I am very glad to hear that you are enjoying its sound. I must admit I still get anxious as to whether my circuit really sounds as good as I think it does.
As to the motorized pot with a long shaft, I can't say that I've evr seen one, but it is easy enough to build a shaft coupler to add an extension shaft. I've built about a half dozen of the things now using only a hand drill, a hack-saw, a half inch piece of aluminum rod, some #4 screw and a #4 tap. They don't look exactly pretty, but they work very well. If your interested, I'll sketch out some instructions ...
As to the motorized pot with a long shaft, I can't say that I've evr seen one, but it is easy enough to build a shaft coupler to add an extension shaft. I've built about a half dozen of the things now using only a hand drill, a hack-saw, a half inch piece of aluminum rod, some #4 screw and a #4 tap. They don't look exactly pretty, but they work very well. If your interested, I'll sketch out some instructions ...
Member
Joined 2002
metalman said:
He could also do what peter daniel does and not need any thing but a hack saw. 🙂
He uses Pvc tube about 1.5" long and a 1/4" shaft either brass / Aluminum or what ever you want to use. IN this picture you'll see the chassis built from peter witch uses bras bar and a piece of pvc tube. If you heat it then press it on it works perfect no screws no drilling.
An externally hosted image should be here but it was not working when we last tested it.
Thanks!
I should have said how long a shaft... I only need a inch shaft or so. Round all the way. Every motor pot I've seen so far has had that dang notch in the shaft.
I have some pot extension hardware from a torn down 'scope I could use with no problem, just trying to avoid the complication and the extra 'drag' it would put on the motor.
I should have said how long a shaft... I only need a inch shaft or so. Round all the way. Every motor pot I've seen so far has had that dang notch in the shaft.
I have some pot extension hardware from a torn down 'scope I could use with no problem, just trying to avoid the complication and the extra 'drag' it would put on the motor.
No need to get anxious. The thing sounds real good. If you put your atten. on the output and use the output balanced, then it sounds real great🙂
Member
Joined 2002
Ok so my x-bosoz pre amp with balanced out put and with the pot after the pre-amp sounds like CRAP!! EKKS..
Member
Joined 2002
mpmarino said:
Bad.
Totally distorted and when turned up a little the bass is way to distorted.. I have never ever heard of putting a pot on the end of the pre-amp.
It makes no sense to me. First of your driving the pre-amp into full load at full level then attenuating it at the end so if the pre-amp is clipping you'll hear it. I have always had the pot at the front..
Anyway's back to the closet it goes and out comes the passive pot / opamp based one.
Jason,
If you are passing a normal consumer level signal into the XBOSOZ it will not clip unless you have changed the gain. Not even close.
The problem may infact be that the output impedance of your attenuator/pot is way too high for your power amp's input impedance. What is the input impedance of your power amp? And what is the impedance of your pot?
Obviously lot of folks have had very good results with attenuators/pots at the output of preamps. You can also do the attenuation on the input, just turn up the bias a bit on the XBOSOZ so you minimise the transistor noise.
My attenuator has an output impedance of 750 ohms, and my power amp has an input impedance of ~2.2K, and that is working out quite nicely. The amps are DC coupled.
Cheers!
Russ
If you are passing a normal consumer level signal into the XBOSOZ it will not clip unless you have changed the gain. Not even close.
The problem may infact be that the output impedance of your attenuator/pot is way too high for your power amp's input impedance. What is the input impedance of your power amp? And what is the impedance of your pot?
Obviously lot of folks have had very good results with attenuators/pots at the output of preamps. You can also do the attenuation on the input, just turn up the bias a bit on the XBOSOZ so you minimise the transistor noise.
My attenuator has an output impedance of 750 ohms, and my power amp has an input impedance of ~2.2K, and that is working out quite nicely. The amps are DC coupled.
Cheers!
Russ
Member
Joined 2002
Russ White said:
That's the weird thing if i use rca in and xlr out they sound good but with that hiss at lower levels i can hear it witch drives me nuts but at a higher level its not there ( shadowed ) I don't know what the input impedance of the aleph mini's are.
