Author Topic: New Info Discussed, Class A, AB, B, and C operation/mode  (Read 5782 times)

Offline steve

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New Info Discussed, Class A, AB, B, and C operation/mode
« on: February 08, 2023, 10:43:20 AM »
How Class A1 (normally called Class A), AB1, B, and C Operation Work and Differences.
Class A2 means grid current flows over a portion of the cycle

I thought it would be informative to discuss the differences between
Class A, AB1, B, and C operation. By doing such, one will more fully
understand how each component in your system operates.

Knowledge is power and the more you understand, the less chance
of being misinformed. I am going to keep this discussion as simple as
possible for our newbie friends. I will not cover every detail nor every proof.

However, there will be information presented that has never before been
mentioned, let alone discussed, as far as I have seen.

Caveat: Lets leave out transformers from our discussion.

Note: It might be good idea to print out all the figures at the bottom
of this post to examine while reading.

So let's get started.

What is a sine wave? A sine wave is a constantly varying voltage. Figure 1 is a
pictorial of one 360 degree sine wave. 120 vac at the wall outlet is
basically a sine wave.

So is music made up of sine waves? The answer is yes.
Although looking at a musical signal with an oscilloscope might look
haphazard, with sharp peaks, those sharp peaks are simply varying
high frequencies. Even a solo instrument's signal might look haphazard
due to natural harmonics from the instrument.

It will be easier to understand the different classes of operation if we use
a single frequency sine wave as pictured in Figure 1. As mentioned earlier,
the entire signal is one complete sine wave, 360 degrees. Half of a sine
wave is 180 degrees. One fourth of a sine wave is 90 degrees, one eighth
of a sine wave is 45 degrees etc.

Class A operation.

Suppose we have a single vacuum tube and we have it drawing
current (idle current, Point Q of Fig. A1) with no signal present. Now we apply
the input signal to the tube's grid and the output appears as X and Y
output in fig. A1. Notice X and Y has the same shape, the whole wave
as the input sine wave signal.

Very important. The only requirement of Class A is 360 degree conduction.
There is no center of the Load line requirement or any other requirement or consideration.

The input voltage applied to the tube grid controls the current flowing
through the tube to the plate. It is similar to the foot peddle (grid) controlling
the output of an engine (plate current).

Virtually all phono stages, pre-amplifiers, input and phase
splitters in amplifiers are operated Class A. The next/following
tube stage presents a fairly constant load. That is good news.

Let us continue for tubes operated in Class AB1, B, and C.
Will all classifications work in linear audio applications? Class B is
generally for PA systems, low quality audio and Radio Frequency (RF).
Class C is usually for RF, and industrial applications.

Class AB1, B, and C are defined as operating a single tube when the
current through the tube can be stopped, cut off, meaning 0 ma.
(ma is milliamps) at different portions of the waveform. So what is the
difference between AB1, B, and C operations?

First, we need to see something significant in figure Fig. A1 below, Class A operation.
It has to do with the tube's idling current at the Q point, which, in this
case is set to 65 ma, half way between 0 ma and maximum 130 ma. in our
example. Notice we can go 65 ma. to 0 ma. and 65 ma to 130 ma.

For an output stage, we generally want maximum audio power output,
although any idle current could be used for Class A as long as the tube
conducts 360 degrees. (In fact, less distortion is present if we up the idle
current above 65ma, but output power will be less.) Back to our discussion.

Above and below current differences are equal. So X and Y are equal output
and mimic the input signal, except larger amplitude. We need to understand
Class A operation, 360 degree conduction, as it allows us to understand
Class AB1, B, and C operation correctly. Please re-read if necessary.

Let's bypass fig. AB1, for now.

Let's jump to fig B, Class B operation/mode. Notice the Q point is different.
It is not 65 ma idle current but now 0 ma idling. We still have the same exact value
input signal, but only X appears at the output, Y being absent.
Only half the input signal is at the output. What happened to the other half?

