1.) If you want to use trioded 4P1L at 130V, 15mA operating point, must to use about -10V bias.
-10V bias is about 9V on filament bias resistor + half of filament voltage of 4P1L ... at starved filament current. You must to set R.C. regulator to 580-585mA.
2.) The "load" resistor value is the line stage loading resistor (need for capacitor coupling, usually 220k...470k) paralleled with next stage input impedance. If the next stage is SS amplifier, the 22k is possible ... 6k8 is not ordinary value.
3.) What is the "output voltage"?
sample:
-10V bias is about 9V on filament bias resistor + half of filament voltage of 4P1L ... at starved filament current. You must to set R.C. regulator to 580-585mA.
2.) The "load" resistor value is the line stage loading resistor (need for capacitor coupling, usually 220k...470k) paralleled with next stage input impedance. If the next stage is SS amplifier, the 22k is possible ... 6k8 is not ordinary value.
3.) What is the "output voltage"?
sample:
Thank you for your response. I need to apologize for not being specific enough in my question (new years hangover tunnel vision....)
My question is about the gyrator board, I posted the question here in 4P1L thread as I am trying to use the gyrator circuit depicted here. I want to use it with a RE134, Ua 130V Ia 15mA.
In my bench test I connected a 22k across "Anode" and "GND" and set voltage across that resistor to 130V. Then I changed that 22k to 8k6, assuming 8k6 connected to "Anode" and "GND" would simulate an RE134 run with 15mA. I had nothing connected to "Out".
My question is about the gyrator board, I posted the question here in 4P1L thread as I am trying to use the gyrator circuit depicted here. I want to use it with a RE134, Ua 130V Ia 15mA.
In my bench test I connected a 22k across "Anode" and "GND" and set voltage across that resistor to 130V. Then I changed that 22k to 8k6, assuming 8k6 connected to "Anode" and "GND" would simulate an RE134 run with 15mA. I had nothing connected to "Out".
If you want to test only gyrator, resistor as static load (without tube) to ground is perfect.
This layout working, gyrator acts as "constant output voltage device" (setting 130V)... until current absorbed by the load (22k or 8k6 resistor) available.
If you measure such -similar- voltages as in my schematic with 22k load (about 6mA) and different values with 8k6 load (15mA), something in the gyrator is limiting.
This layout working, gyrator acts as "constant output voltage device" (setting 130V)... until current absorbed by the load (22k or 8k6 resistor) available.
If you measure such -similar- voltages as in my schematic with 22k load (about 6mA) and different values with 8k6 load (15mA), something in the gyrator is limiting.
Hi,
I am planning to build 4P1L Siberian Gen4. From PSUD simulations and reading all this thread from the beginning I have a newbie question. I want to calculate voltage for trafos for heater supplies. I know Rod suggests 14V. But I can simulate correct values only when I put 400 mOhms for capacitors ESR values as showed in Rods manual for connecting RC regulators. ESR for capacitors in datasheet is 24 mOhms - https://www.digikey.lv/en/products/detail/cornell-dubilier-knowles/SLPX223M035H4P3/1882075. If I input ESR values closer to 24 mOhms, 14V for trafos seems a bit high. What am I missing?
Thanks in advance!
I am planning to build 4P1L Siberian Gen4. From PSUD simulations and reading all this thread from the beginning I have a newbie question. I want to calculate voltage for trafos for heater supplies. I know Rod suggests 14V. But I can simulate correct values only when I put 400 mOhms for capacitors ESR values as showed in Rods manual for connecting RC regulators. ESR for capacitors in datasheet is 24 mOhms - https://www.digikey.lv/en/products/detail/cornell-dubilier-knowles/SLPX223M035H4P3/1882075. If I input ESR values closer to 24 mOhms, 14V for trafos seems a bit high. What am I missing?
Thanks in advance!
24mΩ is a low value, even at 22mF.
But it's OK - there is a lot of variable with Raw DC voltages (transformer losses, diode drops, mains supply line voltages...)
You are close enough to build the Raw DC and measure the voltages, when it is connected to the regulator.
If the voltage is still too high - increase the series R (R1 in PSUD2).
It's worth having some low-value resistors in stck, for adjusting the Raw DC.
But it's OK - there is a lot of variable with Raw DC voltages (transformer losses, diode drops, mains supply line voltages...)
You are close enough to build the Raw DC and measure the voltages, when it is connected to the regulator.
If the voltage is still too high - increase the series R (R1 in PSUD2).
