Hello,
This is my first post here so please forgive me if this has been asked and answered elsewhere.
I recently got a box of tubes and thought it might be fun to build something out of them. A headphone amp that could drive a par of 600ohm headphones would be nice. I'm quite good at soldering, putting stuff together in general and have worked with high voltages which is the good bit. The bad bit is that I know very little about tubes and even less about how to design or replaces components of a circuit. I don't even know if the tubes I got are any good for audio. I searched the webb for a bit and then realised that I can't really make any sense of what I'm finding hence on to asking.
And so finally to the questions:
1 - Are any of these tubes good for audio? I realise that I should have made a comprehensive list but at a glance there are one or two labeled ECC83, ECC803S, 12AX7A, E810F, M8137, M8136, E280F, EF86 and twenty 36KD6-40KD6 and nine 40KD6.
2 - If yes, is there any schematics anywhere for a headphone amp in the €200 range, excluding case and tubes?
3 - How do I measure a tube to see if it is OK?
Thank you very much for your time and input!
This is my first post here so please forgive me if this has been asked and answered elsewhere.
I recently got a box of tubes and thought it might be fun to build something out of them. A headphone amp that could drive a par of 600ohm headphones would be nice. I'm quite good at soldering, putting stuff together in general and have worked with high voltages which is the good bit. The bad bit is that I know very little about tubes and even less about how to design or replaces components of a circuit. I don't even know if the tubes I got are any good for audio. I searched the webb for a bit and then realised that I can't really make any sense of what I'm finding hence on to asking.
And so finally to the questions:
1 - Are any of these tubes good for audio? I realise that I should have made a comprehensive list but at a glance there are one or two labeled ECC83, ECC803S, 12AX7A, E810F, M8137, M8136, E280F, EF86 and twenty 36KD6-40KD6 and nine 40KD6.
2 - If yes, is there any schematics anywhere for a headphone amp in the €200 range, excluding case and tubes?
3 - How do I measure a tube to see if it is OK?
Thank you very much for your time and input!
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If you have -good- 10k:600 (4:1) transformer, trioded E280F or E810F with constant current anode load, parafeed to OPT would be enough good.
Sample simulation:
The power supply can be simple, the cascode CCS has enough large PSRR.
Sample simulation:
The power supply can be simple, the cascode CCS has enough large PSRR.
If you're not planning for OTL, ECC88/6DJ8 is a pretty good option;
I've built both single ended and push pull headphone amps with this tube and both sounded great. My favorite headphones amp is this one from Bruce Heran:
https://diyaudioprojects.com/Tubes/6DJ8-Tube-Headphone-Amp/
I've built both single ended and push pull headphone amps with this tube and both sounded great. My favorite headphones amp is this one from Bruce Heran:
https://diyaudioprojects.com/Tubes/6DJ8-Tube-Headphone-Amp/
Thank you, did you do the simulation yourself? And it is only for one channel, yes?
The transformer is something like this https://www.audiophonics.fr/en/audio-transformer/ds2206-audio-transformer-60010k-unit-p-14325.html ?
In the simulation the AC and circuit seems to use the same ground, is that really right?
As you have no experience with tubes I'm afraid most of the information given above must sound like abacadabra to you.
The 600 ohms transformer you mentioned is not an output transformer so cannot be used here.
But you don't need an output transformer; two 40kd6's on top of each other driven by an half of an ecc 83 make a output transformerless amp able to drive your 600ohms headphones. Maybe you can come into contact with an experienced hobbyist and ask him to draw a schematic of half a ecc83 driving a SRPP with two 40KD6's and powersupply of 250V. And maybe that person can also assist you in realising this amp (which is quite simple).
With the money of the sale of the non-used tubes on ebay (keep an extra set in reserve for future use) especially the little triodes you mentionend, you can easily finance your project.
The 600 ohms transformer you mentioned is not an output transformer so cannot be used here.
But you don't need an output transformer; two 40kd6's on top of each other driven by an half of an ecc 83 make a output transformerless amp able to drive your 600ohms headphones. Maybe you can come into contact with an experienced hobbyist and ask him to draw a schematic of half a ecc83 driving a SRPP with two 40KD6's and powersupply of 250V. And maybe that person can also assist you in realising this amp (which is quite simple).
