I will check how much it is from Belgium I always can order more
I think about 5 Euro more or less
I think about 5 Euro more or less
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OK, i will go thru mouser. Guess i didn't look Hard enough first time thru.
THANK YOU for the Assistance.😀
Rick
Well, I did the presets as outlined in post 372 and used my bench power supply with variable voltage and current adjustments. Wasn't having much luck setting the VAS within specs when I noticed I could affect this more with the current adjustment on the power supply than with the trim pots on the board. I went back to square one, re-did the presets, and hooked the board up to the SMPS300E power supply. Immediately the resistor attached to the negative voltage input burnt through and the resistor attached to the positive voltage input turned dark. Went back through the assembly and don't see any components in the wrong place or any solder bridges (I am JIS certified for through-hole). This is my first foray into solid state, I've been building tube amps with point to point wiring for a few years now. Any suggestions on the best way to proceed?
Are you talking about the preliminary 100Ω limiting resistors that get placed in-line for initial testing? The SMPS comes up to voltage very quickly so the resistors in-line may not handle the in-rush of charging the on-board capacitance. Personally, I gust use a multimeter in the positive supply line to measure the current directly but I thought the intermediary step might save some grief if there were a problem.
If you have a current limited bench supply then don't use the resistors and just set the current limit to a reasonable level like 250mA or so. It does sound like something is drawing too much current if the current limit adjustment on the supply was having such an effect. The rails sound like they are folding back.
Post a couple pictures if you can, maybe we can catch an overlooked error should there be one.
If you have a current limited bench supply then don't use the resistors and just set the current limit to a reasonable level like 250mA or so. It does sound like something is drawing too much current if the current limit adjustment on the supply was having such an effect. The rails sound like they are folding back.
Post a couple pictures if you can, maybe we can catch an overlooked error should there be one.
@mlm115 - Did you get the amplifiers up and running?
Anyone else getting builds up and running yet? I'd love to see some more builds if anyone cares to share some pictures and impressions.
Anyone else getting builds up and running yet? I'd love to see some more builds if anyone cares to share some pictures and impressions.
Jason,
As you know I'm planning to build a second VSSA but with parts I've.
What replacements can I use for
Q1Q5 (KSC1845)
Q2Q4 (KSA9922)
Q7 (KSA1220)
Q9 (KSC2690)
As you know I'm planning to build a second VSSA but with parts I've.
What replacements can I use for
Q1Q5 (KSC1845)
Q2Q4 (KSA9922)
Q7 (KSA1220)
Q9 (KSC2690)
What supply voltages are you going to use? Up to about 36V rails you can use BD139 / BD140 for the VAS and almost any device with ECB pin out a Vceo of 45V or greater can replace the KSA992 / KSC1845. You can even twist around the leads and use BC550 / BC560 if you don't mind 'forcing' an alternative device to fit.
Basically the design is pretty forgiving of parts choices so a 'junk bin' build should work out just fine so long as you are conscious of your pin outs and device ratings.
I'd go for the highest gain devices that are readily available that you can get a reasonably close match with, say not more than at 20% spread but ideally as close as possible. Higher gain is most important in the input pair and secondarily in the VAS.
I have built without matching directly from my junk box and have had no issues with the amplifiers. I suspect darn near anything will work.
I have built without matching directly from my junk box and have had no issues with the amplifiers. I suspect darn near anything will work.
Hi Patrick, maybe you can try:
Q1Q5 (KSC1845) --- C2240, C1775, C1841, C945, C1815
Q2Q4 (KSA992) --- A970, A872, A988, A733, A1015
for the VAS you've choice one from here, don't you 🙂 VAS TR
If you can get very close hFE that will be good, because it is easier to dial the offset...
I've try with BC550-560C & found that BC560C always lower hFE
(only few of it can measure hFE of 600 from a 100 pcs 😀)
Maybe that's why Jason use SA-SC series...
Jason, I have one more suggestion.
How if we add one resistor, 1k before the CCS so we can easily measure the input pair current(I've done it in my version 🙂)
If the input pair current set to 2.4mA the base to collector resistor value at VAS transistor must be reduced if we use the original 470 ohm then the VAS current will be too high. You use 390 ohm in your version, I've play with the value & end up with 432 ohm but I reduce the input pair current to about 2.15mA with J-fet CCS.
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Hi John, I never got to concerned about the input pair currents actual value and just allow it to be what ever is required to properly bias the VAS via the 390 ohm resistors. I did choose to use 390 ohm to allow a little more input pair current.
Oh, I see...
I thought you've measured it, so your thought more input pair current is better?
They will get warmer if too much current & if the input not closely match it can be a problem right 🙂
I thought you've measured it, so your thought more input pair current is better?
They will get warmer if too much current & if the input not closely match it can be a problem right 🙂
Good question. I didn't try it with a transformer and cap multiplier. I will try that this week and get back to you. It sounded really, really good on SMPS. I did A/B it against my other VSSA and I thought they sounded basically the same. I will try again.
Blessings, Terry
Blessings, Terry
I did the initial adjustments with a PSU through a variac and light bulb.once I established that there were no issues I switched to the smps. The only transformer I have is a 34-0-34vac so too much without the variac though I think Jason did try his at close to ±50v. I'm not sure if I will have time tomorrow but if I do I'll hook it up and test it.
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