Hello Andrew
It was the Mk1 ?
If you happen to retry it with a higher cdom, keep us in touch, I'm curious to know the sonic results.
Thank
Bye
Gaetan
Hi Todd,
R12/R12B is 2 resistors on the original conceptual schematic, plus it is also on the original AKSA 55. R12/B sets the maximum bias so I think having a place for 2 resistors allows for more options for fine tuning. Hugh may have had other sneaky plans of splitting the resistor and using the centre point for something else. He does that.
Andrew's explanation of PE sounds good to me. I connect it to star earth which in my amps is connected to safety earth.
C1 at 470nF is the "standard" value for the AKSA 55. The N+ use different values and it one area where I'll intend to have a play. Rabbitz uses 1uF in this position which is what I have in my box as an alternative.
Eagle. I learnt how to use it properly. Eagle now supports print to PDF natively which is the same quality as using a PDF printer add-on. It also required tuning of all the Eagle schematic symbols and using the correct font option for schematics. You raised the bar with your DX schematics, I had to do something.
regards
Probably related to the input cap, the input resistance of the B-AKSA is 47K (why is that value used... industry standard?). I've seen a few amps recently with input impedance at 100K or 220K.
Am I right in saying if you have a higher input impedance then you can use a smaller input cap to achieve the same roll off and does it make it more friendly for a passive pre? I'm sure there are issues such as increased noise and I imagine the rest of the circuit would need adjusted values to suit the higher input impedance or can they be left as is.
I tried several values for the input cap and settled on 1uF. With smaller standmount speakers I couldn't pick a difference with the 470nF cap but could with a speaker that goes below 30Hz.
Am I right in saying if you have a higher input impedance then you can use a smaller input cap to achieve the same roll off and does it make it more friendly for a passive pre? I'm sure there are issues such as increased noise and I imagine the rest of the circuit would need adjusted values to suit the higher input impedance or can they be left as is.
I tried several values for the input cap and settled on 1uF. With smaller standmount speakers I couldn't pick a difference with the 470nF cap but could with a speaker that goes below 30Hz.
I suspect it was maybe the intention to tweak with a pot to find the best value, then bypass the pot and use the 2nd resistor to obtain that value, thus eliminating one potential physical point of failure/drift.
Ah yes, the default Eagle symbols are a mess. Good on yah!
..Todd
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Hi Rabbitz,
That jives with my understanding. The input cap and resistor form a high-pass filter, their values and load will determine the LF response limit.
If you're playing vinyl or use a risky vented alignment on your woofers, that filter is a good tool to have if tuned adequately. Otherwise I would [personally] go bigger on the cap (lower HP rolloff).
You live in Newcastle! Nice. A quick hop over to the Hunter for refreshments.
..Todd
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Hi homemodder,
No I have not tried the JLH reg on the B-AKSA yet. I must put that onto my list so I do not forget. I will PM some details to you.
regards
Hi cjcc67,
I haven't had a chance to do any comparisons at all. I been to busy with building the amps and creating documention.
I will be able to compare to a DX amp and a SKA 150 in the future as I have these amps in boxes somewhere.
I see the B-AKSA amp as a DIY experimenter amp. I am doing this for my own interest, getting more hands on experience, and if others are interested or get some benefit from it then all the better.
regards
Hi Todd
Yes it's a nice spot but a bit cold at the moment..... brrrrr. I don't know how you guys in Canada put up with the cold as when it drops below 20°C here I go into hibernation.
They do a nice drop in the Hunter but liquid refreshments are off the agenda these days due to a heart attack a couple of years ago. I have to do soft drinks instead.
I haven't built the B-AKSA yet as waiting for spring to warm things up. I'm still hiding in my cave.
I have built a lot of amps such as the AKSA 55, AKSA 55N, AKSA 55N+, AKSA 55N+ (mongrel), DX HRII, GB150, LF55, LM3875, LM4780, NX150, NXV200, P3A, P101 and some SC amps. There is a theme here as I'm sucked in by the presentation of Hugh's amps and my main amp for the last couple of years has been the mongrel AKSA 55N+. That's not going to change any time soon... or ever.
I'm expecting the B-AKSA to slot in between the P3A and AKSA 55.
Thanks Guys. The P3A could be interesting too. It's also on my shortlist. Greg your boards are nice do you make them yourself? I usually use valve amplification, but my new speakers have cleaned out my bank for a while. I was hoping to find an cost effective short term solution. I have some enclosures and binding posts so only require the transformers and amps!! (build dual mono). Despite all the great things I've read, the AKSA's are out of my budget.
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Hi all,
I have built test amp#4 and amp#5 following the BOM, construction notes and setup procedure found here:
B-AKSA 55
So I hope I have provided just enough documentation, and it is accurate enough, to allow a DIYer that has already built a couple of amps previous to throw one together in a few hours.
Tuning and mods to come. They do have a bit of turn off thump that needs attention.
regards
I have built test amp#4 and amp#5 following the BOM, construction notes and setup procedure found here:
B-AKSA 55
So I hope I have provided just enough documentation, and it is accurate enough, to allow a DIYer that has already built a couple of amps previous to throw one together in a few hours.
Tuning and mods to come. They do have a bit of turn off thump that needs attention.
regards
Thanks for the tip. I want to build monos aren't these stereo with the PSU on the same board?
