to MEPER
Hello MEPER,
I couldn't tell you in a blind test which board is playing. No!
I tested the inputboards playing always the same track / song.
I did on channel A inputboard 1 and on channel B inputboard 2.
I listened mono and stereo. With the balance control I could listen
to the different inputboards.
I heard marginal differences - but not that I would say this inputboard or
the other one is better. For me each has a 'character'. And noise was different.
I was also playing with different Preamps (B1 NUTUBE, BA-3 PRE, ALEPH P1.7, WHAMMY, BALANCED ZEN LINE STAGE). Made a bigger difference to me than switching the inputboards of the M2X.
But I couldn`t say in a blind test - now is playing preamp X and inputboard
Y in M2X. - Never.
My experiences.
Greets
Dirk
Hello MEPER,
I couldn't tell you in a blind test which board is playing. No!
I tested the inputboards playing always the same track / song.
I did on channel A inputboard 1 and on channel B inputboard 2.
I listened mono and stereo. With the balance control I could listen
to the different inputboards.
I heard marginal differences - but not that I would say this inputboard or
the other one is better. For me each has a 'character'. And noise was different.
I was also playing with different Preamps (B1 NUTUBE, BA-3 PRE, ALEPH P1.7, WHAMMY, BALANCED ZEN LINE STAGE). Made a bigger difference to me than switching the inputboards of the M2X.
But I couldn`t say in a blind test - now is playing preamp X and inputboard
Y in M2X. - Never.
My experiences.
Greets
Dirk
None of those sound correct when setting V+ to +23V and V- to -23V, but I agree that the Austin measurement is by far the most worrisome. A correctly functioning Austin card should draw more than 1mA but less than 10mA. 250mA means something has gone wrong quite badly. My initial guess is that one or more of the transistors wasn't installed correctly. For example in my very first Austin prototype, I accidentally swapped an NPN with a PNP. Turkey no worky.
Maybe your multimeter has different ranges (perhaps with different test lead female sockets) for different levels of current measurement. The meter below offers one range for 0-20mA, another range for 0-200mA, and a third range for 0-10000mA (ten amperes). But you need to move your test lead from bottom left to bottom right, before you can measure on the ten amps scale. Make sure you've selected the appropriate range when measuring a small current such as Tucson's supply current. When using the OPA604 opamp, Tucson should measure somewhere between 7mA and 15mA. Not zero.
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My experience with listening tests is that it takes time to find out if you like an amp or not. Usually several days. An amp that sounds very good first time you listen can cause listening fatigue after some days. The mood you are in also have something so say. Amount of earwax…...humidity…..temperature...…..can also change the sound (e.g. speaker suspension and speaker material). Rubber gets softer with temperatur which causes the resonans frequency of an e.g. woofer speaker unit to drop a bit.....etc. etc.....not easy to perform an objective listening test.
In case anybody wants to analyze the Austin circuit and hand calculate its current draw when VCC is +23V and VEE is -23V, I've attached an annotated schematic below.
Austin's supply current is the sum of four individual contributions:
- I1 is the current which flows through current source transistor Q4 and input follower transistor Q2
- I2 is the current which flows through Q3 and Q1
- I3 is the current which flows through the bias generator, IC1 + R7 + IC2
- I4 is the current which flows in the output stage, through Q5 and Q6
Please enjoy!
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Curious about this. What were your findings?
Which was the better match in your opinion? I know this is subjective, still very interested.
Thanks!
Rafa.
answer to RafaPolit
Hello RafaPolit,
I tried such a lot of combinations with the M2X the last few weeks.
I should have made notes.
My opinion about the inputboards of thr M2X:
They influence the sound. But not as much as I thought.
I couldn't say which inputboard is the best. Each is good - I like to describe
it as 'each inputboard has a character'.
The most detailed and 'clean' (clean doesn't mean clinical or overanalytic!) sounding boards are the NORWOOD and the TUCSON (with the SMD OPA 1611). Both offer good bass response and very detailed highs.
