The damping resistor in parallel with the inductor becomes the load. The capacitor across the speaker terminals (or immediately after the inductor) limits the bandwidth over which the load is effective.
N.Thiele was not daft. I'm sure that both Leach and Cherry recognised how this alternative worked.
N.Thiele was not daft. I'm sure that both Leach and Cherry recognised how this alternative worked.
Here is some more info as contributed by Andrew and Jonathan
http://www.diyaudio.com/forums/solid-state/302658-universal-thiele-circuit.html#post4961785
Reg
Prasi
http://www.diyaudio.com/forums/solid-state/302658-universal-thiele-circuit.html#post4961785
Reg
Prasi
There's no PCBs in the Forum shop. I am still waiting for the Email to say they are back in stock.
Month's not over yet according to http://www.diyaudio.com/forums/solid-state/192431-diyab-amp-honey-badger-172.html#post5033354 .
I doubt you will ever get an email, you could start checking the store after one month's over...
reg
Prasi
The quoted link works for me, I am not responsible if it doesn't work for you, check your settings!
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amen, in a local forum, one guy made a redesign using 8 pairs of outputs,
dc protection and speaker delays on board....
and in keeping whith Ostripper's latest works, made a split up version...
PCBs are now back in the store: https://diyaudiostore.com/collections/printed-circuit-boards/products/honey-badger
Design Related Questions
In general, is the schematic dated 7/17/11 still correct for currently made boards?
Undoubtedly mentioned somewhere in this encylopeadic reference is commentary on the adjustable current source. What is the technical justification for a CCS adjustment? Is this feature added in order to accomodate various transistor types for the VAS?
What benefit was expected/realized by adding the cascode stage to the input? How would cascoding be superior to, for example, no cascoding and the use of a 3 or 4 transistor current mirror instead?
I would like to use 4 outputs instead of 6. Would the value of R36 need to be adjusted? Anything in the Zobel network need to be changed?
I notice that there are a lot of people tweaking and altering the original circuit. What is the designer's view on alternate configurations?
Thank you,
RestAssured
In general, is the schematic dated 7/17/11 still correct for currently made boards?
Undoubtedly mentioned somewhere in this encylopeadic reference is commentary on the adjustable current source. What is the technical justification for a CCS adjustment? Is this feature added in order to accomodate various transistor types for the VAS?
What benefit was expected/realized by adding the cascode stage to the input? How would cascoding be superior to, for example, no cascoding and the use of a 3 or 4 transistor current mirror instead?
I would like to use 4 outputs instead of 6. Would the value of R36 need to be adjusted? Anything in the Zobel network need to be changed?
I notice that there are a lot of people tweaking and altering the original circuit. What is the designer's view on alternate configurations?
Thank you,
RestAssured
To answer a couple of my own questions...
RestAssured[/QUOTE]
I think this is correct. Also this technique is used to balance a differential load arrangement which this design is not.
Simply put, you can't get high gain transistors and high C-E voltage specs in the same part. Use high gain transistors with maybe 45 volts C-E, then add a cascode stage to dump the rest of the voltage. Otherwise you are stuck with a 300 volt MPSA42 working at some unknown gain of 40 to 100 if you are lucky. And you have a job ahead of you if you want to select a matched pair. Same explanation for the VA stage.
RestAssured[/QUOTE]
As an ignorant followup question - one that I have not seen addressed in this forum - is the subject of power up behavior. We are all familiar with what happens in the power supply at turn-on and the heavy current inrush due to toroid physics and due to empty filter caps. What general assumptions are made to specify transistor voltages so that parts will not smoke at power-up? Should we assume that the input differentials and the VAS transistors could individually be subjected to the full rail-to-rail voltage even for an instant? Thus if +/- 60 volt rails are used, must the transistors all be able to withstand at least 120-150 volts. I've seen the results of poor design choices in commercial amps like this. Smoked parts when using the power switch. Works fine if brought up slowly on the variac. Naturally the problem was not seen in production testing because each amp powers up differently based upon part tolerance.
RA
RA
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Regarding power-up.... people forget the (front-end) resistors on the rails, V2.2 I think (R32/R33 1/2W) 22R and 220uF have to charge up to 60V during power up. So a 17W few msec inrush on LTSpice sim, not sure what people are using but careful the resistors can fail open circuit. Old carbon comps can handle this 34X overload but metal films are in a gray area I think.
Attachments
Who Specified the Drill Sizes?
Purchased a couple of new boards that are now available again. Goof-up in the pcb drill size for a majority of the holes. My usual stock of Mouser 1/4w 1% resistors have leads that are .022" in diameter. These leads will NOT go through the pcb holes. I know, there are micro-sized 1/4w resistors with smaller leads, but why specify such teeny holes when it is totally unnecessary?
To do this right, the holes for 1/4w resistors have to be re-drilled with a #72 or #73 drill. I haven't done any transistors yet. With drills this size, buy a handful because they snap easily if you don't hold them pefectly square to the work.
Another thing I have noticed about Eagle and other board software. The libraries specify nearly the exact length of a part - such as a resistor - whilst ignoring the physical realities of lead bending. Just look at the silk screen. The correct picture is there, and the holes are drilled next to the end caps. The given hole-to-hole distances of resistors and many other parts assume that the lead can be bent at 90 degrees right at the end cap. That is a quick way to crack the end caps and can make a resistor intermittant or open. Perhaps little attention has been paid to this problem because it is assumed that all new designs will be SMD.
RA
Purchased a couple of new boards that are now available again. Goof-up in the pcb drill size for a majority of the holes. My usual stock of Mouser 1/4w 1% resistors have leads that are .022" in diameter. These leads will NOT go through the pcb holes. I know, there are micro-sized 1/4w resistors with smaller leads, but why specify such teeny holes when it is totally unnecessary?
