nikongod

Happy Birthday!

I spent some more time looking at the 6C45pi tube curves. It is very attractive for its absurdly absurd absurdity. I really like how linear it looks into a 6.6Kohm load (40 ohm load on the 18ct:1 setting) at 150v/30ma idle. I am a little put off by its very high gain and input capacitances because of miller effect though. I think this tube would work really well if a 10K:600ohm input transformer were used with a low impedance attenuator between it and the tubes, but Im petty set on the attenuator I have coming. For a later date How do people hook up the cathodes of the 6c45 in a longish tail pair? The bias point above only needs Vgk of ~1.4V which dosnt buy much in the way of a shared cathode resistor after the stopper resistors are considered. I considered a CCS to a negative supply, but that prevents the use of a CCS to feed the CT of the transformer. Maybe a big fat plate choke for up there. Moar iron=moar better? Maybe its just superfluous in a forced balanced amp. I'd certainly appreciate more info on this. I found the circuit I was trying to describe BTW. Im going to actually bread-board this one like a good boy, and I guess I'l decide then what Im going to do with the cathodes. Im sticking with the 6h30 for this one, but I do appreciate the help and advice.

I have been reading more about this, and from what I have found the impedance seen by the tube depends whether its in class-A or class-B. class-A gets 1/2 of the whole primary, class-B gets 1/4. I thought some more about the gain & amp in general, and Im not sure where to go there. My plan at the moment is to use a CCS to feed the center tap of the transformer (with no shunt reg, I dont think it will be necessary here), with each triode set up as a common cathode with its own resistor and cap. This will buy me a little gain compared to my original boring plan of a differential pair with the CCS tying the 2 cathodes together. Im not sure I like cathode LED's but I'l probably try them too. a headphone sized red-light-district amp could be fun. I thought about the 6c45 but I am frankly afraid of them. I got TVC's with +6, +12db taps from an estate sale. I hope I have gain covered.

Happy birthday naamanf! Have a great one!

Have you considered the PS for the Cavalli Bijou? It has clearly proven its self for a single HV supply headphone amp application. Isnt the Exstata PS dual rail? I would make the (possibly very poorly informed) guess that the bijou PS is overkill for the Akido though. One of the original design goals of the Akido was good to outstanding PSR. Overkill is nice, but you can always upgrade the PS later if you need to. It was digger945's LV akido I heard. If I recall it had a Tangent TREAD running everything. He replaced the LM-317 output devices with dn2540 or 10M45 too I think its all in the LV akido thread on head-fi

Indeed! I had the LV akido on loan a while ago. I liked the amp quite a bit, although I cant compare to the EHHA, as I have not heard one much. My impressions of the amp (compared to the Melos SHA-Gold eargasmatron) are that the LV akido was a bit more detailed & controlled than the Melos but at the same time still had a littttle tube "sweetness" to it. I would not call this amp warm, as I think wam is a more fuzzy and undefined sound (specifically being drunk in front of a fire, thats a warm sound) I think sweet is better here. Sweetness is a gentle smoothness to me, but is not fuzzy like warmth. It is well defined, but begs for you to listen to more.

did you account for the input impedance of the volt-meter loading down the output impedance of the bias supply? Every STAX amp i have measured (attempted to...) measure bias on at the jack says ~200-260V (its been a while)

Happy Birthday!

Happy Birthday!

Happy Birthday Colin!

Happy Birthday!

Happy Birthday!

Happy Birthday!

audiogon's contact info can be found, but they hide it. If you click "learn" on the top of the homepage the next page has a link that says "contact a'gon" Sorry to hear you are in this mess, Hope you get out of it OK. As stupid as it sounds (maybe its stupider than even I think) try contacting the embassy for whatever country this guy lives in. They may be able to tell you what the deal is with regards to international wire transfers and this sort of thing. Maybe its a worse idea than I think, so maybe after confirmation from someone else.

Sorry to hear about your car repair troubles Today I shoveled, a lot. Moved the power switch on The Silver Ghost from where the really neat looking neon pilot lamp is now to the front and installed the really neat looking neon pilot lamp. I also reterminated my HD800 with a 4-pin XLR.

Thanks for posting that video, I watched it end to end last night and its quite thought provoking.

I would go to home depot and buy a few packs of screws in "good guess" sizes. ALTERNATELY if you have feet for the things that you are looking to replace take them to home depot (or a better mom and pop shop if you are lucky enough to still have one) and use their screw gauge on the feet.

