It’s just that delay and reverb synthesis are still different concepts, when your keyboard will be like this parameters as predelay / early reflections / reverberant field / tail , then we’ll discuss what kind of unsuccessful keyboard you have))). but this is a conversation about nothing. I don't press any keys to get the reverb effect))),
I simply subjectively evaluate the sound of music through an amplifier.
The digital processor appeared back in 1978, and are still actively used together with plugins..
@Hennady Kovalsky when you feel your design(s) are final versions I would like you to compare and comment on late member Diego's DLH amp. That will be my first amp build, if I ever get to it, since I enjoyed following him too and Im now in possession of two boards.
No pressure and only if you have time to kill:
https://www.diyaudio.com/community/threads/dlh-amplifier-the-trilogy-with-plh-and-jlh-amps.311567/
Cheers!
No pressure and only if you have time to kill:
https://www.diyaudio.com/community/threads/dlh-amplifier-the-trilogy-with-plh-and-jlh-amps.311567/
Cheers!
the reason for the question was that the modified version of the amplifier sounds different from the original version from 2005, which I assembled earlier, and I still remember how it sounded.
Here is a comparison in the attachment, and this is an option with an output capacitor versus a bipolar one and almost twice the supply voltage:
And here it is naturally not a matter of “sticking” keys on the keyboard))).
And the fact that the modified version with an output capacitor and unipolar power supply in the model already “outperforms” the original 2005 version in terms of distortion level is a real reason to think about the prospects of the modified version for improving sound quality.
as well as the option with a mosfet output with a "current dumping bridge":
Here is a comparison in the attachment, and this is an option with an output capacitor versus a bipolar one and almost twice the supply voltage:
And here it is naturally not a matter of “sticking” keys on the keyboard))).
And the fact that the modified version with an output capacitor and unipolar power supply in the model already “outperforms” the original 2005 version in terms of distortion level is a real reason to think about the prospects of the modified version for improving sound quality.
as well as the option with a mosfet output with a "current dumping bridge":
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Certainly
Option 1 is now assembled:
How it turns on and off is absolutely inaudible.
the sound appears as if from nowhere, because... I can tell that the amplifier is turned on only by the LED, which is actually why I installed it.
Subjective sound -
*voice is highlighted and in the foreground, all the small nuances can be heard,
*in one of the compositions I heard a xylophone in the “background”, and only in the right channel, which only played along; I did not pay attention to this on other amplifiers.
* reverb processing is very audible, if you don’t pay attention it doesn’t distract at all, I just noted the greater intelligibility of this effect compared to other amplifiers. ,
*very “subtle high frequencies, which are rather synthesized artificially, because I myself have a musical education and played in a group, so I know how the instruments sound and how the sound engineer sets them up.
listening power rarely exceeds 4 watts
Acoustics 2-way, reference, sensitivity 91dB, impedance 8 ohms, low-frequency speaker with phase-equalizing "bullet", tweeter - silk, wires 2x2.5mm.sq. Supra Classic.
See photos of the assembly of the blocks of this amplifier and its modifications earlier in the topic.
Option 2 is now in its original form:
As it turns on and off, you can hear the click of the speaker protection relay.
On power transistors 3055, after about an hour small wheezing appeared at medium frequencies, I increased the current to the maximum - this effect did not go away, it was decided to replace it with power transistors 15003.
After replacing all the pairs on two channels, I began to play a little brighter at the top, but after about an hour, barely audible wheezing still appeared, I decided to redo the compensation, it became better, but the voltage at the amplifier output began to fluctuate, then +10mV, then -15mV, then after an hour +30mV, you set it to 0, close the lid and after about an hour it starts to run again, the current was brought up to 2.5A, so it was impossible to touch the radiator, it more or less stabilized on the contrary when the current decreased to 1.5 A, but At full power, the protection of one of the channels began to turn on, again overcompensated, everything returned to normal.
I compared the subjective sound with a tube amplifier (I think GM 30 - I could be wrong), something very ultra-linear. In general, the quality of the JLH 2005 was not comparable to a tube amplifier.
Next, I decided to replace a pair of power transistors with 4 pairs of output transistors, it became better - the wheezing went away, but I was already tired of the amplifier itself, so I got rid of it at the first opportunity; it had expensive rhodium-plated wires and connectors, and also high-quality selected transformers with interwind shield and Goss Band.
according to the 3rd option - only the model, the parameters were oriented according to the first modified option from the topic.
