Dave,
Thank you for posting the data sheet. You are very kind.
I have emailed Brett and he has given me a reply.
I have now decided to give it a go. I will build Brett's 12B4A line preamp. At this stage, I am planning to use a tube rectified, adjustable PSU from a kit and start from there.
I will post my result when I complete it. I am sure the result will be very positive.
My thanks to all who have posted here and given me plenty of enlightenments.
Regards,
Bill
Thank you for posting the data sheet. You are very kind.
I have emailed Brett and he has given me a reply.
I have now decided to give it a go. I will build Brett's 12B4A line preamp. At this stage, I am planning to use a tube rectified, adjustable PSU from a kit and start from there.
I will post my result when I complete it. I am sure the result will be very positive.
My thanks to all who have posted here and given me plenty of enlightenments.
Regards,
Bill
Hi,
The project is in progress.
Before I decided to go for Brett’s 12B4A, I had ordered a power supply board with an adjustable output from 70V to 400V. The purpose is to use the board to experiment different preamps if needed. Maybe one day I will build Frank’s ultimate preamp, the Aikido preamp, and others. Of course, for the final preamp that suits my need, I will build a matching PSU for it. For now, I am targeting building Brett’s 12B4A using this board first, unless Brett is unhappy with it.
Everything in the schematic is built onto one board. What do you think of this power supply? Will it do the job? Is this PSU bad? OK? Good?
http://home.iprimus.com.au/cbsoftware/lsdy.jpg
Please also help me with these questions:
1. On this board, I presume that all these 3 tubes use AC for filament. Please correct me if I am wrong.
2. Can you point me to the best sources in OZ for getting the transformer?
3. I think I will put things into an enclosure for my initial project work since the PSU is on a PCB, and I have an existing rack enclosure for my existing preamp that can be re-used, as it has got a volume control, input selector and plenty of RCA terminals. What do you recommend for the 12B4A circuit board? I guess I will use point to point wiring. Fibre board? Aluminium flat? Vero board?
Regards,
Bill
The project is in progress.
Before I decided to go for Brett’s 12B4A, I had ordered a power supply board with an adjustable output from 70V to 400V. The purpose is to use the board to experiment different preamps if needed. Maybe one day I will build Frank’s ultimate preamp, the Aikido preamp, and others. Of course, for the final preamp that suits my need, I will build a matching PSU for it. For now, I am targeting building Brett’s 12B4A using this board first, unless Brett is unhappy with it.
Everything in the schematic is built onto one board. What do you think of this power supply? Will it do the job? Is this PSU bad? OK? Good?
http://home.iprimus.com.au/cbsoftware/lsdy.jpg
Please also help me with these questions:
1. On this board, I presume that all these 3 tubes use AC for filament. Please correct me if I am wrong.
2. Can you point me to the best sources in OZ for getting the transformer?
3. I think I will put things into an enclosure for my initial project work since the PSU is on a PCB, and I have an existing rack enclosure for my existing preamp that can be re-used, as it has got a volume control, input selector and plenty of RCA terminals. What do you recommend for the 12B4A circuit board? I guess I will use point to point wiring. Fibre board? Aluminium flat? Vero board?
Regards,
Bill
It's not how I'd do it, but it should work OK.HiFiNutNut said:
Looks to me like it's not specified. The filaments for both tubes are in parallel and run off to J3 on the left. Could be either I s'pose. Doesn't it say anything in the instructions or specs on what to use?
www.evatco.com.au have a selection of Hammonds
I small piece of Al / fibreglass PCB with sockets for the tubes would do and point to piont wire it using some of the standard tagstrips that any of the electronics stores/wholesalers sell. When you have all the parts collected, spend a bit of time working out how to lay them out.
Brett,
Thanks for your reply.
There are no instructions coming with the completed board. It arrived last night. But what can I complain? It cost only about AUD$50 and the components on the board certainly look a bit better than the Jaycar stuff. As expressed, the purpose is to get me quickly started building. When the amp is completed, I will probably build the ultimate PSU to match the amp. For now, I am anxious to hear the sound from the 12B4A.
My existing preamp box has a Jaycar aleph 50k potentiometer as the volumn control, as I had long been looking for a good volume control with a reasonable price without success. Only recently I found a guy in Sydney selling 24 step ladder type attenuators with mil spec resistors for something like $50 as a kit or $70 assembled. Do you think I should get one? What value is best for a generic use in a tube preamp?
Regards,
Bill
Thanks for your reply.
