So p-p means "point to point"? "Peak to peak"? When you say crest to trough, are you talking about the visual on a scope? Have you a link to information on this term? I just can't find it and would like to get a better grasp on it. The formula I saw to figure RMS was VAC/R*VAC
Thanks, Terry
Thanks, Terry
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Terry, p-p refers to the visual you see on an oscilloscope, the highest peak to the lowest peak (or trough if you prefer). I just had a look in some of my books and found the term referenced in only Ben Duncan's book 'High Performance Audio Amplifiers'. I did find it referenced in my old college texts as well. I think the nomenclature is just treated as a standard part of general electronics lingo.
Vrms=Vp-p/(2*1.41), remember the AC RMS value represents the equivalent of the DC value for the same average dissipation into a resistive load.
It's not just a way of representing what you see on the scope, it's a way of defining the signal magnitude where there are several ways of describing the same thing.
The first is a peak to peak definition that describes the signal magnitude as described by the difference between the largest and smallest values you can measure. The signal could take the form of any shape, sine, square, saw, triangle etc.
The second would be half this value and is the reason why I always say peak to peak with my AC readings. Sometimes people specify a half value. Ie from the zero crossing point, up to the peak value. This is because in physics and mathematics the amplitude of a sine wave is described as being half the peak to peak value.
Then you've got the RMS value, which as Kindhornman mentioned means root mean square. This is a way of taking the peak value and turning it into an average value that would correspond to a DC figure. This is necessary for calculating average power levels.
Remember though that a scope is simply a graphical way of representing something we can measure in nature. Even if you don't have a scope, the sine wave signal magnitude on the output of the amplifier is still the same.
Maybe you've hooked your digital multimeter up to the output of the amplifier and you set your drive level until the meter reads 2.83vRMS. This is exactly the same as saying 8v peak to peak. All you do to convert one into the other is multiply 2.83 by 1.41, then multiply it again by 2.
Why is 2.83vRMS used? Because to calculate power you take the RMS voltage, square it, then divide by the load impedance.
In other words, 2.83x2.83 = 8.0089.
Divide this by 8 and you end up with 1. Ergo, 1 watt is being dissipated in an 8 ohm load if you can measure 2.83vRMS across it with your multimeter.
I made this IPS from a Blameless schematic posted in another thread. Can one of you take a look at it and let me know if you think it would be suitable for the Slewmaster? When I run it it seems to have about 6mA output so something probably needs to be changed to lower it. Anyway, please take a look and give me your thoughts.
Blessings, Terry
Blessings, Terry
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Hi Terry
There are a number of things about that schematic that don't look quite right to me. For example the inverse parallel diodes (D2 & D3) at the LTP collectors seem to serve no purpose except to equalise these junctions when there is a large imbalance > the diode VB drop. D1 and R33 serve no useful purpose, and the components around the VAS are a mess (bottom right corner).
Instead, may I present for your consideration the Blameless design from my thread here: http://www.diyaudio.com/forums/solid-state/253215-my-blameless.html
This represents the 'as built' design with the output stage, bias generator and other miscellaneous components stripped in order to interface with the SlewMaster board. I've adjusted R7 to supply approx. 2mA current to the LTP and adjusted R12 to optimise the current through the VAS.
Of course OStripper's Wolverine IPS in this same thread is another Blameless, with more parts and complexity, and no doubt with OStripper's design expertise, it also holds the promise of better sonics.
With that said I lent my amplifier to a friend and fellow forum member who undertook some critical listening and comparison with his favorite amplifier and this "Blameless" performed very well in his opinion.
I have spent a lot of time experimenting with the P3A, building Carlos' designs and one of Bigun's. One of the things that these very good amps all have in common is a bootstrapped VAS. I think I will play with this design further, substitute a bootstrap capacitor for the CCS and eliminate the VAS driver transistor. Terry, let me know if you are interested in seeing what I have in mind.
There are a number of things about that schematic that don't look quite right to me. For example the inverse parallel diodes (D2 & D3) at the LTP collectors seem to serve no purpose except to equalise these junctions when there is a large imbalance > the diode VB drop. D1 and R33 serve no useful purpose, and the components around the VAS are a mess (bottom right corner).
Instead, may I present for your consideration the Blameless design from my thread here: http://www.diyaudio.com/forums/solid-state/253215-my-blameless.html
This represents the 'as built' design with the output stage, bias generator and other miscellaneous components stripped in order to interface with the SlewMaster board. I've adjusted R7 to supply approx. 2mA current to the LTP and adjusted R12 to optimise the current through the VAS.
Of course OStripper's Wolverine IPS in this same thread is another Blameless, with more parts and complexity, and no doubt with OStripper's design expertise, it also holds the promise of better sonics.
With that said I lent my amplifier to a friend and fellow forum member who undertook some critical listening and comparison with his favorite amplifier and this "Blameless" performed very well in his opinion.
I have spent a lot of time experimenting with the P3A, building Carlos' designs and one of Bigun's. One of the things that these very good amps all have in common is a bootstrapped VAS. I think I will play with this design further, substitute a bootstrap capacitor for the CCS and eliminate the VAS driver transistor. Terry, let me know if you are interested in seeing what I have in mind.
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Hi Terry, as usual, adjustment of LTP's long tail current will at the same time proportionally influence the VAS quiescent current. Coming from 6mA to 4.5mA requires slight increase of R7. You can see it, running a simulation of your model.
Cheers,
Valery
You can try this http://www.diyaudio.com/forums/solid-state/186981-bootstrapsccs-t-tmc-5.html#post2589808 or this http://www.diyaudio.com/forums/solid-state/221901-little-gem.html.
Both use bootstrap VAS combined with CCS.
I don't think you can substitute a bootstrap capacitor for the CCS.
, D2,D3 serve to limit VAS current during overdrive and limitation conditions, without unstability , sticking (so ensuring fast recovery)and local oscilations like with usally used transistor driven from VAS emiter resistor. This is obsolete in your schematic, suplemented with simple current limiting 1k (R17) resistor in colector of VAS enhancer. This is maybe a simple , but a bit "suboptimal" solution..D1, R33 serve to set without input signal zero DC across D2, D3 , so during normal working conditions D2, D3 have no influnce on circuit. Try both solutions in simulation.
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@ 5th element
This is what I made to get a square wave out of my laptop.R11 can be a 20k pot if you want to get a close 50-50 duty cycle. Rise and fall times are better than my 10 MHz scope can measure. The 5V is from an old cell phone charger.
( schematic, 1k output, 1MHZ output)
This is what I made to get a square wave out of my laptop.R11 can be a 20k pot if you want to get a close 50-50 duty cycle. Rise and fall times are better than my 10 MHz scope can measure. The 5V is from an old cell phone charger.
( schematic, 1k output, 1MHZ output)
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R9 is what controls the amount of current the VAS current source supplies, so simply increasing that will adjust the VAS current to a lower value.
Once you learn to recognize the CCSs in the design for the input stage (LTP tail current source) and voltage amplifier (VAS current source) you just have to remember that altering the resistance in the emitter circuit of the CCS transistor alters the current through it.
You're right - sorry, did not notice VAS is not current-mirrored, but CCS-ed at a first quick glance. Of course, R9 is the right one.
Cheers,
Valery
That has a similar parts count to the "wolverine".
If you are building "from scratch" , the actual wolverine is the best bet.
It's dual independent CCS's and diode/semi options for saturation conditions
make it as "tame" as the CFA's in this category.
Also . it is the "next generation" badger ... which when combined with a
true EF3 ... should be deep in PPM territory - (VERY low THD).
OS