I recently completed my foray into Class D by building an Amp6. It's been burning in now for about 72 hours and I have found the bass lacking to my ears. I am use to a vintage integrated tube amp 
with tone controls so that may be an issue, but I would like a little more "slam" coming from my Kirksaetters. Any ideas on how to improve bass on the Amp6 would be greatly appreciated. 
with tone controls so that may be an issue, but I would like a little more "slam" coming from my Kirksaetters. Any ideas on how to improve bass on the Amp6 would be greatly appreciated. Try a snubber across the 1800uF bulk capacitor. Check the snubber threads, I use a value of 2.2uF + 4.7 ohms in parallel with 0.1uF.
I dont necessarily get lots more bass, but the bass sounds cleaner & more dynamic.
Regards,
Dean
I dont necessarily get lots more bass, but the bass sounds cleaner & more dynamic.
Regards,
Dean
Thank you for the snubber suggestion. 🙂
Do you think my choice of 3.3uf input caps has something to do with the bass issue? I used Sonicaps (Gen 1) in place of the stock electrolytics. I am aware that some people find the Sonicaps slightly thin and bright instead of lush like an Auricap. What if I bypassed the 3.3uf Sonicaps (Gen 1) with a smaller Sonicap (Gen 2) as their website suggests? I wonder if that would improve things a little?
Do you think my choice of 3.3uf input caps has something to do with the bass issue? I used Sonicaps (Gen 1) in place of the stock electrolytics. I am aware that some people find the Sonicaps slightly thin and bright instead of lush like an Auricap. What if I bypassed the 3.3uf Sonicaps (Gen 1) with a smaller Sonicap (Gen 2) as their website suggests? I wonder if that would improve things a little?
I have certainly not found the AMP6 to be bass shy, either to the ear or in measurement. But I always use a 10,000uF stiffener cap, sometimes two.
A lot of tube amps tend to be "loose" in the low end, allowing the speakers to overshoot on the bass notes. This can sound nice for small drivers (I don't know the Kirksaetters). Class-D amps tend to have much more control of the speaker than tube amps do. Thus a "drier" bass, but a more accurate bass. It can take some getting use to. 🙂 For some speakers a looser amp will actually be better, as it adds some low end that small drivers are often missing.
That said, try adding a good quality stiffener cap to the regulated side of the supply and see if that helps. It's easy to do and undo.
Better input caps can also help the bass. There won't be more of it, but it can sound much fuller. I find even good electrolytics sound dry in the lower registers. YMMV
On a technical note, can you measure the DC voltage on the regulated and unregulated side of the power supply? If your unregulated voltage isn’t high enough, you’ll certainly loose bass and dynamics.
OK, time to stop. Much more than you wanted to know!
A lot of tube amps tend to be "loose" in the low end, allowing the speakers to overshoot on the bass notes. This can sound nice for small drivers (I don't know the Kirksaetters). Class-D amps tend to have much more control of the speaker than tube amps do. Thus a "drier" bass, but a more accurate bass. It can take some getting use to. 🙂 For some speakers a looser amp will actually be better, as it adds some low end that small drivers are often missing.
That said, try adding a good quality stiffener cap to the regulated side of the supply and see if that helps. It's easy to do and undo.
Better input caps can also help the bass. There won't be more of it, but it can sound much fuller. I find even good electrolytics sound dry in the lower registers. YMMV
On a technical note, can you measure the DC voltage on the regulated and unregulated side of the power supply? If your unregulated voltage isn’t high enough, you’ll certainly loose bass and dynamics.
OK, time to stop. Much more than you wanted to know!
panomaniac said:
Hi,
I'm new to this forum and I read your answers with a lot of attention...
I would like to understand where do you connect this "stiffener" cap (I don't understand the exact meaning of this word...)?
Is it connected in parallel to C1819?
Should it be as close as possible to C1819 or is it possible to use 10 cm of wire to connect this cap?
Actually, I'm about to finish my AMP6 and I would prefer to make the modification before to integrate it in a small case.
