Ivan,
it seems to me that you are not comparing like to like.
A passive volume control, whether just in front of a the power amp, or just in front of a buffer should be able to perform very well when the correct component values are selected.
Adding a gain stage to that passive set up then needs extra attenuation can never be better than the passive volume control. It will have extra noise, it will have extra interference, it will have extra response anomalies, it will have stability issues if not very carefully compensated.
it seems to me that you are not comparing like to like.
A passive volume control, whether just in front of a the power amp, or just in front of a buffer should be able to perform very well when the correct component values are selected.
Adding a gain stage to that passive set up then needs extra attenuation can never be better than the passive volume control. It will have extra noise, it will have extra interference, it will have extra response anomalies, it will have stability issues if not very carefully compensated.
Any amplifier including P3A will present a problem in dynamics in low to very low listening levels . beyond other situations anything that has input Z bellow 47K will suffer from this problem .
Passive preamps will work better with a Z of 100K or above which include other type of issues except loss in dynamics .
Buffer will take you the next level and increase dynamics ( depending also in the implementation and/or position of the pot ( before or after the buffer ) while if the B1 comes in mind, to my opinion is the cleanest you will ever get .BUT it tends to round the edges just a bit . .
An active preamp will solve most of problems in dynamics , add gain where its really needed ( low levels 0 but will introduce something like noise/ distortion /phase issues /and some more . Marginal though but some more.
Key is how to make a preamp that sounds like a passive or a B1 but with click of gain for the low levels . Difficult task and it is twice as much power supply depending than the very forgiving class AB amplifiers of most topologies .
Happy regards
Sakis
Passive preamps will work better with a Z of 100K or above which include other type of issues except loss in dynamics .
Buffer will take you the next level and increase dynamics ( depending also in the implementation and/or position of the pot ( before or after the buffer ) while if the B1 comes in mind, to my opinion is the cleanest you will ever get .BUT it tends to round the edges just a bit . .
An active preamp will solve most of problems in dynamics , add gain where its really needed ( low levels 0 but will introduce something like noise/ distortion /phase issues /and some more . Marginal though but some more.
Key is how to make a preamp that sounds like a passive or a B1 but with click of gain for the low levels . Difficult task and it is twice as much power supply depending than the very forgiving class AB amplifiers of most topologies .
Happy regards
Sakis
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I know of impedance matching and other good engineering practices but it seems that extra distortions generated with active preamps is exactly what I prefer. I came to that conclusion when applied different gain settings for the same preamp. No matter how impractical it may be (high loudness level with low volume settings) I always prefer the sound of higher gain, meaning higher levels of distortion. Technically correct solutions seem too "washed out" for me. Of course, it doesn't mean that I prefer grossly distorted sound. I just need some right quantity of "spice" to it.
With B1 I am a bit confused because I have schematics with j-fet and bipolar transistors. I do not know what is correct schematics at this moment.
About Preamp
Yes, you are all correct about preamp: its benefit and drawback. What I want to add is that if you go the "no-preamp" way, all of the chain from pickup to speaker must be optimized for that option. In my own experience, the most frustrating similar task has been in trying to compensate for what has been missing with non-oversampling DAC.
Yes, you are all correct about preamp: its benefit and drawback. What I want to add is that if you go the "no-preamp" way, all of the chain from pickup to speaker must be optimized for that option. In my own experience, the most frustrating similar task has been in trying to compensate for what has been missing with non-oversampling DAC.
With j-fets at the input of any audio amplifier circuit "rounding of" the sound is unavoidable. Speaking of opamps, for that reason there is no point in using anything better or more expensive than TL072. One may spent huge amounts of money and get basically that same "rounded" sound. OP275, OPA2134 or extremely expensive OPA627 all share that same signature j-fet sound. If one likes that signature sound at all TL072 will suffice. In preamps I even like TL072 more that modern high spec j-fet opamps. But I must admit that I am not fan of that j-fet signature sound at all and yet I like to have j-fet based preamp for simple reason to experience subjective change in sound from time to time. I usually use j-fets for a couple of days and than return to bipolars for a couple of months.
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This makes good sense to me. Which means I don't understand why an active pre-amp would be needed - I read the subjective viewpoints but I'm not sure of the engineering reasons - other than ensuring the volume control doesn't roll-off the high frequencies, or isn't made from poor materials ?
Sorry
Hi everyone,...
Sakis please forgive me, we have a misunderstand few time ago in another thread. I hope you don't mind cos my English is not so good.
So I decide to build the P3A & will compare between standard and mod version, thanks for so many clues here.
I will start to make my own boards just wish me okay
Can you tell me the good value for the degeneration resistors at ltp pair?
Ivanlukic,
Hi I've just building the B1 with symmetrical psu, why don't you try it it is simple (but the parts is not so simple to search)...