The MOUNTAIN VIEW was favoured by me if i was listening to Jazz or
music with vocals in the foreground. It gave the voices something special -
I can't describe it in words - like a feeling. But in my setup it was the noisiest
of the inputboards.
The AUSTIN board is also good. But I was listening to it the shortest time.
I did not build the ISHIKAWA board - Toshiba JFets are too rare - also
the LS - Fets. I need them for something else.
Then I tried different preamps.
To make it short: my preferred ones with the M2X are
BA-3 Pre and the B1 NUTUBE. The B1 NUTUBE adjusted to 9.7 V and
the loudspeakers with inverted polarity at the M2X. The B1 NUTUBE gave
the best roominformation.
The Aleph P1.7 and the BZLS (Balanced Zen Line Stage with added CCS)
sounded softer or perhaps reduced in the highs. A bit darker. But not bad!
The Whammy wasn't a good combination with the M2X. Although I like
the Whammy as a preamp in other combinations. And I think it is a very very
good headphoneamp (Thanks Wayne! At the moment I have a JRC Opamp in it).
As a conclusion: You can play around that much with different inputboards
in the M2X and changing Preamps - and every combination is a little bit different. No one is really bad for me.
It is like cooking a meal two times - a little bit more salt, a little more spices
and suddenly it tastes different - although it was the same recipe.
And not to forget - I have definitely different speakers than yours!
In my opinion the most important link in the chain - The loudspeaker
changes the voltage and current out of the chain into soundwaves.....
Build the M2X - it is worth every minute and money you spend on it!
Test yourself! - your listening results will be different to mine - I am pretty sure - because you will have another taste....
Cheers
Dirk
Hello RafaPolit,
I tried such a lot of combinations with the M2X the last few weeks.
I should have made notes.
My opinion about the inputboards of thr M2X:
They influence the sound. But not as much as I thought.
I couldn't say which inputboard is the best. Each is good - I like to describe
it as 'each inputboard has a character'.
The most detailed and 'clean' (clean doesn't mean clinical or overanalytic!) sounding boards are the NORWOOD and the TUCSON (with the SMD OPA 1611). Both offer good bass response and very detailed highs.
The MOUNTAIN VIEW was favoured by me if i was listening to Jazz or
music with vocals in the foreground. It gave the voices something special -
I can't describe it in words - like a feeling. But in my setup it was the noisiest
of the inputboards.
The AUSTIN board is also good. But I was listening to it the shortest time.
I did not build the ISHIKAWA board - Toshiba JFets are too rare - also
the LS - Fets. I need them for something else.
Then I tried different preamps.
To make it short: my preferred ones with the M2X are
BA-3 Pre and the B1 NUTUBE. The B1 NUTUBE adjusted to 9.7 V and
the loudspeakers with inverted polarity at the M2X. The B1 NUTUBE gave
the best roominformation.
The Aleph P1.7 and the BZLS (Balanced Zen Line Stage with added CCS)
sounded softer or perhaps reduced in the highs. A bit darker. But not bad!
The Whammy wasn't a good combination with the M2X. Although I like
the Whammy as a preamp in other combinations. And I think it is a very very
good headphoneamp (Thanks Wayne! At the moment I have a JRC Opamp in it).
As a conclusion: You can play around that much with different inputboards
in the M2X and changing Preamps - and every combination is a little bit different. No one is really bad for me.
It is like cooking a meal two times - a little bit more salt, a little more spices
and suddenly it tastes different - although it was the same recipe.
And not to forget - I have definitely different speakers than yours!
In my opinion the most important link in the chain - The loudspeaker
changes the voltage and current out of the chain into soundwaves.....
Build the M2X - it is worth every minute and money you spend on it!
Test yourself! - your listening results will be different to mine - I am pretty sure - because you will have another taste....