To do this right, the holes for 1/4w resistors have to be re-drilled with a #72 or #73 drill. I haven't done any transistors yet. With drills this size, buy a handful because they snap easily if you don't hold them pefectly square to the work.
Another thing I have noticed about Eagle and other board software. The libraries specify nearly the exact length of a part - such as a resistor - whilst ignoring the physical realities of lead bending. Just look at the silk screen. The correct picture is there, and the holes are drilled next to the end caps. The given hole-to-hole distances of resistors and many other parts assume that the lead can be bent at 90 degrees right at the end cap. That is a quick way to crack the end caps and can make a resistor intermittant or open. Perhaps little attention has been paid to this problem because it is assumed that all new designs will be SMD.
RA
So far I have only had to drill three holes oversize to fit 18 off (36 lead ends) 0.6W metal film resistors.
But I agree the holes are far too small, another 0.1mm bigger (0.7mm instead of 0.6mm and then through plated) would be more universal. And the pin pitch is too tight. Another 1.27mm, or even 2.54mm longer to allow gentle bending of the resistor lead outs.
And the top side of all the through plated holes have no pad specified.
This PCB needs to be revised, before the next order is placed.
But I agree the holes are far too small, another 0.1mm bigger (0.7mm instead of 0.6mm and then through plated) would be more universal. And the pin pitch is too tight. Another 1.27mm, or even 2.54mm longer to allow gentle bending of the resistor lead outs.
And the top side of all the through plated holes have no pad specified.
This PCB needs to be revised, before the next order is placed.
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The boards are the same as they have ever been, and when last asked, OSTripper said no modifications were required. I'm sorry your resistors don't fit! Andrew's suggestions have now been officially noted in our back-end documentation system. We'll try to get him to update the file for the next PCB order (which won't be for quite a while). In the meantime, yes, you'll need to work around the issue.
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I now have all the resistors fitted and only 4 holes need to be drilled out to a slightly bigger size. Maybe extra solder on the resistor leads?
The through hole plating is probably bringing the clear hole size down to ~0.55mm
This is perfect for signal diodes and small zeners. But too small for the majority of resistors. Some of my non power resistor stock use 0.6mm and 0.7mm wire leads.
There are no problems with any of the power resistors holes. Actually some of the power resistor holes are possibly a bit too big.
The 0.1" pitch socket pins that I have measure 0.51mm diameter and fit easily into the small transistor holes and into the small capacitor holes.
This seems to confirm that the through plated holes are ~0.55mm after plating.
The through hole plating is probably bringing the clear hole size down to ~0.55mm
This is perfect for signal diodes and small zeners. But too small for the majority of resistors. Some of my non power resistor stock use 0.6mm and 0.7mm wire leads.
There are no problems with any of the power resistors holes. Actually some of the power resistor holes are possibly a bit too big.
The 0.1" pitch socket pins that I have measure 0.51mm diameter and fit easily into the small transistor holes and into the small capacitor holes.
This seems to confirm that the through plated holes are ~0.55mm after plating.
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Since we are dealing with CNC equipment, AND we know that a specific run of boards all go through the same process machinery there cannot be significant variations in hole sizes from one board to the next.
More likely, there are subtle variations in the lead diameter of various brands of resistors. The rest of the world can live with this lead size variation because correctly specified lead holes make allowance for these tolerances. So, simply stating that only a certain percent of the holes have to be drilled out just makes my point. A .022" lead will not fit into a .022" hole. Obviously the Eagle library for this type of resistor needs some tweaking for larger hole spacing and larger hole diameter. Nobody from the previous run noticed this little problem?
RA
More likely, there are subtle variations in the lead diameter of various brands of resistors. The rest of the world can live with this lead size variation because correctly specified lead holes make allowance for these tolerances. So, simply stating that only a certain percent of the holes have to be drilled out just makes my point. A .022" lead will not fit into a .022" hole. Obviously the Eagle library for this type of resistor needs some tweaking for larger hole spacing and larger hole diameter. Nobody from the previous run noticed this little problem?
RA
Ostripper's boards have big pads, so that soldering resistors unto pads is no problem, most holes are plated thru holes, drilling thru them might harm those...
i solder components off the boards by at least an eighth of an inch in my builds to give them air circulation all around their body...higher wattage resistors gets more clearance...
i solder components off the boards by at least an eighth of an inch in my builds to give them air circulation all around their body...higher wattage resistors gets more clearance...
Purchased a couple of new boards that are now available again. Goof-up in the pcb drill size for a majority of the holes. My usual stock of Mouser 1/4w 1% resistors have leads that are .022" in diameter. These leads will NOT go through the pcb holes. I know, there are micro-sized 1/4w resistors with smaller leads, but why specify such teeny holes when it is totally unnecessary?
To do this right, the holes for 1/4w resistors have to be re-drilled with a #72 or #73 drill. I haven't done any transistors yet. With drills this size, buy a handful because they snap easily if you don't hold them pefectly square to the work.
Another thing I have noticed about Eagle and other board software. The libraries specify nearly the exact length of a part - such as a resistor - whilst ignoring the physical realities of lead bending. Just look at the silk screen. The correct picture is there, and the holes are drilled next to the end caps. The given hole-to-hole distances of resistors and many other parts assume that the lead can be bent at 90 degrees right at the end cap. That is a quick way to crack the end caps and can make a resistor intermittant or open. Perhaps little attention has been paid to this problem because it is assumed that all new designs will be SMD.
RA
I totally agree that the holes are too small. I think I've reported this already a while ago (have to admit I can't remember where, maybe via the online store feedback thingy?). I ended up drilling all resistor holes because it was a PITA hit-and-miss when fitting the resistors (I mostly used Dale CMF).