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DIY Workshop ŧ Bijou All Tube Futterman Headphone Amplifier - Release | copyu Member Joined: Jul. 28, 2007 |  Message [#620] posted on: 12-18-2008 12:20 PM CST (US).   |  |  whitelabrat, I appreciate the advice very much. Thanks for the insight. I'm just about to grab the info from the Hammond website. [Actually, I have the cardboard boxes for both transformers, with tiny wiring diagrams, but can hardly read them. It could be my eyesight, I suppose...too much amp-building?] Cheers! |
| whitelabrat Member Joined: Jul. 28, 2007 | Message [#621] posted on: 12-18-2008 12:50 PM CST (US). | | Here ya are: http://www.hammondmfg.com/300series.htm You'll want to double check me, but I'd say you'll want to tie these together: Neutral: White + Brown You also want to look at: http://www.caval...hp?page=h370dax |
| copyu Member Joined: Jul. 28, 2007 | Message [#622] posted on: 12-18-2008 12:56 PM CST (US). | | 115VAC primaries, eh? That makes me think! (I was tempted to say, maybe 117VAC [r.m.s]) which is "called" 120VAC...and a transformer has a tolerance of what...? 20%, perhaps? [I'm not sure about this...just guessing.] I sounded out several Japanese engineers, recently, and they said that TEPCO [Tokyo Elec Power Co] delivers 100VAC exactly, but none of them had ever taken measurements from a power outlet. [It's a matter of "trust" for them, I think...] I'm still trying to get my head around these possible 'tolerances' and the requirements of the PS circuit, especially the regulators...Maybe I have to dig out some text-books and refresh my aging memory on transformers, etc... Oh no! Not again! 100V is better than 80% of 120V and *even better* than 80% of 117 or 115V...getting up to about 87%. Is it enough? I don't know! I'm talking myself into using the 370DAX. Comments still welcome! Thanks, whitelabrat. |
| copyu Member Joined: Jul. 28, 2007 | Message [#623] posted on: 12-18-2008 01:21 PM CST (US). | | Hmmm...20% tolerance, too, could be "upwards" or "downwards" from the desired parameters...I don't want to commit any fallacies in my reasoning, here...
You da man! I have to agree. Thanks for the links, whitelabrat. |
| boilerbots Member Joined: Dec. 15, 2008 | Message [#624] posted on: 12-20-2008 10:25 PM CST (US). | | First stick your AC volt meter in the electrical outlet and see what you get. You voltage will probably be within a volt or two of this all the time. Here in the US, some people have 110V and some 120V so the transformer was designed for this. Maybe the 100V winding is for Japan. There are some serious Tube shops in Tokyo if you need help I am sure you could find it. What is most important is that the average or RMS voltage output from the transformer and the rectifier is over the desired 250V DC output voltage. The limits of the circuit appear to be 450V electrolytic caps that come in the GlassJar Audio kit. The FETs are rated for 500V, so the cap will go before the FETs. Just wire up the 370DAX for 100V input, and check the voltage in the first cap after the EZ80 or EZ81 to see that you are below their 450V limit and then you will know that everything is good. With even a slight load the voltage will drop on those caps. I am building mine know and am curious to see if it can the 250V rail can hold 250V at a high enough load. |
| copyu Member Joined: Jul. 28, 2007 | Message [#625] posted on: 12-21-2008 06:40 AM CST (US). | | Thanks, boilerbots, What you say makes sense to me. I appreciate your input and clear instructions. That's another vote for the 370DAX and I'm convinced it's the way to go. Actually, I didn't want to do too much studying and experimenting, but I feel I really have to, now. Oh, well, I guess that's what DIY is really all about. I might as well give both x-formers a go, while I'm at it...it may just help someone else. On another note, I have friends and relatives in 220-240VAC countries, so if they ever convinced me to part with my Bijou, or to build them one, it would be much simpler to set it up for them. I'm sold on the 370DAX idea and won't be snipping any leads from the x-former. I'll find a safe and (hopefully) not-too-ugly way to terminate and hide the surplus leads. Cheers |
| fordgtlover Member Joined: Feb. 22, 2007 | Message [#626] posted on: 01-02-2009 06:32 PM CST (US). | | I've been using the 6N1P for the last month or so. Unfortunately, I've notice a very faint high pitched squeal while using them. I have swapped about 6 tubes, but they're all the same. I have just put the Amperex 6922 back in and the squeal has gone. Any thoughts? For reference, I am also using the 6N6P and EZ81 and a 370DAX. |
| johno9 Member Joined: Jan. 26, 2009 | Message [#627] posted on: 01-26-2009 12:31 PM CST (US). | | Fired up my Bijou yesterday. B+(Hammond 370DAX xfmr)adjusted to 250VDC with the 100K resistor. With the amp boards my adjustment maxes out at 247VDC. Reason for concern? Also, I measure 80mV and 50mV on the output of each channel (no input or output connections. Reason for concern? |
| fishski13 Member Joined: Jun. 14, 2008 | Message [#628] posted on: 02-02-2009 04:27 AM CST (US). | | yea..i was getting the same with my 6n1p recently, after many hours mind you. the noises would come and go randomly, day or night. haven't heard any squeals over the past 3 days or so though. i haven't owned many tube varieties, but these have been the only ones that have given me any trouble.
