After a lot of reading, I've also decided to build a SPP as my first tube (speaker) amp. Just to make sure I order the right things, can you guys confirm that the following makes sense? I'm planning to do a standard UL and SS rectification build.
Power transformer:
275-0-275, 200 mA
6.3 VAC, 5A
Output transformers:
TTG-EL84PP
Tubes:
I am slightly confused reading through the threads and the wallofsound documentation (great btw!) in regards to the JJ EL84s. In some older posts they are described as being very sturdy and taking high voltages, whereas in newer discussions JJs seem to be the ones that need higher cathode resistors... did they change? Or am I safe with 270ohm if my transformer is 275-0-275? Or should I do 300ohm just in case?
Feedback:
I don't have an oscilloscope unfortunately. Has someone built the SPP with the Toroidy output transformers using feedback and could share the value they came up with?
Thanks!
Power transformer:
275-0-275, 200 mA
6.3 VAC, 5A
Output transformers:
TTG-EL84PP
Tubes:
I am slightly confused reading through the threads and the wallofsound documentation (great btw!) in regards to the JJ EL84s. In some older posts they are described as being very sturdy and taking high voltages, whereas in newer discussions JJs seem to be the ones that need higher cathode resistors... did they change? Or am I safe with 270ohm if my transformer is 275-0-275? Or should I do 300ohm just in case?
Feedback:
I don't have an oscilloscope unfortunately. Has someone built the SPP with the Toroidy output transformers using feedback and could share the value they came up with?
Thanks!
I have used the same Toroidy outputs and without feedback cap I get the following trace (10kHz, 8ohm dummy load).
Not sure if I need to add a cap or not?
Not sure if I need to add a cap or not?
Baobei:
If you are going the SS rectifier route 275-0-275 should be fine.
It's not that the JJ EL84s can't handle the voltage, they have a bit lower max POWER dissipation than most of the russian-made EL84 types. That's why I suggested that the 300 ohm cathode resistors might be a good idea.
Depending how comfortable you are at going off-plan you might consider implementing the adjustable bias mod I described in posts 20 and 23. It's possible to do this after the initial build if desired.
Be sure to read post 15 where I recommend using a choke in the power supply. Also in this post I've labelled R3 as 10K. This was/is wrong. It should be the originally specified 30K.
Good Luck, Steve
If you are going the SS rectifier route 275-0-275 should be fine.
It's not that the JJ EL84s can't handle the voltage, they have a bit lower max POWER dissipation than most of the russian-made EL84 types. That's why I suggested that the 300 ohm cathode resistors might be a good idea.
Depending how comfortable you are at going off-plan you might consider implementing the adjustable bias mod I described in posts 20 and 23. It's possible to do this after the initial build if desired.
Be sure to read post 15 where I recommend using a choke in the power supply. Also in this post I've labelled R3 as 10K. This was/is wrong. It should be the originally specified 30K.
Good Luck, Steve
I've found some Russian EL84 (JJs seem to be sold out everywhere and Psvane's are a bit over budget). I might order the parts for the adjustable bias mod, but will most likely build the standard version first. Btw, how would I know that the DC imbalance is becoming a problem for the OPTs? (Except measuring)
Assuming free choice, what would be the ideal VAC for a SS rectification build? 275-0-275 or 280-0-280?
Assuming free choice, what would be the ideal VAC for a SS rectification build? 275-0-275 or 280-0-280?
I've not experienced it myself but it's been reported by guitar amp techs that severe DC imbalance can be audible as hum in the speaker. 275, 280 not that much difference. Line voltage fluctuations will make more of a difference. If you find there is way too much B+ this can be reduced by adding another cap and resistor in the power supply. I did this on mine, see attached crude sketch. In this is needed it might be easier to mount the diodes off-board to save hacking the board.
Attachments
Thanks, parts are ordered. Line voltage is pretty on point here usually, but I‘ll see where B+ ends up. Btw, any comment on Jacques‘ measurement?
Cheers, Simon
Cheers, Simon
I don't know a lot, sometimes not much at all, but I think you could have a lot worse 10 KHz square wave. If it were mine I wouldn't mess with it.
S.
S.
I build the Tubelab SPP, and I love my amp! 275-0-275 with SS rectification is perfekt, just like Hammond 370HX!. Changed the transformer, because it was made for 220v primary, so I bought a Hammond 370 HX , and the Hammond works perfekt. https://www.diyaudio.com/community/threads/made-myself-a-el84-pp-tubelab-clone.381104/
I realized that I never posted a picture of my final amp, so here you go. I increased the filter caps as I had a bit of hum, but now it's very quiet (on 96db speakers). A very fun build and it sounds fantastic!
Help! My SPP Rectifier Socket or PCB Board Pinout Is Out To Lunch!
Triple checked installation both visually and with the DVM's continuity buzzer. Photo shows location of Pins 1 and 8 which makes the Pretty Red HV wires, for example, going to Pins 5 and 7.
Triple checked installation both visually and with the DVM's continuity buzzer. Photo shows location of Pins 1 and 8 which makes the Pretty Red HV wires, for example, going to Pins 5 and 7.
Hello,
Regarding the last two post.
First photo i am sure you can improve things by better wire routing and making some wires shorter. Where is the first power supply cap?
Did you read about keeping the first cap wires short and not creating a loop.
The second photo, even on my small phone screen i can see you need to do something about your soldering skills.
Greetings Eduard
Regarding the last two post.
First photo i am sure you can improve things by better wire routing and making some wires shorter. Where is the first power supply cap?
Did you read about keeping the first cap wires short and not creating a loop.
The second photo, even on my small phone screen i can see you need to do something about your soldering skills.
Greetings Eduard