It's worth having some low-value resistors in stck, for adjusting the Raw DC.
I used the double 12V@2A output of a Hammond 266L24 and put a 159ZC on one side for L filtering, using a resistor that matches the resistance of the inductor widing on the other side. Loaded down in filament bias it all fell into place with 4-5V headroom on top of my 7-8V of bias on the 4P1L grid.
First of all, the method of calculating is not quite right, you have to start from the back to the front.
Must be decided the filament bias resistor value (in my sample 12R), the filament current (0.65A) and the tube's filament voltage (2.1V).
The required voltage on R.C regulator is:
U= (If*Rfilbias)+Uf in this case 9.9V.
If the R.C. regulator headroom is 4V, the raw supply output must be 9.9+4=13.9V or greater.
This value and transformer estimated secondary voltage will be the starting point.
If you use single secondary and Graetz rectifier, the one of least voltage loss diode is the schottky. I usually use MBR series.
The first capacitor quality is important, must to tolerate such high ripple current, which is originates from it's value, and the schematic other parameters.
If you choose large first capacitor (the 22000uF is HUGE!), the charging current pulse will be enormous, the diodes and the PT dissipating much more than necessary.
Choosing smoothing is depends of required hum value on output (in this case on filament bias resistor+filament).
If - for example - few-few ten uV is enough (caution filament biased DH tube amplifier stage is VERY sensitive to filament voltage/current quality!), must to appreciates regulator (in this case R.C. regulator) PSRR.
I measured Rod's regulators, each of them outperforms 70dB PSRR, usually are over 80dB.
If you assume 10uVpp noise (hum) on output and 80dB PSRR, the allowable input (on raw supply output) noise is 100mVpp.
This will be the target value of raw supply output: equal or more than 13.9V DC, 100mVpp hum at 0.65A load.
Sample:
As you can see, the moderated constant current and relatively low value first capacitor (which ripple current capacity must be greater than simulated) requires relatively large current tolerance diodes and enough large current on secondary.
Even the consumed power not so large, the transformer must be -at least- double (sometimes greater) power capacity, else will be heating.
Must be decided the filament bias resistor value (in my sample 12R), the filament current (0.65A) and the tube's filament voltage (2.1V).
The required voltage on R.C regulator is:
U= (If*Rfilbias)+Uf in this case 9.9V.
If the R.C. regulator headroom is 4V, the raw supply output must be 9.9+4=13.9V or greater.
This value and transformer estimated secondary voltage will be the starting point.
If you use single secondary and Graetz rectifier, the one of least voltage loss diode is the schottky. I usually use MBR series.
The first capacitor quality is important, must to tolerate such high ripple current, which is originates from it's value, and the schematic other parameters.
If you choose large first capacitor (the 22000uF is HUGE!), the charging current pulse will be enormous, the diodes and the PT dissipating much more than necessary.
Choosing smoothing is depends of required hum value on output (in this case on filament bias resistor+filament).
If - for example - few-few ten uV is enough (caution filament biased DH tube amplifier stage is VERY sensitive to filament voltage/current quality!), must to appreciates regulator (in this case R.C. regulator) PSRR.
I measured Rod's regulators, each of them outperforms 70dB PSRR, usually are over 80dB.
If you assume 10uVpp noise (hum) on output and 80dB PSRR, the allowable input (on raw supply output) noise is 100mVpp.
This will be the target value of raw supply output: equal or more than 13.9V DC, 100mVpp hum at 0.65A load.
Sample:
As you can see, the moderated constant current and relatively low value first capacitor (which ripple current capacity must be greater than simulated) requires relatively large current tolerance diodes and enough large current on secondary.
Even the consumed power not so large, the transformer must be -at least- double (sometimes greater) power capacity, else will be heating.
You Who runt the 4p1l with starved filament,
What voltage are u using?
I am going to use paralell filaments
What voltage are u using?
I am going to use paralell filaments
I recently completed my build and connected it up to my system for the first time. The sound is fantastic and shows lots of promise. Even with large aluminum mounting plates there is still some microphony with the cover off when clapping or using the selector switch.
However I am dealing with a terrible 120hz buzz. I'm looking for some assistance in my troubleshooting and need help determining if I should continue to look at my ground connections or the B+ power supply board.
I also have a situation where depending on how I place the raw filament DC umbilical there is some mild RF pickup and can hear faint radio music.
The whole build is made up of Ale Moglia and Rod Coleman boards. In one chassis are two raw DC boards for the filament regulators and two of Ale's HT supply.
