Thanks, good to know. But I wonder if the 2SA1837 will handle 63V if I use the correct the bias setting.
Yes, I know that the pinout is different. Thanks for reminding me.
I have both the 2SA1837 and KSA1381. Been toying with the idea of experimenting to hear which one sounds best - and if there is a difference at all. Maybe the 2SA1837 can't handle 63V?
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Yes, 2SA1837 can handle 63v. I have taken it to 200v before. It will probably sound better if given more bias current.
Thanks for confirming, X.
Do you think R15 = 11R will be ok for higher bias. What about the other HPA mods, like changing R14 to 2.2R? Would that be necessary?
Thanks for being willing to answer all our questions, X. You are really very generous with your time and knowledge.
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Both sound good but be sure to reduce voltage as 100mA x 63v is 6.3w and half comes out of 2SA1837. 3w will take a good sized heatsink.
Hmm, there was bound to be a compromise. Think I'll just stick with the KSA1381 for now and get it working first. R15 is soldered in already.
Input caps
I was wondering if someone has experimented with the input caps yet, and if bypass caps here makes a difference? Currently I use 4.4uF (two 2.2uF Vishay MKT1822 in parallel) caps on the inputs (C122, C132) and they sound wonderful. They should, according this guy. But I am hoping someone have done some cap rolling here.
PS: this is another update to the original schematic and bom – the input caps can be made 2.2uF to 4.7uF (instead of 10uF). See posts #587 and #588.
I experience the same with my Aksa Lender / ACA combo!
I was wondering if someone has experimented with the input caps yet, and if bypass caps here makes a difference? Currently I use 4.4uF (two 2.2uF Vishay MKT1822 in parallel) caps on the inputs (C122, C132) and they sound wonderful. They should, according this guy. But I am hoping someone have done some cap rolling here.
PS: this is another update to the original schematic and bom – the input caps can be made 2.2uF to 4.7uF (instead of 10uF). See posts #587 and #588.
I am using Clarity 6.8uF 250v MKP on one Preamp and Dayton 10uF 250v MKP on another. Hard to tell difference but the purple clarity caps look cooler! 🙂
There is a good cap review in this thread somewhere. It actually said my MKP Chinese Audiofiler ones ranked pretty high despite only being $3 caps.
I have had great luck with 10uF Silmic II actually. $0.35ea. 🙂
There is a good cap review in this thread somewhere. It actually said my MKP Chinese Audiofiler ones ranked pretty high despite only being $3 caps.
I have had great luck with 10uF Silmic II actually. $0.35ea. 🙂
Well thank you X. If you cannot tell the difference then this is not a big deal. MKP seems fine and safe here - no need for snake oil caps for more magic.
Interesting that input and output caps seems to be a bigger discussion point in headphone amp threads - maybe easier to notice subtle differences with a good headphone setup?
I’m not saying that there is no difference. Just very subtle and in blind ABX with electronic switcher box, I bet very hard to tell. The Clarity caps are reasonably priced and I would not say they are snake oil by any means. It’s when you get >$50 caps it’s diminishing returns. There are “cap porn” threads on the Multiway Speaker forum where people use $4000 Duelund gold or silver foil in wax or oil or wax paper, etc.
Duelund Silver Foil & Wax/Oil Bypass Caps
Duelund Silver Foil & Wax/Oil Bypass Caps
I really need to know the current consumption - for sizing the SMPS. (I went with the 15dB gain setup)
Could someone measure (or calculate) the current draw of one of these babies, please?
Could someone measure (or calculate) the current draw of one of these babies, please?
I can fit a Meanwell RS-15 (15W) into the available space. A higher wattage SMPS will be a problem, space-wise.
For non HPA version the current is about 35mA per channel, so 70mA total. Let’s double for good measure at 150mA. That’s at 48v so power is 7.2w. If using DC step up efficiency is 90% so need 8w. At 12v Wall smps you need 670mA.
I use 800mA 12v class 2 transformer and it works fine so this makes sense.
I use 800mA 12v class 2 transformer and it works fine so this makes sense.
Thanks X. That helps a lot.
I'll be using a 5-56V, 2A step-up converter as shown below and even at 80% efficiency, the current is only 9W according to your calculation. So, the 15W SMPS will be ample. That makes life a little easier organizing everything inside the enclosure. Yes, the SMPS is going inside.
I'll be using a 5-56V, 2A step-up converter as shown below and even at 80% efficiency, the current is only 9W according to your calculation. So, the 15W SMPS will be ample. That makes life a little easier organizing everything inside the enclosure. Yes, the SMPS is going inside.
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Isn’t it a problem having a smps that’s too large? If so, what’s too large?
I have a 30w one for the preamp. I am afraid it is too big. I read somewhere that smps performs better (less noise) close to peak demand. Idk how close that is though.
I have a 30w one for the preamp. I am afraid it is too big. I read somewhere that smps performs better (less noise) close to peak demand. Idk how close that is though.