You're right. I wanted to raise the B+ a little without overloading the rectifier. Looks like the software has done the trick.
It calculated I'd get 228V with
0.47/100/200
1K/500 ohms
with 20 mV ripple.
I heated up my soldering iron and made the changes.
And bam 228V exactly. Great
Spinning some Dire Straits and it sounds great.
It calculated I'd get 228V with
0.47/100/200
1K/500 ohms
with 20 mV ripple.
I heated up my soldering iron and made the changes.
And bam 228V exactly. Great
Spinning some Dire Straits and it sounds great.
Not much to look at yet. All breadboarded.
I want to build a SS rectifier now to compare. Any suggestions? Got to be simple with easily available parts (no chokes).
Also I want to look into building a power end to integrate with this now.
So many ideas and designs about.
Can you suggest and good design that would be simple to integrate into the Aikdio front end that I have here??(I'll be using a CDP so the gain is going to be high as we know).
Maybe either a separate circuit/box or even intergrated into the Aikido as it is now.
I've been collecting tubes the last few weeks (ebay can be addictive), just got some SV83's being shipped. Don't know why but I got a quad for just 8 USD.
It was suggested I buy EL84's instead but I was trigger happy and bidded.
They require a lower voltage so maybe be easier and cheaper to build.
Still looking for some EL34/84 and KT88's. Not so easy to find the latter 2 for lower prices.
Brit01 said:
Use PSUDII to model the SS rectified PS. I would do a CRC since you do not have a choke. A CRC will allow you to "tune" B+ in by varying the value of the first cap, same as your present design. A SS diode design will end up with a somewhat higher (B+) than your existing design. You'll probably end up around 300V B+ with your existing transformer.
You can add R-C sections to the CRC design for better filtering and reducing B+ CRCRC. PSUDII is your friend here.
Create the heater bias voltage divider by hanging the same two R values as your present design to ground and connecting the heater transformer center tap between them.
For cheap breadboarding I would use plain vanilla 1N4007's or UF4007's or so and for the final design I would spring for FRED diodes cheap $$ for increased performance. It's also a good practice to bypass the diodes with 10nf HV ceramic caps to mellow out the switching spikes.
Two big differences between SS and tube rectification are 1.) the SS rectification drops a lot less voltage than tubes, and 2.) it's not nearly as sensitive to the value C1 (no arc-over worries).
One downside to SS rectification is that you lose the slow warm up of the B+ (causing cathode stripping), but many folks on the forum don't think that's a big issue with B+ less than 1KV or so.
have a newbie question:
Currently I have the heater bias point from Bas's psu wired to a virtual CT on the 12.6V heater secondary.
With a SS circuit shown previously how does this work?
Would I attach the virtual CT at the top of the junction of the 2.25uF Cap? Between the C and RC section?
Currently I have the heater bias point from Bas's psu wired to a virtual CT on the 12.6V heater secondary.
With a SS circuit shown previously how does this work?
Would I attach the virtual CT at the top of the junction of the 2.25uF Cap? Between the C and RC section?
Brit01 said:
You need to create a voltage divider for the heater bias. Solder a 200K R and 100K R in series from B+ to ground between your filter string and the load. Connect your heater virtual center tap between the R's.
So, in between C4 and the CC load on your PSUD model, solder a 200k R and 100K R in series, be sure the 200K R is on top of the 100K R.
Example: Say your B+ is 250V
so E=IR, I=E/R
From B+ to ground, I=250V/300K (both R's)=.833 ma current from B+ to ground.
Calculate the voltage drop across each R
For the upper R, E=IR=.83ma/200K=166.66V
For the lower R, .83ma/100K=83.33V
Sanity check: 83.33V+166.66V=249.99V is the voltage drop across both R's.
Check the power dissipated thru each R: P=VI
for the upper R P=166.66V*.00083a=.132w
for the lower R P=83.33V*.00083a=.069w
The upper R dissipates twice the power as the lower, since it's twice the R.
Connecting your heater CT between the R's lifts the heater by 83.33V. You can use other values of R's to raise or lower the heater bias anywhere you want.
Large R values are used to keep from burning too much power, the whole chain is using .132+.069=.2w.
I have to say after playing around with Bas's 6X5GT psu a little the bass has improved nicely. The bass guitar really comes out better on Dire Straits. I changed the last RC from 1K/100uF to 500/200uF
I am now using CRCRC:
0.47/100/200
1K/500
I'm also using the 1uF Auricap and 0.47uF PIO in parallel on the output.
I am now using CRCRC:
0.47/100/200
1K/500
I'm also using the 1uF Auricap and 0.47uF PIO in parallel on the output.
I've got my case and all the circuitry built and tested, except for the signal wiring. At this point I'm kind of lost.
I've got all of the RCA jacks isolated from the chassis and earth ground.
Do the negatives from the L&R inputs connect to each other?
Then to earth ground? through a capacitor?
Do the output negatives also connect to earth ground? (potential ground loop?)
Where does the negative originate that connects to the negative L&R of the Volume pot?
I'm not using a buss bar ground.
Should there be a star ground for all of these? Being one point that then connects to the earth ground? again via a capacitor?
Why are resistors used sometimes at the earth ground point of the negative signal?
I understand the hard part .....B+ and Bias, but I'm lost with the signal negative(S). AARRRGGGG
Help
Ron
I've got all of the RCA jacks isolated from the chassis and earth ground.
Do the negatives from the L&R inputs connect to each other?
Then to earth ground? through a capacitor?
Do the output negatives also connect to earth ground? (potential ground loop?)
Where does the negative originate that connects to the negative L&R of the Volume pot?
I'm not using a buss bar ground.
Should there be a star ground for all of these? Being one point that then connects to the earth ground? again via a capacitor?
Why are resistors used sometimes at the earth ground point of the negative signal?
I understand the hard part .....B+ and Bias, but I'm lost with the signal negative(S). AARRRGGGG
Help
Ron
Renron said:
Yes, all the negatives for L+R (shields in my case) connect together. At the input, all of the signal -ve's are tied together at the volume control on my Aikido, and then connected to ground.
I ended up with a 20 ohm (I think) ground lift R to reduce hum further, so the ground from the vol control is connected to one side of the R and the other is to chassis ground. I also ended up tying the ground off of the PS to this R also, this made a big difference in my case.
This is where the "art" may deviate from the science, as you can play around with grounding schemes to reduce hum. Grounding both ends of the shields may lead to ground loops although I did not try this on my amp to see if it was any better/worse.
The negatives that are tied together at the vol pot started out at the RCA inputs, go through the input selector, then to the vol pot, then to the 20R to ground. I tried to stay close to star ground where everything ends up at the 20R ground lift, and my mains safety ground is right next to the R.
I did not use a buss bar ground either, just 20 ga wire, although I experimented with stripped 12 AWG solid romex house wire along the way. I am contemplating trying sheilded coax for the ground runs also but I have no idea if this makes sense or not.
I posted a sketch of my grounding in post #274 of this thread. YMMV
It won't hurt to play around with the ground sig wires, connecting the PS ground to my chassis made the biggest difference by far in my case. I tried jumpers on the PCB grounds, caps on the PCB grounds, and ended up leaving them off.
After the initial playing of tunes through the stereo with a fair bit of hum, I looked at the output RCA jack on the scope and could quantify if my grounding changes were helpful. Without a scope, use your ears.
My sketch shows one input, I recently wired in one of JB's input selectors, and have not fired up the preamp yet, so I may again be chasing hum.