When I finish with the first option - I’ll design a case for it and select some parts, then most likely I will try the 3rd option, because there are fewer changes in the ready-made JLH 2005 kit (clone)
Option 1 is now assembled:
How it turns on and off is absolutely inaudible.
the sound appears as if from nowhere, because... I can tell that the amplifier is turned on only by the LED, which is actually why I installed it.
Subjective sound -
*voice is highlighted and in the foreground, all the small nuances can be heard,
*in one of the compositions I heard a xylophone in the “background”, and only in the right channel, which only played along; I did not pay attention to this on other amplifiers.
* reverb processing is very audible, if you don’t pay attention it doesn’t distract at all, I just noted the greater intelligibility of this effect compared to other amplifiers. ,
*very “subtle high frequencies, which are rather synthesized artificially, because I myself have a musical education and played in a group, so I know how the instruments sound and how the sound engineer sets them up.
listening power rarely exceeds 4 watts
Acoustics 2-way, reference, sensitivity 91dB, impedance 8 ohms, low-frequency speaker with phase-equalizing "bullet", tweeter - silk, wires 2x2.5mm.sq. Supra Classic.
See photos of the assembly of the blocks of this amplifier and its modifications earlier in the topic.
Option 2 is now in its original form:
As it turns on and off, you can hear the click of the speaker protection relay.
On power transistors 3055, after about an hour small wheezing appeared at medium frequencies, I increased the current to the maximum - this effect did not go away, it was decided to replace it with power transistors 15003.
After replacing all the pairs on two channels, I began to play a little brighter at the top, but after about an hour, barely audible wheezing still appeared, I decided to redo the compensation, it became better, but the voltage at the amplifier output began to fluctuate, then +10mV, then -15mV, then after an hour +30mV, you set it to 0, close the lid and after about an hour it starts to run again, the current was brought up to 2.5A, so it was impossible to touch the radiator, it more or less stabilized on the contrary when the current decreased to 1.5 A, but At full power, the protection of one of the channels began to turn on, again overcompensated, everything returned to normal.
I compared the subjective sound with a tube amplifier (I think GM 30 - I could be wrong), something very ultra-linear. In general, the quality of the JLH 2005 was not comparable to a tube amplifier.
Next, I decided to replace a pair of power transistors with 4 pairs of output transistors, it became better - the wheezing went away, but I was already tired of the amplifier itself, so I got rid of it at the first opportunity; it had expensive rhodium-plated wires and connectors, and also high-quality selected transformers with interwind shield and Goss Band.
according to the 3rd option - only the model, the parameters were oriented according to the first modified option from the topic.
When I finish with the first option - I’ll design a case for it and select some parts, then most likely I will try the 3rd option, because there are fewer changes in the ready-made JLH 2005 kit (clone)
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I will present a slightly different type of circuit that implements the most symmetrical control of power transistors of the same conductivity.
Adding a common-mode current stabilizer allows you to reduce the current of the output power transistors by 30%.
The common-mode stabilizer is implemented on the second operational amplifier of the OPA2132 assembly; the task of the common-mode current stabilizer is to monitor the symmetry of the initial current of the output stage for high-level signals. In pure A class, for this it is necessary to increase the initial current with a margin. There is no need to do this with in-phase stabilization.
No matter how strange it may be, in terms of its parameters and operating algorithm, the circuit is similar to the JLH topology with the difference that the main amplification is carried out by the operational amplifier, and the common-mode stabilizer eliminates parasitic current modulation at high signal levels. In principle, this can be seen from the distortion; an increase in power does not lead to a significant increase in distortion.
According to the scheme itself:
Adding a common-mode current stabilizer allows you to reduce the current of the output power transistors by 30%.
The common-mode stabilizer is implemented on the second operational amplifier of the OPA2132 assembly; the task of the common-mode current stabilizer is to monitor the symmetry of the initial current of the output stage for high-level signals. In pure A class, for this it is necessary to increase the initial current with a margin. There is no need to do this with in-phase stabilization.