Jase
I'm seeing none of those symptoms. The only time I have any noticible hiss is when the volume is max or near max with the source paused or off.
I can crank the volume up all the way with no audible distortion. In fact, I suspect the pre can do quite a bit more gain cleanly if built to do so. There is certainly enuff voltage swing; I'm guessing.
I run a mini a and a a30 right now.
I suspect your attenuator as well.
I can crank the volume up all the way with no audible distortion. In fact, I suspect the pre can do quite a bit more gain cleanly if built to do so. There is certainly enuff voltage swing; I'm guessing.
I run a mini a and a a30 right now.
I suspect your attenuator as well.
Member
Joined 2002
mpmarino said:
The other attenuater the Passive Rca based one works perfectly in passive mode and before the bosoz.. But if i use the bozoz with xlr out and rca in i get his. Im going to try a few things tonight and see if they get resolved.
I'll post pics. The bosoz sounds really good in rca mode but id like to release the real sounds 🙂
Jason, I have answers to a few of your questions:
I have checked, both by calculation and by measurement of the working circuit, and the circuit can tolerate 4.5V(RMS) simultaneously at the positive and negative input connections (out of phase of course) without clipping the outputs, which is a 9V(RMS) differential signal input. So unless you are feeding some serious high level input signals, I doubt it is forcing the circuit into clipping unless there is something else wrong.
That the circuit is having different behaviours at different frequencies is a bit of a clue. I'll let that sink in and see if it triggers any usefull thoughts.
Your miniA's, if built to the BrianGT specs should have an input impedance of about 20K. Even if you output attenuator is 10K you should still get excellent results. I have a 10K balanced output attentuator on my pre, and it has no problems driving amplifier loads as low as 2K. Putting the attenuator on the outputs is very non-standard, but it was a Nelson Pass design feature from the original BoSoZ article, not something kooky that Russ and I came up with.
The thought that is nagging me is that there seems to be too much gain in your pre. What leads me to this is that the sound of clipping is pretty hard to mistake, so when you say it is clipping I am inclined to believe you. As the circuit has lots of headroom built in to prevent clipping, unless the gain is much higher than it is supposed to be, the clipping shouldn't happen. The second factor that makes me suspect too much gain is the hiss you are hearing, which by your description is much higher than the rest of us are experiencing. This could also be caused by the gain being too high (and vice versa the feedback being too low). So what I suggest is measure the resistance across the following resistors with the circuit turned off:
Feedback Resistors: R18, R19
Input Resistors: R14, R15
Drain Resistors: R1+R6, R2+R7
For the drain resistors the R1+R6 means measure the two together (they are in parallel with each other).
Report the numbers back and we'll see if they tell us anything.
Do you ever get over to Vancouver. I live in North Van, and I'd be happy to try troubleshooting yours. Your experiences definitely seem to be out of step with the norm, and I can understand why you are so frustrated with it. It should be working better! Likewise, if I get up-Island I'll give you a shout and drop in.
Cheers, Terry
I have checked, both by calculation and by measurement of the working circuit, and the circuit can tolerate 4.5V(RMS) simultaneously at the positive and negative input connections (out of phase of course) without clipping the outputs, which is a 9V(RMS) differential signal input. So unless you are feeding some serious high level input signals, I doubt it is forcing the circuit into clipping unless there is something else wrong.
That the circuit is having different behaviours at different frequencies is a bit of a clue. I'll let that sink in and see if it triggers any usefull thoughts.
Your miniA's, if built to the BrianGT specs should have an input impedance of about 20K. Even if you output attenuator is 10K you should still get excellent results. I have a 10K balanced output attentuator on my pre, and it has no problems driving amplifier loads as low as 2K. Putting the attenuator on the outputs is very non-standard, but it was a Nelson Pass design feature from the original BoSoZ article, not something kooky that Russ and I came up with.
