Hello,
I'm nearly finished a DAC (http://kepfeltoltes.hu/161026/DSC_0069_www.kepfeltoltes.hu_.jpg) and my next project would be something I work on for long time. Headphone music listening gets more important also for family reasons.
I built years ago a friend designed OTL amp. I never made enclosure for it and I have some concerns with it, like during sw on / off, the cap discharge and charge through the can. It is also huge in size, has two choke, a 280VA power transformer, 5U4G rectifier ...
But, it sounds great. Nothing can beat it what I heard so far. I had a few.
The direction I think about is something I can move in the house easier. Not OTL, with output transformer which would also act as insulation from high voltages. It is also a safety concern. Kids are playing around, I do not want HV DC on the output if the output capacitor fails. Also, I hope much better power much. I mean, it will probably be inefficient, but burning 200W for 200mW output is too bad. I hope with a proper impedance match with transformer output, I can use small tubes and for example 6x4 rectifier.
The problem is, I can not find a design I can start on.
Do you guys have idea?
Thanks!
JG
I'm nearly finished a DAC (http://kepfeltoltes.hu/161026/DSC_0069_www.kepfeltoltes.hu_.jpg) and my next project would be something I work on for long time. Headphone music listening gets more important also for family reasons.
I built years ago a friend designed OTL amp. I never made enclosure for it and I have some concerns with it, like during sw on / off, the cap discharge and charge through the can. It is also huge in size, has two choke, a 280VA power transformer, 5U4G rectifier ...
But, it sounds great. Nothing can beat it what I heard so far. I had a few.
The direction I think about is something I can move in the house easier. Not OTL, with output transformer which would also act as insulation from high voltages. It is also a safety concern. Kids are playing around, I do not want HV DC on the output if the output capacitor fails. Also, I hope much better power much. I mean, it will probably be inefficient, but burning 200W for 200mW output is too bad. I hope with a proper impedance match with transformer output, I can use small tubes and for example 6x4 rectifier.
The problem is, I can not find a design I can start on.
Do you guys have idea?
Thanks!
JG
If you've got nothing against parafeed : http://www.diyaudio.com/forums/tube...ns-parafeed-headphones-amp-2.html#post4037465
I used inexpensive edcor's transformer but you could use the very good sowter parafeed transformers for headphones.
I used inexpensive edcor's transformer but you could use the very good sowter parafeed transformers for headphones.
that is interesting. One thing I do not like is the semiconductor current regulation. Maybe I'm wrong. Probably. But still, a few years ago I built single ended class A tube amp with 2A3s and I just love it. I had several amps before but this is just a level up.
It is not because I do not like semiconductors and like tubes. It is actually the opposite. I do not like tubes. Inefficient, expensive to work with, high voltage .... brrr. But, the main thing, I like to listen to it for hours, as much time I have and I do not get tired, but relaxed. With even the best headphone amps I had, some sounded great, balanced, detailed, but somehow I get tired of that.
Interesting, if I terminate the tube amp with 10 ohms (what I had) and parallel I connect the headphone, I get what I want. Easy listening, but detailed in the same time, with great soundstage. Also the OTL amp I mentioned sound the same, but that is huge also.
I try to go on a known (or I think known) way, with no feedback single ended triode output, but instead of having a high power amp to be able to drive OTL, use a proper sized tube in relative efficient setting (but still class A) and have an output transformer. That is the direction I set for myself.
I'm thinking of hybrid solution too, having voltage amplification with tube and x1 FET/biplolar output stage, no feedback.
If you know such a hybrid design, let me know please.
Thanks,
JG
It is not because I do not like semiconductors and like tubes. It is actually the opposite. I do not like tubes. Inefficient, expensive to work with, high voltage .... brrr. But, the main thing, I like to listen to it for hours, as much time I have and I do not get tired, but relaxed. With even the best headphone amps I had, some sounded great, balanced, detailed, but somehow I get tired of that.
