Oh yeah, I should mention that I just finished building a modified BOSOZ (all modifications suggested by Mr. Pass), and it is a simple circuit to build, and it is very impressive. In the last three days since I got it up and running, I've spent more time enraptured by music than I have spent listening to it it within the last three years.
Why do I suddenly feel WAY to big for my britches.
Well, thank you very much for suggesting that my schematic is worthy of consideration. As to posting it ... well ... actually I already have HERE
Now I gotta go find where my socks landed after they got knocked off.
EDIT:
Forgot to mention, of course, that to use as a converter, you need to connect the negative signal terminal of the single-ended side.
i.e. if SE input, ground -in, if SE ouput, ground -out.
Well, thank you very much for suggesting that my schematic is worthy of consideration. As to posting it ... well ... actually I already have HERE
Now I gotta go find where my socks landed after they got knocked off.
EDIT:
Forgot to mention, of course, that to use as a converter, you need to connect the negative signal terminal of the single-ended side.
i.e. if SE input, ground -in, if SE ouput, ground -out.
I have studied your schemtic, thank you very much !
Other questions :
a)What is the gain of the line-amp, how to calculate it ?
b) If I use it as SE input and SE output, will the sound get worse due to the somethng like "Half Load" ? Someone said in such case,the unused o/p should loaded with a "R & C".
c) Do you have the PCB layout ?
Best Regards !
Other questions :
a)What is the gain of the line-amp, how to calculate it ?
b) If I use it as SE input and SE output, will the sound get worse due to the somethng like "Half Load" ? Someone said in such case,the unused o/p should loaded with a "R & C".
c) Do you have the PCB layout ?
Best Regards !
The gain of my posted circuit is just a hair over 13dB. I don't have an exact way to calculate it, but it is roughly related the ratio of feedback to input resistor, i.e. (R15+R19)/R19. The actual circuit gain is about 2dB below that calc.
With my BZLS I just simply ground the negative input and output when I use SE on both ends. If there is a performance penalty to doing so, I haven't been able to detect it. That being said, I don't know if there is any benefit to loading the negative output. Perhaps others more knowledgable could comment.
Nope. It is a pretty simple circuit, and I only planned on building it once, so I didn't bother with the effort of creating a PCB and just built it on perfboard. I do have a layout for that, which is attached below.
Cheers, Terry
Attachments
My CD player outputs the standard 2Vrms, and my poweramp has a gain of just over 26dB. In that combination, the top volume level I have set the preamp at so far in my listening sessions is 22dB below max volume. Unless your amp's gain or the CD player signal is abnormally low, I don't think you'll run into problems.
Cheers, Terry
Cheers, Terry
thomasfw
Sorry for the dealy in my response. I have been quite busy and didn't gat a chance to look over the X2 service manuals until last night. Before I make any comparison comments, let me first say that I have not yet had the please of listening to any actual Pass Labs Products, including the X2, so I can't really make any informed listening comparisons. That being said, I'll say what I can for the X2 Rev 0 & 1 vs. my circuit.
Main Similarities:
* The configuration of a single constant current source that biases the differential pair is nearly identical on both circuits.
* The general topology is very similar.
* Both circuits will be successful in driving nearly any combination of cable and amplifier input impedance.
* Both use a series attenuator volume control.
Main Differences:
* The gain of the X2 is set primarily by the FET source resistors, where the gain in my circuit is set by local X-feedback.
* I have a lower voltage across my gain stage but use cascoding to reduce the distortion of each FET. The X2 reduces each FET's distortion by using higher voltages.
* My circuit will be more extended in both the low and high frequencies, due to the use of feedback and cascoding.
* The X2 uses a 2 deck attenuator before the gain stage. My preamp uses a 4 deck attenuator on the gain stage output, probably giving it an edge on output noise at low volume settings.
* The X2 does balanced to SE conversion in a separate circuit, where my circuit does any combination of balanced/SE input/output conversion within the one circuit.
If I had to guess, I'd probably say that my circuit probably measures better, but may sound less natural in comparison. My circuit might sound ever so slightly more dynamic. But as I said, I'm really just guessing, and I'm clearly just an amatuer designer, whereas Nelson has decades of experience, oodles of test equipment, a dedicated room for listening evaluations, and can evaluate using the best audio system achievable. If you want guaranteed top performance, I'd play it safe and go the X2.
All of that said, if there is anyone out there in the greater Vancouver area with an X2, an Aleph P etc. who would be willing to do some comparative listening against my preamp, I'd love to have the opportunity. I tried to suggest the same to the local Pass Labs dealer, and I got laughed at and then instructed to leave the store.