There are no instructions coming with the completed board. It arrived last night. But what can I complain? It cost only about AUD$50 and the components on the board certainly look a bit better than the Jaycar stuff. As expressed, the purpose is to get me quickly started building. When the amp is completed, I will probably build the ultimate PSU to match the amp. For now, I am anxious to hear the sound from the 12B4A.
My existing preamp box has a Jaycar aleph 50k potentiometer as the volumn control, as I had long been looking for a good volume control with a reasonable price without success. Only recently I found a guy in Sydney selling 24 step ladder type attenuators with mil spec resistors for something like $50 as a kit or $70 assembled. Do you think I should get one? What value is best for a generic use in a tube preamp?
Regards,
Bill
Bad circuit- the heater-to-cathode max voltage rating is grossly exceeded. You need separate heater supplies for the two tubes.
Hi,
Hifinut,
Lose the Zener and that other diode in the regulated PS and replace it with a 85A2/OG3.
Lose the decoupling cap as well and adjust R23 and R25.
There's a mod on this at diyclub.biz where you culled the diagram from.
Cheers,😉
Hifinut,
Lose the Zener and that other diode in the regulated PS and replace it with a 85A2/OG3.
Lose the decoupling cap as well and adjust R23 and R25.
There's a mod on this at diyclub.biz where you culled the diagram from.
Cheers,😉
Frank, thank you for pointing me to the mod.
So do you guys think this will be better? If it is, I will have some fun doing the mod.
(I think it should be OK to post the schematic here because it is freely available on the internet. The URL for the original document is here: http://eshop.diyclub.biz/article_info.php?articles_id=3. I will delete this image / schematic in a couple of days)
Regards,
Bill
So do you guys think this will be better? If it is, I will have some fun doing the mod.
(I think it should be OK to post the schematic here because it is freely available on the internet. The URL for the original document is here: http://eshop.diyclub.biz/article_info.php?articles_id=3. I will delete this image / schematic in a couple of days)
Regards,
Bill
D'oh. Good call. My memory said 300V for some reason.SY said:
Bill, small transformers for the extra supply are about $A10 from local suppliers eg Jaycar MM2013 an they're useful things to have around anyway.
Hi,
I can't help but wonder how long that 6Z4 is going to last with such a big cap right at it's output...
Has anyone actually built this thing? Simmed it? I doubt it...
Any way you look at it, it's still over the top for what you want it to do.
100ma current capability for a linestage is huge, a 6080 alone is going to draw a couple of amps too.
Maybe a 6C19-P would be better suited or, sticking with the 6080, a single triode could be used per channel as series pass device but then I'd double the error amp and voltage reference part so you end up having a dedicated regulator per channel.
Alternatively, that's what I'd do, if you need 300V output from the reg, you could use my 300V reg using the EL86/12AX7 cascode combo.
If you only require 250VDC then the one with the ECL85 should be even cheaper to build.
One reg per channel is best as you don't want to end up with interchannel IMD....
I confess having a bit of a penchant for a dual mono approach to audio stuff but it doesn't hurt....
Cheers, 😉
I can't help but wonder how long that 6Z4 is going to last with such a big cap right at it's output...
Has anyone actually built this thing? Simmed it? I doubt it...
Any way you look at it, it's still over the top for what you want it to do.
100ma current capability for a linestage is huge, a 6080 alone is going to draw a couple of amps too.
Maybe a 6C19-P would be better suited or, sticking with the 6080, a single triode could be used per channel as series pass device but then I'd double the error amp and voltage reference part so you end up having a dedicated regulator per channel.
Alternatively, that's what I'd do, if you need 300V output from the reg, you could use my 300V reg using the EL86/12AX7 cascode combo.
If you only require 250VDC then the one with the ECL85 should be even cheaper to build.
One reg per channel is best as you don't want to end up with interchannel IMD....
I confess having a bit of a penchant for a dual mono approach to audio stuff but it doesn't hurt....
Cheers, 😉
I have removed two copyrighted drawings. Please get permission from the copyright holder before posting them again. I left these as links to the copyright holder's site and fixed your links.
Hi,
So the conclusion is that the PSU kit I got is simply not good. I have decided to abandon it. I think some parts can be reused in the future, so it was only a minor loss if any, given the cheap price I paid.
Anyway, now I need a PSU that will work with Brett's 12B4A. Brett's preamp schematic have been posted in this forum for a number of times, however, I have not found any associated power supply schematic.
Brett, would you mind posting or emailing me the schematic you use for your 12B4A?
Alternatively, I could build Frank's 300V reg using the EL86/12AX7 cascode combo. The schematic has been posted in the forum.