Interesting, if I terminate the tube amp with 10 ohms (what I had) and parallel I connect the headphone, I get what I want. Easy listening, but detailed in the same time, with great soundstage. Also the OTL amp I mentioned sound the same, but that is huge also.
I try to go on a known (or I think known) way, with no feedback single ended triode output, but instead of having a high power amp to be able to drive OTL, use a proper sized tube in relative efficient setting (but still class A) and have an output transformer. That is the direction I set for myself.
I'm thinking of hybrid solution too, having voltage amplification with tube and x1 FET/biplolar output stage, no feedback.
If you know such a hybrid design, let me know please.
Thanks,
JG
To me that sounds like what you really want is some different headphones (which ones do you have?), an adapter for some additional output impedance or an EQ. Trying to do the same with an amplifier tends to be a very inefficient approach.
I don't even think it's so much the distortion levels, but rather that your hearing might prefer a more polite presentation than what your headphones give on a plain vanilla amp.
Hi, I partly agree with that, but the question is what we call polite. On live concerts I do not have that feeling, not getting tired like I do get now with my current headphone amps. Also, I like details and the current speaker amp is excellent in that. Take this album for example : https://www.amazon.com/Dafos-Hart/dp/B000008GEY , I like it very much and it is also very detailed on my current amp. It is not that it would wash away the harsh details, it is not that what makes me tired.
Currently I have an old Sennheiser 565 ovation. I recently had a HD650 and I did not like that. The 565 has much less base, but what it has is tight and accurate. I've used a friends HD800 during summer. That is obviously better and I think I will buy one soon.
Another thing on the amp, the reason why I'm sure it (at the moment) is the amp my weak point, because if I take the time, disconnect speakers, connect load and the headphone to the 2A3 PSE speaker amp, that is just great. Very detailed, but still, I want to listen to music for hours with that.
Another thing come to my mind: I have used Ion Obelisk amp before and I liked that. Now it is on the TV when we watch films. I will give it a try as headphone amp.
In any way, I think the way to the sound what I want is through no feedback, single ended A output. Triodes at least at the voltage amplification and powered through a 6x4 or like, not diode rectification.
Regards,
JG
Currently I have an old Sennheiser 565 ovation. I recently had a HD650 and I did not like that. The 565 has much less base, but what it has is tight and accurate. I've used a friends HD800 during summer. That is obviously better and I think I will buy one soon.
Another thing on the amp, the reason why I'm sure it (at the moment) is the amp my weak point, because if I take the time, disconnect speakers, connect load and the headphone to the 2A3 PSE speaker amp, that is just great. Very detailed, but still, I want to listen to music for hours with that.
Another thing come to my mind: I have used Ion Obelisk amp before and I liked that. Now it is on the TV when we watch films. I will give it a try as headphone amp.
In any way, I think the way to the sound what I want is through no feedback, single ended A output. Triodes at least at the voltage amplification and powered through a 6x4 or like, not diode rectification.
Regards,
JG
Hello,
It works the other way around too.
The transformer was designed and made to the 2A3 PSE also. If I would build the amp again, I would not get the transformer made because now I know ready made ones for the same config, but it is O.K. to make it for the headphone amp too. If there will be ready made available, I will choose that. If not, it is more difficult, but doable.
Regards,
JG
It works the other way around too.
The transformer was designed and made to the 2A3 PSE also. If I would build the amp again, I would not get the transformer made because now I know ready made ones for the same config, but it is O.K. to make it for the headphone amp too. If there will be ready made available, I will choose that. If not, it is more difficult, but doable.
Regards,
JG
For an hybrid, just use a good gain stage (without too much gain, a common problem in tube circuits) and stick that output stage to it : SOHA II Schematics – Cavalli Audio . It works quite well, is SE in class A and can be sized to your needs.
My reason to go to parafeed and use a CCS was that it allows:
- the triode to be in charge of amplification all on its own. The CCS removes the interaction from the power supply.
