PS, I am familiar with wiring pots as I've been a luthier all my life and I've made many electric guitars and been a pro repairer for rock and roll for about 45 years. Usually we use metal pots and always solder the earth on the back of them. These pots are plastic however and I wasn't sure what to do with the earth. I tried connecting the earth wires to them and taking them off but no difference. I think maybe I should try it the way I would wire a volume pot on a guitar.
well, it depends of which guitar pot 🙂
CCW lug is GND, wiper goes to amp , CW lug takes input signal from source
if connected that way, and you still have hum, wire screening and/or length is critical
CCW lug is GND, wiper goes to amp , CW lug takes input signal from source
if connected that way, and you still have hum, wire screening and/or length is critical
The volume control goes after a (usually) single stage of pre-amplification (this can also have a gain of 1...), to ensure the impedance seen by the source is constant. It also goes before a unity gain buffer, which will ensure a low impedance drive for the output amplifier. Notice: I just described a properly designed pre-amplifier🙂 (some integrated amplifiers are also done like this, i.e. the right way...)
It is better to use a DSP to control the volume (Jriver, HQPlayer), then to just insert a volume control before the amp.
The 1/8" - to - RCA adapters' cables are known for very poor shielding... Make one yourself, use Mogami microphone cable.
Good luck,
Nick
It is better to use a DSP to control the volume (Jriver, HQPlayer), then to just insert a volume control before the amp.
The 1/8" - to - RCA adapters' cables are known for very poor shielding... Make one yourself, use Mogami microphone cable.
Good luck,
Nick
Ok , so I'm about to order the parts for my Aleph J and just wanted to confirm a couple of things.
1) R8 gets a 1K resistor instead of a variable(multi turn) resistor.
2)C6 and C7 are left out. Why are they now excluded?
Is this correct ?
1) R8 gets a 1K resistor instead of a variable(multi turn) resistor.
2)C6 and C7 are left out. Why are they now excluded?
Is this correct ?
FLOHMAN’s fantastic Aleph J Build Guide for Noobs answers these (very good) questions here:
Parts: the Rest of the BOM
Parts: the Rest of the BOM
Thanks for the link ,it's very helpful.
However I didn't see an explanation for omitting C6 and C7 which just seem to be bypass caps for C2 and C3.
Is there no benefit to bypassing the electrolytic caps ?
However I didn't see an explanation for omitting C6 and C7 which just seem to be bypass caps for C2 and C3.
Is there no benefit to bypassing the electrolytic caps ?
Last edited:
Sorry, Fred. the misspelling was a typo, not ignorance.
Rtate: control-F comes in handy a lot in these circumstances.
I’m not being a smart-***. Actually, I just sent flohmann a bunch of suggestions to improve the build guide, and probably half of those recommendations were based on the fact that I didn’t carefully read what was already there.
So, in penance, here you go:
“C6 and C7 can present a challenge because of the very limited space on the board for them. If you cannot find a part that fits, you can simply omit them and the amp will work fine. They do not appear in the official First Watt Aleph J schematic. So why are they on our board and in the BOM? There seems to be a widespread practice of using a small film capacitor alongside every larger electrolytic capacitor in the audio signal path. Something about electrolytic capacitors inherently performing more poorly than film capacitors at high frequencies, and thus the use of a film cap in parallel compensates to some degree for this shortcoming of the electrolytic cap on its own. (In the case of my build, I mistakenly ordered WIMA caps with the wrong lead spacing, but I managed to bend the leads and fit them into the board anyway. You should probably go with the correct caps from the BOM instead.)”
Building: Amp Boards
Rtate: control-F comes in handy a lot in these circumstances.
I’m not being a smart-***. Actually, I just sent flohmann a bunch of suggestions to improve the build guide, and probably half of those recommendations were based on the fact that I didn’t carefully read what was already there.
So, in penance, here you go:
“C6 and C7 can present a challenge because of the very limited space on the board for them. If you cannot find a part that fits, you can simply omit them and the amp will work fine. They do not appear in the official First Watt Aleph J schematic. So why are they on our board and in the BOM? There seems to be a widespread practice of using a small film capacitor alongside every larger electrolytic capacitor in the audio signal path. Something about electrolytic capacitors inherently performing more poorly than film capacitors at high frequencies, and thus the use of a film cap in parallel compensates to some degree for this shortcoming of the electrolytic cap on its own. (In the case of my build, I mistakenly ordered WIMA caps with the wrong lead spacing, but I managed to bend the leads and fit them into the board anyway. You should probably go with the correct caps from the BOM instead.)”
Building: Amp Boards
Rtate -
Some people think is doesn’t matter at all.
Some think it’s intensely important.
Some think that bypassing makes all electrolytics sound equal and the bypasses are the equalizer.
Lots of opinions in audio...
Some people think is doesn’t matter at all.
Some think it’s intensely important.
Some think that bypassing makes all electrolytics sound equal and the bypasses are the equalizer.
Lots of opinions in audio...
Sorry, Fred. the misspelling was a typo, not ignorance.
