You can use high quality (Vishay Dale for example) metal film here. I have had luck with cheap no name carbon thin film here though. Depending on your needs 4k7, 6k8, 8k2, etc can be good. I think ACA is 15dB do aim for another 15dB.
I only see now that your reply regarding the power supply is embedded in my quote above. Thanks X.
Hey X, Hugh, et all:
I've got a few quick questions about power supply for the AKSA pre-amp.
I have a spare Abeltec(1) 53v dual rail smps I was considering using. Perhaps a CRCRC or similar to drop the voltage down to ~48v+/- ?
Would be convenient if that could work. I have lots of spare parts on hand to make a crc* .
I tried to simulate a crcrc in PSUD to figure out the voltage drop, but I'm clearly doing something wrong. I'm not sure how to calculate the component values, so I am admittedly guessing a good bit.
Thanks!
Gable
1 - Abletec Switch Mode Power Supply +53V at 1.4A, -53V at 1.4A, +7.5V at 1.6A, +5.6V 1A
I've got a few quick questions about power supply for the AKSA pre-amp.
I have a spare Abeltec(1) 53v dual rail smps I was considering using. Perhaps a CRCRC or similar to drop the voltage down to ~48v+/- ?
Would be convenient if that could work. I have lots of spare parts on hand to make a crc* .
I tried to simulate a crcrc in PSUD to figure out the voltage drop, but I'm clearly doing something wrong. I'm not sure how to calculate the component values, so I am admittedly guessing a good bit.
Thanks!
Gable
1 - Abletec Switch Mode Power Supply +53V at 1.4A, -53V at 1.4A, +7.5V at 1.6A, +5.6V 1A
Pcgab,
That Abletec is a very nice SMPS capable of 250w continuous load and 900w peak load for 10mS. I use it with nice big Class AB speaker amp. It is clearly overkill for a Preamp. Just use a small 12v 800mA Class 2 transformer wall wart (used for routers and DSL modems etc), you must have at least 5 spares in your house. Use that to power the DC-DC step up board to 52v then let cap Mx take it to 48v. Or 48v and drop to 44v still very good. It will be much quieter than he Abletec. After all my testing of noise in the FFT I found that the “GCI” brand Class 2 wall transformers are the quietest when used with step up and cap and. Like a battery quiet.
Get this and save your Abletec for a real amp.
Amazon.com: GEREE 250W Boost Converter DC/DC 8.5-48V to 12-50V Output Step-up Module Mobile Power Supply Max 10A: Home Audio & Theater
That Abletec is a very nice SMPS capable of 250w continuous load and 900w peak load for 10mS. I use it with nice big Class AB speaker amp. It is clearly overkill for a Preamp. Just use a small 12v 800mA Class 2 transformer wall wart (used for routers and DSL modems etc), you must have at least 5 spares in your house. Use that to power the DC-DC step up board to 52v then let cap Mx take it to 48v. Or 48v and drop to 44v still very good. It will be much quieter than he Abletec. After all my testing of noise in the FFT I found that the “GCI” brand Class 2 wall transformers are the quietest when used with step up and cap and. Like a battery quiet.
Get this and save your Abletec for a real amp.
Amazon.com: GEREE 250W Boost Converter DC/DC 8.5-48V to 12-50V Output Step-up Module Mobile Power Supply Max 10A: Home Audio & Theater
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I have not found a need for the CLC. It depends on your locality. Some places seem to benefit from it. I have heard in Germany mains are really dirty with RF and have DC even.
Well that's easy enough. I have 2 of those boost converters on hand already, and I have some spare 12v supplies, if not probably a spare 15v or 18v.
You have a post/thread reference to a decent cap mx?
Thanks for the help X!
The Aksa Lender Preamp has the cap Mx and CRCRC built in already (look in lower right of schematic). You just need to hook up the DC DC step up to it.
You might want to look at the GB thread. All the schematics are in the GB thread.
Now that is awesome, I totally forgot about that!
The same approach of built in Cap Mx and CRCRC is being implemented in the new desktop version of the PCA. BDHM is working on the layout and it should be close to production.
My experience with using wall warts and DC-C-step ups ans cap Mx with CRCRC's has been very successful in completely eliminating any mains (60/120/180/240) peaks in the FFT down to the instrument noise floor. So essentially, you get same low noise as if using battery. So makes sense to employ this on all builds that don't require huge currents (like big Class A amps). Still working the SMPS/Cap Mx/CRCRC angle on that...
Ive been watching the pca thread, as I'm definitely going to build a desktop version. I have 300-400 bf862's, so I should be able to find the exact right pair.
I ordered one of the HP smps', they're so inexpensive it was a no-brainer.
Considering remote volume control for the AKSA pre-amp. A controller board with input selection, remote power on/off, and volume control would be awesome.
There are probably some existing solutions that I could leverage. Need to do some more research.
Cheers,
Gable
I've been waiting for some free time to start my build, but in the meantime I would love to hear some subjective opinions how this pre stacks up to other commonly available diy builds. I have two different Aikido 's, a Doug Self design, and Salas's DCB, they all sound very good, but some play better with some amps than others.
I have a DCG3 but this Aksa Lender Preamp specializes in higher output swing while maintaining a nice harmonic distortion profile and low THD. The DCG3 is a great Preamp design. My subjective opinion is that the soundstage and imaging on the Aksa Lender is better - wider and more depth. I feel that a BJT, especially the 2SA1837 is more resolving and refined compared to an IRF9610 as an output device. Having the output transistor emitter drive the output node (as in Aksa Lender output topology) is more accurate than having the drain of a mosfet drive the output node and rely on feedback to make it accurate again. Perhaps Vunce can chime in on his experience?
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