Here is what happened. With the dim bulb hooked up all my voltages were within reason so I continued with testing as I kept adding tubes my heater voltages reduced along with B+ at the end I removed the dim bulb and all voltages were within tolerance
Ahh! I see, you measured 8.4 Vdc at the 5842 heater pins without the tubes inserted, i.e. unloaded. So there was no drop across R3 such as when the heaters are drawing current.
Hi, I want try 21 Century Maida HV reg (from Neurochrome) on my tse. I am not so sure about the changes (and grounding). I plan to have a 150u cap (in place of C4) in between the rectifier and the Maida board, then I will strip out C15/R30/C5/D7. Should I also get rid of C14 on mosfet branch? As I understand the Maida docs, less capacitance downstream of the reg is better.
Also, I am not sure about where to run the in and out grounds for the reg. Do they both just go to central ground, or perhaps the out ground goes to the central ground, and the in ground just connects to C4 and the HV centre tap(see my diagram below). Any suggestions appreciated.
Henry
Also, I am not sure about where to run the in and out grounds for the reg. Do they both just go to central ground, or perhaps the out ground goes to the central ground, and the in ground just connects to C4 and the HV centre tap(see my diagram below). Any suggestions appreciated.
Henry
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A 150uF input capacitor in C4 will probably make fireworks of your GZ34. Research the maximum input capacitor to use with GZ34.
I would not change the downstream components from the point where you want to install the Maida reg in place of R4; you need at least the bleeder resistor R30. C14 might be required.
Before going this route it would be useful to investigate the B+ voltages you will end up with. Do not forget that there is a minimum voltage drop required in order for the Maida to function properly. To make it work with your existing power transformer you might consider SS rectification. That also has the advantage of allowing higher capacitance on the input capacitor.
I would not change the downstream components from the point where you want to install the Maida reg in place of R4; you need at least the bleeder resistor R30. C14 might be required.
Before going this route it would be useful to investigate the B+ voltages you will end up with. Do not forget that there is a minimum voltage drop required in order for the Maida to function properly. To make it work with your existing power transformer you might consider SS rectification. That also has the advantage of allowing higher capacitance on the input capacitor.
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Thanks for pointing that out, the 50uf that is in the tse2 Bom is what I will go with. The transformer is the xpwr131 which has 330v secondaries so it should be fine to reach a good B+. I have other transformers I could swap in. I think you need 15 above the desired B+ (measured from the troughs) and the Maida is adjustable ( https://neurochrome.com/products/21st-century-maida-regulator ).
What about grounding?
@henryyyy you're welcome to email me directly. You can do so by adding @neurochrome.com to my user ID here or by going through the Contact Us form on my website.
Anyway. I would keep C5, C15, and R10. Just make sure the sum of C5 and C15 is no more than 47 uF. Personally, I would make C5 = 10 uF; C15 = 100 nF but the values aren't critical as long as you have a reasonable amount of decoupling capacitance.
R4 is eliminated. That's where the Maida Regulator will go. Connect the input of the Maida Regulator across C4. Connect the output across C5. The terminals for the choke come in handy for this. You do not need to cut the ground connection between C4 and C5.
As others have pointed out, make sure you don't exceed the maximum capacitance for your regulator tube of choice.
Tom
Anyway. I would keep C5, C15, and R10. Just make sure the sum of C5 and C15 is no more than 47 uF. Personally, I would make C5 = 10 uF; C15 = 100 nF but the values aren't critical as long as you have a reasonable amount of decoupling capacitance.
R4 is eliminated. That's where the Maida Regulator will go. Connect the input of the Maida Regulator across C4. Connect the output across C5. The terminals for the choke come in handy for this. You do not need to cut the ground connection between C4 and C5.
As others have pointed out, make sure you don't exceed the maximum capacitance for your regulator tube of choice.
Tom
You will also need D7 across the output of the Maida. The B+ voltage is tube rectified. The B- which supplies bias to the output tubes via the mosfets is solid state rectified. This is done for a reason. B- comes up first which keeps the output tubes in cutoff. The DHT's warm up faster than the 5AR4 so they are ready, but still held in cutoff as the 5AR4 applies B+. The bias supply moves from a large negative voltage to the proper value as the 5AR4 heats gently starting the output tubes. During warmup some of the negative voltage will find its way through the voltage divider associated with the bias pots and put a negative voltage across C5 which is now the output of your Maida. It may not like this. D7 will clamp it to about half a volt.