Thanks
Bonjour Niiico,
The stiffener cap should go as close to the board as you can get it. Basically you want a low resistance, low inductance path from the cap to the board so that energy can be supplied quickly to the amp.
10 cm is a bit long. 1/2 that would be better. But if you can use a large wire, it will help. Yes, it is connected in parallel to C1819
The "stiffener" cap works as an energy reservoir to supply the amp during loud passages and peaks. Even though the AMP6 has an onboard regulated supply, it is not perfect. Adding a large capacitor(s) helps to keep the voltage stable. It supplies the peak energy needed to give you good dynamics and bass. To the ear it results in a stronger, more dynamic amp with a fuller low end..
Bref, ca rende l'ampli moin "mou", si tu veux- plus rigid.
Ca n'est pas au gout de tout le monde, mais je le trouve beaucoup plus realiste et musical.
The stiffener cap should go as close to the board as you can get it. Basically you want a low resistance, low inductance path from the cap to the board so that energy can be supplied quickly to the amp.
10 cm is a bit long. 1/2 that would be better. But if you can use a large wire, it will help. Yes, it is connected in parallel to C1819
The "stiffener" cap works as an energy reservoir to supply the amp during loud passages and peaks. Even though the AMP6 has an onboard regulated supply, it is not perfect. Adding a large capacitor(s) helps to keep the voltage stable. It supplies the peak energy needed to give you good dynamics and bass. To the ear it results in a stronger, more dynamic amp with a fuller low end..
Bref, ca rende l'ampli moin "mou", si tu veux- plus rigid.
Ca n'est pas au gout de tout le monde, mais je le trouve beaucoup plus realiste et musical.
The regulated side is C1819, the gold and black Panasonic cap. Unregulated is C99, the big black cap.
Ground is common between them.
Ground is common between them.
panomaniac said:
Ok, thanks for the explanation. What kind of cap should I use? Will any 10000uF 16V be ok?
That's what I was thinking about, but I wasn't sure.
How do you put the cap on the AMP6 ? There is no place on the board and if we want to reduce the connection cables?...
En tout cas, merci panomaniac pour toutes ces explications.
niiico said:
Any10000uF or more cap will help, but the better the quality, the better you'll like it. I use Nichicon "Gold Tune" series that are designed for audio power supplies.
In the UK, many users have liked the Aerovox brand. You should be able to find either of those in France or something just as good.
It will not fit on the board. Just put it as close as you can. 5 or 6 cm of thick wire is OK.
The DC measures fine according to specs, so to get more bass I bypassed the 3.3uf Sonicap input caps with .1uf Illnois MWR caps. This in effect took the edge off the highs and brought the bass more forward. It certainly does not rock and roll but the bass is at least now present on my Kirksaetter's. Thanks to everyone for their help.
panomaniac said:
Hi panomaniac,
I'm also a beginner and would like to ask you for help since I'm going to bi amp my Car System with 2 Amp6 assembled into 1 small aluminium box.
One Amp6 will power up my 6.5" Morel midbasses and I will use on it a 10,000 or 15,000 stiffener cap as you recommend to improve the low frequencies.
The another Amp6 will power up the mid highs/full ranges and would like to know if it can be modded to improve the high frequencies too.
PS: The input 3.3uf supply caps will be replaced by Solen Metallized Polypropylene Caps and the aluminium box will receive Connex RCA jacks and gold plated safety binding posts as well. Internal connects will be done with Van den Hul or Belden large wire (as short as possible).
Many thanks for yr comments about this little project.
Rgds
SoundBrazil
That all seems correct for an auto setup. On the high/mid side, you don't need 3.3uF, 0.3uF should be enough. No harm using the bigger cap, but you don't need it.
You will want to eliminate the voltage regulation on the PCB. The car electrical system does not have enough voltage headroom for the AMP6 regulator. Also, you will not need the diode bridge. You will need good filtration, though, as car electrics are very "dirty".
You might also drop your input resistors to 10K, or even lower, if your head end will push it (shouldn't be a problem). Lower input impedance can help keep noise out of the signal.