Q point is set at 0 ma. As the signal goes positive,
more current flows through the tube, so X output appears due to more current.
However, how can we go less than 0 ma. current as the input signal
voltage goes negative and the tube stays shut off? We cannot. Thus no Y output
signal voltage. Thus only Ĺ of the input signal appears at the output (180 degrees).
Again, this is a classic definition of Class B operation, higher efficiency,
higher power output, higher distortion.

Class B presents severe distortion to the input signal, and is generally
used in RF and industry. It can be used in audio if we go Push Pull, but it
will produce crossover distortion, higher distortion in general, so is mostly
used in PA systems etc, where fidelity is not important.

A couple of points.

1. The crossover distortion one sees in Class B, Class C operation
is caused by the output transformer. The tubes are easily capable of millions of hz,
so the output tubes are not the cause of switching problems. It is the mismatch of
the output devices and steep slope of the output waveform that causes the problem.

2. The gradual slope of the output signal, and slower increase of the plate current in the
off tube in Class A and AB1 eliminates any crossover distortion. If present, extremely low
value.

Fig. AB1 operation is between Class A and Class B.

Let us check out fig. AB1 operation. Once again we have our input
signal sine wave, and X and Y output voltage. However, we have
some Y output sine wave signal present. Notice, however, the tube's idle
current, Q is between our Class A and Class B Q points, 65 ma and 0 ma
respectively.

In our AB1 example, the idle current is set to 45 ma (could be 55ma, 35ma). Ok,
as the input signal is increased from no signal, X and Y output rise equally,
Class A operation, until the negative input signal causes the tube current to reach 0 ma.
or cutoff. At that point the tube cannot go less current, so Y signal cannot continue to follow
the negative input signal.

So what good is it if X output signal becomes larger than Y? How about adding
a second output tube which mirrors the first tube, except it
handles the negative portion of the input signal. Then X and Y output sine wave
mirrors the input sine wave signal. They naturally blend together when properly designed.
That is called Push Pull AB1.

So is there any advantage in designing Push Pull? If designed properly, efficiency is much
higher than class A, much more power output with much less harmonic and intermodulation distortion
is produced. There is no notch distortion that Class B produces.

Very important. Up until each tube at cutoff, both output tubes operate in Class A mode.
Each tube conducts during the whole 360 degree cycle.

A quote from RCA Radiotron Designers Handbook, 1960, by 26 electrical engineers.
(The engineers checked each other's work.)

"A Class A amplifier is an amplifier in which the grid bias and alternating grid voltages are such
that the plate current of the output valve or valves flows at all times. The suffix 1 indicates that
grid current does not flow during any part of the input cycle."


One can also eliminate the inherent negatives of a class A output stage.
See below *.

For example, a 6L6GC, beam power tube in AB1 mode can produce
55 watts rms output in Class AB1 operation. In Triode mode, we can figure
about half the power output of beam power mode. That is approximately
30 watts output. The tube operates in Class A mode for at least 7.5 watts
output before sliding into AB1 operation.

Even at 1 watt Class A output, a typical speaker can at least peak
into the mid 80s+ spl, depending upon the efficiency of one's speakers.
And the harmonic distortion is extremely low. My entire KT88 amp
produces only 0,05% at 1 watt output, with no global or stage to stage
negative feedback.

Ok, we have discussed Class A, AB1, and B operation. Let us check out
fig. C1, Class C operation.

The first thing one notices is that Q idle is below 0 ma. How can that be?
Notice the perforated line to Q. What is actually pictured is the grid bias
is so negative that less than half, in fact, a very small portion of the input
signal is even large enough to cause plate current flow through the tube. Thus X
appears to be small and Y does not exist at all. A larger, huge input signal
must be presented to obtain lots of power output in Class C mode. The tube
conducts less than 180 degrees. Usually much less.

The plus is that the efficiency can reach 80%, but the minus is that
the distortion is huge. Class C operation is usually for radio
frequencies (RF) and Industrial applications.

So what have we learned?