I will try it with P3A too I've read that this is a good combo.
here if you wanna see B1 I've made.
Regards
Hi everyone,...
Sakis please forgive me, we have a misunderstand few time ago in another thread. I hope you don't mind cos my English is not so good.
So I decide to build the P3A & will compare between standard and mod version, thanks for so many clues here.
I will start to make my own boards just wish me okay
Can you tell me the good value for the degeneration resistors at ltp pair?
Ivanlukic,
Hi I've just building the B1 with symmetrical psu, why don't you try it it is simple (but the parts is not so simple to search)...
I will try it with P3A too
I've read that this is a good combo. here if you wanna see B1 I've made.
Regards
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Buy and read Cordell's book. He explains LTP degeneration and how to calculate different values of degeneration.............So I decide to build the P3A & will compare between standard and mod version, thanks for so many clues here.
I will start to make my own boards just wish me okay
Can you tell me the good value for the degeneration resistors at ltp pair?
..............
You can use this to select for yourself and see the benefits/demerits of each value.
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Joined 2009
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Hi Andrew, I'm too lazy to reading a book.
diyAudio is my only book
In the book also so many technical word that I can't understand correctly,
I often use google translator & you know the result not accurate.
Here I can ask you guys who know much better than novice like me.
Ok, I'm waiting
while then I must finish my pcb, parts, etc...
Kind Regards
John
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John, for the most part there are well kown benefits of degeneration, even relatively small amounts so you will find very few designs without it. The added resistance creates a voltage drop in phase with the signal current and since this voltage appears at the emitters it is like a local feedback mechanism. This reduces the overall gain of the LTP but improves it's linearity which is important since the LTP is your 'error amplifier' for global feedback. The other thing is that the fixed degeneration resistors add to the intrinsic resistance of the emitters which varies from part to part slightly so that the total effective emitter resistance of the two LTP devices are better matched - again better accuracy of the LTP as an error amplifier. The LTP tail current can be increased, which increases the transconductance of the devices, to compensate for the reduced gain that the degeneration produces. There are more subtle affects, which can also be important. The more linear LTP reduces inter-modulation distortion of the amplifier and higher tail current improves the slew-rate of the amplifier.
In simply topologies like this I found that I prefer low degeneration, in the range 10R to 33R. Some people like to really push it hard and go for very high degeneration of up to 1k with high tail current and then make up the loss in gain at other points in the amplifier. This approach gives the LTP a much wider dynamic range for linear operation but I've not tried this myself and I don't think it's well suited to the P3A topology.
In simply topologies like this I found that I prefer low degeneration, in the range 10R to 33R. Some people like to really push it hard and go for very high degeneration of up to 1k with high tail current and then make up the loss in gain at other points in the amplifier. This approach gives the LTP a much wider dynamic range for linear operation but I've not tried this myself and I don't think it's well suited to the P3A topology.
P12 ckt test
Did anyone try the P12 mentioned by Ivanlukic in the post found here http://www.diyaudio.com/forums/solid-state/164756-p3a-comparsion-table-long-19.html#post3423446
I have tried a variation of this after seeing the Leak Delta 70 and having had a good opinion of it ( long ago !). Anyone tried this version (P12) ?
My version has very good mid range and bass is good but nothing to write home about. Treble is clean but seems to lack some sparkle ! Overall nice but not great. Wonder if the P12 addresses these issues.
Did anyone try the P12 mentioned by Ivanlukic in the post found here http://www.diyaudio.com/forums/solid-state/164756-p3a-comparsion-table-long-19.html#post3423446
I have tried a variation of this after seeing the Leak Delta 70 and having had a good opinion of it ( long ago !). Anyone tried this version (P12) ?
My version has very good mid range and bass is good but nothing to write home about. Treble is clean but seems to lack some sparkle ! Overall nice but not great. Wonder if the P12 addresses these issues.
Expect a P12 to have a rich content of harmonics and present a tubish like sound while the description you placed above fits to this style of amplifiers ..
Slow ,,i think so you may never put next to each other an apple and an orange ,,,i think that these are totally different style of amps
Kind regards
Sakis
Slow ,,i think so you may never put next to each other an apple and an orange ,,,i think that these are totally different style of amps
Kind regards
Sakis
Hi sakis
After listening to the amp for the past 2 weeks, my observations of sound impressions is the same as what you wrote in the first post !
The amp gives a new perspective to most of my music collection.
My new fullranger speaker build seems less important now !!
many thanks to all the contributors of this thread.
kp93300
After listening to the amp for the past 2 weeks, my observations of sound impressions is the same as what you wrote in the first post !
The amp gives a new perspective to most of my music collection.
My new fullranger speaker build seems less important now !!
many thanks to all the contributors of this thread.
kp93300