From this chassis two separate umbilical cords connect the HT and LT power to the main preamp chassis. Inside this are two of Ale's cap multiplier boards. The B+ voltage is connected to the Gyrator boards. 4P1L tubes and associated wiring are mounted on a heavy sandwiched aluminum plate assembly.
I have tried rewiring the preamp chassis a number of different ways with connecting grounds at various points. At this stage now compared to before I can meter out any ground point inside the main chassis to the HT board ground takeoff and get a value less than 0.2-3 ohms whereas before some points were an ohm or more.
This has been my first build from only a circuit with no previous experience in tube preamp layout.
I got to thinking I may have taken the Bartola HT supply design tooo lightly, simply copying the values from what I found on the website. In this case Ale had used a LC filter section compared to my decision to use CRC.
With that said I noticed that my first cap after the rectifier bridge is a 2uF Wima MKP poly.
The rough chain is bridge-2uf MKP-100ohm-100uf Epcos electro-100ohm-150uf Nichicon electro-0.1uf K40Y-40uf Wima DC link.
Doing some reading on filtering and I think I made the mistake of having the incorrect type and way too small a value. I'm hoping someone can comment on this design and if I right in saying I should replace this first cap with an electrolytic.
I downloaded Duncan PSUD and have been trying to do some modelling. I was looking to increase that first cap value to 47-100uf and possibly as high as 370uf.
Attached are some pictures of the build. The iteration that has all the colored lines has been reduced to the one which now keeps each channel ground path separate. I also have now made sure that the input and output grounds are taken from the 100nf FT3 bypass cap by the gyrator board. This is on the other side of the cap board where previous I was taking grounds and many different points, mixing channels and also picked up on a mistake in how I was connecting anode power.
I appreciate any help that can be provided. The quality of sound I'm hearing warrants getting this sorted and after 4 years waiting for the right chassis, parts and putting in the build time I want to get this singing.
However I am dealing with a terrible 120hz buzz. I'm looking for some assistance in my troubleshooting and need help determining if I should continue to look at my ground connections or the B+ power supply board.
I also have a situation where depending on how I place the raw filament DC umbilical there is some mild RF pickup and can hear faint radio music.
The whole build is made up of Ale Moglia and Rod Coleman boards. In one chassis are two raw DC boards for the filament regulators and two of Ale's HT supply.
From this chassis two separate umbilical cords connect the HT and LT power to the main preamp chassis. Inside this are two of Ale's cap multiplier boards. The B+ voltage is connected to the Gyrator boards. 4P1L tubes and associated wiring are mounted on a heavy sandwiched aluminum plate assembly.
I have tried rewiring the preamp chassis a number of different ways with connecting grounds at various points. At this stage now compared to before I can meter out any ground point inside the main chassis to the HT board ground takeoff and get a value less than 0.2-3 ohms whereas before some points were an ohm or more.
This has been my first build from only a circuit with no previous experience in tube preamp layout.
I got to thinking I may have taken the Bartola HT supply design tooo lightly, simply copying the values from what I found on the website. In this case Ale had used a LC filter section compared to my decision to use CRC.
With that said I noticed that my first cap after the rectifier bridge is a 2uF Wima MKP poly.
The rough chain is bridge-2uf MKP-100ohm-100uf Epcos electro-100ohm-150uf Nichicon electro-0.1uf K40Y-40uf Wima DC link.
Doing some reading on filtering and I think I made the mistake of having the incorrect type and way too small a value. I'm hoping someone can comment on this design and if I right in saying I should replace this first cap with an electrolytic.
I downloaded Duncan PSUD and have been trying to do some modelling. I was looking to increase that first cap value to 47-100uf and possibly as high as 370uf.
Attached are some pictures of the build. The iteration that has all the colored lines has been reduced to the one which now keeps each channel ground path separate. I also have now made sure that the input and output grounds are taken from the 100nf FT3 bypass cap by the gyrator board. This is on the other side of the cap board where previous I was taking grounds and many different points, mixing channels and also picked up on a mistake in how I was connecting anode power.
I appreciate any help that can be provided. The quality of sound I'm hearing warrants getting this sorted and after 4 years waiting for the right chassis, parts and putting in the build time I want to get this singing.
Please shows picture of PSU mains connector and chassis grounding point.
If you want to sketch the grounding schema of PSU and preamp box, it would help a lot.