A. Class A is used in virtually all small signal applications since the load is relatively constant.
B. Class AB1 Push Pull and A are used in most output applications.
C. In Class AB1, both output tubes X and Y run Class A until each
     tube reaches 0 ma. cutoff on positive and negative peaks of the
     input sine wave cycle.
D. The damping factor (DA) is virtually constant over the entire waveform. Not so with SETs,
     which varies from low damping to no damping factor at plate cutoff, maximum power output.
     See * below.
E. There is no crossover distortion, no notch in AB1 operation.
F. There is a smooth blending in properly designed Class AB Push Pull stages.
G. Class B is used as Push Pull, almost exclusively for PA systems, RF, and in industrial.
    It is virtually never used in high fidelity audio components.
H. Class C is never used in linear analog audio designs.
I. 120 hz power supply hum is virtually eliminated in PP operation.

* For a single output tube amplifier, different considerations apply.
For instance, we want the amplifier's output impedance (Z) to be
constant with varying power output and over the entire signal cycle,
360 degrees. To accomplish this, the tube's plate resistance (Ra) must
remain constant.

However, Fig. D shows the Ra line of a typical single
ended triode tube varies/curves drastically as the current changes.
Of course as the current changes, the output power also changes.
At peak power output, the damping factor varies from
maximum damping of the SET amplifier design to virtually no damping
near cutoff. Push Pull remains virtually constant under the same conditions,
so the PP amplifier controls the driver.

There are other pros and cons that we might discuss later.
I hope this has helped in understanding how Class A, AB1,
B, and C amplifiers work.

One can check out:

RCA Tube Manual
RCA Radiotron Designers Handbook, 1960, written by 26 electrical engineers.
College textbook "Semiconductor and Tube Electronics" by James G Brazee
And other electrical engineering textbooks.

steve
« Last Edit: February 26, 2024, 05:31:22 PM by steve »
Steve Sammet (Owner, Electron Eng, SAS Audio Labs, Ret)
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Offline rollo

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #1 on: February 08, 2023, 11:23:47 AM »
  Steve thank you for taking the time to post this, Very informative. A bit over my head though


charles
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Offline steve

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #2 on: February 08, 2023, 01:06:21 PM »
  Steve thank you for taking the time to post this, Very informative. A bit over my head though


charles

I was kind of long winded, but I wanted to provide some reasoning. I have condensed
down to these points. This does not imply all the points though.

I think these are the most important, and never mentioned, let alone understood.

1. Push Pull Class AB amps, both output tubes actually run Class A for several watts output
    before sliding into AB. Speakers can easily be driven into the 90s or higher SPL at
    Class A amplification levels.

2. Even at higher AB levels, each output tube handles ~2/3 to 3/4 of the signal waveform,
    depending upon the idle current setting.
   
3. That there is no signal gap between output tubes in Push Pull AB as point 2
     mentions.

4. Notch distortion occurs in Class B operation. Should never occur in AB mode.

5. There is no disassembly of the signal and then putting it back together in Push Pull.

6. Speakers are damped by the amplifier output impedance. We calculate the
    Damping Factor (DF) assuming the damping is even across the entire signal waveform.
    It is not in SET operation/mode. It is in Push Pull.

    The SET amp damping of the speaker varies down to No damping as the
    volume/output power reaches maximum. But at virtually any volume level,
    the Damping varies. PP does not have that problem.

Hope this is clearer.

cheers

steve



« Last Edit: February 11, 2023, 09:11:28 PM by steve »
Steve Sammet (Owner, Electron Eng, SAS Audio Labs, Ret)
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Acutex 320 STR Mov Iron Cart
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Offline GDHAL

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #3 on: February 08, 2023, 01:14:54 PM »
Thank you, Steve . Can you let me know what is "new" about the information that you're posting? I never heard or read of class ab1, until now (your post).

I have read all of this though:

https://en.wikipedia.org/wiki/Power_amplifier_classes

Also of interest and related to the conversation/thread, this is what an engineer at musical fidelity (which I'm quite certain many of our forum members respect as being a recognized, reputable, and quality brand for many years) has to offer (which I have in writing) when I posed the question about my M6si amp, specifically asking when it crosses out of class A into class A B.

