Bottlehead Forum
General Category => General Discussion => Topic started by: aragorn723 on April 01, 2014, 11:10:12 AM
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Hi,
I have been looking at some of the bottlehead headphone amps, but don't think i can swing one. How does this circuit look? Is it worth building?
http://www.diyaudioprojects.com/Solid/12AU7-IRF510-LM317-Headamp/
Thanks,
Dave
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I would guess that Head Fi is the place to ask. Probably a lot more people over there have built one.
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Hi,
I have been looking at some of the bottlehead headphone amps, but don't think i can swing one. How does this circuit look? Is it worth building?
http://www.diyaudioprojects.com/Solid/12AU7-IRF510-LM317-Headamp/
Thanks,
Dave
I have built a few hybrid amps like the one you linked to. I was never too crazy about how they sounded. That's just me though. You might be able to live with it. My advice is to save up until you can buy something like a crack headphone amplifier. I often find that there is little or nothing to be saved by sourcing parts yourself.
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That looks suspiciously like a Little-Bear / Bravo amp to me, its a fun little amp to tinker with and experiment on in a novelty kind of way but no where near the same league as Crack.
IMO stick to a solid state headphone amp like the O2, Schiit etc until you can save up for a Crack. In my experience with cheap valve amps there is always more wrong with them than right, and ultimately they just end up as a paper weight.
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A crack might be an option eventually, but I have 2 concerns-
high voltage-i haven't worked with AC before, are the directions on the Crack really clear about how to carefully work with the energized crack, how to bleed the capacitors so you can work on it after it being powered up..etc
my current headphones are Grado SR125's, which are 35 ohm, from reading on this site, the crack doesn't work well with that?? So this would probably mean buying new headphones too?
Thanks,
Dave
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Dave,
The instructions are very clear. The only time you "work" with high voltage is making the voltage measurements during checkout.
The voltage discharges itself in a minute when you turn off the Crack.
But the Crack is not best suited to the Grado headphones, as you said. You will get music but not the kind of magic as with a higher impedance headset.
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Operating a 12AU7 on a 12-volt plate supply is not that great an idea; the very nonlinear grid current would be a problem. There are tubes designed to operate that way, the 6GM8 is the classic example.
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That's an interesting little tube i've not heard of. I have been using a portable headphone amp modified with a 6111 tube for listening to tunes in work, curious to see what i could do with this tube since its nominal voltage is so low. Going to buy one to experiment with.. thanks!
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Welborne Labs made a battery powered preamp with it, some years ago. IIRC is had a decent reputation for sonics. Of course, whenever there is a popular product the price of the tube goes up for a while - hopefully this was long enough ago that the prices have fallen again.
This class of tubes was made for car radios, in the transitional days when transistors were much more expensive than tubes. The power devices could be transistors because that would remove the cost of a high-voltage power supply, but the rest could be done with low-voltage tubes. As you can imagine, the period when these were made was short, so the supply is low relative to TV tubes, but the demand is almost non-existent. Prices can be all over the map - shop around!
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The DIY circuit looks nice and simple to construct if this is your first electronics project involving tubes, and also with the low voltage power supply of 12V, no injuries or shock hazard 8)
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Sounds like this circuit isn't a good way to go, though I do like the idea of having a battery-powered tube amp! The Quickie has really sold me on battery power, it really makes a big difference with sound. Thinking outside the box here, Bottlehead just created a set of headphones specific to the crack, how about a set of headphones specifically designed for the Quickie? Seems like the challenge there is finding a reasonably-priced set of headphones with a high impedance to start with-I checked a few places for headphones over about 300ohms, there really aren't any for much less than $400.. Although, this could be a perfect solution, maybe find a way to use the Quickie as both a preamp and headphone amp?? Btw, I found another company called Red Wine Audio, that sells some super-expensive battery powered stuff (preamps, amps, headphone amps) that look cool, but this is commercial and could run a few thousand bucks! Anyways, the point being, there must be a way to make a battery powered headphone amp work well, maybe with a CCS?
Dave
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You could wire the output transformers in the quickie through a switch so you can use it as a preamp, or a headphone amp. I use mine with low impedance headphones and it performs just as well as with high impedance, it really depends on which taps you use on the output transformers. Its not the most powerful headphone amp ever made, that would be the advantage of a hybrid design as with an opamp in the output stage as it will give you the power but with a low impedance output to drive just about any headphone.
The real question is do you need portability, weight and microphonics pretty much rule out the quickie for that, or is it just a battery powered solution you are after?
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It doesn't have to be battery power or portable. Here's the situation, I have a 1 year old son who goes to bed early, and live in a fairly small place (plus the wife doesn't exactly like some of my music 8) ). So the goal is to have something nice to listen to at night that doesn't cost much. It doesn't have to be super loud, just a decent volume. Thanks,
Dave
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Mcandmar,
What headphones do you use? Thanks,
Dave
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Mcandmar,
What headphones do you use? Thanks,
Dave
90% of the time i use my Alessandro Ms-Pros which are a variation of the Grado RS1, or sometimes the Sennheiser HD650s. For work i have a pair of Sennheiser in ears i use with my portable rig. The most recent addition is the Bottlehead Crackphone which i am still building and evaluating, these will probably end up replacing the in ears.
There is also three other Grados models, Sennheiser 212Pros, bunch of vintage JVC cans and a few others that aren't even worth mentioning collecting dust. But the short answer is Ms-Pros, they are just in a different league to anything else i own.
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so the MS-Pros are the ones you use with the Quickie?
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Yes, or a pair of Grado 225i's which i have comfy pads on for watching tv. The Pros and S.E.X. amp are really only used for proper music listening.
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Sounds like it will work with the grados, do you wind up having to crank the volume way up, or is there some volume to spare? Also, how do you wire the Quickie to act as a preamp and headphone amp? Thanks!
Dave
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Volume is pretty much all the way, low volume listening would be around 3/4 of the way up. I use a stepped attenuator so 2-3 clicks above that would be the normal range i use, another 2-3 clicks would be at full volume. Never really bothered me as loud enough is loud enough.
Have a read through this thread re making a headphone amp http://bottlehead.com/smf/index.php/topic,2.0.html (http://bottlehead.com/smf/index.php/topic,2.0.html). If you look at the 3rd image you have a brown wire connecting to a resistor and capacitor on the center pin of the RCA jack. All you need to do is insert a switch between that wire and the jack. The pre-amp circuit will always be on, you will only be switching the output transformer in/out of the circuit.
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Mcandmar,
That looks pretty easy, maybe down the road I can switch the headphones if i get the itch :) It looks like the link has directions for the 1.0 Quickie, mine is the 1.1 with the PJCCS. Will the headphone mod still work with this? Also, what kind of switch do I need? Thanks,
Dave
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Yes it will work fine with a 1.1 with or without PJCCS. A dual pole single throw should do the job, commonly referred to as a DPST switch. Anything will do but these are the easiest to fit as you only have to drill one small hole to mount them.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.microminiatures.co.uk%2Facatalog%2FDPST-%28ON%290FF%28ON%29261.jpg&hash=0bd08cfd155c3c9d1a475cda8b059f8e632f77c2)