Just finished my Aleph 2, and there was no smoke or minor explotions, so I am rather happy with my self. The sinks is warming equal on all four sides and the measurepoinst are fine, as far as I can comprehend.
What I not so pleased with is that I have to put the volume pot on the Bosoz all the way just to hear a breeze of sound at normal level. I have followed the track of Mr. Thomas Chao project at http://www.penguinlovers.net/audio/aleph2_proj.html which is a nice ABC for beginners- as myself.
The Bosoz is based from the pcb of Kristijan and has a R15 of 220 ohm. I mention this because at first I thought is is the gain of the preamp thats causing the low output.
I am using the unbalanced RCA input only.
Any idea what is wrong or what I can do to increase the output level of my Aleph 2 babies?
What I not so pleased with is that I have to put the volume pot on the Bosoz all the way just to hear a breeze of sound at normal level. I have followed the track of Mr. Thomas Chao project at http://www.penguinlovers.net/audio/aleph2_proj.html which is a nice ABC for beginners- as myself.
The Bosoz is based from the pcb of Kristijan and has a R15 of 220 ohm. I mention this because at first I thought is is the gain of the preamp thats causing the low output.
I am using the unbalanced RCA input only.
Any idea what is wrong or what I can do to increase the output level of my Aleph 2 babies?
If you're using the amp with an unbalanced source, you should ground the unused input (usually the - input). That will give you 6dB of gain right there. Also remember that the Alephs had 20dB gain; about 6dB less than a 'normal' amp. All in all that's about 12dB. The gain can be changed if you want, but the grounding the unused input trick is quick, easy, and free.
Grey
Grey
Thanks for your reply.
I have used the attached schematic for the connections and using the switch does not make any different. I am now trying to connect xlr plugs on my bosoz to see if that do the trick. At the same time I was hoping to X-it, using the schematic of Henrik, but now I can't figure out where I should put the In+ and In- from the input of the PCB from Kristijan to my Dact CT3. Any idea?
See the attached files.
I have used the attached schematic for the connections and using the switch does not make any different. I am now trying to connect xlr plugs on my bosoz to see if that do the trick. At the same time I was hoping to X-it, using the schematic of Henrik, but now I can't figure out where I should put the In+ and In- from the input of the PCB from Kristijan to my Dact CT3. Any idea?
See the attached files.
Still no volume...
William
Do I also ground the - IN in balanced mode? I have just made the output on the Bosoz with XLR and there is still no increased volume. I can hardly hear the music when the pot is on full.
GRollins
Do you know where I can adjust the gain on the Aleph or where to search to find the "bottleneck" in my amp. (I am using BrianGT boards)
and any idea what value to use to adjust the gain on the Bosoz?
I really need some help here...
William
Do I also ground the - IN in balanced mode? I have just made the output on the Bosoz with XLR and there is still no increased volume. I can hardly hear the music when the pot is on full.
GRollins
Do you know where I can adjust the gain on the Aleph or where to search to find the "bottleneck" in my amp. (I am using BrianGT boards)
and any idea what value to use to adjust the gain on the Bosoz?
I really need some help here...
Pboden: I may be wrong, but I thought Thomas used a board he got from a diy source overseas. I have a Brian GT board and am planning to do a Aleph 5. I think I see a slight difference in the polarity/configuration of the input connections on the Brian GT board and the one in Thomas' article. Course the print is small and it may just be my aging eyes 
Not sure if this would cause your problem, but I have big notations on my copy of the Thomas article to make sure the layout on his board and the BrianGT board I have is identical.
Larry Wright
Seattle area
Not sure if this would cause your problem, but I have big notations on my copy of the Thomas article to make sure the layout on his board and the BrianGT board I have is identical. Larry Wright
Seattle area
Does your preamp work properly? your x picture doesn't look quite right. There should be 10K to ground from the old input connections, IIRC. The way you have it drawn it has no gain.
You might want to try hooking your cd player directly to the amp (without a speaker connected) to verify the amp operation and see if you have gain. Is the output voltage 20 db higher than the input?
If not, check your feedback resistors are the right values in the right positions? I messed that up on my A75 the first time around and had no gain.
You might want to try hooking your cd player directly to the amp (without a speaker connected) to verify the amp operation and see if you have gain. Is the output voltage 20 db higher than the input?
If not, check your feedback resistors are the right values in the right positions? I messed that up on my A75 the first time around and had no gain.
