My recollection is an ft of 4mhz is more or less a min for the power transistors. Indirectly it relates to the slew rate needed to produce a pure sine wave. Bandwidth. Higher levels of gain should help rather than hinder as his info on this in respect to distortion shows.
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As he mentions the critical spec wise transistor is the driver. No adequate substitute as he puts it, Min ft of one of the suggestions is 60mhz,. The other one is a gain selected part. The 2N697, highest of a pair.
Plastic over metal. Max junction temp is reduced. Can't be sure but it looks like Hood used some that could be bought predrilled for TO3 that were ~4C/Watt or drill yourself versions that were readily available. He doesn't give sizes so can't be sure. I've used these myself. It's pretty easy to do better these days even at a smaller size. The sums do need doing what ever transistors are used.
One thing Mr Hood's quaint construction method does is minimise stray capacitance effects if done with a reasonable amount of thought. I wouldn't have thought this would be a problem on this design but when on a pcb it's much harder to be sure as it will depend on the layout more.
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As he mentions the critical spec wise transistor is the driver. No adequate substitute as he puts it, Min ft of one of the suggestions is 60mhz,. The other one is a gain selected part. The 2N697, highest of a pair.
Plastic over metal. Max junction temp is reduced. Can't be sure but it looks like Hood used some that could be bought predrilled for TO3 that were ~4C/Watt or drill yourself versions that were readily available. He doesn't give sizes so can't be sure. I've used these myself. It's pretty easy to do better these days even at a smaller size. The sums do need doing what ever transistors are used.
One thing Mr Hood's quaint construction method does is minimise stray capacitance effects if done with a reasonable amount of thought. I wouldn't have thought this would be a problem on this design but when on a pcb it's much harder to be sure as it will depend on the layout more.
And I would like to point out three important things:
a) TO-3 transistors are the worst sounding. This is due to the shape of the package.
b) to achieve maximum "symmetry" and homogeneity, use the same transistors for TR 1, TR2, TR3 (original scheme).
c) leave out the bootstap capacitor (C1). This is a real sound obstruction. It is one rotten teeth of this circuit;-)-;
a) TO-3 transistors are the worst sounding. This is due to the shape of the package.
b) to achieve maximum "symmetry" and homogeneity, use the same transistors for TR 1, TR2, TR3 (original scheme).
c) leave out the bootstap capacitor (C1). This is a real sound obstruction. It is one rotten teeth of this circuit;-)-;
Regarding the ST MJ15003 ... I'm not sure that ST sell these devices in TO-3 any longer. There is no reference on their website, so, gone, along with their 2N3055, and possibly all of their TO-3 assemblies. The TIP3055 with 3MHz ft is probably the closest now in TO-247.
Their website mentions a second generation of base island technology, so without an up to date datasheet of ST's MJ15003, it is hard to say what its thermal performance will be. And really folks should look at the datasheets to answer many of the questions we see raised. The websites of the manufacturers will usually show whether devices are still active or "NRND".
Though I have to add that recent datasheets sometimes do not contain as much information that earlier ones did, and you don't get everything you really need to know from the datasheet to determine some SPICE parameters - so I would also add that if a SPICE model is provided that may give more information. But ... there are still some characteristics like quasi-saturation which aren't fully documented so may not appear in simulations, nor breakdown characteristics for example.
Their website mentions a second generation of base island technology, so without an up to date datasheet of ST's MJ15003, it is hard to say what its thermal performance will be. And really folks should look at the datasheets to answer many of the questions we see raised. The websites of the manufacturers will usually show whether devices are still active or "NRND".
Though I have to add that recent datasheets sometimes do not contain as much information that earlier ones did, and you don't get everything you really need to know from the datasheet to determine some SPICE parameters - so I would also add that if a SPICE model is provided that may give more information. But ... there are still some characteristics like quasi-saturation which aren't fully documented so may not appear in simulations, nor breakdown characteristics for example.
If you leave out the bootstrap capacitor you will limit the output power because of premature clipping, and make the driver transistor have to increase it's current deviation to obtain what output you can get. That means higher distortion.
