Thanks, I will give it a try, maybe with some cheap headphones first before connecting my Fostex TH-900 to it.
Another ideia is to use an very slow bias PSU. I use one with 20 seconds to apply the approx. -4V bias, gradually (using an very little trafo, and also enormous capacitance in an RC filter for further delaying the bias supply). With zero bias the SIT will have approx. 1R dc and will don't develop the starting thump.
Personaly i have modify psu of one amplifier who have on/off thump
and solution was extend by in rush current CL-60 thermistor and capacitor
like in classic First Watts amplifiers psu's. Photos from 6L6 guide Thanks.
What your psu transformer primary 120 V ?
Best regards 🙂
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My psu extension to avoid thump was much simpler with only one primary if is your case
i just cut hot ( phase ) wire and connected CL-60 in serie and on switch
one capacitor connected to on/off between phase and neutral wire or directly to switch.
Capacitor who can accept 250 V or more in this case and no polarised type.
Btw my psu modification work perfectly in 20 watts Hiraga amplifier
psu are filtered with 2x450 000 uF caps and in rush current was huge.
No thumb now only silent switch operation.
Kind regards 🙂
Thanks soundhappy.
I don't have caps of correct value/rating at hand, but I did a quick test with these 2 big caps (image attached). There is a very slight thump with these oversized caps, but not enough to worry me about damaging anything, and hopefully thump will become negligible when smaller caps are used, or else I'll try your power supply mod.
BTW, the LuminAria sounds pretty nice as a headphone amp 🙂
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All honour is for First Watt Mr Pass simple solution i just adapted to Hiraga amplifier and can work great in L'Amp or Luminaria.
For your specific needs they are precise formula for choice of CL.
All i know about big in rush current they electricaly stress components & vfet's and shorten his service lifes.
BTW nice big caps i like it hmmm with great old school Tokin Fantastic !
Best regard
CL-60 Amphenol Advanced Sensors | Mouser
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All honour is for First Watt Mr Pass simple solution i just adapted to Hiraga amplifier and can work great in L'Amp or Luminaria.
For your specific needs they are precise formula for choice of CL.
All i know about big in rush current they electricaly stress components & vfet's and shorten his service lifes.
BTW nice big caps i like it hmmm with great old school Tokin Fantastic !
Best regard
CL-60 Amphenol Advanced Sensors | Mouser
Soundhappy
I really like the way your amplifier enclosure is built with the perforated black metal top cover. Very nice! The perforated metal is one of my favorite enclosure materials. I have alway liked to be able to see inside circuitry.
Yes is interesting design all perforated cover and metal base
disipate portion of the heat not only heat sinks.
Great idea is to connect L'Amp vfet amplifier circuit to psu with BIG
6x150 000 = 900 000 uF caps bank or +
That is Mr Hiraga class A style
fews watts with " muscular " psu.
Hope this inspire L'Amp future builders.
Never to much heat sinks or psu caps
Best regards
ps. inside circuit photo
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Huge
Rating = 25 V of this ones perfect for L'Amp 193V.
Higer voltage for others L'Amp circuits = 50 V rate
Yours are best for l'Amp version width Tokin sits 100 V
Many smaller low esr caps work great , important is
to go around 1Farad of total capacity say Hiraga San.
Something to experiment no doubt in L'Amp
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Yes is interesting design all perforated
fews watts with " muscular " psu.
Hope this inspire L'Amp future builders.
Never to much heat sinks or psu capstone
Best regards
ps. inside circuit photo
Thank you for the driver board photo. Very nice! What type are the 0.47 ohm resistors?
Also interesting how you thermally coupled the two small transistors. In the past I have done similar by placing them face to face and putting compound between. I'll bet it sounds really great.
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Mr. Hiraga designs are "low" voltage nothing above 50V if I remember?! 1F bank is "jouable", possible and if money is not a problem! Not only electrolytics but a smart mixing of various capacitors (MKP, mylar and others).
He also mentionned the usage of batteries (in the past only lead acid) and lay down that it should be the best supply. Today, the chemistry for supply batteries is varied. I read a lot about LiFePO4, simple in handle then safe in charging and discharging. BMS and charger existing (DIY or COTS) and I suppose the cost are not even more then a monster capacities bank. Ok, you need the paralleling of some capacitors as Mr. Hiraga says. No study or article exists about the usage of this kind of batteries in audio applications.
But sure, with this kind of batteries you don´t have problems with inrush currents, you need a good switch (military surplus) or a automotive relay or simply a good switching mosfet (don´t need to be audio type)...
I´m surprising that we always coming back to Mr. Hiraga´s studies and designs! And not only the french guys (better for reading his publications)...
I´m in negotiations with the purchase of 20 pieces 2SK180 (23€ for one piece). I owned it already virtually...
He also mentionned the usage of batteries (in the past only lead acid) and lay down that it should be the best supply. Today, the chemistry for supply batteries is varied. I read a lot about LiFePO4, simple in handle then safe in charging and discharging. BMS and charger existing (DIY or COTS) and I suppose the cost are not even more then a monster capacities bank. Ok, you need the paralleling of some capacitors as Mr. Hiraga says. No study or article exists about the usage of this kind of batteries in audio applications.
But sure, with this kind of batteries you don´t have problems with inrush currents, you need a good switch (military surplus) or a automotive relay or simply a good switching mosfet (don´t need to be audio type)...
I´m surprising that we always coming back to Mr. Hiraga´s studies and designs! And not only the french guys (better for reading his publications)...
I´m in negotiations with the purchase of 20 pieces 2SK180 (23€ for one piece). I owned it already virtually...
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Hi Mike
They are metal oxide film type 🙂
@ Diyers
One question : In L'Amp what difference or benefits from use double winding secondaires
of psu in parallel ( 2 ) contrary to use only one secondary with the same total power ratio and voltage ?
Greetings
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@ Jps1964
Think of battery for vfet amplifier oh yeah no background noise
just best pure sound possible 😉
About Tokins we are on forum aware so is to late ask about of 1Y and 1Z batch
if other batch number they are possibly ok anyway
try test them with curve tracer sadly probably this 1Y ones is not working units for audio
🙂
This photo can be old one and no actual batch 🙂
so best to do is ask the seller if you can ?
If they are 1Y i remember Cwtim01 and Mr Rothacher write on forum
about this no hope for good curves after his tests ....search in thread posts.
Greetings