Cheers
Dirk
Hi Mark -
I retested the daughter boards using my Fluke 88 which has a mA selection for DC and AC, results:
Austin 1 = 8.26mA
Austin 2 = 8.30mA
Tucson 1 = 4.49mA
Tucson 2 = 4.36mA
Mountain View 1 = 23.81mA
Mountain View 2 = 23.89mA
I'm very glad I followed your advise to test on the bench, I had swapped the base and Collector pins on Q2 & Q4 causing the high amp draw.
I hope to test the power supply in chassis Monday, which leaves just the amp boards untested. Those I will power up one at a time for testing.
When I 'm ready to adjust RV1, is DC offset the only measurement necessary for proper adjustment?
Zen Mod & TungstonAudio - When you installed the motor run capacitors, did you use two per channel? I have the caps, however I only have two in stock. I'm using a single 300vA transformer/power supply, not dual mono.
I retested the daughter boards using my Fluke 88 which has a mA selection for DC and AC, results:
Austin 1 = 8.26mA
Austin 2 = 8.30mA
Tucson 1 = 4.49mA
Tucson 2 = 4.36mA
Mountain View 1 = 23.81mA
Mountain View 2 = 23.89mA
I'm very glad I followed your advise to test on the bench, I had swapped the base and Collector pins on Q2 & Q4 causing the high amp draw.
I hope to test the power supply in chassis Monday, which leaves just the amp boards untested. Those I will power up one at a time for testing.
When I 'm ready to adjust RV1, is DC offset the only measurement necessary for proper adjustment?
Zen Mod & TungstonAudio - When you installed the motor run capacitors, did you use two per channel? I have the caps, however I only have two in stock. I'm using a single 300vA transformer/power supply, not dual mono.
My M2x has a single 400VA transformer & PSU. (I chose this route because it was easier to maintain good physical separation between the transformer case and my unshielded Edcors.) I installed two pairs of the motor run capacitors, each pair next to one of the main channel boards. This helped fill out the soundstage and give better separation between instruments in the recording.
I have also commented on the fact that some of the IPS boards may help in this regard by adding extra capacitance between VPOS & VNEG. I plan to test this theory by building a veroboard version of Ishikawa that has extra capacitance between the supply rails. At the moment, though, I'm simply enjoying my veroboard version of the Mtn View with a precision voltage reference in place of the red LED (and yes, 470 uF between the supply rails).
As you have ordered a single dual rail SLB PSU, you will be pleased to know that I tested the SLB PSU (a single one with a single Antek) on the M2X, and managed to get zero ground loop hum by careful connection of the RCA input jack ground to the PSU star hub ground. I am measuring 100uV rms noise at the speaker outputs, the lowest I have ever been able to get on the M2 or M2X. I think that the SLB PSU is a good choice for the M2X or any 25w Pass Class A amp. I am using a 22v 300VA trafo and this provides enough headroom for the voltage drop through the cap Mx to get +/-25v at the amp.
The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
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one motor run cap as bypass for one last cap in rail
so , if you have 2 rails in amp (common PSU for both channels) - 2 motor runs
if you have 4 rails in amp ( separate PSU for channel) , 4 motor runs (2+2)
I have tried to search for PSRR in this thread as I am interested in how good the amp is to reject ripple. It is said to be very good but is there a "number" for it. E.g. if my PSU has 20 mV of ripple at 2A current pr. rail how much will be present at the output caused by this ripple?
Something I have thought a lot about is how much need there is for a fast reacting PSU when running in class A mode with a constant bias current. Is bias really constant or will it raise a bit following the dynamics in the music….so we still need a fast PSU (like in class AB)?
It seems there is not any difference in designing a PSU for a class AB compared to class A amp? …..at least I have not found it yet …..other than I have used and have also seen other use chokes in PSU......and chokes are known for they "like" to keep current constant. But for M2X my PSU will be a more conventional CRC like PSU (maybe CRCRC).
Something I have thought a lot about is how much need there is for a fast reacting PSU when running in class A mode with a constant bias current. Is bias really constant or will it raise a bit following the dynamics in the music….so we still need a fast PSU (like in class AB)?