Got my TSE II up and running thanks to the help of this thread and some amazing members.
Special shout-out to George for personally answering a few questions I had during the build. Wouldn't have been possible without all the great information and time others have put in before me.
Running all Hammond:
Power trans 372HX
Output trans 1628sea
193G choke
Psvane 300b biased at 75ma
Raytheon 5842- set at 175v
Tung Sol 5AR4
Mundorf Supreme coupling caps. Overall pretty impressed and happy with the final product. Might try and use the 16 ohm tap on the output transformers to get the 2.5k load, doesn't seem to have the gain of the other tubelab amps, still plenty loud though 😁
This joins Tubelabs other creations in my setup, the SSE and SPP. Now time to get this burned in!
Special shout-out to George for personally answering a few questions I had during the build. Wouldn't have been possible without all the great information and time others have put in before me.
Running all Hammond:
Power trans 372HX
Output trans 1628sea
193G choke
Psvane 300b biased at 75ma
Raytheon 5842- set at 175v
Tung Sol 5AR4
Mundorf Supreme coupling caps. Overall pretty impressed and happy with the final product. Might try and use the 16 ohm tap on the output transformers to get the 2.5k load, doesn't seem to have the gain of the other tubelab amps, still plenty loud though 😁
This joins Tubelabs other creations in my setup, the SSE and SPP. Now time to get this burned in!
Attachments
Assuming I can still get a TSE-II pcb at the tubelab paypal (after all, George didn't promise anything about boards in 2025), I am going to dive into this project. I have been trying to read up and learn about this design. There is one thing that confuses me on the schematic. It looks like the 5V heater is connected to the B+ voltage at the bottom of the tube rectifier. Being new to tubes, I will assume that I don't know how to schematic a tube rectifier.
The reason that I was looking at that part of the circuit is that I have a leftover Hammond 290CX transformer (yes, leftover from another tube project so I'm not entirely a tube noob. Or is that tube knob?) I think the 290CX was designed as a guitar amp transformer with a different physical orientation than is typical. Comparing to the 372HX, the 290CX has only 4 amps 6.3V compared to the 372HX having 6 amps but that should be the problem for the 5842 because it only requires 300 mA per tube. The big difference is the 290CX has 650V C.T. instead of the 600 for the 372HX. It seems like I should be able to drop a 50 measly volts somewhere in the power supply. I'm thinking turning the CLC power supply into a CLCRC with some off board components. Am I off my nut or does this idea merit a few more dead brain cells? My thought is the cost of the power transformer is worth an upgrade on tubes for this amp.
Thanks in advance.
The reason that I was looking at that part of the circuit is that I have a leftover Hammond 290CX transformer (yes, leftover from another tube project so I'm not entirely a tube noob. Or is that tube knob?) I think the 290CX was designed as a guitar amp transformer with a different physical orientation than is typical. Comparing to the 372HX, the 290CX has only 4 amps 6.3V compared to the 372HX having 6 amps but that should be the problem for the 5842 because it only requires 300 mA per tube. The big difference is the 290CX has 650V C.T. instead of the 600 for the 372HX. It seems like I should be able to drop a 50 measly volts somewhere in the power supply. I'm thinking turning the CLC power supply into a CLCRC with some off board components. Am I off my nut or does this idea merit a few more dead brain cells? My thought is the cost of the power transformer is worth an upgrade on tubes for this amp.
Thanks in advance.
There will be plenty of boards available in 2025. I have a few of each board left in stock, and 16 pounds of new stock somewhere out there in Fedex land. They are supposed to be delivered on Thursday, but Fedex hasn't been too reliable here lately.
Tweaking the value of C4 will adjust the B+ voltage. This works best if a choke is used in place of R4. A choke is recommended to eliminate hum with sensitive speakers.
