ZM, Indra1 and mjf:
That certainly helped! I replaced the two R7 2.2k resistors with 475R and the voltages on the drains shot past 8.5 VDC before I pulled the plug. I added a 340R resistor in series with each 475R and now the voltage on the drains is 7 VDC (R ch) and 7.01 VDC (L ch).
Unfortunately, there still appears to be an issue with the bridged ACA -- music still sounds distorted. I'll start noodling on it and will report back. In the meantime, many, many thanks!
Regards,
Scott
That certainly helped! I replaced the two R7 2.2k resistors with 475R and the voltages on the drains shot past 8.5 VDC before I pulled the plug. I added a 340R resistor in series with each 475R and now the voltage on the drains is 7 VDC (R ch) and 7.01 VDC (L ch).
Unfortunately, there still appears to be an issue with the bridged ACA -- music still sounds distorted. I'll start noodling on it and will report back. In the meantime, many, many thanks!
Regards,
Scott
Folks:
As mentioned in the ACA thread, my BOZ now seems to be working fine. The distorted music persists, and I suspect it may be a function of having too much gain in the integrated amp. NP's BOZ white paper explains that the gain in the MOSFET version of the BOZ is driven by R108 and the MOSFET. Can someone explain the procedure for decreasing the gain in a jfet-based BOZ?
Regards,
Scott
As mentioned in the ACA thread, my BOZ now seems to be working fine. The distorted music persists, and I suspect it may be a function of having too much gain in the integrated amp. NP's BOZ white paper explains that the gain in the MOSFET version of the BOZ is driven by R108 and the MOSFET. Can someone explain the procedure for decreasing the gain in a jfet-based BOZ?
Regards,
Scott
ZM:
The volume pot is between the BOZ and the bridged ACA boards. No, I didn't try the bridged ACA first without a preamplifier; the project was conceived as a BOZ/bridged ACA from the start. You make a good point -- I was concerned that there wouldn't be enough gain if I used a BA3 or skipped the preamp/buffer altogether, but my concern may well have been misplaced.
I will bypass the ACA, see how the amp performs and report back. In the meantime, is there a reason not to try reducing the gain of the BOZ?
Regards,
Scott
The volume pot is between the BOZ and the bridged ACA boards. No, I didn't try the bridged ACA first without a preamplifier; the project was conceived as a BOZ/bridged ACA from the start. You make a good point -- I was concerned that there wouldn't be enough gain if I used a BA3 or skipped the preamp/buffer altogether, but my concern may well have been misplaced.
I will bypass the ACA, see how the amp performs and report back. In the meantime, is there a reason not to try reducing the gain of the BOZ?
Regards,
Scott
first try ACA only with volume pot in front of it , leave JFet BOZ out of picture
if there is enough signal for ACA (you'll hear clipping , believe me , if that's the case) , then it's time to make nice buffer after volume pot , practically in between volume pot and ACA .......... insted of JFet BOZ
even in case of using JFet BOZ , place fro volume pot is in between source and JFet BOZ ....... not after silly fragile thingy
so , you're practically driving it (BOZ) in clipping , all the time ..... modern sources are simply too loud , full throttle
if there is enough signal for ACA (you'll hear clipping , believe me , if that's the case) , then it's time to make nice buffer after volume pot , practically in between volume pot and ACA .......... insted of JFet BOZ
even in case of using JFet BOZ , place fro volume pot is in between source and JFet BOZ ....... not after silly fragile thingy
so , you're practically driving it (BOZ) in clipping , all the time ..... modern sources are simply too loud , full throttle
ZM:
Success. Complete success, in fact. Bypassing the attenuator cleared up the music but the gain was inadequate -- some degree of amplification was needed. So the attenuator was wired before the BOZ, as you recommended, and that cured everything. The amp sounds terrific.
Knuckleheads with the desire to build (like me) unfortunately sometimes have to lean on others. This project came together quickly but I stumbled at the end, unable to resolve a series of little problems. So I'd like to take a moment and publicly thank you, mjf, Indra1 and Alan4411 for your help. I'll post photos of the amp tomorrow but wanted to express my appreciation right away. If any of you guys ever find yourself near Philadelphia, PA, USA, I'd like to buy you a beer. Or take you out to dinner. No dancing, though.
Thank you.
Regards,
Scott
Success. Complete success, in fact. Bypassing the attenuator cleared up the music but the gain was inadequate -- some degree of amplification was needed. So the attenuator was wired before the BOZ, as you recommended, and that cured everything. The amp sounds terrific.
Knuckleheads with the desire to build (like me) unfortunately sometimes have to lean on others. This project came together quickly but I stumbled at the end, unable to resolve a series of little problems. So I'd like to take a moment and publicly thank you, mjf, Indra1 and Alan4411 for your help. I'll post photos of the amp tomorrow but wanted to express my appreciation right away. If any of you guys ever find yourself near Philadelphia, PA, USA, I'd like to buy you a beer. Or take you out to dinner. No dancing, though.
Thank you.
Regards,
Scott
now , enjoy yourself , being satisfied you're going to give her a good gift .....
after few days - observe on which position is volume pot (usual hours on clock position , from 07.00 to 05.00) for loudest you can expect ?
if that's past 12.00 , or even better somewhere around 02.00 or 03.00 - that's best
if lower (more left ) than 11.00 , you need less gain from JFet Boz
edit: for more insight , read What is Gain Structure?
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