Hi Salas
I am about to order the obbligato output caps.
The difference in size and cost for 4.7u to 6.8u is not uge.. should I try the bigger ones ? (Can I expect even more bass ?)
Ricardo
I am about to order the obbligato output caps.
The difference in size and cost for 4.7u to 6.8u is not uge.. should I try the bigger ones ? (Can I expect even more bass ?)
Ricardo
Optivol
is a simple shunt LED/LDR optocouplers, the series resistor are 27k (at fist I put a Dale but tantalum is a must ) that work well in jfet riaa (you can remove the resistor on out caps) change if the amp need...
the pot control the light on led ,ie you can put where you want !and ldr near the out
need 24vdc or so ,for 17€ shipping incluse
you can only win !! a lot better then alps blu
problem,now is out of stock but contact Greg ,is fine men ,for preorder
alternative the ligthspeed on Diyaudio that are full ldr but parts and match are problem (you can order two matched optivol)
decent pot start with TKD at 61$
alternative 41-step Attenuator but $$$ link
is a simple shunt LED/LDR optocouplers, the series resistor are 27k (at fist I put a Dale but tantalum is a must ) that work well in jfet riaa (you can remove the resistor on out caps) change if the amp need...
the pot control the light on led ,ie you can put where you want !and ldr near the out
need 24vdc or so ,for 17€ shipping incluse
you can only win !! a lot better then alps blu problem,now is out of stock but contact Greg ,is fine men ,for preorder
alternative the ligthspeed on Diyaudio that are full ldr but parts and match are problem (you can order two matched optivol)
decent pot start with TKD at 61$
alternative 41-step Attenuator but $$$ link
from Zen mod, ldr+JC buffer kit .....are you sure that need buffer?
http://www.diyaudio.com/forums/showthread.php?s=&threadid=139113
http://www.diyaudio.com/forums/showthread.php?s=&threadid=139113
Thank you nicoch... I will email Greg.
What about the 6.8u output caps ? Can I expect any gains ?
Ricardo
What about the 6.8u output caps ? Can I expect any gains ?
Ricardo
RCruz said:
4.7uF is more than enough even down to 10k loading. Bigger means more aluminum foil for no reason.
Thank you again.
I believe I will try to feed the Riaa directly into the power amp using a pot only and see what gain do I have.
It might clean up things a lot.
PS:
I like the optocoupler option, so I will mail Greg about them.
Ricardo
Thank you Salas... 4.7u it will be.
I believe I will try to feed the Riaa directly into the power amp using a pot only and see what gain do I have.
It might clean up things a lot.
PS:
I like the optocoupler option, so I will mail Greg about them.
Ricardo
Thank you Salas... 4.7u it will be.
with 27k can be 1mf if I remember well ,I have used 2,2//0,47....
with optivol if you lower to much the rserie (now my is 18k) you lost a bit the 0 volume out.....(no signal)
with optivol if you lower to much the rserie (now my is 18k) you lost a bit the 0 volume out.....(no signal)
Generally speaking, the smaller (your system can support), the better. Salas is absolutely right. Check the input impedance of the following component and calculate the right value for 10 - 15 Hz.RCruz said:
As we are dealing with a less than perfect source, even if you cut a bit of low frequencies, is not that bad. Think about all the problem related to the warp of records and/or plinth resonance.
Thank you .
Now i understand the issues related with big caps.
I will stick to the 4.7u I am using now (quite good) and upgrade to a better quality cap.
Ricardo
Now i understand the issues related with big caps.
I will stick to the 4.7u I am using now (quite good) and upgrade to a better quality cap.
Ricardo
Hi Salas
Just replaced all the resistors and placed everything in a new case.
It played for a while but only in one channel.. the right one only thundered and spet.
After cleaning the pcb, I have only rubble and no sound coming from the speakers.
What should be wrong ?
GND connections ?
Ricardo
Just replaced all the resistors and placed everything in a new case.
It played for a while but only in one channel.. the right one only thundered and spet.
After cleaning the pcb, I have only rubble and no sound coming from the speakers.
What should be wrong ?
GND connections ?
Ricardo
Maybe too hot a desoldering & soldering cycle took out some semiconductor(s)? I would check the Zener voltage and the BC550 collector voltage. Also the drain voltages, and compare to the healthy channel. Also check for wrong new resistor values. If the channel that played initially, is silenced too now, then the problem may took the PSU too. Check for having correct B+.
Hi Salas
After a new clenup, the good sounding channel is grouling while the other is playing....
Zeners are good (both 8.4v)
Collector bC550 (Good channel 12.9 bad channel 12.33 ~ 12.29)
Between R6 º C2 (Good 12.2 bad 9 ~ 12)
Output cap (Good 10.37 bad 9.86 ~11.1)
Where should be the problem ?
Ricardo
After a new clenup, the good sounding channel is grouling while the other is playing....
Zeners are good (both 8.4v)
Collector bC550 (Good channel 12.9 bad channel 12.33 ~ 12.29)
Between R6 º C2 (Good 12.2 bad 9 ~ 12)
Output cap (Good 10.37 bad 9.86 ~11.1)
Where should be the problem ?
Ricardo
The way you describe it, the bad channel oscillates. I would see to change its BC550 first. Do you have a spare? B+ is stable?
Also measure ground points to chassis. Maybe some impurity sits in the small channels between ground planes and traces in your ground plane surrounded build. Lift the ground plane before you do more.
Just lifted ground plane... and replace BC550 on the bad channel.
Now I get 4.8 ~5.0 v on both output caps
BC550c collector good 12.8 bad 12.3 ~12.4
Now I get 4.8 ~5.0 v on both output caps
BC550c collector good 12.8 bad 12.3 ~12.4
Continue with the JFETs one by one stage. Are you sure that the new resistors are all correct values in correct places and the ground scheme did not change?4.8-5V before caps?
