Yes, you are reading me wrong. Ofcourse many schematics posted on this forum are tentative or prototype's and ofcourse there's nothing wrong with posting such schematics. My point however is that a poster of a schematic should make this clear. In this case the schematic was posted as representing a working amplifier, with measured voltages.
Starting to use expressions like 'p**ing contest' and 'willy waving' is not only sad but they don't even apply to the situation at hand (what/where is the contest?). I do however think that my Latin quotes are applicable to the situation at hand, given your reactions.
See post #7. Your welcome.
Starting to use expressions like 'p**ing contest' and 'willy waving' is not only sad but they don't even apply to the situation at hand (what/where is the contest?). I do however think that my Latin quotes are applicable to the situation at hand, given your reactions.
See post #7. Your welcome.
Last edited:
How? I'm a Celt, I don't speak Latin. I know the Latin names of a few trees, and a few commonly used Latin/Greek acronyms, however we speak English,the language of this forum. Say what you have to say in English. Spouting Latin comes across as pretentious and pompous, or willy waving in the parlance of the street.
I had a go at you because you were having a go at the OP, unjustly in my opinion, so what if a few voltages are out? We all make mistakes, it's how we learn, oh, and the way you did it. I was going to apologize, then out comes the Latin... QED.
In what way is my post #7 "having a go at OP' than? How could I have written post #7 more factual than I did?
It is OP (and you too) that tried to downplay the inconsistencies (see post #8 where the errors are called small and where OP tries to put things in my mouth that I didn't write).
Did you even check what I wrote in post #7? There's more than 10 mA unaccounted for in the first stage and the phase inverter. And still it's unknown what the tubes, other than the 2 x 6P3S, are.
Under these circumstances I find the claimed distortion of less than 0.3 % at 20 Watt without GNFB hard to believe. Note that I didn't write that it can't be true, but only that I find it hard to believe (see post #13).
You started writing things like "p##ing contest", not me.
Here's what the quotes mean: The truth causes hate. But one should not hold back the truth out of fear of hurting somebodies feelings.
But I will refrain from Latin quotes in the future since they seem to upset others.
It is OP (and you too) that tried to downplay the inconsistencies (see post #8 where the errors are called small and where OP tries to put things in my mouth that I didn't write).
Did you even check what I wrote in post #7? There's more than 10 mA unaccounted for in the first stage and the phase inverter. And still it's unknown what the tubes, other than the 2 x 6P3S, are.
Under these circumstances I find the claimed distortion of less than 0.3 % at 20 Watt without GNFB hard to believe. Note that I didn't write that it can't be true, but only that I find it hard to believe (see post #13).
You started writing things like "p##ing contest", not me.
Here's what the quotes mean: The truth causes hate. But one should not hold back the truth out of fear of hurting somebodies feelings.
But I will refrain from Latin quotes in the future since they seem to upset others.
Last edited:
so I bought a china pcb for dynaco 410A kit.I would like to replace 6SL7 with 6N9S and 6V6 with 6P3S.Referring to this schematich what resistors changes you suggest ? audio transformer I think will be 6600 ohm
Attachments
Last edited:
It will work with minor adjustment. The gain would be 3x less with 6sn7 and gNFB level would be less. Increase the input level (up to 3V) and increase 47 Ohms to change feedback level if necessary, you can change the two 270k ( to e.g. 270k/280k) for better AC balance. Ultra-linear needs about 25V for full output.
Attachments
Last edited:
on long tail phase splitter value of c3 usually is about 100 nf,now is 470 uF ,is it correct or too hight ?
That is not LTP, it's para-feed spilter. The ecap is just bypassed the gNFB to this tube and not the other. If you don't have nfb, the resistor 47 and ecap is unnecessary.
6N9S == 6SL7...
6N8S == 6SN7...
6P3S == 6L6...
6P6S == 6V6...
No changes are needed to the PCB to run 6N9S instead of 6SL7. No changes are needed to run 6L6 in a 6V6 circuit either... You will need 300mA more heater current per tube vs using 6V6/6P6S though.
Also the first stage cathode is grounded through the gNFB and OPT by the look of that schematic. If you disconnect gNFB the amp won't work. The value of the resistor that is only half there and unmarked is the cathode resistor. If it's left out, there is no DC connection from first stage cathode to ground.
It's also very possible that that schematic doesn't match what's on the actual PCB.
6N8S == 6SN7...