I initially thought that I would have a PSU with adjustable output voltage in order to play with different preamps in the future. It comes out that all of the highly recommended line preamps, i.e. Brett's 12B4A, Frank's ultimate line stage preamp, and the Aikido, all use 300VDC B+. So in this case, I think I should be happy to have a PSU with a fixed, regulated 300VDC, as long as it can deliver sufficient current for all of those amps. PLEASE also note that one day I will probably build the phono stage as well, so if the PSU can deliver enough current then it will save me building a separate PSU.
Part of the reason that I have not thought of Frank's PSU previously was that I thought it was for monoblock therefore it might not deliver enough current if I used it for stereo. Building 2 monoblock is of course the ultimate but the cost and efforts would nearly be doubled. but if I can't find any simple PSU that has satisfactory performance then I may opt to build 2 of Frank's PSU.
Your advice?
Regards,
Bill
P.S. SY, thanks for fixing the links. I have deleted the images. I was aware of the copyright issues but was certain that the owner would not mind as for him this would cause no damage but on contrary a sort of "advertising". I only planned to display them for at most a couple of days.
So the conclusion is that the PSU kit I got is simply not good. I have decided to abandon it. I think some parts can be reused in the future, so it was only a minor loss if any, given the cheap price I paid.
Anyway, now I need a PSU that will work with Brett's 12B4A. Brett's preamp schematic have been posted in this forum for a number of times, however, I have not found any associated power supply schematic.
Brett, would you mind posting or emailing me the schematic you use for your 12B4A?
Alternatively, I could build Frank's 300V reg using the EL86/12AX7 cascode combo. The schematic has been posted in the forum.
I initially thought that I would have a PSU with adjustable output voltage in order to play with different preamps in the future. It comes out that all of the highly recommended line preamps, i.e. Brett's 12B4A, Frank's ultimate line stage preamp, and the Aikido, all use 300VDC B+. So in this case, I think I should be happy to have a PSU with a fixed, regulated 300VDC, as long as it can deliver sufficient current for all of those amps. PLEASE also note that one day I will probably build the phono stage as well, so if the PSU can deliver enough current then it will save me building a separate PSU.
Part of the reason that I have not thought of Frank's PSU previously was that I thought it was for monoblock therefore it might not deliver enough current if I used it for stereo. Building 2 monoblock is of course the ultimate but the cost and efforts would nearly be doubled. but if I can't find any simple PSU that has satisfactory performance then I may opt to build 2 of Frank's PSU.
Your advice?
Regards,
Bill
P.S. SY, thanks for fixing the links. I have deleted the images. I was aware of the copyright issues but was certain that the owner would not mind as for him this would cause no damage but on contrary a sort of "advertising". I only planned to display them for at most a couple of days.
Hi,
Not only that but there's one such regulator per tube as well.
So you have one per tube per channel making for four regulators in total for the entire preamp.
Don't forget either that each stage had yet another massive capacitor bank behind each regulator (2*330µF/385V caps @ 300VDC). All that for a circuit that hardly draws any current so in essence what you have is a dedicated battery supply for each and every stage.
One such regulator and reservoir cap bank may cope with the draw of a single 12B4A but using a single reg for 2 stereo channels will not only be too much (or close to) but IMO does away with an important part of the entire concept anyway, namely to avoid cross-channel IMD.
What you could do however is build a single 350VDC (or thereabout) regulator and use dedicated chokes + caps to provide a steady supply to each channel/stage.
Otherwise a dedicated left and right hand channel regulator of sufficient current capability to supply the biggest consumer (probably the 12B4A but I'm guessing).
The Aikido needs a common supply for the SRPP and WCF stages per channel for the PS noise cancellation to work.
The 12BH7A WCF and Brett's 12B4A can also work fine from one supply per channel.
Ultimately, regulator or not, the final results will also be influenced by the quality of the caps sitting behind the regs; changing from off-the shelf electrolytic to good quality stuff a la Unlytic is certainly an audible upgrade.
Hope this helps, 😉
Not only that but there's one such regulator per tube as well.
So you have one per tube per channel making for four regulators in total for the entire preamp.
Don't forget either that each stage had yet another massive capacitor bank behind each regulator (2*330µF/385V caps @ 300VDC). All that for a circuit that hardly draws any current so in essence what you have is a dedicated battery supply for each and every stage.
One such regulator and reservoir cap bank may cope with the draw of a single 12B4A but using a single reg for 2 stereo channels will not only be too much (or close to) but IMO does away with an important part of the entire concept anyway, namely to avoid cross-channel IMD.