- the use of better transformers than traditionnal gapped SE transformers if wanted.
- a nice thd profile, typical of SE amplification.
A nice variation I've made in the past is to use a µ-follower with a mosfet as the top element, into a transformer. It really makes the results more linear but it increases the contribution of the SS parts.
The 6E5P is a nice tube btw, really suited to this kind of power. I've wanted to try a 4P1L too though.
Hello Ben,
Thanks a lot! I have not seen the Cavalli Audio site for long time. (I was also looking for the HeadWize site and could not find :-(
This is great material. A lot to learn from here.
Also, I'm sure your parafeed with constant current sources is a great amp. I'm a bit lost now, a few thing happened. We had another day of testing with a friend. He has the HD800 with it's own amp (same f*** expensive, unbalanced in was used, balanced out for the 800, unbalanced for my headphone).
We had the big sennheiser amp and my amps. A CK2III what I swithced on a day before, a TPA6120 based amp supplied from large 2 cell LiPo, an ION Obelisk and a 2A3 PSE, a TC Audio Connect 8 and the friend designed huge headphone amp what I almost need a trolley to carry.
Interesting is that they sounded pretty different. I thought the IC amp will be the weakest, but surprisingly not. It was not bad at all. Ages better than my phone output (sony xperia something compact) or the Konnekt 8 output, which was like there is a think curtain between us and the musicians. Konnekt 8 is a negative surprise. That has a proper dedicated headphone amp in a SIL package. I would prefer my phone over that.
The CK2III is not bad after warmup, but I do not like to listen to.
The positive surprise is the Obelisk. It is not gentle at all, transients are well detailed. The base is a bit weak also, but tight and accurate. But, really good to listen to and I do not know why. For the first impression it is nothing great, but not bad. Still, it is great to listen to. A bad point is that, with my 565 ovation, the base is more weak now. Or not weak, it is there but less for sure.
The speaker amp 2A3 PSE was really good, but the large dedicated OTL SE amp too. Both was significant warmer than the sennheiser amp, which is a good amp, but not my taste. The triodes sounded more living for me, while the sennheiser has better base. More precise and more in volume, sometime even too much with the hd800 for my ears what is biased by the weak base of the old 565. I would choose the triodes even I love the fact that the sennheiser amp does not need maintenance and smaller etc. Much better to handle.
The bottom line for me, I probably make a box for my big amp and use that until I see a known good triode SE design with transformers for 1/3rd of the weight
Regards,
JG
Thanks a lot! I have not seen the Cavalli Audio site for long time. (I was also looking for the HeadWize site and could not find :-(
This is great material. A lot to learn from here.
Also, I'm sure your parafeed with constant current sources is a great amp. I'm a bit lost now, a few thing happened. We had another day of testing with a friend. He has the HD800 with it's own amp (same f*** expensive, unbalanced in was used, balanced out for the 800, unbalanced for my headphone).
We had the big sennheiser amp and my amps. A CK2III what I swithced on a day before, a TPA6120 based amp supplied from large 2 cell LiPo, an ION Obelisk and a 2A3 PSE, a TC Audio Connect 8 and the friend designed huge headphone amp what I almost need a trolley to carry.
Interesting is that they sounded pretty different. I thought the IC amp will be the weakest, but surprisingly not. It was not bad at all. Ages better than my phone output (sony xperia something compact) or the Konnekt 8 output, which was like there is a think curtain between us and the musicians. Konnekt 8 is a negative surprise. That has a proper dedicated headphone amp in a SIL package. I would prefer my phone over that.
The CK2III is not bad after warmup, but I do not like to listen to.
The positive surprise is the Obelisk. It is not gentle at all, transients are well detailed. The base is a bit weak also, but tight and accurate. But, really good to listen to and I do not know why. For the first impression it is nothing great, but not bad. Still, it is great to listen to. A bad point is that, with my 565 ovation, the base is more weak now. Or not weak, it is there but less for sure.