The thought that is nagging me is that there seems to be too much gain in your pre. What leads me to this is that the sound of clipping is pretty hard to mistake, so when you say it is clipping I am inclined to believe you. As the circuit has lots of headroom built in to prevent clipping, unless the gain is much higher than it is supposed to be, the clipping shouldn't happen. The second factor that makes me suspect too much gain is the hiss you are hearing, which by your description is much higher than the rest of us are experiencing. This could also be caused by the gain being too high (and vice versa the feedback being too low). So what I suggest is measure the resistance across the following resistors with the circuit turned off:
Feedback Resistors: R18, R19
Input Resistors: R14, R15
Drain Resistors: R1+R6, R2+R7
For the drain resistors the R1+R6 means measure the two together (they are in parallel with each other).
Report the numbers back and we'll see if they tell us anything.
Do you ever get over to Vancouver. I live in North Van, and I'd be happy to try troubleshooting yours. Your experiences definitely seem to be out of step with the norm, and I can understand why you are so frustrated with it. It should be working better! Likewise, if I get up-Island I'll give you a shout and drop in.
Cheers, Terry
I will add a bit to the discussion. Jason, if you are using the 25k quad pot I sent you, it is exactly the same part I was using between the X-Bosoz and BrianGT boards on my Aleph. I actually made Aleph-2's by using a double set of FET boards, but that would not change the input impedance of the Brian GT board that is the same as the mini-Aleph. It sounded just fine hooked up as shown in Terry's drawing I sent you a copy of.
So I would suspect Terry might be right that something is wrong with the Bosoz. I saw higher than expected gain until I found the blown zeners. (I kept trying to debug the wrong channel, thinking the lower gain one was bad.)
I do have to put in a plug for Russ, though. The setup does sound better with the Joshua Tree Attenuator, but I had a standard to work from which was that 25k quad pot.
Good luck and the sound is worth it.
Craig
So I would suspect Terry might be right that something is wrong with the Bosoz. I saw higher than expected gain until I found the blown zeners. (I kept trying to debug the wrong channel, thinking the lower gain one was bad.)
I do have to put in a plug for Russ, though. The setup does sound better with the Joshua Tree Attenuator, but I had a standard to work from which was that 25k quad pot.
Good luck and the sound is worth it.
Craig
Member
Joined 2002
I have to admit i'm a little leery now to buy stuff for this pre till i have it semi working good. Id be happy to send it over to metal man to test out and play with if he wanted to. It does sound good in single ended mode but xlr no way.. I know it is not the amps because they work perfectly and you can't say its them because all 4 work exactly the same. All are matched parts down to the output resistors.
It's late right now but ill get to this tomorrow morning sometime as i want to see what i can do. I think this pre-amp has potential.
I was going to ask to test the volume pot out from russ and them to see if it would make a difference but i dunno..
Do we need a drawing of how i have it connected now ?
It's late right now but ill get to this tomorrow morning sometime as i want to see what i can do. I think this pre-amp has potential.
I was going to ask to test the volume pot out from russ and them to see if it would make a difference but i dunno..
Do we need a drawing of how i have it connected now ?
Member
Joined 2002
Ok i have changed the configuration
cdplayer ( rca ) > passive pot ( rca ) > Single-ended input to bosoz pre-amp to output xlr i get that hushhhhhhhh sound when nothing playing and even if no source connected to the pre-amp. So i suspect something.
BUT in when the pre-amp with single ended in and out the pre-amp works really nice and clean.
Jase
cdplayer ( rca ) > passive pot ( rca ) > Single-ended input to bosoz pre-amp to output xlr i get that hushhhhhhhh sound when nothing playing and even if no source connected to the pre-amp. So i suspect something.
BUT in when the pre-amp with single ended in and out the pre-amp works really nice and clean.
Jase
Member
Joined 2002
BrianDonegan said:
Can some one post a picture of the board where these resistors are so i can check these i cant find a clear pic and if i look at my board it's hard to see because the resistors cover up the part #'s.
Jase
Member
Joined 2002
R14-15 on both channels are 8.8k
R18-19 is 20k per channel.
Now what ?
i also left the pre-amp off for 24 hours before testing this and drained the psu's.
jase
R18-19 is 20k per channel.
Now what ?
i also left the pre-amp off for 24 hours before testing this and drained the psu's.
jase