LuDEF

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Zen Mod

Zen Mod

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Joined 2003
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tombo56 said:
And difference between dual mono and super regulators is another two classes, so I’m in the stratosphere. No wonder I feel dizzy while amp is switched on. :)
Click to expand...

I'm stubborn, so I don't like neither regs nor cap multis for power stages

but I like real chokes in filters :)

anyway, that's first glimpse of your listening experience, or you are just happy looking at it?

:clown:
 
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04dgmsilv

Member
Joined 2006
Zen Mod said:
OK, keep me informed

if needed, I'll send another pair, whenever
Click to expand...

Success, replaced the LU, left the gate resistors at 200R (100+100) and it has been cooking for the last ~2 hrs and no hint of oscillation and easy to dial in like the other channel.

Any issues with having unmatched pair of LU in there?

On another note, this is the first Antek transformer (400va) I've had now that has a buzz...

Thanks again
 
Zen Mod

Zen Mod

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Joined 2003
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no issues with unmatched

remember, this amp is of "deliberately spoiled symmetry" :rofl:

we can call that approach ZMymmetry........... even if Pa is one who brought it around

:cheers:

now - seriously - what's easing things is that OS is sort of source follower, so differences in transfer characteristics of part are less critical
 
T

tombo56

Member
Joined 2019
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Zen Mod said:
but I like real chokes in filters :)
Click to expand...

Remind me, what was your previous forum nick? :D

I agree on technical dislike for cap multis. Contrary to chokes, they don’t store energy. They are just ripple suckers providing high output impedance on PS output, and that is what we usually don’t want.
Super regs are another story. You just didn’t try a good one suitable for the power amplifier.

Micro ohm output impedance, few uV noise, over 100 dB PSRR, 2 digits amperage capacity, micro second transient response, single transformer enough: what’s there not to like except increased complexity?
I’ve noticed JLH thread where several members replaced CRC with super regulators with perfect anecdotal effect where a wife heard positive difference right away.

I’m untalented for the audio poetry and amplifier components are just breaking in but it is technically and sound wise mighty fine amplifier. First impressions are ‘blinded by the light’ of novelty type, but I think that long term impressions will remain very favorable.
 
Zen Mod

Zen Mod

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I agree with you an all counts ...... but as I said - I'm stubborn :clown:

Sole one being more stubborn than me is Pa, always ignoring proper shunt regs for preamps (that being just one example) ...... though - he transferred preamp making duties to Wayne, that being less adventurous (for him) :rofl:

audio poetry ........ yup, even with all details and tiny levels revealed, still having foot-tapping character

and, when you recall a fact that amp is without loop NFB....... so, in the end, I feel as lucky finder

amps are growing on several amp fields, and I was lucky to stumble on this peculiar one

:clown:
 
Zen Mod

Zen Mod

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G

grataku

Member
Joined 2000
tombo56 said:
Ordinary build using 4U case. Bias current is rock solid. From cold start, it needs almost 2 minutes to reach steady state. After several hours, it will change less than 30 mA.
Offset voltage starts from -60 mV, then during Iq rise, briefly reaches +270 mV and then falls down reaching steady state of +- 10 mV. It does not change more than 20 mV range.
Heatsink temperatures at supply of +- 25 V and Iq 1.5 A are below 40 C.

Nothing left to desire.

I started measurements with output noise. Unweighted output noise in 22 Hz to 22 kHz bandwidth is 25 uV. That is among best of all FW amplifiers.
Noise is at -110 dB relative to signal level of 1 V rms, so even with super sensitive loudspeakers in quiet room, it won’t be an issue.
Click to expand...

Looking good!!

2 questions:
1-how hot do the mosfet and the bd139-140 on board get (I forget the number 510?).
You seem to be using a larger heatsink than I bought.
2-what PS board are you using?
 
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tombo56

Member
Joined 2019
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Small heatsinks are enough. Q101/Q102 pair, that uses the same single heatsink, dissipates only 0.45 W. That small heatsink has 25° C/W.
Q103 and M101 dissipate 0.75 W each, so 20° C temperature rise. That’s nothing.

So, why do I have larger heatsinks? Output offset voltage change span is proportional to the temperature change span of Q103 and M101. Larger heatsinks reduce total DC voltage change by 20 mV. But that’s nitpicking.
Hmm, isn’t audio all about that? :yes:

With either heatsinks, DC offset is small and its stability is very good.

Power supply is excellent prasi’s LT4320 CRC PSU board (synchronized active rectification) design:
LT4320 based active rectifier

Resistor in that CRC chain is replaced with the super regulator (LDO variant of Jung super regulator):
An arguably better replacement for the resistor in a CRC power supply - R21 PS module
 
S

Skip Pack

Member
Joined 2004
Notchhing Circuit Boards

I am about to start putting my LuDef together, and I'm working on the the layout of the boards wrt the chassis/box/heatsinks. In this case there's not enough room to use the right angle/mezzanine mount ZM used so I need to mount the boards parallel to the case sides/heatsinks. I think the best way would be for me to notch the boards for the two big mosfets and the LU1014D. My question here is: 'Is there any conductive material (traces or groundplane) in the strip of circuit board beyond the white line?' If there is, would notching the board up to that white line be likely to cause problems?

If this is unclear, I'll doctor some pictures. Thanks, Skip
 
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