Rtate: control-F comes in handy a lot in these circumstances.
I’m not being a smart-***. Actually, I just sent flohmann a bunch of suggestions to improve the build guide, and probably half of those recommendations were based on the fact that I didn’t carefully read what was already there.
So, in penance, here you go:
“C6 and C7 can present a challenge because of the very limited space on the board for them. If you cannot find a part that fits, you can simply omit them and the amp will work fine. They do not appear in the official First Watt Aleph J schematic. So why are they on our board and in the BOM? There seems to be a widespread practice of using a small film capacitor alongside every larger electrolytic capacitor in the audio signal path. Something about electrolytic capacitors inherently performing more poorly than film capacitors at high frequencies, and thus the use of a film cap in parallel compensates to some degree for this shortcoming of the electrolytic cap on its own. (In the case of my build, I mistakenly ordered WIMA caps with the wrong lead spacing, but I managed to bend the leads and fit them into the board anyway. You should probably go with the correct caps from the BOM instead.)”
Building: Amp Boards
Rtate: control-F comes in handy a lot in these circumstances.
I’m not being a smart-***. Actually, I just sent flohmann a bunch of suggestions to improve the build guide, and probably half of those recommendations were based on the fact that I didn’t carefully read what was already there.
So, in penance, here you go:
“C6 and C7 can present a challenge because of the very limited space on the board for them. If you cannot find a part that fits, you can simply omit them and the amp will work fine. They do not appear in the official First Watt Aleph J schematic. So why are they on our board and in the BOM? There seems to be a widespread practice of using a small film capacitor alongside every larger electrolytic capacitor in the audio signal path. Something about electrolytic capacitors inherently performing more poorly than film capacitors at high frequencies, and thus the use of a film cap in parallel compensates to some degree for this shortcoming of the electrolytic cap on its own. (In the case of my build, I mistakenly ordered WIMA caps with the wrong lead spacing, but I managed to bend the leads and fit them into the board anyway. You should probably go with the correct caps from the BOM instead.)”
Building: Amp Boards
Electrolytic capacitors are not designed to couple AC, in particular, if used where the DC voltage difference at their pins is close to 0.
I remember a few decades ago when I was playing with electrolytes... the best result I obtained was with two capacitors connected in series (instead of using only a single cap), to mimic NP capacitor, and then the middle point connected to either Vcc (V+) or Vee (V-), depending on how the resulting capacitor is constructed, i.e. either with negatives connected together, or with positives.
The above is an electrolyte used to couple the sound. Another use is just to filter the noise (de-couple the noise from DC supply lines). Here, a small cap in parallel is used to provide low ESR at a wide frequency range...
So, the above two scenarios are completely different.
I remember a few decades ago when I was playing with electrolytes... the best result I obtained was with two capacitors connected in series (instead of using only a single cap), to mimic NP capacitor, and then the middle point connected to either Vcc (V+) or Vee (V-), depending on how the resulting capacitor is constructed, i.e. either with negatives connected together, or with positives.
The above is an electrolyte used to couple the sound. Another use is just to filter the noise (de-couple the noise from DC supply lines). Here, a small cap in parallel is used to provide low ESR at a wide frequency range...
So, the above two scenarios are completely different.
Rtate -
Some people think is doesn’t matter at all.
Some think it’s intensely important.
Some think that bypassing makes all electrolytics sound equal and the bypasses are the equalizer.
Lots of opinions in audio...
If ever I was feeling frisky enough to do an alternate PCB layout I would provide enough space for those bypass caps to be able to slot Vishay MKP1837 film caps in there. But that be just me. And I am a lazy mofo. But I do know Chokey will back me up on this idea. Putting it on the reverse side will just put my OCD over the edge.
Last edited:
Unfortunately MKC is unobtainium where I live.
Compromises always required when living in Africa. 🙁
Compromises always required when living in Africa. 🙁
WIMA MKC was discontinued in Y2000, when the polycarbonate dielectric became unavailable: link to WIMA announcement
Team, was hoping to build the acclaimed Alpha J but the tent pole are the 2SK270BL or 2SJ74BL...aka Q1A & Q1B.....any chance their some available??
thanks
Brian
thanks
Brian
oh yeah
MKC Rulez
MKP is for Sissies
Sonic differences between MKP and MKC?
Russian K73 seems similar... or not?
Thanks
Read: "Capacitor Sounds" white papers from Linear Audio website, in particular 4, 5 and 6 (which relate to amplifiers the most). Polypropylene has the lowest distortions of them all.
Other dielectrics may sound better in a particular system, for whatever reason (personal taste), but once you've read the white papers, you'll be able to make your own conclusion. Then try for yourself, in your system.
Other dielectrics may sound better in a particular system, for whatever reason (personal taste), but once you've read the white papers, you'll be able to make your own conclusion. Then try for yourself, in your system.
Distorsion values seems similar in PP and PC...
@ZM Pleaseeeee... I have to order components for my AJ!
@ZM Pleaseeeee... I have to order components for my AJ!