Let us know how it goes.
You will want to eliminate the voltage regulation on the PCB. The car electrical system does not have enough voltage headroom for the AMP6 regulator. Also, you will not need the diode bridge. You will need good filtration, though, as car electrics are very "dirty".
You might also drop your input resistors to 10K, or even lower, if your head end will push it (shouldn't be a problem). Lower input impedance can help keep noise out of the signal.
Let us know how it goes.
If you want more bass you need more capacitance.
But don't forget, big caps are rubbish in high frequencies.
Try a few 6,800uF caps in parallel( six per rail should be enough).
But don't forget, big caps are rubbish in high frequencies.
Try a few 6,800uF caps in parallel( six per rail should be enough).
First of all, thank you very much guys!!
Well, the high side will work from 500Hz and up, since these drivers are full ranges. So, what are the most suitable cap's value in this case?
Which components have I to keep out of the PCB in order to eliminate the voltage regulator? Just Q3 or also R100, R101 and R102 as well? Also, what is(are) the diode bridge in the Bill Of Materials? (D5 to D12?)
Concerning the filtration, what components (according to the BOM) are the most critical? Which should be a good replacement for each one of them?
Finally, I will replace R22 and R24(39K) by another 10K resistors, is that ok? And will I have any problem in the bass side with using only one big capacitor of 15000uf as our friend XELB advised? Note that this side will work until 500Hz only. Can the big cap just replace the 2200uf supplied cap or must it be installed in parallel with it?
😕 😕 😕
Wow... sorry if I gave much work for you!!!
Thank you and will let you know as soon as I have it running! 😀
Well, the high side will work from 500Hz and up, since these drivers are full ranges. So, what are the most suitable cap's value in this case?
Which components have I to keep out of the PCB in order to eliminate the voltage regulator? Just Q3 or also R100, R101 and R102 as well? Also, what is(are) the diode bridge in the Bill Of Materials? (D5 to D12?)
Concerning the filtration, what components (according to the BOM) are the most critical? Which should be a good replacement for each one of them?
Finally, I will replace R22 and R24(39K) by another 10K resistors, is that ok? And will I have any problem in the bass side with using only one big capacitor of 15000uf as our friend XELB advised? Note that this side will work until 500Hz only. Can the big cap just replace the 2200uf supplied cap or must it be installed in parallel with it?
😕 😕 😕
Wow... sorry if I gave much work for you!!!
Thank you and will let you know as soon as I have it running! 😀
If you will use the amp only for 500Hz, you can use just one cap.
Normally it's above 5k Hz that big caps lose their ability.... 😉
Normally it's above 5k Hz that big caps lose their ability.... 😉
XELB said:
Here we are talking about input caps, not PSU caps.
For 500Hz and above, 0.3uF is all you need. Remember, the Sonic Impact uses a 0.3uF input cap, and its roll off starts at 100Hz.
As for 10K resistors on the inputs, they are NOT the onboard resistors, leave those a 22K. I meant the off board resistors between signal and ground. Usually this is the volume pot 100K-50K. Just tie your signal to ground via 10K right at the RCA. Before the input caps!
I'll have look at the board and BOM for the PSU questions. For the moment leave off Q3, R100, R101, R102 and CMP15.
I still believe you need a big stiffener cap even for the mids. There is a LOT of energy in the mids. Looking at the power supply fluctuations, much of it comes from voice, brass, load piano, that sort of thing.
SoundBrazil said:
Be careful putting two amps in the same chassis. Since their switching frequencies aren't synchronized you may end up hearing them reproduce audible beat frequencies. I'd physically separate the amps as far as possible from each other to help avoid this.
SoundBrazil said:
What's the sensitivity rating of your 6.5" Morels? The Amp6 sure sounds good at low power, but it's low power output will really limit the SPL you'll get from the Morels. In the car you have to compete with much higher levels of background noise than you do at home, so your speakers have to play louder to reach the same perceived level of loudness.
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