1N4007 vs. UF4007

Repairs, trouble shooting, modding and so on.

1N4007 vs. UF4007

Postby David B » Sun Nov 18, 2012 12:09 pm

Does anyone have experience using UF4007 in place of 1N4007 rectifier diodes?
I read they can lower background buzz & hum. Any change in feel or tone using the UF's?

Thanks,

David
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Re: 1N4007 vs. UF4007

Postby Roe » Mon Nov 19, 2012 5:13 pm

there's a slight change for the better. less noise and more clarity, less buzz
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Re: 1N4007 vs. UF4007

Postby dai h. » Tue Nov 20, 2012 8:47 pm

my understanding was that regular 1N4007 were not particularly a problem in terms of noise and that (as part of good general layout practices) you want to keep the loop from B+ AC windings to diodes to first filter + then - then to ground (will be B+ cnt. tap wire on 50W) back towards source (PT B+ winding) physically compact since this can radiate noise. Where you can't do this particularly well (like on a vintage amp you don't want to alter or if it's a big PITA), one idea is to provide a bit of electrostatic (capacitive) shielding to hopefully attenuate buzz (higher harmonics of hum) by using some insulated wire around some of the parts of that loop as a a sort of "served shield" as done around the fast/slow switch area in a Trainwreck Komet (cheaper and easier vs. trying to put everything inside a braided tube--although you can find braided tubed wiring in various diameters). (Note: the insulated wire would connect to ground (chassis) at both ends.) Another related idea was to install 10 ohm (5W IIRC) wirewound Rs at each side of the FW rect. (i.e. a 10 ohm in series w/the two 1N4007 for each side). (Vaguely) this was supposed to damp the charging peak (high current pulse x2 line freq.) reduce radiated noise of the aforementioned loop(?). (Idea from Paul Ruby and possibly others?)

re: fast recovery diodes I think I tried some a very long time ago in a 50W and BBE Sonic Maximizer. In the Marshall it seemed to make the transients faster (might have just been my imagination or confusing it with other things I did to the amp). In the BBE it seemed to make things more weird and audible (spliced in portions of guitar solo leads) but overall a more painful sort of sound (also, not scientific at all but that is what I remember perceiving at the time--I put the regular type diodes back in).
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Re: 1N4007 vs. UF4007

Postby David B » Tue Nov 20, 2012 10:52 pm

Thanks Roe, I'll order some for my next project.Gotta try


Dai,
I have seen the shielding you refer to in old HiF gear. I find it interesting an amp like an Express doesn't really have the B+ AC windings to diodes to first filter + then - then to ground (will be B+ cnt. tap wire on 50W) back towards source (PT B+ winding) physically compact, well the filters are off to the side with IMO long wire runs, IIRC Ken used regular 1N4007's in his amps..
Did you convert the amp and maximizer + taste test at the same time or separately?
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Re: 1N4007 vs. UF4007

Postby dai h. » Wed Nov 21, 2012 12:19 am

David,

I don't remember exactly (since it was long ago), but probably not at the same time. I was doing a lot of of swapping, throwing "audio grade" or "better" parts at various things hoping for improvements (being quite ignorant--still am but just not quite as much lol). Some of the changes did seem to improve things and some didn't seem to do anything or made things worse. For instance the BBE (422A) I changed op amps (TL074 and 64--diff ones in ea. ch. to MC33078? 9?--sort of a quad ver. of 5532), alu electros to film and Black Gates (and a tantalum IIRC), Rs to some audio grade carbon film, power filters to Panasonic audio types and the change to fast recovery diodes was one of the last things I tried (if mem. serves). What motivated me at the time was that even in bypass, the BBE seemed to degrade the signal compared to not having it in the signal path (more hiss and just apparent general degradation). Overall the BBE seemed a pretty subtle effect more noticeable on some sources than others (recording with samples seemed more noticeably improved while other stuff seemed better without) and nothing fundamentally essential. Also the type of op amp I used was maybe not the correct sort to use (bipolar transistor input vs. the original FET input types--since later on, I saw in a schemo of latter models keeping FET in op amps towards the input but the later stage changed to 5532--so went from x1 quad op amp to x2 dual). Also (I don't know how to explain, but) for some sources (My Bloody Valentine) the BBE would make the sound weird (something to do with compression or something?--I have no idea).
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Re: 1N4007 vs. UF4007

Postby Maschine » Wed Nov 21, 2012 9:45 am

Eric Johnson can hear the difference, alas, I cannot. :wink:
.....if it doesn't have tubes.....
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Re: 1N4007 vs. UF4007

Postby David B » Thu Nov 22, 2012 3:41 pm

Not sure if my ears would hear any difference either but a reduction in noise is a plus … Just for the heck of it one could built a dual recto 1N-UF switching thingy
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