Happy birthday Jeff!

hd800

I think the SR325 drivers are used as "cores" to modify, and become the magnum drivers. Could be wrong, but the drivers have to come from somewhere.

:jbl:Happy Birthday!

I found a thread about the Raven in the K&K section of audioasylum here that commented on a some people being unable to get enough gain out of the thing without the input/gain stage which got me second guessing the feasibility of running the secondaries like I want to (Reading it a bit more the OP may be based on the LL1680 transformer which explains a lot of that). I guess different peoples' standards of enough gain may differ. Gain of 1/2, 1, and 2 is plenty for me for 32, 150-300 and 600 ohm headphones respectively. After seeing that I was curious if this may not work out well for some reason I had not considered. I can only see it going well but maybe I have tunnel vision from my enthusiasm. I like how switching secondaries works as an effective "gain switch" matched to the target load, I dont need that much gain that I need a gain stage, and the increasing output impedance from setting the transformer up for higher impedance loads dosnt bother me. Did I ignore some key point? Wiring the switches to switch the secondaries will be an interesting challenge (I think it will be the crux problem of this amp), but does anyone think I missed something that should be consided?

Hello Head-Case I am working on an amp using this transformer in a PP output from a 6h30 tube. I would like to know if anyone has had experience with wiring the secondaries in various series/parallel configurations as indicated on the datasheet for different stepdown ratios to drive different load impedances The schematics & articles I could find which use this transformer for headphone use (the Raven, and a few from Andrea Ciuffoli) dont make mention of using the secondaries this way, where other a few others with sowter & "unknown to me iron" do. I think its something worth exploring, but would like to know ahead of time if its a waste of time.

Its really easy to get balanced outs from either input if you have a phase splitter/diff pair integrated into the amp Input transformers are always nice. If feedback loops cross-couple the 2 phases converting to SE may not be so simple. I could not think of a good way to do this on the silver ghost (SE & balanced in, SE&balanced out with global feedback) so I just left it open loop. Assuming the output impedance of the amp is reasonably low: Without something to split phase that accepts SE and balanced inputs I think the easiest thing would be to ground the inputs to the "negative phase amplifiers" when SE inputs are used and make them work as channel specific active grounds to the XLR's and do the TRS output the same way regardless of what input is used. This could all be done easily with a single source selector switch. If the output impedance of the amp is on the OTL tube high side things look bleak without a phase splitter. Using the "negative amp" as an active ground shoots the amp in the foot. Most of the SP amps I have seen fail big time for this when using XLR outs & RCA ins. A couple SP amps used input transformers and avoid this. RSA gets around this on the B52 (and I think the Apache, although why he didnt do the thing above, IDK) with some relays to ground the -pin on the XLR when an RCA input is used. I guess Ray deserves credit for only making the end user touch 1 knob rather than mucking about with switches on the back panel like others, although why none of the OTL tube designers integrate a phase splitter into their amps is beyond me. its still only 1 knob for source selector on the RSA, it just controls a more complicated relay network.

If the output phases are at ground, just figure out a way to get ground up to the outputs. The problem is not really that it cant be done with adapters & dongles. The problem is that these dongles need to be built for one type of amp and once you have built this adapter and set it loose in the wild who knows what people will do with it. Will whoever has this dongle take the 4-pin --> 1/4" adapter which grounds to the shell/chassis and plug it into the second example amp I gave, blowing everything up? Will they take an adapter you built for a specific amp that behaves well when the negative phases are tied together and mount it on an amp that dosnt appreciate that treatment? Who knows. On that note: if you have room for 2*3 pin you have enough panel space for the "dual" 3-pin/1/4"TRS jacks or 1*4pin & 1*1/4"TRS. Every connection on them is separate from the others so you can easily control what goes where and how. If the amp is designed to have the outputs at ground potential just use the ground reference as the return from the SE headphone jack. Depending on what you think about active ground it wont work as well as that, or certainly balanced. Thats OK, if there are XLR's on a single ended amp people will re-terminate their headphones to use them... Its a no-brainer on an amp which is actually balanced. If you built a 4-channel amplifier whose output is not at ground potential (both outputs at say +12.000V to facilitate DC coupling without voltage shifters) and have separate outputs for SE and balanced just cap couple the SE outputs.