What you could do however is build a single 350VDC (or thereabout) regulator and use dedicated chokes + caps to provide a steady supply to each channel/stage.
Otherwise a dedicated left and right hand channel regulator of sufficient current capability to supply the biggest consumer (probably the 12B4A but I'm guessing).
The Aikido needs a common supply for the SRPP and WCF stages per channel for the PS noise cancellation to work.
The 12BH7A WCF and Brett's 12B4A can also work fine from one supply per channel.
Ultimately, regulator or not, the final results will also be influenced by the quality of the caps sitting behind the regs; changing from off-the shelf electrolytic to good quality stuff a la Unlytic is certainly an audible upgrade.
Hope this helps, 😉
Frank,
No wonder yours is called the "ultimate" line preamp.
I guess that when you said 4 PSU are needed you had included the phono stage as well. If one is building only your line preamp then only 2 PSU are needed. Let me know if I am wrong.
In that case, I guess I could build 2 of your PSU and they would be sufficient for a line stage of either the 12B4A, 12BH7A or Aikido.
The idea of building a "350VDC (or thereabout) regulator and use dedicated chokes + caps to provide a steady supply to each channel/stage" is a good one.
I will think about them during the weekend.
Thank you for your advice.
Regards,
Bill
No wonder yours is called the "ultimate" line preamp.
I guess that when you said 4 PSU are needed you had included the phono stage as well. If one is building only your line preamp then only 2 PSU are needed. Let me know if I am wrong.
In that case, I guess I could build 2 of your PSU and they would be sufficient for a line stage of either the 12B4A, 12BH7A or Aikido.
The idea of building a "350VDC (or thereabout) regulator and use dedicated chokes + caps to provide a steady supply to each channel/stage" is a good one.
I will think about them during the weekend.
Thank you for your advice.
Regards,
Bill
Now a pair of Westinghouse "Reliatron" 12B4A have arrived.
For the plate resistor, I have got 5 x 2W metal film resistors to be connected in parallel to make up the voltage rating. I don't know where I can get a high quality 10W resistor. Some people say that carbon resistors sound better. I think I will use what I have for the time being. I can change it later if some one gets me to believe what I have are no good.
The next stage of the preamp is an active XO with an opamp input buffer so the impedance will really depend the input ground reference resistor I use. I think I will make it 100k. I hope that is high enough. In that case, I will ditch the cathode bypass cap. I don't think I need higher gains and I think the 2.6k output impedance of the preamp should work with 100k input impedance of the next stage.
I think I could possibly build the preamp's main circuit in a couple of hours, given that an existing enclosure with a power socket, switch, input and output terminals, volume control and input selector has already been built.
Now this is my biggest headache - the PSU! Specifically the high voltage regulation.
I have played with PSUD2 without much luck. I couldn't find information about the resistance of transformers. For the output, I am not so sure about whether I should use resistive load or constant current load. If it is resistive load, would it be 6k + plate resistance + 700ohms?
Anyway, I have just come across the SuperReg kit from Vaccum State Electronics: http://www.vacuumstate.com/kits.htm . The following are some of the descriptions:
**********
It uses a high voltage adjustable current source feeding a high voltage adjustable shunt regulator. It offers millivolt levels of output regulation, extremely low noise, and a wideband output impedance circa 10 milliohms. It can be adjusted to your exact voltage requirements between 100 and 400 VDC, and supply up to 100mA into your circuits. 400V is the maximum safe voltage limit of the components used, but much more current can be obtained if you fit bigger heatsinks. It needs to be powered from a DC supply between 50 & 100V higher than your chosen output voltage. Please be aware that it is only a regulator–it does not contain a power transformer, diodes or filter caps.
**********
What do you think of it? It is quite pricy for a small number of components but I am happy to pay for it considering it is an intellectual product, but only if it sounds exceptionally good. How does it compare to a simple LCLCL or CRCRC circuit?
Alternatively, if you have any good circuit / topology to recommend please throw it in. Is there any freely available circuit like that of the VSE on the internet?
What I want is to build a very stiff PSU that has 300VDC and can deliver ample amount of current so that I can use it to build / experiment preamps and phono stage in the future.
Thank you for helping me getting this far. Please help me to move on building the preamp. Without your help I will have to abandon the project.
Kind regards,
Bill
For the plate resistor, I have got 5 x 2W metal film resistors to be connected in parallel to make up the voltage rating. I don't know where I can get a high quality 10W resistor. Some people say that carbon resistors sound better. I think I will use what I have for the time being. I can change it later if some one gets me to believe what I have are no good.