With the money of the sale of the non-used tubes on ebay (keep an extra set in reserve for future use) especially the little triodes you mentionend, you can easily finance your project.
Vacuum tube headphone amps usually need output transformers to step down their fairly high output impedance to the lower impedance of headphones.
That said, 600 ohm headphones would make a light enough load for many kinds of vacuum tube buffers and/or headphone amps with out output transformers (output-transformer-less or "OTL").
The problem is if you also want to use more typical 32 ohm or 60 ohm headphones as well. That is a completely different problem, which is best solved by using an output transformer. I made something that worked out pretty well that seems able to drive 60 ohm cans as well as 300 ohm cans. I'm not saying it's the greatest thing ever made, or even that it's particularly good or clever, but it sounds good enough that I haven't changed anything for over 5 years, and I play it almost every night (it's my bedtime headphone amplifier). https://www.diyaudio.com/community/...ly-built-something.324664/page-4#post-5582295
I'm using that design but with 12GN7A tubes because they sound fine (not too microphonic) and they last a long time.
But my design would not be the best if you'll only be using the amp you build with your 600 ohm cans. In that case, there are many "OTL" headphone amp designs that will work well.
That said, 600 ohm headphones would make a light enough load for many kinds of vacuum tube buffers and/or headphone amps with out output transformers (output-transformer-less or "OTL").
The problem is if you also want to use more typical 32 ohm or 60 ohm headphones as well. That is a completely different problem, which is best solved by using an output transformer. I made something that worked out pretty well that seems able to drive 60 ohm cans as well as 300 ohm cans. I'm not saying it's the greatest thing ever made, or even that it's particularly good or clever, but it sounds good enough that I haven't changed anything for over 5 years, and I play it almost every night (it's my bedtime headphone amplifier). https://www.diyaudio.com/community/...ly-built-something.324664/page-4#post-5582295
I'm using that design but with 12GN7A tubes because they sound fine (not too microphonic) and they last a long time.
But my design would not be the best if you'll only be using the amp you build with your 600 ohm cans. In that case, there are many "OTL" headphone amp designs that will work well.
Yes, there is much to learn and a bit hard to keep Fokus but I'll just yodel along 😉
Using some of the 40KD6 tubes would be great. As long as I have a schematic and a BOM I think I'll be able to sort the actual build.
Thank you, I'll see what I can figure out. Maybe I need new headphones 🙂. I set 600 ohms because that is what my DT880 are that I'm used to listening to. But according to the Beyerdynamic FAQ there is very little difference in sound if any between impedances so maybe I should pick a tube design first and headphones second.
600 ohm headphones are a great thing to have if you want to build a tube headphone amplifier, and the DT880 is a very well regarded set of headphones.
Vacuum tubes work better into higher impedance loads like your 600 ohm headphones. If you replace them with the usual 32 ohm headphones, any tube headphone amp you use won't work as well (higher distortion, less power, etc.). In other words, a pair of DT880 with 600 ohm impedance will increase your chances of success building a headphone amp with tubes.
There are a kazillion designs that will work well. The problem will be choosing what you want to build!
Incidentally, there are suitable line output transformers with 600 ohm secondary to match your headphones, if you go with a push-pull amplifier circuit. This is one that's not very expensive.
Edcor 2.5 watt, 10k:600 (4.1:1 stepdown)
https://edcorusa.com/products/copy-...-matching-transformers?variant=43401667412217
I wish I knew what the primary inductance is, but I don't.
This is a popular design that uses this transformer with a 6DJ8 twin triode and an approximately 135V DC power supply.
https://diyaudioprojects.com/Tubes/6DJ8-Tube-Headphone-Amp/
![6DJ8-ECC88-Tube-Headphone-Amp-Schematic[1].png](https://www.diyaudio.com/community/attachments/6dj8-ecc88-tube-headphone-amp-schematic-1-png.1461744/ "6DJ8-ECC88-Tube-Headphone-Amp-Schematic[1].png")
I'm not saying this is the very best design of its type, but I believe it's a good starting point. Very few parts, easy to build.
There are ways to improve this design, if you want to get more involved with it...