BobEllis said:
You might want to try hooking your cd player directly to the amp (without a speaker connected) to verify the amp operation and see if you have gain. Is the output voltage 20 db higher than the input?
I'll try that.
If not, check your feedback resistors are the right values in the right positions? I messed that up on my A75 the first time around and had no gain.
Sorry for my ignorance, but where do I locate the feedback resistor?
Right positions??? Do you mean on the board or the right way in the right positions? (I mean that polarisation of a resistor is not importaint... is it? )
I meant the wrong values in those positions. Polarity of a resistor doesn't matter. Did you check the output level of your preamp? If you used lower values for the output capacitors you'll have reduced bottom end.
On the original Aleph2 schematic R5, R7, C8 and C5 form the feedback network. If R7 is smaller than 100K, you'll get proportionally less gain. If R5 is too big you'll get less gain, too.
C5 serves to make the gain go to 0 at DC. If it is too small, the low frequency cutoff will be higher. If you left it out, you'll have no gain at all. If you want to have your amp DC coupled, you need a jumper where C5 should be. Try jumpering C5 temporarily to see if it is bad.
Similarly, C8 limits the high frequency response by increasing feedback with frequency. If it is too big you'll roll off your top end. I don't think this is the problem from the way you describe the sound. However if C8 is shorted, we're effectively at R7 too small again.
How I would approach troubleshooting:
1. Disconnect the speaker. Use a dummy load if you have one, if not it's OK.
2. Verify that you have a suitable input voltage - measure the voltage at the input pins using a steady tone from a signal generator or test CD. You'll need over 2 volts between the + and - inputs to get to maximum output. If you don't get at least a volt, look to the preamp for troubleshooting.
3. If you have good input, measure the output signal. Is the voltage 10 times the input? (assuming that you built a standard Aleph2)
4. If not, check the feedback circuit as described above. Measure the values in circuit.
5. If you still have a problem, measure the DC voltages shown in the schematic and report back. Also measure the voltage at the gates of Q1 and Q2 - it should be at ground, if not they could be your problem.
BTW, in the balanced mode you do not ground the inverting input. just realize that your BOSOZ is a less than perfect unbalanced to balanced converter, so your inverted output will swing less than the normal output.
Good luck
On the original Aleph2 schematic R5, R7, C8 and C5 form the feedback network. If R7 is smaller than 100K, you'll get proportionally less gain. If R5 is too big you'll get less gain, too.
C5 serves to make the gain go to 0 at DC. If it is too small, the low frequency cutoff will be higher. If you left it out, you'll have no gain at all. If you want to have your amp DC coupled, you need a jumper where C5 should be. Try jumpering C5 temporarily to see if it is bad.
Similarly, C8 limits the high frequency response by increasing feedback with frequency. If it is too big you'll roll off your top end. I don't think this is the problem from the way you describe the sound. However if C8 is shorted, we're effectively at R7 too small again.
How I would approach troubleshooting:
1. Disconnect the speaker. Use a dummy load if you have one, if not it's OK.
2. Verify that you have a suitable input voltage - measure the voltage at the input pins using a steady tone from a signal generator or test CD. You'll need over 2 volts between the + and - inputs to get to maximum output. If you don't get at least a volt, look to the preamp for troubleshooting.
3. If you have good input, measure the output signal. Is the voltage 10 times the input? (assuming that you built a standard Aleph2)
4. If not, check the feedback circuit as described above. Measure the values in circuit.
5. If you still have a problem, measure the DC voltages shown in the schematic and report back. Also measure the voltage at the gates of Q1 and Q2 - it should be at ground, if not they could be your problem.
BTW, in the balanced mode you do not ground the inverting input. just realize that your BOSOZ is a less than perfect unbalanced to balanced converter, so your inverted output will swing less than the normal output.
Good luck
The Alephs are running
I now have full impuls on my Alephs. R6 and R7 have somehow been mixed up, either by me or Digikey. They where at 100 ohm instead of 100K.
The sound is just great. I have had some amps in my time, but I belive this is bullseye. Thank you all for the inputs and help. This forum is just great.
Pictures is coming up soon.
I now have full impuls on my Alephs. R6 and R7 have somehow been mixed up, either by me or Digikey. They where at 100 ohm instead of 100K.
The sound is just great. I have had some amps in my time, but I belive this is bullseye. Thank you all for the inputs and help. This forum is just great.
Pictures is coming up soon.
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