Some criticism:
1.) connecting individual RCA connectors cold points together (and "grounding it) isn't good solution. I use hot and cold wires from each input-output to the gain module. Each module has separated virtual grounding point and connecting together only one point, where the PSU cold wire connecting too.
If I use separated PSU modules for channels, the wiring (HT hot-cold, LT hot-cold) also separated (floating from chassis), and channels cold points has only one connecting point.
2.) Modules "grounding" -cold- wire/s/ connecting point/s/ NOT equal of chassis grounding point! Due to the grounding -hum- problems usually must to use hum blocker solutions (R, R//C, diode bridge etc.).
My -two box- preamps the amplifier box is usually floating, individual "grounding" wire connecting it to PSU box, where the grounding solution will be implemented.
p.s.
Read comments here:
If you want to sketch the grounding schema of PSU and preamp box, it would help a lot.
Some criticism:
1.) connecting individual RCA connectors cold points together (and "grounding it) isn't good solution. I use hot and cold wires from each input-output to the gain module. Each module has separated virtual grounding point and connecting together only one point, where the PSU cold wire connecting too.
If I use separated PSU modules for channels, the wiring (HT hot-cold, LT hot-cold) also separated (floating from chassis), and channels cold points has only one connecting point.
2.) Modules "grounding" -cold- wire/s/ connecting point/s/ NOT equal of chassis grounding point! Due to the grounding -hum- problems usually must to use hum blocker solutions (R, R//C, diode bridge etc.).
My -two box- preamps the amplifier box is usually floating, individual "grounding" wire connecting it to PSU box, where the grounding solution will be implemented.
p.s.
Read comments here:
Exactly better.
The AC connector safety ground point must to tied with very short wire to metal part of chassis. It's not part of grounding scheme.
If the amplifier working (be sure, that each "ground" -channel 0 points, capacitors, connectors etc.- independent from metal sheet), the hum (exist, or not, disturbing, or not) decides, which type hum blocker needs (if needs): 10-100R to "house ground", R//C, or diodes too.
samples:
The AC connector safety ground point must to tied with very short wire to metal part of chassis. It's not part of grounding scheme.
If the amplifier working (be sure, that each "ground" -channel 0 points, capacitors, connectors etc.- independent from metal sheet), the hum (exist, or not, disturbing, or not) decides, which type hum blocker needs (if needs): 10-100R to "house ground", R//C, or diodes too.
samples:
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I have put together this preamp with alot of the same identical components, same caps same valves sockets, same wires, same boards, I have made the same comments about the promising sound quality AND I am having the same issues with microphony and with gnd hum. Unreal.
I am starting to wonder if we are the same person... 🤣
I have had some success disconnecting the input RCA block gnd and running with an RCA in/RCA out to try to isolate the issue. This thing is super finnicky with gnd wiring!
I also rewired it with the other tubes (forget the number but they are encased and have the top bakelite handle) these are supposed to be NON microphonic but they are nearly as bad + they don't sound as nice as the 4P1L.
I had to put it down but I will pick it up again around thanksgiving. I am thinking to rebuild the whole thing from scratch and to go with the low gain or the transformer loaded version 3. I definitely DO NOT need 19dB of gain. I am trying to find the silicone ring to slip on the glass to see if it helps with the microphony as well.
Grataku,
Did you also use the Bartola HT supply board? What was your choice of cap types and sizes along with resitors? I copied the values listed in the pdf which turns out was for Ale's implementation of LCLC.
His schematic notes a 2uf poly Wima MKP cap before the first inductor. The manual calls this a "tunning" cap which I guess is for the damping/resonance of the inductor.
I've been trying to do some reading on power supply design and I believe in my case where I am trying to use CRCRC followed by the capacitor multiplier, that having that MKP cap is incorrect.
My understanding so far is the first cap after the rectifier bridge must both be an electrolytic and probably much bigger. The question is what is that value and should I pay attention to and change the subsequent caps that are electros of values 100uf and 150uf.
At one point my ground hum would not appear until a ways up on the Alps blue velvet control. I was getting wild harmonics of 480 and 960hz equal to or louder than the 120hz fundamental. I also caught my mistake of feeding the B+ output of the gyrator to the opposite channel such that the ground path was returning to the other board from which the power came.
I am pretty confident in where I have my ground points and that they are correctly isolated from the chassis using plastic washers on RCA and plastic standoffs for the boards. Will draw the circuit grounds at some point in the future once I get satisfaction my B+ is properly designed.
Interesting the hear the 2P29 did not perform better in your setup despite having significantly lower filament requirements and a reputation of low microphony.