About 0.1W 8 ohms or half that into 4 ohms.
N.B. it does not "switch over" as it were, merely one transistor starts conducting more than the other in a smooth continuous manner (as demanded by speaker). Also Class A/B does not really technically exist. Ours are Class B amplifiers properly setup and vanishingly small distortion as a result.


Suffice it to say I'm friendly with some other engineers, as in people that have PhD in electrical, mechanical, industrial and computer engineering. I queried what was meant by NB. The response I have from my electrical engineer friend:

"I would think N.B., rather than referring to anything of a technical nature, is referring to the Latin expression "nota bene" ("note well"). The answer indicates that the amp does not employ a "sliding bias" or other comparable mechanism that would allow it to operate in class A up to a significant power level, and operate in class B or AB (which does exist, contrary to what he said) at higher power levels".

Best.

Hal

EDIT: oh and this is a schematic of Jerry Garcia's MC2300 amp he used for quite a number of years ...you'll notice it's a class B output stage... not coincidental that my amp should be class B (ab)  8)
.. http://www.tubebooks.org/file_downloads/McIntosh/MC2300.pdf
« Last Edit: February 08, 2023, 02:26:24 PM by GDHAL »
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Offline steve

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #4 on: February 09, 2023, 06:27:32 AM »
Thank you, Steve . Can you let me know what is "new" about the information that you're posting? I never heard or read of class ab1, until now (your post).

I have read all of this though:

https://en.wikipedia.org/wiki/Power_amplifier_classes

Also of interest and related to the conversation/thread, this is what an engineer at musical fidelity (which I'm quite certain many of our forum members respect as being a recognized, reputable, and quality brand for many years) has to offer (which I have in writing) when I posed the question about my M6si amp, specifically asking when it crosses out of class A into class A B.

About 0.1W 8 ohms or half that into 4 ohms.
N.B. it does not "switch over" as it were, merely one transistor starts conducting more than the other in a smooth continuous manner (as demanded by speaker). Also Class A/B does not really technically exist. Ours are Class B amplifiers properly setup and vanishingly small distortion as a result.


Suffice it to say I'm friendly with some other engineers, as in people that have PhD in electrical, mechanical, industrial and computer engineering. I queried what was meant by NB. The response I have from my electrical engineer friend:

"I would think N.B., rather than referring to anything of a technical nature, is referring to the Latin expression "nota bene" ("note well"). The answer indicates that the amp does not employ a "sliding bias" or other comparable mechanism that would allow it to operate in class A up to a significant power level, and operate in class B or AB (which does exist, contrary to what he said) at higher power levels".

Best.

Hal

EDIT: oh and this is a schematic of Jerry Garcia's MC2300 amp he used for quite a number of years ...you'll notice it's a class B output stage... not coincidental that my amp should be class B (ab)  8)
.. http://www.tubebooks.org/file_downloads/McIntosh/MC2300.pdf

I updated with more explanation.

My previous post, to Charles, all the points mention what others do not. You might want
to check some YT videos etc and the very poor info provided concerning Push Pull operation.

Wiki is the first time I have ever seen my point 1 even being mentioned any where over the decades.
Good to see for a change.

The wiki explanation of AB is not totally accurate. One quick example, as compared to my point 2.
(I do have some classified documents at home that I cannot reveal.)

Class AB1 refers to no grid current being drawn. AB2 represents grid current being drawn. Very high Mu
triodes require grid current in order to obtain high power output, justify the tube being used.  In fact,
such tubes are often operated with zero bias, so no bias supply is needed. However, notch distortion
from no grid curren to grid current occurs, so the driver needs to provided some power to alleviate the
problem. It gets technical so won't go further.

The 811A is one such zero biased tube, Mu ~160. The 812A, Mu ~35, good power can be had in Class AB1
with no power driver per se. A bias supply is normally used though.

