Thanks STOXX. I have not used the 7815/7915. Based on the data sheet, it doesn't seem to be oscillation prone. 100uF on the output will kill the transient response of the regulator. Just trying some easy steps to optimize what is already there. Substituting a couple of film caps for electrolytics is pretty easy.
I tried MOFI with film caps in place of the 100uF, and IMHO it sounds better. Using a 0.47uF on the 7815 side and 1uF on the 7915 side. 400V large, axial and it looks ridiculous (all I had). I know it is regulating better without the larger 100uF cap. The lead spacing on the 100uF cap is 4mm.
Ali sells 1uF 63V 5mm lead spacing (63V105J-P5) for the 7915. 0.1uF 100V 5mm lead spacing (100V104J-P5) for the 7815. These values are from the data sheet. They are said to be PP, but probably polyester, which is perfectly fine. WIMA in polyester with 5mm lead spacing are available in many variations.
Ali sells 1uF 63V 5mm lead spacing (63V105J-P5) for the 7915. 0.1uF 100V 5mm lead spacing (100V104J-P5) for the 7815. These values are from the data sheet. They are said to be PP, but probably polyester, which is perfectly fine. WIMA in polyester with 5mm lead spacing are available in many variations.
Bought a pre-built unit from the bay. $25. Sounds fabulous. No clue if the components are authentic but I tend to doubt it. I am comparing to my Transcendent Sound grounded grid, Korg 10-R, and Musical Fidelity M1-CLIC preamps.
No hint of digital grit yet plenty of high end, dynamics and bass outstanding. Midrange sweet as can be, full and rich.
Kinda stunned at how great it sounds...
I am pushing the power supply to the max though with 18 vac 1 amp transformer, and using an external input attenuator for volume control.
No hint of digital grit yet plenty of high end, dynamics and bass outstanding. Midrange sweet as can be, full and rich.
Kinda stunned at how great it sounds...
I am pushing the power supply to the max though with 18 vac 1 amp transformer, and using an external input attenuator for volume control.
how's that for a build 😉
I will look at repurposing an old Hafler DH-101 for enclosure and multi-input switching. I have two DH-101s with bad pots that are now unobtanium. Plenty of room in those chassis and I have replacement gold plated RCA jack sets from updatemydynaco but they may be sold out of those now...
I will look at repurposing an old Hafler DH-101 for enclosure and multi-input switching. I have two DH-101s with bad pots that are now unobtanium. Plenty of room in those chassis and I have replacement gold plated RCA jack sets from updatemydynaco but they may be sold out of those now...
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I just ordered a second preamp unit; might as well re-purpose both DH-101s at the same time...
To my ears this unit sounds better than a DH-101 ever did...
To my ears this unit sounds better than a DH-101 ever did...
I may try a toroid or rcore next but this one sounds great right now with the preamp so why change?
My watt meter indicates the preamp and transformer are using a total of .05 amps after initial power on (energizing the trannie and caps I guess). ZERO hum, ZERO transformer vibrations. I am driving an Ayima A07 into Elac DBR-2 speakers. But that is for testing. I may give my Class A Musical Fidelity amp or even my 25wpc OTL Tube amp for a try. I do mostly quasi near field listening.
My dim bulb tester (60 watt/120v) lights for about 1/2 second at power up.
My watt meter indicates the preamp and transformer are using a total of .05 amps after initial power on (energizing the trannie and caps I guess). ZERO hum, ZERO transformer vibrations. I am driving an Ayima A07 into Elac DBR-2 speakers. But that is for testing. I may give my Class A Musical Fidelity amp or even my 25wpc OTL Tube amp for a try. I do mostly quasi near field listening.
My dim bulb tester (60 watt/120v) lights for about 1/2 second at power up.
And as other smarter people than myself have pointed out, 18v supply can heat-stress the regulators for no sonic benefit. 15v would be a much better choice.
On Ali in the parts list under power requirements, it lists "AC 12-0-12 to 18-0-18 I >= 0.3A Best AC 15-0-15 1A".
With a 12.6-0-12.6 2A transformer, I measure +18V and -18V at the cap. The 7815/7915 need 17V minimum to regulate. 12-0-12 300mA would probably barely make it over 17V.
With a 12.6-0-12.6 2A transformer, I measure +18V and -18V at the cap. The 7815/7915 need 17V minimum to regulate. 12-0-12 300mA would probably barely make it over 17V.
thank you,, good to know. as I said above "15v would be a much better choice."
and I have read that if using a toroid, I can expect a larger inrush current at powerup. don't need that and this core transformer does not generate enough heat to be an issue- just slightly warm after 8 hours continuous duty of the preamp...
and I have read that if using a toroid, I can expect a larger inrush current at powerup. don't need that and this core transformer does not generate enough heat to be an issue- just slightly warm after 8 hours continuous duty of the preamp...
By the way, the IC is socketed. Is there consensus yet on whether an authentic chip is a worthwhile replacement? And if so where to obtain?
The 5532 in the MOFI version appear to be genuine. A simple test is a diode test on the inputs. Pins 2 and 3 should measure diode voltage drop in both directions, because there are diodes across the inputs in both directions. See functional block diagram 8.2 of data sheet. Same result for pins 5 and 6. Not sure if this is always valid, but I would reject chips that don't pass this test.
I have a medley of dual opamps I can try on the board. Some may not work. AD746, LM1458, Oracle_II-2, LT1229, ADA4522-2, SA5532 and a Philips NE5532 from 1993, ha. I have other opamps too but I got to dig 'em up. I also have single to dual adapters sooooo I can try another bazillion opamps I have here.
Now why don't I have this board up and running? Time to get to it...
Cheers.
Now why don't I have this board up and running? Time to get to it...
Cheers.