The speaker amp 2A3 PSE was really good, but the large dedicated OTL SE amp too. Both was significant warmer than the sennheiser amp, which is a good amp, but not my taste. The triodes sounded more living for me, while the sennheiser has better base. More precise and more in volume, sometime even too much with the hd800 for my ears what is biased by the weak base of the old 565. I would choose the triodes even I love the fact that the sennheiser amp does not need maintenance and smaller etc. Much better to handle.
The bottom line for me, I probably make a box for my big amp and use that until I see a known good triode SE design with transformers for 1/3rd of the weight
Regards,
JG
> tube amp with output transformer
Key problem is that transformer.
A 3K-10K to 600CT would suit the build. In a hasty search I am not seeing one that is rated for DC current.
Edcor USA has GXSE Series (no exposed terminals) with suitable primaries but stock secondaries only speaker impedances. Edcor will custom-wind for another $20. With waiting and shipping, not a real easy solution.
Any 2 Watt in 8-16 Ohm winding will do your 200mW in 150+ load. These can be found as small 5W guitar-amp parts. Performance at ~~2W level with ample NFB may be objectively fine.
Key problem is that transformer.
A 3K-10K to 600CT would suit the build. In a hasty search I am not seeing one that is rated for DC current.
Edcor USA has GXSE Series (no exposed terminals) with suitable primaries but stock secondaries only speaker impedances. Edcor will custom-wind for another $20. With waiting and shipping, not a real easy solution.
Any 2 Watt in 8-16 Ohm winding will do your 200mW in 150+ load. These can be found as small 5W guitar-amp parts. Performance at ~~2W level with ample NFB may be objectively fine.
I built a parafeed amp with the Edcor WSM/XSM 10k:150 matching transformers and was pleased with the result. I used a 10M45 and 6C45Pi for a really simple and low parts count amplifier. I added a switch to be able to use the entire secondary or half of it for high z or low z headphones.
The output transformer secondaries are the sticking point. It is difficult to find things that will work with various headphone impedance for affordable prices. Lundahl and Sowter have models, but they ain't cheap. Edcor also has a model with a 7k/10k primary and 300/32 ohm secondary, but it is non-gapped and only comes with PCB pins. A frame mount version of that would be great for general DIY.
The output transformer secondaries are the sticking point. It is difficult to find things that will work with various headphone impedance for affordable prices. Lundahl and Sowter have models, but they ain't cheap. Edcor also has a model with a 7k/10k primary and 300/32 ohm secondary, but it is non-gapped and only comes with PCB pins. A frame mount version of that would be great for general DIY.
Edcor PCW10K-7K/300-32 That's the ones I used in my 6e5p build. They are pretty decent for the money. The dcr of the secondary in particular is quite low (6r for the 32r tap-23r for the 300r tap).
Problem is that they're a good value in the US. In Europe, once you add shipping and taxes... don-Audio has those edcor in stock but they want 34.22€ a piece. It's a bit steep of an increase for a 11.5$ product.
Yikes, that is a large increase. At that point Sowter or Lundahl are a little closer to making sense if building something really nice.
I don't know if Hammond is any more available over there (seems like they have decent distribution), but the 119DA seems like a candidate as well:
Hammond Mfg. - "Classic" 600 Ohm - Speaker Matching Transformer - Hammond P/N 119DA
Turns ratios are 12.2:1 or 8.6:1 on the center tap and full secondary respectively. Gives an ok impedance range for something like 12B4 or 6C45Pi I'd reckon.
They're about $30 a piece here in the US.
I don't know if Hammond is any more available over there (seems like they have decent distribution), but the 119DA seems like a candidate as well:
Hammond Mfg. - "Classic" 600 Ohm - Speaker Matching Transformer - Hammond P/N 119DA
Turns ratios are 12.2:1 or 8.6:1 on the center tap and full secondary respectively. Gives an ok impedance range for something like 12B4 or 6C45Pi I'd reckon.
They're about $30 a piece here in the US.
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