Wiki has a pretty good section pertaining to Class B. 0,1 watts Class A is typical to help minimize
the notch etc, over time. Large amounts of output stage negative feedback is needed to lower the
notch distortion.

Tube Class AB1 produces a few watts out in Class A mode without any sliding bias etc. This via actual
basic scope, voltage, power, distortion measurements over the decades, in the lab.
As far as harmonic distortion in Class A mode at 1 watt, my entire tube amp has 0,05% distortion
without any global negative feedback.

I am wondering why he used the term "significant" power output Class A. Gets confusing who the
friend is addressing. I hope the designer was not thinking that I was slighting their products.
Maybe he is addressing his own amps.

cheers

steve


« Last Edit: February 12, 2023, 10:09:41 AM by steve »
Steve Sammet (Owner, Electron Eng, SAS Audio Labs, Ret)
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Offline steve

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #5 on: February 20, 2024, 08:37:31 PM »
I performed a review and cleaned up some possible ambiguity for those who found the
initial post confusing. Hopefully, the post will be easier to understand.

Cheers and all the best.

steve
Steve Sammet (Owner, Electron Eng, SAS Audio Labs, Ret)
SAS "V" 39pf/m 6N copper ICs,
SAS Test Phono Stage
Acutex 320 STR Mov Iron Cart
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Offline Nick B

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #6 on: February 21, 2024, 06:46:19 AM »
Thanks, Steve. A bit difficult to follow as Iím not technically inclined. Have you designed Class A, AB, AB1 and even ever dabbled in Class D?

Nick
Orchard Starkrimson Ultra amp
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Offline GDHAL

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #7 on: February 21, 2024, 07:23:49 AM »
I performed a review and cleaned up some possible ambiguity for those who found the
initial post confusing. Hopefully, the post will be easier to understand.

Cheers and all the best.

steve

Hi Steve. I've never heard or read of "AB1" and some of the other classes that you mention. May I suggest you update this article?
https://en.wikipedia.org/wiki/Power_amplifier_classes

Thank you.
GoldenEar Triton Reference (pair), Musical Fidelity M6si, Schiit Yggdrasil-OG-B, Oppo UDP-205, Emotiva ERC-3, LG OLED65C9PUA, Salamander Synergy Triple Unit SL20, Audeze LCD-X, GIK acoustic paneling
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Offline steve

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #8 on: February 26, 2024, 07:26:01 PM »
Thanks, Steve. A bit difficult to follow as Iím not technically inclined. Have you designed Class A, AB, AB1 and even ever dabbled in Class D?

Nick

Yes Nick. I designed SET 6550/KT88/triode connected amps for a couple of years, an OTL amplifier triode wired,
200 watts output, and monoblock Class AB1 amplifier 25 watts output. Sold a few SETs and AB1 amps, but could
not really find a chassis that could handle shipping.

I found that I could design a Class AB1 amp that was near perfect, better than the others, with just the reactance speaker interface causing a sonic difference. That problem was virtually alleviated via matching both the speaker
wires and speaker crossover to the monoblocks.

The AB1 monoblocks feature separate power transformers, thus separate power supplies for each stage.
All polypropylene filter capacitors, except for the high voltage caps which are basically bypassed by a
poly capacitor, and cathode bypass capacitors across a low impedance cathode resistor path.

Along with the 11A line preamplifier, this setup creates a system with all the power supplies, except for the HV supply, having an poly decoupling capacitors. I found that eliminating each electrolytic decoupling capacitor improved the sound.

I checked out a schmetic or two of Class D, but never ventured into such.

cheers

steve
« Last Edit: February 27, 2024, 11:50:31 AM by steve »
Steve Sammet (Owner, Electron Eng, SAS Audio Labs, Ret)
SAS "V" 39pf/m 6N copper ICs,
SAS Test Phono Stage
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Offline steve

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #9 on: February 26, 2024, 07:30:27 PM »
I performed a review and cleaned up some possible ambiguity for those who found the
initial post confusing. Hopefully, the post will be easier to understand.

