I have not had any problem since removing the motor run cap, but would this addition be helpful in the case of the TSE-II?
In your shoes I would put my nice 100uF motor run cap to use in parallel with C5, and add the CL-140 as George suggested, but with a 5AR4 rectifier. Using the 5U4 with the addition of the CL-140 could cause a B+ lower than you would like. Try out the options and see what you like.
Yes, that Kemet motor run cap is nice.
But I don’t fancy sparks much.
So, if I put it back in, it needs to be with that CL-140 in series with the HV CT.
I am also considering a Weber Copper Cap as a replacement for the tube rectifier.
Here we go, time to enjoy the music…
First, I went back to a 5AR4 rectifier and I restored the motor run cap.
Minimal rework of the wiring as well.
Then, mandatory shots of the thing at work:
@Tubelab_com Thank you, George!
I know it makes little sense for you to spend time in this thread providing your expertise for free.
And yet, you do it and I am sure it is often a thankless task.
So, thanks!
First, I went back to a 5AR4 rectifier and I restored the motor run cap.
Minimal rework of the wiring as well.
Then, mandatory shots of the thing at work:
@Tubelab_com Thank you, George!
I know it makes little sense for you to spend time in this thread providing your expertise for free.
And yet, you do it and I am sure it is often a thankless task.
So, thanks!
Glad it worked out - congratulations! What did you change to lick the arcing problem?
I abandoned the idea of adding thermistors because the motor run cap is in parallel with C5, not C4.
So, I simply removed the 5U4 and put that old Psvane 5AR4 in. Verified all voltages and bias. More B+, but no issues.
Then reintroduced the motor run cap and repeated checkout one more time.
No problem.
My speakers are barely sensitive enough to make good use of this amp. The amp has some of the cleanest bass in any tube I have heard.
Now hunting down flat pack cabinets for a pair of full range drivers. It’s HARD. Very few make them and it’s either out of stock or too expensive.
And I am definitely not a woodworker.
🤦♂️
Francois G, there are lots of great sounding and very efficient speaker designs using PA woofers and horn tweeters. I use a variation on the "Pi Four" and it sounds fantastic, and there are flatpacks available. Or there is a whole online community that builds similar designs out of used or home built cabinets and different components.
http://www.pispeakers.com/catalog/p...ucts_id=108&osCsid=iosjik8ndoocai2rlcoannj2r6
http://www.pispeakers.com/catalog/p...ucts_id=108&osCsid=iosjik8ndoocai2rlcoannj2r6
I have upgraded to a pair of EML 300BXLS tubes and now I wanted to raise B+ to 500V.
This is giving me some problems with the negative supply.
The positive supply is no problem, I have replaced all electrolytics with 900V film caps.
I just forgot about the 2 100uF 450V electrolytics in the negative supply and blew C6 and also R5. I have tried changing the value of R5 in an attempt to lower the voltage over C6, but that didn't work.
I have a 470-0-470V power transformer with separate 6.3V and 5V transformers, so it is possible to reduce the 470-0-470V a bit with a bucking transformer without affecting the heater voltage.
I guess I could try to replace the 100uF 450V with a higher voltage film cap, but it looks like there is more on this negative supply than just the bias.
So I am not really sure where to start, looks like there are more modifications needed than I expected.
This is giving me some problems with the negative supply.
The positive supply is no problem, I have replaced all electrolytics with 900V film caps.
I just forgot about the 2 100uF 450V electrolytics in the negative supply and blew C6 and also R5. I have tried changing the value of R5 in an attempt to lower the voltage over C6, but that didn't work.
I have a 470-0-470V power transformer with separate 6.3V and 5V transformers, so it is possible to reduce the 470-0-470V a bit with a bucking transformer without affecting the heater voltage.
I guess I could try to replace the 100uF 450V with a higher voltage film cap, but it looks like there is more on this negative supply than just the bias.
So I am not really sure where to start, looks like there are more modifications needed than I expected.
@debije I can't speak to the bucking transformer option.
Which value did you change R5 to? Did you measure the voltage drop?