The next stage of the preamp is an active XO with an opamp input buffer so the impedance will really depend the input ground reference resistor I use. I think I will make it 100k. I hope that is high enough. In that case, I will ditch the cathode bypass cap. I don't think I need higher gains and I think the 2.6k output impedance of the preamp should work with 100k input impedance of the next stage.
I think I could possibly build the preamp's main circuit in a couple of hours, given that an existing enclosure with a power socket, switch, input and output terminals, volume control and input selector has already been built.
Now this is my biggest headache - the PSU! Specifically the high voltage regulation.
I have played with PSUD2 without much luck. I couldn't find information about the resistance of transformers. For the output, I am not so sure about whether I should use resistive load or constant current load. If it is resistive load, would it be 6k + plate resistance + 700ohms?
Anyway, I have just come across the SuperReg kit from Vaccum State Electronics: http://www.vacuumstate.com/kits.htm . The following are some of the descriptions:
**********
It uses a high voltage adjustable current source feeding a high voltage adjustable shunt regulator. It offers millivolt levels of output regulation, extremely low noise, and a wideband output impedance circa 10 milliohms. It can be adjusted to your exact voltage requirements between 100 and 400 VDC, and supply up to 100mA into your circuits. 400V is the maximum safe voltage limit of the components used, but much more current can be obtained if you fit bigger heatsinks. It needs to be powered from a DC supply between 50 & 100V higher than your chosen output voltage. Please be aware that it is only a regulator–it does not contain a power transformer, diodes or filter caps.
**********
What do you think of it? It is quite pricy for a small number of components but I am happy to pay for it considering it is an intellectual product, but only if it sounds exceptionally good. How does it compare to a simple LCLCL or CRCRC circuit?
Alternatively, if you have any good circuit / topology to recommend please throw it in. Is there any freely available circuit like that of the VSE on the internet?
What I want is to build a very stiff PSU that has 300VDC and can deliver ample amount of current so that I can use it to build / experiment preamps and phono stage in the future.
Thank you for helping me getting this far. Please help me to move on building the preamp. Without your help I will have to abandon the project.
Kind regards,
Bill
HiFiNutNut said:
Allen's regulator is qyuite impressive... you won't find much better available to just buy. We have one here assembled not installed yet.
Something like 3/4 A.
That's enuff to regulate an entire stereo SE amp.
Some will knock it because it uses transisitors ....
dave
Thanks, Dave. That gives me a lot of reliefs and comforts.
I am sure that Frank's PSU is good and I have not eliminiated it as an option. However, considering I will eventually need 4 such PSUs to run the preamp, with 12 light bolbs and perhaps 4 transformers (plus those for filaments perhaps) only for the PSU, I guess that being the "ultimate" I should tackle it later. Being a newbie it is better to build something simpler at the beginning.
I have read through every thread in this forum with regards to the 12B4A preamp and tried to learn things out of them. Brett has offered to help designing the PSU but through private emails I understand that he is moving house and undergoing a very busy time so I wouldn't feel good to bother him. I recalled he mentioned that he was happy with either a simple LCL or shunt regulator type PSU. Therefore I was interested in the SuperReg.
I just sent Joe an email for an enquiry. Minutes later I found Allen's book on the VSE site. I guess the book has the schematic of the SuperReg. If that is the case, another option for me is to buy the book and build the SuperReg instead of relying on getting a kit. From what I read in the forum it is a good book and I can learn much from it.
Regards,
Bill
I am sure that Frank's PSU is good and I have not eliminiated it as an option. However, considering I will eventually need 4 such PSUs to run the preamp, with 12 light bolbs and perhaps 4 transformers (plus those for filaments perhaps) only for the PSU, I guess that being the "ultimate" I should tackle it later. Being a newbie it is better to build something simpler at the beginning.
I have read through every thread in this forum with regards to the 12B4A preamp and tried to learn things out of them. Brett has offered to help designing the PSU but through private emails I understand that he is moving house and undergoing a very busy time so I wouldn't feel good to bother him. I recalled he mentioned that he was happy with either a simple LCL or shunt regulator type PSU. Therefore I was interested in the SuperReg.
I just sent Joe an email for an enquiry. Minutes later I found Allen's book on the VSE site. I guess the book has the schematic of the SuperReg. If that is the case, another option for me is to buy the book and build the SuperReg instead of relying on getting a kit. From what I read in the forum it is a good book and I can learn much from it.
Regards,
Bill
HiFiNutNut said:
I've the book. Recommended. I'd still look at the kit... shunt regs like this can be a bit tricky to get stable, and the kit has all the bits worked out.
dave
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