Cheers and all the best.

steve

Hi Steve. I've never heard or read of "AB1" and some of the other classes that you mention. May I suggest you update this article?
https://en.wikipedia.org/wiki/Power_amplifier_classes

Thank you.

Hi Hal,

If I get a chance, I have some postings, if I can find them, that I would not mind presenting to Wiki concerning
that page.

Cheers

steve
« Last Edit: February 26, 2024, 07:34:31 PM by steve »
Steve Sammet (Owner, Electron Eng, SAS Audio Labs, Ret)
SAS "V" 39pf/m 6N copper ICs,
SAS Test Phono Stage
Acutex 320 STR Mov Iron Cart
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Offline Nick B

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #10 on: February 26, 2024, 09:16:56 PM »
Thanks, Steve. A bit difficult to follow as Iím not technically inclined. Have you designed Class A, AB, AB1 and even ever dabbled in Class D?

Nick

Yes Nick. I designed SET 6550/KT88/triode connected amps for a couple of years, an OTL amplifier triode wired,
200 watts output, and monoblock Class AB1 amplifier 25 watts output. Sold a few SETs and AB1 amps, but could
not really find a chassis that could handle shipping.

I found that I could design a Class AB1 amp that was near perfect, better than the others, with just the reactance speaker interface causing a sonic difference. That problem was virtually alleviated via matching both the speaker
wires and speaker crossover to the monoblocks.

The AB1 monoblocks feature separate power transformers, thus separate power supplies for each stage.
All polypropylene filter capacitors, except for the high voltage caps which are basically bypassed by a
poly capacitor, and cathode bypass capacitors across a low impedance cathode resistor path.

Along with the 11A line preamplifier, this setup creates a system with all the power supplies, except for the HV supply, having an all poly decoupling capacitors. I found that eliminating each electrolytic decoupling capacitor improved the sound.

I checked out a schmetic or two of Class D, but never ventured into such.

cheers

steve

Thanks, Steve. Quite interesting! If I recall correctly, Iíve not owned a Class A amp over the years and my current amp, the Orchard Starkrimson Ultra, is my second venture into Class D and is quite good. Of course other amps are still interesting, but price and especially weight (of 60 lbs+ Ö) makes me appreciate a good Class D design nowadays.

On a different note, what dac ..or latest modsÖ.are you using nowadays?

Nick
Orchard Starkrimson Ultra amp
Supratek Chardonnay preamp
JMR Voce Grande speakers
Border Patrol SEi dac
Holo Red streamer
Hapa Aero digital coax
WyWires Silver cables
TWL Digital American II p cord
Audio Envy p cords
Roon, Tidal, Qobuz
PI Audio UberBUSS

Offline steve

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #11 on: February 27, 2024, 12:37:47 PM »
Hi Nick,

I still have the modi 2, fully upgraded now. Being partially upgraded, it did slightly lacked some width
vs the Denafrip 5k dac but beat the Chord Dave in frequency balance. I have not compared the modi to
them since, but the fully upgraded modi 2 sounds even better. The only down side is the large chassis to
house the caps and modi 2. So it is not pretty looking being a test subject.

It all started because I was given the modi 2 for free and just wanted to tinker with it.
Frankly, I had no idea of how much it could be improved, but now I don't even consider purchasing
another dac.

ps. My monoblocks weigh approximately 25lbs.

cheers

steve
« Last Edit: February 27, 2024, 12:47:40 PM by steve »
Steve Sammet (Owner, Electron Eng, SAS Audio Labs, Ret)
SAS "V" 39pf/m 6N copper ICs,
SAS Test Phono Stage
Acutex 320 STR Mov Iron Cart
SAS 11A Perfect Tube Preamp
SAS 25 W Ref Triode/UL Monoblocks
2 way Floor Standing Test Speakers

Offline GDHAL

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Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #12 on: February 27, 2024, 12:46:21 PM »
Hi Nick,

I still have the modi 2 fully upgraded now. Being partially upgraded, it did slightly lacked some width
vs the Denafrip 5k dac but beat the Chord Dave in frequency balance. I have not compared the modi to
them since, but the upgraded modi 2 sounds even better. The only down side is the large chassis to
house the caps and modi 2. So it is not pretty looking being a test subject.