You might have meant replace it by a CCS, but that is not what you said.
You might have meant replace it by a CCS, but that is not what you said.
From memory and using a scope the bootstrap allow the drive to go very close to the rail. He mentions that the value needs changing if the low frequency end needs extending. As work and plenty of kit available it's a pity a current probe wasn't used as well.
How does it work though. There is a specified loudspeaker impedance also supply voltage and changes in some values. Not any ohmage of any speaker you might want to connect. The speaker is part of the circuit. On class B that doesn't apply at all in a trival sense. One this amp it does.
How does it work though. There is a specified loudspeaker impedance also supply voltage and changes in some values. Not any ohmage of any speaker you might want to connect. The speaker is part of the circuit. On class B that doesn't apply at all in a trival sense. One this amp it does.
The man's name is Andrei, he is 31 years old. A director by education, a programmer by profession, he is engaged in the development of computer games. He appointed a meeting in a backyard in the courtyard along Palantaya Street. According to him, this is a favorable place, which is exposed to minimal electromagnetic radiation. At the meeting, he asked to put the phone in airplane mode, and measured the background with his device. Making sure that everything was in order, he told his story...
https://pg12.ru/news/73642
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Better in what way? Sure, TIP35 can deliver more current, handle higher peak loads but how about linearity at 1 amp? Neither type is particulary good but TIP35/36 are not really suitable for good quality audio amplification at all - unless you just want the loudest noise for the lowest cost. However, we are discussing an amplifier design that's said to be among the best, if not the best for sound quality at very low cost. That should be our priority or choose another design that is specified for TIP35 or 36 by someone with suitable technical qualifications.
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The TIP35 datasheet I have shows that the gain holds up a little better than the 3055 between 1 and 2 A - probably because it has a higher current capability. It may, therefore, be slightly better than a 3055, but marginal I suspect. It really depends on the 3055's that you have got, NanoFarad. If they are epi they should have ft's of >= 2.5MHz while the TIP35 are rated at >=3MHz, which probably means they will sound the same. Also the gains are probably around the 100 mark at 1A - that will depend on the manufacturer though. ON Semi's I have measured have been very close to typical (150) ; others (including the old RCA original) have had lower gains. I have also measured ON Semi fhfe's at 60kHz and as that is above audio, 3055 epi devices should work OK in the JLH design, and I suspect TIP35's won't be very different. If you plan to use 4 ohm speakers then the TIP35 may be the better choice. As mentioned earlier in this thread, JLH seemed to imply that the distortion was the same for all loads; but his reference was 15 ohms from my reading of the original article. For 4 ohm loads, higher current transistors with higher gain at high current would be beneficial.
Note that the minimum gain of a TIP35 is only 25 at 1.5A - so you could have low gain devices still meeting spec!
Note that the minimum gain of a TIP35 is only 25 at 1.5A - so you could have low gain devices still meeting spec!
I think the problem is further complicated because these and other old favourite power semi types are still around in various forms - some are even offered by major global distributors, others only appear in certain regions. Otherwise, they they keep reappearing as fakes of one kind or another, perhaps with an unrecognized brand, scant documentation and a simplified, generic datasheet which tells you little more than basic parameters that could fit almost any other BJT than the one in your hand
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For any of you with a long memory and still enjoy a laugh, you may recall these original style, alleged TO218 versions of TIP35. They are actually in a TOP-3 package which was intended by TI to replace typical, lightly loaded TO3 power transistors without also needing to replace or fettle heatsinks. TOP-3 style was then superseded by TO218 and now we have TO247 style packages so the product must be NOS and over 30 years old but it looks like someone picked the wrong image or recently found a stash of them and figured they'd make a handsome profit here in Oz!
https://www.jaycar.com.au/tip35c-np...ohb77PGEhT_Mf-7OZVl0q6h2N7O_7wZxoC89oQAvD_BwE
https://www.jaycar.com.au/tip35c-np...ohb77PGEhT_Mf-7OZVl0q6h2N7O_7wZxoC89oQAvD_BwE
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