Moe,
I'm glad you at last discovered my thread. If you get around to trying my circuit, PLEASE let me know how it compares.
Cheers, Terry
Sorry for the dealy in my response. I have been quite busy and didn't gat a chance to look over the X2 service manuals until last night. Before I make any comparison comments, let me first say that I have not yet had the please of listening to any actual Pass Labs Products, including the X2, so I can't really make any informed listening comparisons. That being said, I'll say what I can for the X2 Rev 0 & 1 vs. my circuit.
Main Similarities:
* The configuration of a single constant current source that biases the differential pair is nearly identical on both circuits.
* The general topology is very similar.
* Both circuits will be successful in driving nearly any combination of cable and amplifier input impedance.
* Both use a series attenuator volume control.
Main Differences:
* The gain of the X2 is set primarily by the FET source resistors, where the gain in my circuit is set by local X-feedback.
* I have a lower voltage across my gain stage but use cascoding to reduce the distortion of each FET. The X2 reduces each FET's distortion by using higher voltages.
* My circuit will be more extended in both the low and high frequencies, due to the use of feedback and cascoding.
* The X2 uses a 2 deck attenuator before the gain stage. My preamp uses a 4 deck attenuator on the gain stage output, probably giving it an edge on output noise at low volume settings.
* The X2 does balanced to SE conversion in a separate circuit, where my circuit does any combination of balanced/SE input/output conversion within the one circuit.
If I had to guess, I'd probably say that my circuit probably measures better, but may sound less natural in comparison. My circuit might sound ever so slightly more dynamic. But as I said, I'm really just guessing, and I'm clearly just an amatuer designer, whereas Nelson has decades of experience, oodles of test equipment, a dedicated room for listening evaluations, and can evaluate using the best audio system achievable. If you want guaranteed top performance, I'd play it safe and go the X2.
All of that said, if there is anyone out there in the greater Vancouver area with an X2, an Aleph P etc. who would be willing to do some comparative listening against my preamp, I'd love to have the opportunity. I tried to suggest the same to the local Pass Labs dealer, and I got laughed at and then instructed to leave the store.
Moe,
I'm glad you at last discovered my thread. If you get around to trying my circuit, PLEASE let me know how it compares.
Cheers, Terry
Dear Terry,
Thank you for your so detail reply !
I have make up my mind to use yours to build a "Pre-amp" with the configuration of X2 (2 stages per channel same as the block diagram)
I would like to have "slight more gain" in output stage !
What should I do ? Is just simply change the value of the resistor
and what is the value and limitation ?
Once again, I still interested in adding a "Remote control IC volume" ! Is it a bad idea to add such thing in a "Hi End" product ?
For the power amp, still at the cross road of Aleph2 & Aleph X !!!
Thomas
Thank you for your so detail reply !
I have make up my mind to use yours to build a "Pre-amp" with the configuration of X2 (2 stages per channel same as the block diagram)
I would like to have "slight more gain" in output stage !
What should I do ? Is just simply change the value of the resistor
and what is the value and limitation ?
Once again, I still interested in adding a "Remote control IC volume" ! Is it a bad idea to add such thing in a "Hi End" product ?
For the power amp, still at the cross road of Aleph2 & Aleph X !!!
Thomas
thomasfw,
To increase the gain of my circuit, just increase the values of R15 & R16. Max gain is achieved by disconnecting the feedback resistors R15 and R16 which gives approximately 38dB. If you have a specific gain number in mind, let me know and I can get back to you with exact resistor values.
Terry
To increase the gain of my circuit, just increase the values of R15 & R16. Max gain is achieved by disconnecting the feedback resistors R15 and R16 which gives approximately 38dB. If you have a specific gain number in mind, let me know and I can get back to you with exact resistor values.
Terry
thomasfw,
Your understanding is correct.
For 12dB Gain set R15 & R16 to 42K
For 20dB Gain set R15 & R16 to 115K
One last comment, I recently put a 47uF cap in parallel with each voltage reference (indicated by Zeners in my schematic), and it made a slight improvement in the sound quality, but dropped any trace of circuit noise to dead silence even at max volume setting.
Why 47uF? Because it was the small value caps I happened to have on hand. Anything 5uF or higher should do the trick.
Cheers, Terry
Your understanding is correct.
For 12dB Gain set R15 & R16 to 42K
For 20dB Gain set R15 & R16 to 115K
One last comment, I recently put a 47uF cap in parallel with each voltage reference (indicated by Zeners in my schematic), and it made a slight improvement in the sound quality, but dropped any trace of circuit noise to dead silence even at max volume setting.
Why 47uF? Because it was the small value caps I happened to have on hand. Anything 5uF or higher should do the trick.
Cheers, Terry
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