To think it all started because I was given the modi 2 for free and just wanted to tinker with it.
Frankly, I had no idea of how much it could be improved, but now I don't even consider purchasing
another dac.

cheers

steve

Steve !!!! You have a Denafrips DAC at $5k price point, that must be the 'termimator". Glad for you. A bit jealous actually   :shock:

When/if I next upgrade DACs that's on my short list, however, I already have others I'm mind that best it, but you have to pony up another three grand, so  :(

Anyway, best of luck with it.  :)
GoldenEar Triton Reference (pair), Musical Fidelity M6si, Schiit Yggdrasil-OG-B, Oppo UDP-205, Emotiva ERC-3, LG OLED65C9PUA, Salamander Synergy Triple Unit SL20, Audeze LCD-X, GIK acoustic paneling
http://halr.x10.mx/other.html

Offline steve

  • Audiologist
  • *
  • Posts: 1249
Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #13 on: February 27, 2024, 12:50:14 PM »
Hi Nick,

I still have the modi 2 fully upgraded now. Being partially upgraded, it did slightly lacked some width
vs the Denafrip 5k dac but beat the Chord Dave in frequency balance. I have not compared the modi to
them since, but the upgraded modi 2 sounds even better. The only down side is the large chassis to
house the caps and modi 2. So it is not pretty looking being a test subject.

To think it all started because I was given the modi 2 for free and just wanted to tinker with it.
Frankly, I had no idea of how much it could be improved, but now I don't even consider purchasing
another dac.

cheers

steve

Steve !!!! You have a Denafrips DAC at $5k price point, that must be the 'termimator". Glad for you. A bit jealous actually   :shock:

When/if I next upgrade DACs that's on my short list, however, I already have others I'm mind that best it, but you have to pony up another three grand, so  :(

Anyway, best of luck with it.  :)

I don't think you will regret purchasing the Terminator If you decide that way. It does sound wonderful.
An audio friend, Dan, loaned me the dac for the comparison.

Cheers

steve
« Last Edit: February 27, 2024, 01:33:58 PM by steve »
Steve Sammet (Owner, Electron Eng, SAS Audio Labs, Ret)
SAS "V" 39pf/m 6N copper ICs,
SAS Test Phono Stage
Acutex 320 STR Mov Iron Cart
SAS 11A Perfect Tube Preamp
SAS 25 W Ref Triode/UL Monoblocks
2 way Floor Standing Test Speakers

Offline Nick B

  • Audio Neurotic
  • *****
  • Posts: 4140
Re: New Info Discussed, Class A, AB, B, and C operation/mode
« Reply #14 on: February 27, 2024, 02:23:37 PM »
Hi Nick,

I still have the modi 2, fully upgraded now. Being partially upgraded, it did slightly lacked some width
vs the Denafrip 5k dac but beat the Chord Dave in frequency balance. I have not compared the modi to
them since, but the fully upgraded modi 2 sounds even better. The only down side is the large chassis to
house the caps and modi 2. So it is not pretty looking being a test subject.

It all started because I was given the modi 2 for free and just wanted to tinker with it.
Frankly, I had no idea of how much it could be improved, but now I don't even consider purchasing
another dac.

ps. My monoblocks weigh approximately 25lbs.

cheers

steve

Hi Steve,

I had a hunch you still had that Modi 2. Glad you were able to improve it to such a great extent.

Nick
Orchard Starkrimson Ultra amp
Supratek Chardonnay preamp
JMR Voce Grande speakers
Border Patrol SEi dac
Holo Red streamer
Hapa Aero digital coax
WyWires Silver cables
TWL Digital American II p cord
Audio Envy p cords
Roon, Tidal, Qobuz
PI Audio UberBUSS