It seems there is not any difference in designing a PSU for a class AB compared to class A amp? …..at least I have not found it yet
…..other than I have used and have also seen other use chokes in PSU......and chokes are known for they "like" to keep current constant. But for M2X my PSU will be a more conventional CRC like PSU (maybe CRCRC).
I don't think I have seen any posts in this thread which contain any of the info you seek. But maybe someone else will remember one that I have forgotten. Or maybe some fancy Google Advanced Search wizardry will find what nobody is able to remember.
The earlier threads about the original First Watt M2 (without removable daughter cards) might have some of it.
edit- but of course the different daughter cards might change the PSRR of the entire amplifier. The ones that use IC opamps (Norwood, Tucson) probably have different PSRR than the ones that use discrete transistors (Ishikawa, Austin, Mountain View).
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The earlier threads about the original First Watt M2 (without removable daughter cards) might have some of it.
edit- but of course the different daughter cards might change the PSRR of the entire amplifier. The ones that use IC opamps (Norwood, Tucson) probably have different PSRR than the ones that use discrete transistors (Ishikawa, Austin, Mountain View).
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I found this in M2 thread regarding PSRR:
"Remember that M2 has excellent PSRR.
The M2 circuit completely eliminates the weakest link in conventional power amplifiers, where noise and spuriae from the supply can mix with the signal and find their way onto the output. That weak link is the voltage gain stage a/k/a "VAS". M2 uses an autotransformer instead of a VAS, and it's not connected to either power supply. Voila, that entry point for supply noise has been sealed off and eliminated."
"Remember that M2 has excellent PSRR.
The M2 circuit completely eliminates the weakest link in conventional power amplifiers, where noise and spuriae from the supply can mix with the signal and find their way onto the output. That weak link is the voltage gain stage a/k/a "VAS". M2 uses an autotransformer instead of a VAS, and it's not connected to either power supply. Voila, that entry point for supply noise has been sealed off and eliminated."
Yep, I remember that one. It doesn't seem to answer your question But is there a "number" for PSRR? i.e., no measured numerical data.
The second stage ("VAS") is not an entry point for supply noise, leaving only the first stage ("input buffer") and the third stage ("power output stage") as possibilities. And both of those are unity gain followers in the original M2.
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The second stage ("VAS") is not an entry point for supply noise, leaving only the first stage ("input buffer") and the third stage ("power output stage") as possibilities. And both of those are unity gain followers in the original M2.
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I guess a push-pull design with a +- supply is better to reject PS ripple than a SE design. But it seems a 9240 transistor is not a perfect "mirror" of a 240 which would have been the best case for rejecting ripple…...in the output stage.....logical thinking?
But I always think of this Niels Bohr quote when I try to be logical:
"No, no, you're not thinking; you're just being logical"
He was probably a clever man.
But I always think of this Niels Bohr quote when I try to be logical:
"No, no, you're not thinking; you're just being logical"
He was probably a clever man.
The Melbourne input daughterboard has been tested with the M2X. It works very well and the sound is excellent. Wide, wide soundstage, superb imaging, deep incredible bass. No noise or hum. Important to tie Melbourne GND to PSU star GND, not local GND on M2X. Also needs to be DC coupled to prevent oscillation from LC tank circuit created by output coupling cap and Edcor. Also, tie RCA panel jack GND to the star hub GND on PSU as well and cut the GND connection from the M2X input to the RCA jack. That solved a huge ground loop hum problem. This is useful on the basic M2X with a Tucson even.
Melbourne Daughterboard for M2X
Anyhow, the Melbourne is now verified to work inside the M2X, and provides a nice 15.6dB of gain that is useful for weak sources like phones and Mp3 players, Amazon Dot, etc.
Melbourne Daughterboard for M2X
Anyhow, the Melbourne is now verified to work inside the M2X, and provides a nice 15.6dB of gain that is useful for weak sources like phones and Mp3 players, Amazon Dot, etc.
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