Ss rectifier in 5f1 (plug in replacement)

[splendid]

G'day! Had to share this one, been done a million times I know but I just wanted to state what an improvement on the 5f1 circuit a couple of diodes can make, I took the 5y3 out (it rattled like a Volvo anyway) and replaced it with a Bakelite octal socket wired with 1n4007 diodes.

Powered it up, waited for smoke and amp death, then played at full volume for an hour. Checked the temps on the pt, ot and tubes, all cool as cucumbers!
The headroom has improved, better response and tighter bass.
I was apprehensive to do this mod but curious since the build, if your tubes and pt can handle a little extra grunt I say try it, you can always plug the clunky old 5y3 back in if you get bored of awesomeness :-)

And yes, it's my faithful old vox pathfinder, gutted and filled up with 5f1 goodness :-D

[TheSmokingMan]

next time try the uf4007, its a noticeable difference

[splendid]

Really? Ill have to knock together another little plug! Great!

[dmondo]

hey Splendid, really interesting post - I've just finished building a Boothill 5F1 amp,it works fine, but I'm interested to know what it is that you're talking about ?
I wouldn't mind a little more clean headroom - I changed the ax7 for an at7 and that's better - but I'm a newb at this stuff and need a diagram or similar.
Any links or more information, much appreciated ?

[charisjapan]

Hey Splendid,

I'm also interested in how you built that SS plug. The only ones I've seen have 4 diodes, and I can only see three in your pic.

Here's what I was going to make, but it would be nice to fit it into a plug. (Weber's Copper Cap is available here, but pretty expensive)

no uf4007s at my supplier.

Thanks.

[Keyser Soze]

If you are looking for results like Splendid achieved then you probably do not want a copper cap anyway - they are intended to mimic the performance of a specific tube rectifier, not provide the higher operating voltages that are gained from straight solid state rectification.

Ultra fast diodes help reduce switching noise, which can be a concern in single ended amps, and are typically only a penny or two more than standard diodes. So they are a nice upgrade, but not essential.

Most commonly they are designated with the UF in the front of the item name, but not always. Sometimes you just need to look in a parts list under diodes and/or rectifiers and find key words like 'fast recovery', or 'ultrafast', or 'hyperfast.'

The key values for this application are a minimum 1 amp, and an 800 or 1000 volt peak repetetive reverse voltage ratings.

[splendid]

I used 1n4007 diodes. You can use just two , I use 4 for the sake of caution, really great improvement in tone, more than expected, running electro harmonics 6v6 which seems to handle the extra volts just dandy!

This will give you pins to solder diodes to,you don't even need to disconnect the original 5 volt filament supply, just plug and play baby!! :-D

[splendid]

A couple of diodes do the trick, I use four for the sake of caution, you can use two and they'll work just fine, what a cheap improvement!!! Bang for your buck I say

[aunchaki]

Last year I bought a Tweed Champ clone from hackworth1 (already built, not a kit). He had three on hand: one with a "proper" tube recifier, one with a SS replacement plug-in rectifier, and one with a built-in (non-reversible) tube rectifier.

We chatted about the differences. I decided to go with the third one (built-in SS rectifier. All I can say is that my Champ sounds awesome!

[P Rails]

There really no benefit (sag/compression) using a tube rectifier in class A single ended. SS diodes are cheap and generally longer lasting. Adding diodes just increased your voltage 1.2 times (x1.2) which increased your head room a bit.

Some using SS diodes insert a 150R/10W between diodes and first cap to simulate a tube rectifier. If you like the compressed classic fender amp sound there's a couple ways to get close even in class A single ended. It's considered increasing "squish" rather than "compressed" sound.

1) using lower value (33uf and under) filter caps combined with higher value dropping resistors.

2) high value screen resistor: 10k to 15K

I used these on a lower voltage (300 plate) champ type build (6V6) and it sounds like a tweed at lower volume and then like tweed on roids when pushed at higher volume.

[dmondo]

Hey guys - I have put the SS ( 4 x uf4007 Diode ) rectifier together and tried it, and it's working well. Thanks heaps for that info. Looks pretty crap tho and naked wires = problematic !
Can anyone help me with where I would get the Bakelite octal socket from ?
Does it have a Model No. or any part No. or someway I can google it ?
Or any suggestions as to how to encase it better ?

[TheSmokingMan]

once you've got the diodes solidly in place I'd say goop it over in epoxy

[splendid]

Got a heap of these old sockets from dismantled organs, you could use the base off an old octal valve and use some potting epoxy to fill it up after diodes are installed!

I'm gathering parts for a mutant Princeton reverb (12" Neo speaker, jj 6v6s, deluxe reverb pt and ot) seriously considering going plug in ss in leu of the rectifier!

[splendid]

Just found these on flea bay

http://www.ebay.com.au/itm/8-Pin-Oct...0#ht_867wt_823

They would do swimmingly

[dmondo]

Hey guys - really appreciate the replies. I've decided to just use a valve socket ( $5 & I'll make some pins with twisted wire - soldered ) and probably some heat-shrink, or some kind of cover, to keep it safe.
Do Diodes get hot ?
Would heat be a problem if I "goop'd it over with epoxy" ?
Again - thanks heaps, makes things a lot easier.

[splendid]

They should be cool as cucumbers, you could also open the amp up (utilising all standard safety precautions) and solder the diodes directly to the octal socket lugs. If one were so inclined :-)