Hi, it's my first post and I'm really just getting started in this hobby so please bare with me.
I recently found a great deal on a pair of power transformers rated for 120v/60hz suitable for tube amplifiers. The first issue is that I live in Italy where we have 230v/50hz power outlets (actually in my house it's closer to 240v). The previous owner had connected the primaries in series and built two monoblocks, which is also what I was planning to do, but I have read arguments against this approach, so I'd love to know your toughts. I'll leave a picture of one transformer attached.
The second issue is that the previous owner's schematic lacks the power supply circuit (which I'm not able to design myself as I'm quite the beginner, the most I can do is test something in PSUD2) and uses an interstage transformer which is both hard to find and expensive, whereas I'd prefer to use the usual coupling capacitor approach to save some money there (I'll attach the schematic of this circuit too).
So I was wondering if you have some schematics laying around suitable for my power supply to build some kind of single ended power amplifier. For what I've seen my voltage and (especially) current ratings are limiting me to build 300B SET monoblocks (which I'm totally fine with).
The amplifier won't need to be that much powerful as I have a small listening room (4x3.5 meters) and good-enough efficency speakers at 91db/1W, so I guess an 8W output (as I've seen in many 300B SET designs) will be more than enough.
I recently found a great deal on a pair of power transformers rated for 120v/60hz suitable for tube amplifiers. The first issue is that I live in Italy where we have 230v/50hz power outlets (actually in my house it's closer to 240v). The previous owner had connected the primaries in series and built two monoblocks, which is also what I was planning to do, but I have read arguments against this approach, so I'd love to know your toughts. I'll leave a picture of one transformer attached.
The second issue is that the previous owner's schematic lacks the power supply circuit (which I'm not able to design myself as I'm quite the beginner, the most I can do is test something in PSUD2) and uses an interstage transformer which is both hard to find and expensive, whereas I'd prefer to use the usual coupling capacitor approach to save some money there (I'll attach the schematic of this circuit too).
So I was wondering if you have some schematics laying around suitable for my power supply to build some kind of single ended power amplifier. For what I've seen my voltage and (especially) current ratings are limiting me to build 300B SET monoblocks (which I'm totally fine with).
The amplifier won't need to be that much powerful as I have a small listening room (4x3.5 meters) and good-enough efficency speakers at 91db/1W, so I guess an 8W output (as I've seen in many 300B SET designs) will be more than enough.
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A 300b SE usually makes a very nice amplifier. It's what I and many others use. I like 2 stage designs like the one you posted. You can use an interstage or a plate choke and coupling cap. I prefer a plate choke with a Russian FT-2 teflon coupling cap. Even a humble Hammond 157G works, as used by Jim Hagerman in his Tuba headphone amp.
For the 417A you can try an EC86 or the Russian version, 6S3P-EV.
For the 417A you can try an EC86 or the Russian version, 6S3P-EV.
What I see is the max current of secondary with 0 central.
It is too low to think at a good SE
While the value of 358 volt can be fine with a 5U5g rectifier
Regarding the frequrncy it is not a proble, probably you will get a different voltage in the pout ( with the right input voltage)
Also putting in series the prymaries is not a very elegant solution ( but works)
Bout filaments, the 6,3 volt at 8 A are fine for typical tetrode/pentode
Walter
It is too low to think at a good SE
While the value of 358 volt can be fine with a 5U5g rectifier
Regarding the frequrncy it is not a proble, probably you will get a different voltage in the pout ( with the right input voltage)
Also putting in series the prymaries is not a very elegant solution ( but works)
Bout filaments, the 6,3 volt at 8 A are fine for typical tetrode/pentode
Walter
Indeed, the max current is my main concern with together with the series connection of the primaries.
As the latter seems fine and I can try connecting them and reading the scondary voltages, but should I place a 2A fuse between then as someone suggested elsewhere?
For the max current, I'm kinda hoping someone has a viable schematic, as I've looked at several tubes plate rating in single ended operation but they all seem to require too much current. The closest I have yet found is the 300B with a current ranging from 60-77mA which I suppose would limit how much I could push these tubes.
Please let me know if you have any tubes or, better yet, entire schematics that could work with these restrictions.
As the latter seems fine and I can try connecting them and reading the scondary voltages, but should I place a 2A fuse between then as someone suggested elsewhere?
For the max current, I'm kinda hoping someone has a viable schematic, as I've looked at several tubes plate rating in single ended operation but they all seem to require too much current. The closest I have yet found is the 300B with a current ranging from 60-77mA which I suppose would limit how much I could push these tubes.
Please let me know if you have any tubes or, better yet, entire schematics that could work with these restrictions.
Thank you all for the precious suggestions, which I'm sure will be helpful if I manage to modify that circuit properly (that is, swapping the interstage transformer with a coupling cap + choke) and make it work with the low current provided by my transformer.
Anybody compared the sound of 6S45P and 6S3P?
Adventures in HiFI: Battle of the EC86 Tubes / Valves
There's also the Russian 6S1P and 6S2P - both triodes in 7 pin bases. Don't hear anything about those. Mu 27 and 48 so in the ballpark.
The 300B in SE has around 70 mA of bias current + driver (around 15 mA)
Less or more. So you are at higher current that the trafo can delivery
Also the current for filaments of tube rectifier ( in case) for 5U4 is low, it need 3 A.
With 5U4 maybe the HT voltage is within the 300B specs
If you use GZ34 the HT will be high for 300B also if you use diodes.
Consider the Cin of 6s45, it is high.
Walter
Less or more. So you are at higher current that the trafo can delivery
Also the current for filaments of tube rectifier ( in case) for 5U4 is low, it need 3 A.
With 5U4 maybe the HT voltage is within the 300B specs
If you use GZ34 the HT will be high for 300B also if you use diodes.
Consider the Cin of 6s45, it is high.
Walter