Hi, new to the forum and all that 🙂 Recently i came across about 150 old tubes of various types, ECC81/82/83/88, EL34, EL84, EF804(basically a really nice EL86 i think?), 6/12AU6, some big 6G6 ones iirc? and various other tubes.
So far ive built a simple mixed amp with an ECC82 on first breadboard and just yesterday got it working on perfboard(turns out the headphone jacks i can get locally are entirely useless...). Honestly, it sound like total garbage but there is something very satisfying with listening to something you put together yourself haha 😀
So im looking both for tips on improving the amp i just finished(probably needs at least a lower impedance ground and twisted+shielded wires to the jacks?) and mostly for what i should build next.
The main thing thats been keeping me from building anything more advanced is the need for output transformers. I can get a few hundred VDC fairly easy but impedance matching transformers is not something ive got readably accessible.
Mostly interested in headphone amps atm as i dont have any speakers in my apartment but a nice looking tube amp could be fun to have at the campus lab 😀
TL;DR
I have a bunch of tubes, so many that im kind of lost as to what to build with them.
Getting nice output transformers is probably kind of hard and way too expensive for my student budget.
Getting fairly clean power at whatever voltages needed should not be much of an issue.
Also what are some basic improvements to make to the amp ive just built?
I am fairly experienced building electronics, drawing schematics, making PCBs and so on but havent done much with audio/amps/tubes besides reading.
So far ive built a simple mixed amp with an ECC82 on first breadboard and just yesterday got it working on perfboard(turns out the headphone jacks i can get locally are entirely useless...). Honestly, it sound like total garbage but there is something very satisfying with listening to something you put together yourself haha 😀
So im looking both for tips on improving the amp i just finished(probably needs at least a lower impedance ground and twisted+shielded wires to the jacks?) and mostly for what i should build next.
The main thing thats been keeping me from building anything more advanced is the need for output transformers. I can get a few hundred VDC fairly easy but impedance matching transformers is not something ive got readably accessible.
Mostly interested in headphone amps atm as i dont have any speakers in my apartment but a nice looking tube amp could be fun to have at the campus lab 😀
TL;DR
I have a bunch of tubes, so many that im kind of lost as to what to build with them.
Getting nice output transformers is probably kind of hard and way too expensive for my student budget.
Getting fairly clean power at whatever voltages needed should not be much of an issue.
Also what are some basic improvements to make to the amp ive just built?
I am fairly experienced building electronics, drawing schematics, making PCBs and so on but havent done much with audio/amps/tubes besides reading.
Look for some really old tube radios or stereos in thrift stores for cheap and buy them for the tiny output transformer. They are good for under 5 watts usually. You really need to find a pair of the same transformer if possible. Just have fun learning but to build a really listenable amp you need them.
You mention lack of access to output transformers but don't indicate where you are in the world. Salvaging OPT's from old radios and stereo sets has been mentioned, but it is also possible to use other things for OPT's. A power transformer with two 120 volt primaries and one or more low voltage secondaries can often be used for an OPT in a push pull amp, especially a low powered amp for headphones. Toroidals are particularly useful in this regard.
Im located in Sweden, and looking around on the local electronics suppliers i havent found anything that is 10k to 50 or so to match my headphones that i can also buy with my small and shrinking student budget 🙂
Now this is what i was thinking id do, but i am unsure as how to accurately get the impedance here for matching in this case, as im not looking at making something with a lot of power the match would have to be somewhat good at least. I have access to a large amount of transformers in varous forms, PCB, Toroidal, "normal" marked only with voltage ratings. I am also concerned about how the frequency performance would be.
I am fairly sure i have access to something similar to what you mention, center tapped 250V on one side and something lower on the other. Most of the toroidals i have access too go down to quite low voltages but also tend to have quite a few secondary windings, would that be an issue or would that let me match better with some experimentation perhaps? 😀
Thats a good idea but i dont think there are many around anymore, pretty sure most are in the trash at this point sadly. I do know of some old TVs and one or two original radios from the 40s(i think, they have tubes at least) that i maybe could tear apart before they are trashed too.
Got any links to an example? 🙂 Are you talking 250V -> 70V? Pretty sure i could dig up a few of those or similar
I have used this 70 volt line matching transformer as an OPT in a 10 watt guitar amp. It would have better frequency response when used at lower power levels. These need to be used in a push pull configuration.
https://www.parts-express.com/search?keywords=300-040&order=relevance:desc
There is a thread here about using power transformers for OPT's. Member Shoog has made several good amps with repurposed mains toroids. All repurposed power transformers must be used in a push pull or parafeed SE arrangement to avoid saturation.
https://www.diyaudio.com/community/...transformers-as-opts-with-a-little-twist.3743
https://www.parts-express.com/search?keywords=300-040&order=relevance:desc
There is a thread here about using power transformers for OPT's. Member Shoog has made several good amps with repurposed mains toroids. All repurposed power transformers must be used in a push pull or parafeed SE arrangement to avoid saturation.
https://www.diyaudio.com/community/...transformers-as-opts-with-a-little-twist.3743
This is exactly what it needed, added a much better grounding scheme(i think it might be a partial star or at least its similar too i belive?) and it sounds great! Just beautiful honestly, extremely happy with how it turned out! Think it has a slight left-right imbalance as i used fixed resistors instead of tuning the bias myself with a pot but barely noticeable honestly 😀