The negative bias supply draws little current so you may need a much larger R to reduce the voltage adequately.
It wouldnt hurt to try this 500V cap for C6: Rubycon 500HXW100MEFR18X40
Another option is perhaps a reverse biased zener instead of R5, like 1N5358BG. Not sure about added noise though.
Separately, I've been looking into building a 5842 headphone amp and recently also finished a uTracer and have been curve tracing many of them.
Looking for the optimal operating point, I am getting fairly poor results with Va=175V Ia=10mA similar to the TSE points.
This is true for Ericsson 417A, Amperex/GE and Raytheon 5842 which do measure diffierently.
Might be an operator error on my end or not applicable to the TSE due to other reasons, but it seems like lower voltage and higher current leads to much less distortion. It is only a single resistor change and re-adjustment of the trimmer resistor so could be worth a try at something like 135/150V and 20mA.
(The flat load line assumes using a CCS)
Which value did you change R5 to? Did you measure the voltage drop?
The negative bias supply draws little current so you may need a much larger R to reduce the voltage adequately.
It wouldnt hurt to try this 500V cap for C6: Rubycon 500HXW100MEFR18X40
Another option is perhaps a reverse biased zener instead of R5, like 1N5358BG. Not sure about added noise though.
Separately, I've been looking into building a 5842 headphone amp and recently also finished a uTracer and have been curve tracing many of them.
Looking for the optimal operating point, I am getting fairly poor results with Va=175V Ia=10mA similar to the TSE points.
This is true for Ericsson 417A, Amperex/GE and Raytheon 5842 which do measure diffierently.
Might be an operator error on my end or not applicable to the TSE due to other reasons, but it seems like lower voltage and higher current leads to much less distortion. It is only a single resistor change and re-adjustment of the trimmer resistor so could be worth a try at something like 135/150V and 20mA.
(The flat load line assumes using a CCS)
The 500V cap might be a good idea, I couldn't find one when I was looking, so thanks for the make and model number.
I changed R5 to 6.8Kohm. This gives me about 400V on C6 and a B+ of 493V and 90mA on the 300BXLS. I did have to use a bucking transformer. Without it, B+ would go over 530V. I can raise the current a little bit which will also lower B+. There are 2 operating points for the 300BXLS, 475V / 90mA and 500V / 110mA, so I will end up somewhere in between.
I was able to use a bucking transformer with the 470-0-470V transformer because it doesn't have filament taps. I have seperate transformers for this.
So with a 500V cap I would be able to lower the value of R5. This is probably better.
Interesting to see that 175V is not the best voltage for the 5842. I will probably not change it on the TSE-2. I also have an U-tracer, so I could try to measure the 5842 myself when I find some time.
I changed R5 to 6.8Kohm. This gives me about 400V on C6 and a B+ of 493V and 90mA on the 300BXLS. I did have to use a bucking transformer. Without it, B+ would go over 530V. I can raise the current a little bit which will also lower B+. There are 2 operating points for the 300BXLS, 475V / 90mA and 500V / 110mA, so I will end up somewhere in between.
I was able to use a bucking transformer with the 470-0-470V transformer because it doesn't have filament taps. I have seperate transformers for this.
So with a 500V cap I would be able to lower the value of R5. This is probably better.
Interesting to see that 175V is not the best voltage for the 5842. I will probably not change it on the TSE-2. I also have an U-tracer, so I could try to measure the 5842 myself when I find some time.
That would be some interesting finding.
But the Amperex performance at 175V is very appealing in terms of H2%.
I firmly believe even harmonics distortion is the main appeal of tube amplification.
If overall distortion must be reduced to the max, SS cannot be beat.
I will probably end up with something like 485V and current around 95 - 100mA. So it will not be 500V / 110mA.
OK. These guys have a good reputation and a good warranty, so that should be fine.
A lot of the Russian re-issues overstate their max Va and flame out when tested. YMMV.
Ok, Hi Gentlemen! Quick question. Can you tell me the values that the transformer must have if I want to work with 2A3 tubes. The same for output transformers. I would be grateful because I have already read too much information. HELP!
