Nelson Pass said:
I experienced the same type of sound change when I increased the gain on the BOSOZ from 10 to 20 db, highs got crispier, bass ramained pretty much the same. At 10 dB it sounded a little bit darker, almost like a passive preamp. At the time I was using the BOSOZ to power a Sennheiser HD600. It was a dramatic change.
Tweaks
I have been listening to my Alehp X and comparing it to an Aleph. It seems to be a little on the bright side. It also has less gain. I am running +/- 15 volts with about 3.5 amp current draw per channel. The output are IRFP260's one per connection. It is unbalanced with 2.2 uf. caps at the inputs. More current, less feedback? Any Ideas?
I have been listening to my Alehp X and comparing it to an Aleph. It seems to be a little on the bright side. It also has less gain. I am running +/- 15 volts with about 3.5 amp current draw per channel. The output are IRFP260's one per connection. It is unbalanced with 2.2 uf. caps at the inputs. More current, less feedback? Any Ideas?
I'm using 220k resistor for feedback and 33k input to ground. The gain is higher than my Aleph 5.
For sure the Aleph X design needs feedback , and the equilibrium is between gain and feedback.chris ma said:
Too much feedback , low gain
No feedback , too much gain.
I look around the effects of the feedback.Peter Daniel said:
(a) Predictability of voltage gain
(b) Input impedance
(c) Output impedance
(d) Distortion
(e) Offset
(f) Stability against oscillation
I was thinking about (e) and (f), particularly (f). Once with my old DIY amplifier of 200W class A/B, I had a problem with (f). When the amount of the negative FB was rated down to certain level, the output speaker-protection relays started to be busy. It was terrible.
Do not wake up the sleeping baby. 🙂
JH
Re: calculation
Are these wrong figures?
JH
Assuming the ac-current gain of 50%, I see the peak ac-current of about (1 + 0.5) x 2.272A per channel. This might mean that the ac-current swings within 2 x (1 + 0.5) x 2.272A in class-A operation before the clipping. If so, the load power into 4 ohm speaker is estimated about maximum 23W in class-A operation.wuffwaff said:
Are these wrong figures?
JH
jh6you,
I don´t really understand the question. There is only class A with an Aleph at 50%. No AB here
At 50% ac current gain the peak-current is not (1+0,5) but (2) times the bias current. So your peak current is 2xbias per half and this equals the total bias current of an Aleph X
william
I don´t really understand the question. There is only class A with an Aleph at 50%. No AB here
At 50% ac current gain the peak-current is not (1+0,5) but (2) times the bias current. So your peak current is 2xbias per half and this equals the total bias current of an Aleph X
william
Hi William
I understand in this way. From the active current source of one side, the peak current (or the current limitation) is (1 + 0.5) times the bias current, and from the other side, also (1 + 0.5). Therefore, the current does swing through the speaker in between these two peak values.
How the factor 2 instead of (1 + 0.5) comes?
Your explanation would much appreciate.
JH
I understand in this way. From the active current source of one side, the peak current (or the current limitation) is (1 + 0.5) times the bias current, and from the other side, also (1 + 0.5). Therefore, the current does swing through the speaker in between these two peak values.
How the factor 2 instead of (1 + 0.5) comes?
Your explanation would much appreciate.
JH
The factor 2 comes because the 50% current gain means that the current source delivers 50% of the peak current at idle.
If there is insufficient bias and a current gain in excesswuffwaff said:
of 50%, you can shut off the current source on negative
peaks, creating what would be thought of as AB. While the
output is not clipped, this is not desirable as the distortion
is high under these conditions.
I wondered how the 2 current sources work togetherNelson Pass said:
at iddle, both are at 50%, OK
at full power, how is it? One conducts 2Amps (in exampls) and the other -2 (symmetrical amp-> current goes out from a current source, and goes in the other)
am I right?
so, with an input sine wave, for 1/2 period one current source outputs 2amps, the other -2
and for the second 1/2 period, the roles are changed, and the current source that was giving 2 amps gives now -2?
Both current sources are capable of delivering between -2 and +2 amps?
and for the second 1/2 period, the roles are changed, and the current source that was giving 2 amps gives now -2?
Both current sources are capable of delivering between -2 and +2 amps?
Each current source is on the opposite side of the load,
along with its associated gain stage. For this to work,
the current sources are naturally out of phase with each
other.
along with its associated gain stage. For this to work,
the current sources are naturally out of phase with each
other.
I changed the feedback resistors R16 and R30 to 220k, R11 and R33 to 68k to get a little more bias. All 4 Mosfets ar reading .6 volts across .33 ohm resistors. There are four .33 ohm res. in parrallel at the output. Should there only be two? Also R19 and R29 are still 68k. Should they be lower? The amp is sounding better by the day. Thanks.