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| fernan Member Joined: Apr. 14, 2007 | Message [#629] posted on: 02-07-2009 04:04 PM CST (US). | | HI Pardon, there am lost of this thread and evolution of the Bijou enough, the Modīs Regal emphasizes not to use 6N6P, (and the EZ81 use whith 6N6P) I am going to duplicate to the PSU having 3,4A fil. and HT 90mA by ch, the adjustment, although arrives at 250v, does not make no effect or also 2V, (when duplicating them? I do not know), There is some disadvantage more, to use 6N6P-I with the Modīs Regal? Thanks [Edited by fernan on 02-07-2009 at 04:08 PM.] |
| bobfl Member Joined: Mar. 6, 2009 | Message [#630] posted on: 03-06-2009 02:19 AM CST (US). | | Hi I have just joined this forum to follow my dream of Valve (Tube) Audio. The Bijou looks great from what I have been looking at. The only question I cannot seem to find in this lengthy thread is the matching into various headphones. I have an Audio Technia ATH-W1000 which is 40ohm. Can someone tell me if Bijou will match. Bob... |
Stixx  HeadWizer Joined: Feb. 6, 2004 | Message [#631] posted on: 03-06-2009 04:03 AM CST (US). | | Hi Bobfl, I think it's designed to run with headphones of various impedances, and since lower impedance seems to be more popular in the US it surely will support 40ohm. See more information about the Bijou here --> www.cavalliaudi...p?page=overview (in case you didn't know this one already |
)| bobfl Member Joined: Mar. 6, 2009 | Message [#632] posted on: 03-06-2009 07:00 AM CST (US). | | Thanks for that reply. I have read most on the site but there was a distinct lack of reference to output impedance as far as could see. OK I will see about ordering the kit. Bob.... |
| stixx HeadWizer Joined: Feb. 6, 2004 | Message [#633] posted on: 03-06-2009 08:12 AM CST (US). | | see this post... headwize.com/ub...d=64817&fpage=1 Clearly says you can use down to 32ohm . best, |
| whitelabrat Member Joined: Jul. 28, 2007 | Message [#634] posted on: 03-06-2009 10:00 AM CST (US). | | From my experience the output coupling capacitors are the only significant limiting factor of what headphones will work best in an Output Transformerless (OTL) design such as the Bijou. It seems to me that high ohm headphones tend to be less efficient, but also are more tube friendly where a vacuum tube may have more output and lower distortion. But at the same time a low ohm headphone may be more efficient and require less effort by the output stage and thus seem to have an equal amount of output and distortion. For example, I know that I'll be using primarily 100ohm headphones and sometimes 600ohm, so I know that a 100uF output coupling capacitor will do just fine. If I were going to use perhaps Grado headphones which seem to operate at 32ohms I would want at least a 300ohm output coupling capacitor. I think the Bijou is designed to use a 470uF that is bypassed for better high Hz performance. I don't have the math off the top of my head. In any case I think the Bijou should work well for you. |
| whitelabrat Member Joined: Jul. 28, 2007 | Message [#635] posted on: 03-06-2009 10:15 AM CST (US). | | I should also add some correction to my statement, where the Futterman design that the Bijou uses also helps to lower the impedance of the output stage of the amp which helps to facilitate low resistance headphones. Futterman didn't believe in output transformers. |
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