Yes, the 5.0 volt heater winding is connected to B+. This is the case for all DH rectifiers like the 5U4 and 5Y3. It is also common practice with the 5AR4. In my 60+ years of tinkering with vacuum tube electronics I have seen exactly two transformers with an internal short from the 5 volt winding to the 6.3 volt winding. One of them belonged to cogitech. It made life miserable for a bypass cap and took forever to remotely troubleshoot. Shortly after that another one was found, also in an SSE. Both were Hammonds.
The main limitation with 290CX in this TSE application is current capability, both 6.3V & HV - HV only 81 ma vs. 230 ma for 373HX. What power tubes are you planning to use?
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I am planning on using 300b. Reading the specs from the 290CX on my bench;
650VCT @ 207 mA
6.3VCT @ 4A
5V @ 3A
It looks like mine is old and they have changed the specs but still ballpark correct. From the Hammond current spec sheet
650VCT @ 180 mA
6.3VCT @ 4.5A
5V @ 3A
On another subject, what are people using for output transformers these days, especially in the US? It looks like Electra-Print, One Electron, and Transcendar are no longer making output transformers. From what I read, the Edcor GXSE10 are still available but on the small side. I looks like the CXSE25 would be a better choice but we are back up to $300 for a pair. Hammond has the 1628SEA and 1630SEA but they are even more expensive. Has anyone tried the ShlA1 transformers from DIY Hifi Supply?
https://diyhifisupply.com/product/a...-transformers-for-300b-45-2a3-kt88-etc/?gQT=1
The price is good and they weigh more than 3 kg each. I'm not sure what to do with the connection pins but it looks interesting. I could also get some from Primary Winding in the UK but that would end up as expensive as the Hammond 1638/1630SEA.
650VCT @ 207 mA
6.3VCT @ 4A
5V @ 3A
It looks like mine is old and they have changed the specs but still ballpark correct. From the Hammond current spec sheet
650VCT @ 180 mA
6.3VCT @ 4.5A
5V @ 3A
On another subject, what are people using for output transformers these days, especially in the US? It looks like Electra-Print, One Electron, and Transcendar are no longer making output transformers. From what I read, the Edcor GXSE10 are still available but on the small side. I looks like the CXSE25 would be a better choice but we are back up to $300 for a pair. Hammond has the 1628SEA and 1630SEA but they are even more expensive. Has anyone tried the ShlA1 transformers from DIY Hifi Supply?
https://diyhifisupply.com/product/a...-transformers-for-300b-45-2a3-kt88-etc/?gQT=1
The price is good and they weigh more than 3 kg each. I'm not sure what to do with the connection pins but it looks interesting. I could also get some from Primary Winding in the UK but that would end up as expensive as the Hammond 1638/1630SEA.
Apologies, I stand corrected on the current capabilities of the Hammond 290CX.
Your link to DIYHIFIsupply shows some very reasonably priced OTs, if the pricing is current and items available. Where do they ship from? The new tariffs might come to play. I have no experience with their transformers though.
Here is another thread where someone is searching for 300b SE 5k output transformers that you might find useful.
Your link to DIYHIFIsupply shows some very reasonably priced OTs, if the pricing is current and items available. Where do they ship from? The new tariffs might come to play. I have no experience with their transformers though.
Here is another thread where someone is searching for 300b SE 5k output transformers that you might find useful.
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No worries on the 290CX.Apologies, I stand corrected on the current capabilities of the Hammond 290CX.
Your link to DIYHIFIsupply shows some very reasonably priced OTs, if the pricing is current and items available. Where do they ship from? The new tariffs might come to play. I have no experience with their transformers though.
Here is another thread where someone is searching for 300b SE 5k output transformers that you might find useful.
DIYHIFIsupply is in Hong Kong so tariffs are a real issue. I would also have to have at least an email conversation about pricing and availability. I was also worried that it might be a zombie website. Too many of those these days.
Thank you for the link. It gave me some good options to pursue.
The Softone link seems very interesting too. That is the most complete datasheet I have seen for transformers. Also it seems like a great application for R-core.
BTW what is your avatar image? I can't quite make it out but it looks like either the Borg queen or Max Headroom. 🙂
The owner of Softone is a great guy. You can trust the specs.
It’s Dima, from Far Harbor.