Audiojerry: according to the website that Pmkap listed above, the unit can be bridged at the flip of a switch. Given the low power output / lack of power supply reserve that this amp has at 4 ohms, bridging it might actually agravate the "lean sound" of this amp to an even greater extent. This has to do with the fact that bridged amps effectively see half the impedance that is connected to it. As such, an 8 ohm load would look like a 4 ohm load to a bridged amp. If the speaker dropped to 4 or 6 ohms, the bridged circuit would effectively be looking at appr 2 - 3 ohms. Judging by the very small power increase when going from 8 to 4 ohms on this unit, jumping down to what the amp might see as a 2 ohm nominal load might actually give you LESS power than what you have at 4 ohms.
My previous suggestion was to tie the power supply for each channel together in parallel, not bridge the amp. What this does is keep the voltage potential the same, but doubles the amount of current available to the one channel that remains in operation. Judging by the pictures that i've seen, it looks as if this unit uses a common power supply for both channels, so my suggestion is probably a moot point.
Others may think that an increase in current may not be noticeable under most conditions, but the resultant decrease in voltage sag along various low level stages can produce a more consistent & harmonically correct presentation. The fact that the driver stages are fed from the same "under-nourished" power supply as the output stages on this amp doesn't help matters. As such, when one starts to increase the intensity of signal applied to the amp, the driver stages push the output stages harder. As the output stages pull more current to keep up with the greater signal demands, they begin to pull current away from the earlier gain stages. The earlier gain stages are now in a state of reduced linearity due to power supply restriction. The signal degradation that takes place in that situation is now passed onto the output stages, which in turn amplify those non-linearities. As such, it is kind of a "Catch 22" situation i.e. the circuit is chasing its' tail and can only feel pain once it catches up with itself.
The other thing that i noticed was that this amp has little to no power supply reserve ( filter capacitance ) available to it. Given that the amp shares a common supply between both channels ( from what i can tell ) this becomes even more critical. From what i can see in those pictures, it uses two 4700 uF 63 volt caps. If one could get this up to ( at least ) ten times that level, i would think that bass would be much firmer with greater punch. Then again, almost ANY increase in capacitance would probably be beneficial with the low level of reserve that this amp has in it from the factory.
Given the phenomenally small chassis size, one may have to do some creative wiring to achieve something of this nature. Having the caps wired to the point where the power supply actually feeds into each channel rather than at one common point of resevior would also help bass impact. This is due to the reduced amount of delivery time as needed on high level, short duration peaks.
One should be able to do something like this by installing two 10,000 uF caps ( or greater if size permits ) in the two front corners of the chassis and using them to feed the channel closest to them. This would allow one to leave the factory caps where they are or one could replace these with larger caps if they felt the need. Running bypass caps on the larger caps might also help get rid of some of the "shrillness" ( for lack of better word ) that Dls somewhat hints at on various recordings.
I could further into tips / tricks on this amp, but not having one handy to look at or a schematic makes that difficult. Suffice it to say that "beggars can't be choosers" at this price point and the amp is surely lacking in some specific areas. Given that one has very limited work space and heat dissipation with such a design, one might be better off finding an equivalent used amp of larger dimensions and modifying it. This is not to say that the SLA-1 doesn't have potential ( i'm sure it does, just as all stock circuits can be improved upon ), but that one could run into limitations with such a design faster than another design that was less "cramped" for space.
As a side note, the ART Dio ran into the same problem as it is "ten pounds of parts in a 2 pound box", etc... Same company, same design / construction principles, same limitations. Sean
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My previous suggestion was to tie the power supply for each channel together in parallel, not bridge the amp. What this does is keep the voltage potential the same, but doubles the amount of current available to the one channel that remains in operation. Judging by the pictures that i've seen, it looks as if this unit uses a common power supply for both channels, so my suggestion is probably a moot point.
Others may think that an increase in current may not be noticeable under most conditions, but the resultant decrease in voltage sag along various low level stages can produce a more consistent & harmonically correct presentation. The fact that the driver stages are fed from the same "under-nourished" power supply as the output stages on this amp doesn't help matters. As such, when one starts to increase the intensity of signal applied to the amp, the driver stages push the output stages harder. As the output stages pull more current to keep up with the greater signal demands, they begin to pull current away from the earlier gain stages. The earlier gain stages are now in a state of reduced linearity due to power supply restriction. The signal degradation that takes place in that situation is now passed onto the output stages, which in turn amplify those non-linearities. As such, it is kind of a "Catch 22" situation i.e. the circuit is chasing its' tail and can only feel pain once it catches up with itself.
The other thing that i noticed was that this amp has little to no power supply reserve ( filter capacitance ) available to it. Given that the amp shares a common supply between both channels ( from what i can tell ) this becomes even more critical. From what i can see in those pictures, it uses two 4700 uF 63 volt caps. If one could get this up to ( at least ) ten times that level, i would think that bass would be much firmer with greater punch. Then again, almost ANY increase in capacitance would probably be beneficial with the low level of reserve that this amp has in it from the factory.
Given the phenomenally small chassis size, one may have to do some creative wiring to achieve something of this nature. Having the caps wired to the point where the power supply actually feeds into each channel rather than at one common point of resevior would also help bass impact. This is due to the reduced amount of delivery time as needed on high level, short duration peaks.
One should be able to do something like this by installing two 10,000 uF caps ( or greater if size permits ) in the two front corners of the chassis and using them to feed the channel closest to them. This would allow one to leave the factory caps where they are or one could replace these with larger caps if they felt the need. Running bypass caps on the larger caps might also help get rid of some of the "shrillness" ( for lack of better word ) that Dls somewhat hints at on various recordings.
I could further into tips / tricks on this amp, but not having one handy to look at or a schematic makes that difficult. Suffice it to say that "beggars can't be choosers" at this price point and the amp is surely lacking in some specific areas. Given that one has very limited work space and heat dissipation with such a design, one might be better off finding an equivalent used amp of larger dimensions and modifying it. This is not to say that the SLA-1 doesn't have potential ( i'm sure it does, just as all stock circuits can be improved upon ), but that one could run into limitations with such a design faster than another design that was less "cramped" for space.
As a side note, the ART Dio ran into the same problem as it is "ten pounds of parts in a 2 pound box", etc... Same company, same design / construction principles, same limitations. Sean
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