Did you also use the Bartola HT supply board? What was your choice of cap types and sizes along with resitors? I copied the values listed in the pdf which turns out was for Ale's implementation of LCLC.
His schematic notes a 2uf poly Wima MKP cap before the first inductor. The manual calls this a "tunning" cap which I guess is for the damping/resonance of the inductor.
I've been trying to do some reading on power supply design and I believe in my case where I am trying to use CRCRC followed by the capacitor multiplier, that having that MKP cap is incorrect.
My understanding so far is the first cap after the rectifier bridge must both be an electrolytic and probably much bigger. The question is what is that value and should I pay attention to and change the subsequent caps that are electros of values 100uf and 150uf.
At one point my ground hum would not appear until a ways up on the Alps blue velvet control. I was getting wild harmonics of 480 and 960hz equal to or louder than the 120hz fundamental. I also caught my mistake of feeding the B+ output of the gyrator to the opposite channel such that the ground path was returning to the other board from which the power came.
I am pretty confident in where I have my ground points and that they are correctly isolated from the chassis using plastic washers on RCA and plastic standoffs for the boards. Will draw the circuit grounds at some point in the future once I get satisfaction my B+ is properly designed.
Interesting the hear the 2P29 did not perform better in your setup despite having significantly lower filament requirements and a reputation of low microphony.
I am no expert.... but it seems to me that you have multiple loops in there.
1. You are not helping yourself with a long cable run to the front panel switch - far better to keep those wires as short as possible, mount the switch as close as you can to the RCAs and run a shaft to the front panel.
2. The grounding from gyrators to valve sockets seems to have some t-junctions. I think its better to pick a ground point at the ground point on the gyrator or cap multiplier board for each channel and run all grounds directly to there from each point - including the RCAs. Then bring both of those to a single chassis earth via a CL60 or the back to back diodes in parallel with a 10nF cap and 10-20R resistor.
3. You seem to have 2x chassis ground points (maybe I'm seeing that wrong?) - stick with just one.
4. Shielded wiring helps - tie all shields to chassis ground
5. Have you tried grounding the body of the alps pot?
I have built 4 of these, 2x 01A, 2x 2P29L but I did not like the 4P1L as much as the 2P29L. The two chassis solution is a better option for sure, I have some microphonics in my 01A from transformer vibration (all in the one box). You have to be really strict with the grounding - shortest runs possible, I used star for each - don't forget the cathode here is part of the signal ground.
1. You are not helping yourself with a long cable run to the front panel switch - far better to keep those wires as short as possible, mount the switch as close as you can to the RCAs and run a shaft to the front panel.
2. The grounding from gyrators to valve sockets seems to have some t-junctions. I think its better to pick a ground point at the ground point on the gyrator or cap multiplier board for each channel and run all grounds directly to there from each point - including the RCAs. Then bring both of those to a single chassis earth via a CL60 or the back to back diodes in parallel with a 10nF cap and 10-20R resistor.
3. You seem to have 2x chassis ground points (maybe I'm seeing that wrong?) - stick with just one.
4. Shielded wiring helps - tie all shields to chassis ground
5. Have you tried grounding the body of the alps pot?
I have built 4 of these, 2x 01A, 2x 2P29L but I did not like the 4P1L as much as the 2P29L. The two chassis solution is a better option for sure, I have some microphonics in my 01A from transformer vibration (all in the one box). You have to be really strict with the grounding - shortest runs possible, I used star for each - don't forget the cathode here is part of the signal ground.
yes. Honestly I don't remember, I am thinking 10 ohms. No Ls. I would have to open the PS box to find out. I think I used 47u and 100u plus a 6uF film at the end. I had that in stock. I used the russian caps wherever Ale used them.
Basically, I figured R values empirically based on my trafo under load with 60mA output on two channels I drop ~30V on the regulator. I think I am using 200V sec trafo.
Not sure about 'incorrect'. After having 2xCR the third may not matter all that much
The only drawback of a big first position cap is the current spike at charge up. I don't go too crazy with first cap for that reason. The subsequent Rs solve the problem downstream so you can go bigger there.
The circuit seems super sensitive to the way gnd are done. At one point I disconnected/repositioned some gnd and noticed big changes in the hum. The high gain tends to magnify the smallest issue. I tried to keep the wiring as short as possible but it did not solve the problem.
IMO, the PS is very quiet and not the problem at all. I am dropping ~30V across the reg so that burns out most of the mains noise.
Yeah I was surprised too.