Post by michaelw on Apr 13, 2020 23:20:09 GMT 12
gunmetal + wood = classy !
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Pundit
Post by beeman on Apr 14, 2020 8:14:16 GMT 12
Wow - really really nice could happily live with that. No DAC?
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Post by Graham on Apr 14, 2020 10:44:49 GMT 12
Very nice. If it sounds half as good as it looks you have a winner !!
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Pundit
Post by audionut on Apr 14, 2020 11:06:38 GMT 12
Looks fantastic... well done!
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Post by Owen Y on Apr 14, 2020 11:17:57 GMT 12
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Post by colinf on Apr 14, 2020 18:51:26 GMT 12
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Post by Owen Y on Apr 14, 2020 20:13:40 GMT 12
Thanks Chaps. beeman - the DAC is now built-in (see pics, previous page). J's woodwork is a level beyond my 'carpenter' capabilities - the small dovetailing was done with a Japanese 'pull-saw', coping saw & narrow chisel - by hand, no cnc! The thought of doing this by hand is way beyond my patience, let alone skill-set.
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Post by sadface on Apr 16, 2020 10:48:16 GMT 12
That's a classy looking headphone amp.
Can we please see a shot of the back of the amp?
I am guessing that the small toggle switch that we can almost see at the back is for input switching between the dac board and the rca inputs?
Does the DAC board draw its power from the USB bus?
Your completed layout is incredibly neat and tidy. I am very impressed. It appears to be a master study in p2p wiring.
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Post by Owen Y on Apr 16, 2020 11:04:00 GMT 12
That's a classy looking headphone amp. Can we please see a shot of the back of the amp? I am guessing that the small toggle switch that we can almost see at the back is for input switching between the dac board and the rca inputs? Does the DAC board draw its power from the USB bus? Your completed layout is incredibly neat and tidy. I am very impressed. It appears to be a master study in p2p wiring. Thanks sadface. Point-to-point wiring style has a standard high bar that was set back in the days before PCBs (the '50s & '60s) & in more recent times by the Japanese (refer to MJ (Musen to Jikken) magazine). J is a bit of an 'artist' but also young & energetic Yes & yes (switching & USB powered DAC). The full story can be seen here, in J's blog page on the project. (A better pic - still awaiting suitable rubber feet.)
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Member
Post by snewt on May 7, 2020 17:09:55 GMT 12
Congratulations on a gorgeous build. I really enjoyed following the progress of this and was blown away by the workmanship. Soooo, how does it sound after a while?
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Post by colinf on May 14, 2020 1:15:27 GMT 12
Hi Owen, just been going through Audirvana settings. You can change the absolute phase so you can use a phase-inverted headphone amp with it. Looks great with the gunmetal finish! Love the craftsmanship.
AMR-iFi R&D
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Post by Owen Y on May 14, 2020 9:48:01 GMT 12
Thanks colinf - that's interesting to know. I'll advise Jeremy, he has a Macbook, but I think most of his headph' listening is done at work via his work desktop PC.
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Post by Owen Y on Jul 6, 2020 20:05:37 GMT 12
A wee update on this tube headphone amp.... After a couple of months use & listening, we got in some Mills 12W wirewound Rs to replace the RS-supplied regular industrial wirewounds (which were readily available at the time). It just goes to show that, in these simple tube circuits with few components, the parts quality matters a lot. I've used Mills (non-inductive) WWs for years & they've always been reliably good sounding. J commented on "Brighter highs, more forward midrange. Generally more open sounding." I thought much more open, snappier, brighter, more dynamic & overall a good lively 'lift' for the HD650/6xx's - which tend to lean to the 'easy', slightly undynamic side. An early wiring pic showing the Cathode Rs (circled yellow), now replaced with Rs of same type as the input plate load Mills Rs alongside (red arrowed). Another thing, which is consistent with the tube amps in my system, is that there is noticeable 'warm-up' time of around 15 mins, during which the sound improves noticeably.
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Member
Post by mijoh on Jul 7, 2020 23:57:50 GMT 12
I will get some Mills WW for my version of Crack too, still waiting for some parts to arrive.
Some builders have reported sonic improvements by replacing one or both 270 ohm 5 watt resistors with a choke, but I doubt you would have room in there for that.
Replacing the diodes with Cree Schottky diodes have been said to improve bass, definition and lower noise in the Crack. Likewise changing the 100 uF electrolytic's to film types would be good, but in that value some are nearly as big as beer cans and bypassing them with small film caps as you have done is a good compromise.
As you say Owen, it seems to be a circuit that really responds well to the quality of the parts.
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Post by Owen Y on Jul 9, 2020 9:50:21 GMT 12
Yes, hard to beat a good wirewound, IMO. Metal films, most sound a bit unnatural to me - although the Takmans seem good & inexpensive. PSU chokes - CLCLC is nice (Ls give better preservation of LF power, warmth etc), but more cost & space-consuming. 'Choke input' PSU filtering (LCLC etc) is best, but PSU becomes much more complex & less efficient. Schottky diodes - I have lazily assumed that the UF diodes specified would be v good. I have used Schottkys before, but not done any comparisons with other UF-'soft recovery' type diodes. I recall the 'sharpening up' of the sound the first time I replaced regular 1N diodes with Philips fast-soft recovery diodes (in a ARC tube preamp). So, could be worth an experiment here - we might do same. Output caps - yes, this is the big compromise in this OTL cct - a big ugly electrolytic blocking the output. We may try a better bypass film cap and/or a better electrolytic (presently nothing special, with a Jaycar PP bypass). I use the F&T (German) electrolytics now, where I want to be fussy.
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