Vacuum tubes work better into higher impedance loads like your 600 ohm headphones. If you replace them with the usual 32 ohm headphones, any tube headphone amp you use won't work as well (higher distortion, less power, etc.). In other words, a pair of DT880 with 600 ohm impedance will increase your chances of success building a headphone amp with tubes.
There are a kazillion designs that will work well. The problem will be choosing what you want to build!
Incidentally, there are suitable line output transformers with 600 ohm secondary to match your headphones, if you go with a push-pull amplifier circuit. This is one that's not very expensive.
Edcor 2.5 watt, 10k:600 (4.1:1 stepdown)
https://edcorusa.com/products/copy-...-matching-transformers?variant=43401667412217
I wish I knew what the primary inductance is, but I don't.
This is a popular design that uses this transformer with a 6DJ8 twin triode and an approximately 135V DC power supply.
https://diyaudioprojects.com/Tubes/6DJ8-Tube-Headphone-Amp/
I'm not saying this is the very best design of its type, but I believe it's a good starting point. Very few parts, easy to build.
There are ways to improve this design, if you want to get more involved with it...
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Use a MOSFET follower to reduce output impedance and save yourself the cost of a step-down transformer.
Have you googled the prices of ECC803S AND M8137? There is a certain amount of audiiphile prestige when it comes to tubes, and when you get more entrenched in the hobby you discover there are a lot of tubes that are not in vogue that give excellent results. I would be tempted to sell those gems and reinvest the spoils. An open mind, and reading up on simple headphone circuits is worthwhile.
I am also starting to think about a headphone amplifier, probably with Sennheiser HD 600 (300 ohm, not purchased yet), and I was a little put off OTL solutions when I read that some of them have DC on the output when turned on, possibly being able to damage headphones. Is that a real issue?
If that is a risk, then I think I would start with a good pair of quality output transformers (e.g. Lundahl), maybe with some different secondary options, and aim for the lowest component count to build the rest.
What will your source be?
I am also starting to think about a headphone amplifier, probably with Sennheiser HD 600 (300 ohm, not purchased yet), and I was a little put off OTL solutions when I read that some of them have DC on the output when turned on, possibly being able to damage headphones. Is that a real issue?
If that is a risk, then I think I would start with a good pair of quality output transformers (e.g. Lundahl), maybe with some different secondary options, and aim for the lowest component count to build the rest.
What will your source be?
@OldHector
From the always-helpful Merlinb:
- You can take two zener diodes and wire them in series and with opposite polarity from the amplifier output to signal ground. This will clamp large voltage transients down to the value of the zeners.
- If you need the amplifier to deliver 4V peak signal to the headphones, choose something like 6.2V zener diodes. The idea is to not allow the signal voltage to get prematurely clipped by the zeners.
Something like this:
12V zeners are pictured, but that's not meant to suggest that's the 'best' value for any particular situation...
In testing, Merlinb saw that the zeners did not measurably affect the output signal, as long as the signal voltage stayed below the voltage rating of the zener diodes.
The above was taken lock, stock and barrel from Merlin's book Designing High Fidelity Tube Preamps.
The link to my take at a dedicated amplifier for my 600 Ohm AKG K240 headphones (= my final post after 9 prior posts about the design/building process):
Headphones Amp with 2 x (ECC40 + E182CC "Aikido") + PY81 + PL36 triode + 2 x ECC83 + 0B2)
Although this design does not use any of the tube types mentioned in your post #1, I do think that a similar amplifier for your 600 Ohm headphones can be built with the tubes you do have at hand.
Know that a regulated power supply like in my headphone's amplifier is way over the top since the "Aikido concept" is about nulling 'rubbish' on the B+ line in the first place. For me it was just a valid excuse to use more of the tubes I already had at hand. And the regulated power supply does not hurt 'rubbish wise' for sure.
Headphones Amp with 2 x (ECC40 + E182CC "Aikido") + PY81 + PL36 triode + 2 x ECC83 + 0B2)
Although this design does not use any of the tube types mentioned in your post #1, I do think that a similar amplifier for your 600 Ohm headphones can be built with the tubes you do have at hand.
Know that a regulated power supply like in my headphone's amplifier is way over the top since the "Aikido concept" is about nulling 'rubbish' on the B+ line in the first place. For me it was just a valid excuse to use more of the tubes I already had at hand. And the regulated power supply does not hurt 'rubbish wise' for sure.
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