There is a BOM that I released (with help from zman01 - probably linked on post 1. The 18pF can be up to 22pF if you have then. Should be silver mica or NP0/C0G SMT.
R113 is carbon because it affects the sound. Lower distortion and lower 3rd harmonic relative to 2nd harmonic with carbon.
Any reason not to use carbon comp here instead of carbon film? I've heard a people go carbon comp for the first resistor in the signal path.
Carbon comp is not stable in value over long term so your amp gain may not be constant. High quality metal thin film may actually be fine here. I just found lower 3rd order HD with carbon film (which is more accurate than carbon comp). Definitely thick film metal oxide is not a good choice here.
Having said that - if you hand match two carbon comp resistors to within 5% or better go ahead and try them.
Having said that - if you hand match two carbon comp resistors to within 5% or better go ahead and try them.
Some are saying that Carbon comp resistors sound sweeter than carbon film resistor which might sound harsh when used in signal path. I did not get that vibe though ...
Hi Vunce,
Have you had a chance to connect to the Fortes yet? Listening impressions are eagerly awaited.
Have you had a chance to connect to the Fortes yet? Listening impressions are eagerly awaited.
I’ve been trying to come up with a solution for my less than ideal power supply voltage 17.5-19vdc, it varies depending on the time of day.
An old motor head term applies here, ‘There’s no replacement for displacement’.
Which means I need a LARGER transformer 😀
I will hook up the ALPHA to the Forte’s this weekend and report back.
That's about the right size heatsink, Juntuin. We are talking about 35w or so, not insignificant. Same as an ACA amp (1 channel). Looks really nice though.
I thought so, and size fits nicely with pcb also in my opinion 🙂 was surprised that found them in Finland! Usually you can't find anything you need.
I assembled the ALPHA amplifier module and accompanying power supply parts in my audio cabinet and connected to my AKSA Lender preamp (low gain DB installed) and Forte speakers.
Flipped the switch....MUSIC!!
The power supply voltage increased by 1.5v, the only difference from my bench testing is the Fortes are 8ohm and the Speedsters are 4ohms. Would that make a difference?
I was getting a fair bit of background noise, but figured it was just the way everything was put together, long wires, power next to signal wires, etc...
It was driving me crazy so I started to investigate, and it turned out to be the LED recessed lights in my kitchen!!!!! There are 4 different light circuits each with dimmer switches. When all the lights are off the ALPHA is nice and quite 🙂
That is very puzzling to me because I have two dedicated 20amp power lines run directly to the breaker/power panel?? No other amp I have does that when plugged into these lines.
My initial thought as to what I’m hearing is lots of energy up top. I wouldn’t say bright, just different than I’m used too. Also, the input cap is a 10uF Silmic II. I will replace the electrolytic with a Mundorf cap when my final chassis is ready.
Flipped the switch....MUSIC!!
The power supply voltage increased by 1.5v, the only difference from my bench testing is the Fortes are 8ohm and the Speedsters are 4ohms. Would that make a difference?
I was getting a fair bit of background noise, but figured it was just the way everything was put together, long wires, power next to signal wires, etc...
It was driving me crazy so I started to investigate, and it turned out to be the LED recessed lights in my kitchen!!!!! There are 4 different light circuits each with dimmer switches. When all the lights are off the ALPHA is nice and quite 🙂
That is very puzzling to me because I have two dedicated 20amp power lines run directly to the breaker/power panel?? No other amp I have does that when plugged into these lines.
My initial thought as to what I’m hearing is lots of energy up top. I wouldn’t say bright, just different than I’m used too. Also, the input cap is a 10uF Silmic II. I will replace the electrolytic with a Mundorf cap when my final chassis is ready.
The load would not affect quiescent bias in a SE Class A. It may be plugging the amp into a different wall plug makes a difference. You may have dirty mains on your outlets. The LED light dimmers are probanly PWM and emitting noise?
Let us know how it sounds with more tracks. How doesn’t compare to the MoFo with Aksa Lender Preamp?
Let us know how it sounds with more tracks. How doesn’t compare to the MoFo with Aksa Lender Preamp?
Then I would say the slight voltage increase is because the audio system is on a dedicated power line. That is why the noise from the dimmer/LED lights is puzzling to me?
Should the CLC be before or after the Juma capMx?
Dedicated power line:
20amp breaker->#12Romex->PS Audio outlets, no other lights or appliances on the circuit.
what was CLC designed for? It depends on how much of a inrush current load it has. If large, then After cap Mx.
It seems the voltage reading across R131 is affected by temperature. When I lower the fan speed, temperature goes up and voltage goes down. If I increase fan speed temp goes down, voltage goes up.
Jean-Paul,
Thanks for the question, and my apologies for letting you know earlier.
Yes, on the Big Boy, but not required of course for the 20W ALPHA.
You can use 1206 for the cap, or even a disc through hole ceramic, and a 0805 or even 1/4W through hole 47R.
This snubber prevents self-oscillation of the outputs in all use. Very needed in Class AB, not quite so much for Class A, but a very, very good idea.
Hugh
Thanks for the question, and my apologies for letting you know earlier.
Yes, on the Big Boy, but not required of course for the 20W ALPHA.
You can use 1206 for the cap, or even a disc through hole ceramic, and a 0805 or even 1/4W through hole 47R.
This snubber prevents self-oscillation of the outputs in all use. Very needed in Class AB, not quite so much for Class A, but a very, very good idea.
Hugh