6P3S == 6L6...
6P6S == 6V6...
No changes are needed to the PCB to run 6N9S instead of 6SL7. No changes are needed to run 6L6 in a 6V6 circuit either... You will need 300mA more heater current per tube vs using 6V6/6P6S though.
Also the first stage cathode is grounded through the gNFB and OPT by the look of that schematic. If you disconnect gNFB the amp won't work. The value of the resistor that is only half there and unmarked is the cathode resistor. If it's left out, there is no DC connection from first stage cathode to ground.
It's also very possible that that schematic doesn't match what's on the actual PCB.
Last edited:
I think it match +/-
Ultra-linear push-pull 6SL7 +6V6 Tube Power Amplifier Bare PCB 12W *2 AMP PCB 699942040481 | eBay 699942040481
The picture you first posted was missing that 1k resistor in the gNFB network which is indeed the cathode resistor as well.
If the board works with 6SL7 and 6V6, it'll work with 6N9S and 6P6S without any changes. 6P3S/6L6 will also work as it is. Of course you will only get the power of 6V6 from them, but they should last a long time.
If the board works with 6SL7 and 6V6, it'll work with 6N9S and 6P6S without any changes. 6P3S/6L6 will also work as it is. Of course you will only get the power of 6V6 from them, but they should last a long time.
yes resitor nfb was missed but I would like to increase anode voltage on 6P3S and not UL configuration
My experience tells me if you use more voltage and 6P3S, you should use separate cathode resistors for each output tube. That gets messy with cutting traces on the PCB etc.
It also depends on if you will use triode connection or beam mode. Triode would be easy, connect the UL and plate on the PCB with a 220-270R 2W resistor.
If you want to use them as beam tubes, you need to make a ~ 250VDC power supply for the screen circuit.
FWIW, the design you link is the same as the first amp I ever built. I quickly modified it to be a floating paraphase like in this 6L6 design.
It also depends on if you will use triode connection or beam mode. Triode would be easy, connect the UL and plate on the PCB with a 220-270R 2W resistor.
If you want to use them as beam tubes, you need to make a ~ 250VDC power supply for the screen circuit.
FWIW, the design you link is the same as the first amp I ever built. I quickly modified it to be a floating paraphase like in this 6L6 design.
Attachments
Last edited:
With regards to the schematic for the PCB, you can't change the 1K feedback resistor without messing up the front end bias point.The 1K feedback resistor is the bias resistor for the 6SL7s. This puts the bias current through the OPT output, which while only a couple of mA is still a bad design.
Drop a 1K resistor across the 470uF bypass cap for the first stage, increase the 47 ohm to 220 ohm and increase the feedback resistor to 4.7K. This will reduce current through the OPT.
Drop a 1K resistor across the 470uF bypass cap for the first stage, increase the 47 ohm to 220 ohm and increase the feedback resistor to 4.7K. This will reduce current through the OPT.
Last edited:
Hence why I swapped to the design in #34... 😀 Of course I would not build either anymore - I like my MA-1 much better.
Those data are likely with fixed bias.
With cathode bias max. output power will be essentially less.
With cathode bias max. output power will be essentially less.
No. That would be for fixed bias operation. EDIT: Artosalo beat me to it.
9k load (8 is close enough since 9 is hard to source), 500R cathode resistor per tube (600R for Triode mode), bypassed with 330uF - 1000uF (more than enough a low LF corner but won't usually cause instability with gNFB)
See this sheet: https://frank.pocnet.net/sheets/049/6/6L6.pdf
9k load (8 is close enough since 9 is hard to source), 500R cathode resistor per tube (600R for Triode mode), bypassed with 330uF - 1000uF (more than enough a low LF corner but won't usually cause instability with gNFB)
See this sheet: https://frank.pocnet.net/sheets/049/6/6L6.pdf
Attachments
Last edited:
i use 6p3s-e (looks better then 6p3s 🙂 ) with 10K transformer in oddwatt circuit - LM regulator for bias.
Poddwatt: Class-A Stereo Push-Pull EL84 (6BQ5) Vacuum Tube Amplifier
Poddwatt: Class-A Stereo Push-Pull EL84 (6BQ5) Vacuum Tube Amplifier
so how much watt for automatic bias and 6600 ohm load? I was not able to find a datasheet for automatic bias (beam connection not triode mode))
excuse me please but I am a novice....
Last edited: