One thing I noticed today, and I don’t know if an equipment configuration changed or this is a function of balanced inputs. So a question for those using balanced inputs: is the input gain higher on them than single-ended?
Here’s the scenario. Until this amp, everything has been RCA inputs. I have used my Technics amp/preamp, and from my friend’s collection an ACA, an M2X, and an Elekit—all RCA. Into all of those I used a Mac Mini with Audirvana and a Schiit Modi DAC configured with software volume control (I know, I know). The input levels have been consistent the entire time.
Now I have the Aleph J and I set up the same configuration, with the only difference being I have a balanced input on the amp with and XLR-to-RCA adapter on the amp inputs as shown in the attached image. In this configuration, the apparent gain is insane. As a matter of fact, the software volume control is at normal listening level one click off of infinity (-35dB on the display). And it goes up very quickly to uncomfortable levels.
So my question is, does this input stage provide more gain than an RCA input? This adapter does the shorting inside the plug versus a separate RCA with a shorting wire in the plug.
I just think something changed in the software since I can only get the volume control down to -35dB, but thought I’d ask the question in case there’s something I don’t understand about this amp.
Here’s the scenario. Until this amp, everything has been RCA inputs. I have used my Technics amp/preamp, and from my friend’s collection an ACA, an M2X, and an Elekit—all RCA. Into all of those I used a Mac Mini with Audirvana and a Schiit Modi DAC configured with software volume control (I know, I know). The input levels have been consistent the entire time.
Now I have the Aleph J and I set up the same configuration, with the only difference being I have a balanced input on the amp with and XLR-to-RCA adapter on the amp inputs as shown in the attached image. In this configuration, the apparent gain is insane. As a matter of fact, the software volume control is at normal listening level one click off of infinity (-35dB on the display). And it goes up very quickly to uncomfortable levels.
So my question is, does this input stage provide more gain than an RCA input? This adapter does the shorting inside the plug versus a separate RCA with a shorting wire in the plug.
I just think something changed in the software since I can only get the volume control down to -35dB, but thought I’d ask the question in case there’s something I don’t understand about this amp.
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amp is having same gain V/V , being driven SE or Bal
gain is roughly (but almost exact ) ratio feedback resistor value divided with series input resistor value
I'm lazy to check in AJ thread what is that , but I believe some 10V/V, that being approx. 20db
check that adapter - is there really short circuit between pins 1 and 3
if that is the case, and you have all right values of resistor in amp, something else is fishy
gain is roughly (but almost exact ) ratio feedback resistor value divided with series input resistor value
I'm lazy to check in AJ thread what is that , but I believe some 10V/V, that being approx. 20db
check that adapter - is there really short circuit between pins 1 and 3
if that is the case, and you have all right values of resistor in amp, something else is fishy
Very nice!
Remember that playing with the “bias” pot in an Aleph is actually changing the AC current gain of the Aleph Constant Current Source... in English, that means the adjustments are doing more than just changing the Iq (quiescent current, ‘bias’) of the output devices... it also changes how the CCS reacts to the load.
I.E., experiment with it, yes, but go in knowing that more Iq may not be “better”, and that the recommended starting value is the AC current gain that is the sweet spot in terms of most listener’s preference.
Precisely what I found, no real improvement. Still yet, you can never have too much heat sink. Mine lives fine in a deluxe 4U smaller chassis, (300mm deep only). no extra room like a extra deep one would provide.
Russellc
I went ahead and turned off software volume control on the DAC and channeled everything through my AV as a preamp. Was hoping to try as few devices as possible, but we gets what we gets. 😛
Preamp project is next. Then there will be a showdown of sorts.
I’m just reveling in my newfound sound quality in its preferred bias. I’ll leave it alone. So, so nice... 😀
can't wait for social distancing to be a thing of the past and we can arrange a few folk to get together to revel in all this fine DIY .
what preamp did you have in mind?
..dB
oh, and congrats again, it never gets old 🙂
what preamp did you have in mind?
..dB
oh, and congrats again, it never gets old 🙂
Yes yes!
I have an Aleph P board set on its way from a Jim’s Audio in Hong Kong. Hopefully it isn’t stuck in the Suez behind that grounded ship! 😛
Pondering some interesting options like an onboard streaming renderer and motorized volume control with remote. Still researching a few things, and I can’t get too much farther without knowing what Jim’s board set consists of. It’s a bit of a mystery at the moment. And who doesn’t love a good mystery? I’ll be sure to start a build thread on it.
Should we tell Pass Labs that they did the same thing with their XS preamp power supply fuse holder that I did? 😛
Inside Pass Labs XS Preamplifier - YouTube
See around 1:40
Yes, yes....it is slightly colored, but beautifully so. Always a favorite for me to return to. Surprising bass power on correct speakers. A true gem.
Russellc
I believe the ship is now dislodged. Also consider the Iron Pre preamp, not there yet but will be in store soon? As one of the Beta builders, I have found it mates supremely with Aleph J. So nice!
Russellc
Good to know. Teasing, of course. But now it's the only thing I can see when I look at a fuse holder! A good safety lesson to be sure.
As Anand said. There are no split washers in the back panel kit, only flat. So you’ll need to pop out to your local hardware store to pick some up.
After a couple of glorious weeks of listening, I think it’s time to check the biasing. The amp has been on for the entire period, staying nice and warm and dutifully trying to keep the basement temperatures stable. Yesterday while listening, I found that I had to bump my interim preamp (Pioneer AV integrated) up +2dB on the right main to center the image. I presume this will be resolved with amp adjustment?
I haven’t pulled the amp out to check it yet, but thought I’d pose the question.
I haven’t pulled the amp out to check it yet, but thought I’d pose the question.
Chris,
Report back after you have checked your Aleph J build. Your build was meticulous so I doubt it would be related to that. A failing part like a JFET? Or the bias royally falling out of whack? I surmise you would hear a lot more than a miniscule 2dB change between the overall gain of L/R channels. This is also assuming your aural memory is perfect ;-)
If you were nearby, I would hook up your Aleph J and test each channel on my O-scope with a Bode Plot analysis from 10Hz to 100 khz to prove that the gains matched in each of the channels. I don’t use my ears and music signal for that kind of test.
Perhaps look elsewhere such as room effects (which can wreck havoc on the FR at certain frequencies) or even your preamp.
Best,
Anand.
Report back after you have checked your Aleph J build. Your build was meticulous so I doubt it would be related to that. A failing part like a JFET? Or the bias royally falling out of whack? I surmise you would hear a lot more than a miniscule 2dB change between the overall gain of L/R channels. This is also assuming your aural memory is perfect ;-)
If you were nearby, I would hook up your Aleph J and test each channel on my O-scope with a Bode Plot analysis from 10Hz to 100 khz to prove that the gains matched in each of the channels. I don’t use my ears and music signal for that kind of test.
Perhaps look elsewhere such as room effects (which can wreck havoc on the FR at certain frequencies) or even your preamp.
Best,
Anand.
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