No matter how strange it may be, in terms of its parameters and operating algorithm, the circuit is similar to the JLH topology with the difference that the main amplification is carried out by the operational amplifier, and the common-mode stabilizer eliminates parasitic current modulation at high signal levels. In principle, this can be seen from the distortion; an increase in power does not lead to a significant increase in distortion.
According to the scheme itself:
- operational amplifier high-speed dual
- X3 - current adjustment within 660-700mA
- resistor R14 is connected to the stabilized negative supply of the operational amplifier. ( R6 denomination reduced into account the load through R14).
- output power transistors Mosfets IRFP240
Of all three, I only know Mikhael Wiederhold))
The input of the output stage is probably similar to Nikitin's version from an English company, but our implementation is different.
I came up with the common mode stabilizer circuit myself while I was having lunch)))
This means JLH of the modified version in this topic.
Actually, it’s not the same and neither from there.
Nikitin made diagrams for Akulinichev when was a student, Then he moved to England (Creek)
Dear Hennady,
Your flood of ideas is impressive and immediately comprehensible.
But I always end up back at the beginning of the journey and return to the simplest topology, from which Douglas Self, with his recipe and dimensioning instructions, extracts the most feasible - the blameless amplifier.
So the question hovering in the room is why we are not already completely satisfied with this one solution.
You show further solutions -> Circuit technology. But the most practicable solution already seems to exist.
Which of your solutions will you commit to in the future?
In short, for me a JLH inspired development should be BJT based without exception, no MOS-FET.
I really like your thread though.
kind regards,
HBt.
Your flood of ideas is impressive and immediately comprehensible.
But I always end up back at the beginning of the journey and return to the simplest topology, from which Douglas Self, with his recipe and dimensioning instructions, extracts the most feasible - the blameless amplifier.
So the question hovering in the room is why we are not already completely satisfied with this one solution.
You show further solutions -> Circuit technology. But the most practicable solution already seems to exist.
Which of your solutions will you commit to in the future?
In short, for me a JLH inspired development should be BJT based without exception, no MOS-FET.
I really like your thread though.
kind regards,
HBt.
I understand your reservations HBt, but then I said to myself "Why not?"
To Hennady: I think its important that you at the end edit the OP to specify and comment on each final iterations.
You started on One take on JLH, but end with several. Great! Just as long as you help readers a little more in the OP to guide them to what is what😊
Cheers!
To Hennady: I think its important that you at the end edit the OP to specify and comment on each final iterations.
You started on One take on JLH, but end with several. Great! Just as long as you help readers a little more in the OP to guide them to what is what😊
Cheers!
Hello.
in fact, all the ideas are around only the basic topology of symmetrical control of power transistors of the same conductivity type, and naturally without reference to the solutions of individual authors, for example, the diagram is https://www.diyaudio.com/community/threads/hennadys-take-on-the-1969-jlh.409972/post-7642083 a logical continuation of the diagram from the post: https://www.diyaudio.com/community/threads/hennadys-take-on-the-1969-jlh.409972/post-7621829
Additional circuits of the Electronic power supply filter and the common-mode stabilization unit, which is essentially a current servo drive, had to be invented additionally, because they are needed for high-quality sound reproduction.
Common-mode stabilization is necessary for topologies where symmetrical drive of output transistors is required, Circlotron topology or based on Flickinger cascades.
a scheme based on a large number of compromises cannot be final and not subject to modification. Example - the presence of a capacitor at the output of the amplifier and in the return circuit of the NFB is a compromise, because The output capacitor must be covered by an additional NFB.
The second point is the need to increase the damping factor in order to reduce the influence of the length of the acoustic wires on the sound - in the basic circuit there is simply nowhere to take additional reserve in the depth of the NFB.
Everyone has their own understanding of a practical and sufficient circuit for sound. There should always be a choice in the amplifier topology.
Of course, here's the diagram: https://www.diyaudio.com/community/threads/hennadys-take-on-the-1969-jlh.409972/post-7642083
Not quite so, there are conditions that cannot be ignored and to which one cannot “turn a blind eye.”
1. in the original version of JLH only bipolar transistors can be used, in the Modified version both bipolar and mosfets, both vertical and horizontal.
