand you well, if you put "any" cap between the base pin's you get oscillation?

My attempt with putting those cap's is to improve switching behavior of the transistors. But that I have no experience with the LME49811. I never tried it without those capacitor, and I have to admit I got this Idea from Arcam, who does the same trick in the P1 amplifier. See attachment.

Maybe the LME49811 doesn't like this capacitive load.

The second attachment is square wave reproduction with the cap's on a resistive load on my actual design. The compensation here was only 10pF but I have to admit this was on the edge! With some messy loudspeaker leads I got oscillation as well. This was solved however with going safe with 22pF.

With kind regards,
Bas
Attached Images
File Type: png Screen shot 2010-05-31 at 2.16.52 PM.png (86.7 KB, 670 views)
File Type: jpg Screen shot 2010-05-31 at 2.22.05 PM.jpg (61.4 KB, 392 views)

Last edited by Sebastiaan; 31st May 2010 at 12:25 PM.
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Old 31st May 2010, 01:08 PM   #58
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Quote:
Originally Posted by Sebastiaan View Post

If I understand you well, if you put "any" cap between the base pin's you get oscillation?

Hi Bas,

Without cap between the base pins, I get oscillation with capacitive load.

Today, I read a Chinese article reviewing Musical Fidelity A1 2008 edition. The amp uses one-pair STD03N/03P per channel. According to reverse engineered schematic, it does not have such cap surrounding 03N/03P. The bias generation consists of the 03N/03P diodes in series with two 1N4007 and a 200 pot. The emitter resistor is 0.22 R. Bias current is about 600 mA.

Article link http://home.hdavchina.com/space.php?...4465&goto=down

Panson

Last edited by panson_hk; 31st May 2010 at 01:11 PM.
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Old 31st May 2010, 06:30 PM   #59
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Quote:
Originally Posted by panson_hk View Post
Hi Bas,

Without cap between the base pins, I get oscillation with capacitive load.

Today, I read a Chinese article reviewing Musical Fidelity A1 2008 edition. The amp uses one-pair STD03N/03P per channel. According to reverse engineered schematic, it does not have such cap surrounding 03N/03P. The bias generation consists of the 03N/03P diodes in series with two 1N4007 and a 200 pot. The emitter resistor is 0.22 R. Bias current is about 600 mA.

Article link 无线电与电视10Y04 (8) - 《无线电与电视》2010 第4期 - 相册 - admin - 影音中国 — 影音爱好者的家园 - 大型影音爱好者、家庭影院、电影、CD碟片玩家、DIY胆 婕摇IFI发烧友的互动平台。

Panson
Dear Panson,

Thank for this link, can you point me to the part where they show the schematic? It is a labyrinth for me If someone has lot's of experience with those sanken's then it must be Musical Fidelity, since they use them for for ages

Furthermore, Did you use/try small compensation cap's between base and collector? I got oscillations without them. You can try base stoppers of a few ohm.

I think the system shouldn't oscillate without capacitance, so to be honest it is a mystery for me as well but I think parasitic's play a part, combine that with the huge total hFE of the Sanken's u can get in trouble faster then you wish for. In my case my amplifier self destruct itself a few times, but all of that was solved after increase the miller cap to 22pF, And adding 47pF compensation between base and collector. In my case the oscillation also happened with capacitive loads caused by different type of speaker wire. That is why I said the STD3's can be a bit difficult to tame

With kind regards,
Bas

Last edited by Sebastiaan; 31st May 2010 at 06:34 PM.
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Old 1st June 2010, 03:01 AM   #60
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Quote:
Originally Posted by Sebastiaan View Post
Dear Panson,

Thank for this link, can you point me to the part where they show the schematic? It is a labyrinth for me If someone has lot's of experience with those sanken's then it must be Musical Fidelity, since they use them for for ages

Furthermore, Did you use/try small compensation cap's between base and collector? I got oscillations without them. You can try base stoppers of a few ohm.

I think the system shouldn't oscillate without capacitance, so to be honest it is a mystery for me as well but I think parasitic's play a part, combine that with the huge total hFE of the Sanken's u can get in trouble faster then you wish for. In my case my amplifier self destruct itself a few times, but all of that was solved after increase the miller cap to 22pF, And adding 47pF compensation between base and collector. In my case the oscillation also happened with capacitive loads caused by different type of speaker wire. That is why I said the STD3's can be a bit difficult to tame

With kind regards,
Bas
Hi Bas,

The schematic is shown in another issue which is not available from the website. I can scan it and e-mail to you. Please let me know your e-mail address.

I have base stopper resistors already, but did not try putting cap across C and B pins. This is effectively adding a Miller cap in the output stage for which I don't feel "right". I might do that eventually for this Sanken part and/or other high-gain Darlington.

I am in line with you that the amp (simple topology) should not have so many caps around.

Cheers,
Panson
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