2. operating current and the associated heating of the transistor crystal, which affects the quality of the transistor’s characteristics and imposes restrictions on the use of bipolar transistors. You can write any initial current in the circuit, but in practice it is rare that through 1 pair the current gives more than 1 Ampere. With asymmetrical control of the output stage, this current must be increased by the root of 2 (1.41), i.e. this is a current of 1.7 Amperes, with symmetric control this is reduced by the root of 2 (1.41) - this is 700 mA, and with combined control option MOD2024 the initial current is equal to the base = 1 Ampere.
The advantage of mosfets is that heating their crystal has virtually no effect on its characteristics, and since there is no current feedback on the gates, the open loop gain is +3 dB higher, which leads to lower distortion. The worst thing is when the Mosfets are complementary - driving them without additional depth of feedback on the HF has a very bad effect on the sound.
The JLH topology is a special case of symmetrical control of transistors of the output stage of the same conductivity. The problem in the basic JLH circuit is the presence of a nonlinear local NFB through the B-E junction of the upper power transistor.
Sorry to go back to this post, but could you explain what happened here? Input filter affecting IMD?
The reason is the use of old-school 3055 power transistors, their slowness must be taken into account, namely, to reduce the frequency spectrum at the amplifier input. It is also necessary to take into account that the input transistor operates in an ultralinear mode and broadband negative feedback is introduced through a low-resistance divider. Those. theoretically it follows that it is necessary to install more modern power transistors, but this needs to be checked in the model - I did not do this, because the goal was to modify the finished kit. The input filter frequency has now been reduced from 248 kHz to 73.5 kHz.
During the simulation, it was clear that as the cutoff frequency at the amplifier input decreased, the IMD distortion decreased and reached a frequency at which further reduction in frequency does not affect the reduction of IMD distortion.
In the original JLH version, the input capacitance of the power transistors shunts the collector of the driver transistor in frequency, and replacing it with modern transistors will further increase IMD distortion, although many will argue that high frequencies have been added and this is good, but at the same time the integrity of the sound stage "sound reproduction picture will be disintegrate, and this is not very good.
In general, I consider it optimal for an audio amplifier to select the cutoff frequency of the input filter in the range of 64 kHz - 88 kHz.
A higher cutoff frequency is necessary where the slew rate of the signal is important to reduce switching output Stage interference, for example, for an output stage operating in class AB, but this always leads to a subjective “hardness” in the sound of high frequencies, sometimes such hardness is called “transistor” sound.
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In da previous Millenium, we conducted several DBLTs on amps, from which we agreed with Peters Walker & Baxandall, that good amplifiers, operating within their intended range, ie not overloaded, sounded identical.
We also found most (all?) Golden Pinnae amps were NOT good amps, exhibiting instability with load, music & thermal history. No wonder they sound different.
The exception was JLH 1969 which could be detected from other good amplifiers and was PREFERRED
I concluded it was due to its THD profile, mainly 2nd harmonic, rising nicely with level until about 0.1% THD and sorta independent of frequency.
I've tried over the years, to replicate this THD profile with something which wasn't a space heater without success.
I'm not sure reducing THD in a JLH 1969 based amp will retain its performance in DBLTs.
One audible improvement (in DBLTs) was running it from a regulated SMPS ... but this was when it could be overloaded. This is something worth doing on any Class A amp.
If we do a regular test of the spectrum of harmonic distortion at an average listening power at an 8 ohm load, then in the original version of JLH 1969 we will not see a spectrum with a purely 2nd harmonic, so the statement that “you like the sound because of the “2nd harmonic”” is what happens “ myth".
https://www.diyaudio.com/community/threads/hennadys-take-on-the-1969-jlh.409972/post-7620996
What I managed to find out:
This “surround sound” is obtained due to the presence of tracking feedback in the load of the driver stage. Its use increases the output impedance of the amplifier at mid frequencies; and for its high-quality operation, a supply voltage with minimal ripple and as close in shape as possible to a sinusoid is required; this immediately eliminates the use of a circuit from an unstabilized power source using a simple circuit: diode bridge + high-capacity capacitor.
A CRC filter circuit after the bridge is preferable, but is not sufficient to reduce the ripple level.
It is advisable not to use CRCRC or RCRCRC filtering schemes due to significant phase shifts, and the selection of coefficients for its equalization is difficult, because will depend on the magnitude of the load.
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