Lovepedal - Purple Plexi 800 [goop-alarm]

dap9 · Post by **dap9** » 14 Nov 2008, 03:05

Fuzzer wrote:Well, 914's eat like .5 more volts than the schottkys.

Aaahh, so that could be 'sapping' some of the power then, right? Thanks!

Fuzzer · Post by **Fuzzer** » 14 Nov 2008, 04:38

Sure, and those 386 don't like that sag.

dap9 · Post by **dap9** » 14 Nov 2008, 14:03

Fuzzer wrote:Sure, and those 386 don't like that sag.

Great Fuzzer, thanks. I'll order some BAT46s. Just out of curiosity, are all Schottkys "created equally?" Small Bear has some 5158s (or something like that I forget). Or do those have different forward voltages (or whatever).

Lastly, I do have a variety of different diodes around so are there any others that don't cause the sag as much? I tired some 1N34 Ge ones, but they were about the same.

Thanks.

Fuzzer · Post by **Fuzzer** » 15 Nov 2008, 01:17

Well, I have used the ones you mentioned in my builds for protection and they don't eat more than 0.2 [V].

The thing that bugs me is that a germanium one didn't gave you better performance..., you should just try it without the diode. Because if it continues behaving badly then the cause will not be the diode at all.

dap9 · Post by **dap9** » 15 Nov 2008, 03:25

Fuzzer wrote:Well, I have used the ones you mentioned in my builds for protection and they don't eat more than 0.2 [V].

The thing that bugs me is that a germanium one didn't gave you better performance..., you should just try it without the diode. Because if it continues behaving badly then the cause will not be the diode at all.

Jumper it is, good to know! I'll give it a shot. Thanks

briggs · Post by **briggs** » 15 Nov 2008, 11:47

The diodes could actually be removed, they are there for polarity protection, not really to alter the sound in any specific manner...

JHS · Post by **JHS** » 15 Nov 2008, 15:53

briggs wrote:The diodes could actually be removed, they are there for polarity protection, not really to alter the sound in any specific manner...

A protection diodes wired this way limits the current flow to the circuit and reduce the supply voltage a bit too. Dropping the diodes can alter the sound (esp. in battery powerd circuits) acc. to the circuit more or less.

I recommend an A/B listening test to get an idea what will soundwise happen w and w/o those diodes.

JHS

analogguru · Post by **analogguru** » 15 Nov 2008, 19:04

A protection diodes wired this way limits the current...

How this is achieved ?

analogguru

Dirk_Hendrik · Post by **Dirk_Hendrik** » 15 Nov 2008, 19:17

jeez AG... do we have to spell out everything for you???

Just the same as in, for instance, the ADA flanger input stage. There's a diode limiter there. So, conclusion, diodes limit! Since they have a fixed forward bias voltage that cannot be changed it must be the curent that's doing the limiting. Simple....

JHS,
Same question as AG asks above.
Elaborate this interesting limiting remark.

analogguru · Post by **analogguru** » 15 Nov 2008, 19:49

Thats a good attempt

, but I am a little bit confused now:

When the current is limited by the diode, why the protection diode always gets destroyed when I connect reverse polarity to a pedal ?

analogguru

Dirk_Hendrik · Post by **Dirk_Hendrik** » 15 Nov 2008, 20:33

Crap... here we go, freshyear electronics lesson2 (1 was about light bulbs)

As you may remember this is the standard forward bias voltage curve of a diode:

Because a symmetric (non AC biased) sinewave travels all 4 quadrants this curve will, depeding on which quadrant the sine wave is in alter with the wave:

What you definitely will notice in these 4 curves is that the current remains independent of the voltage which still supports the undoubtful fact that there's current limiting in place.

The fact that your diodes fail is probably due to the forward voltage vs reversed current regulations in some parts of the world. That doesn't have anything to do with diode limiting. A simple DC/CD inverter should cure that problem in no time.

have luck.

Fuzzer · Post by **Fuzzer** » 15 Nov 2008, 20:44

briggs wrote:The diodes could actually be removed, they are there for polarity protection, not really to alter the sound in any specific manner...

Sure, the diodes aren't there for sonic purposes, but still better safe and put some kind of protection, I just don't suggest the reverse diode from +V to ground, I have never liked that.

nooneknows · Post by **nooneknows** » 16 Nov 2008, 23:14

chris_d wrote:Folks who like this one, and/or the OCD, what amps are you running through?

I have an OCD clone, that I love, and I'm using it with a stratocaster in my Peavey Classic 30 (clean channel) or in my JCM 800 combo single channel, both sound great.

minatour87 · Post by **minatour87** » 19 Nov 2008, 02:22

due to the tech getting the best of me
i have sweepped a clone and a real PP800 on a spectrum analyzer...
i set the controls about mid range.
sweep from 20hz to 20khz.
the first one is the clone and the second one is the real deal.
i have to admit i can not tell you what the difference is but there is a small difference...
peace minatour87

Ghandi · Post by **Ghandi** » 19 Nov 2008, 08:31

...is the third 47uF parallel to the 100nF cap from pin 6 to ground on the clone?

Jimmy-H · Post by **Jimmy-H** » 19 Nov 2008, 15:14

Ghandi wrote:...is the third 47uF parallel to the 100nF cap from pin 6 to ground on the clone?

Yep!

Ghandi · Post by **Ghandi** » 19 Nov 2008, 16:06

I know that, look who did reverse engineering.

I'm asking minatour87 if he used the third 47uF cap on the clone he tested!?
...since there are some schematics which don't show that cap...

Jimmy-H · Post by **Jimmy-H** » 19 Nov 2008, 16:33

Ghandi wrote:I know that, look who did reverse engineering.

I'm asking minatour87 if he used the third 47uF cap on the clone he tested!?
...since there are some schematics which don't show that cap...

If you look at the pictures in page 1, you see that there are also 3 elco's.
Somebody made a remark of that.
But if you leave it out, it isn't a big deal.
It's just to filter the power.

Ghandi · Post by **Ghandi** » 19 Nov 2008, 17:57

@Jimmy-H,
I know I made the remark on page 1.
the 3 elco's are the 3 47uF caps I'm talking about!

0,1uF and 47,1uF filtering makes a difference I hear (at least) in a blind test
and it could also easily explain the difference minatour87 measured with his septrum clone and a real PP800 on his spectrum analyzer.

Jimmy-H · Post by **Jimmy-H** » 19 Nov 2008, 19:56

I like that Ghandi : "Blind testing"
Do you also use shades when you are testing?

Just kiddin', but do you really hear a difference? (with or without shades.....uuuhhh 47 uF cap)

Lovepedal - Purple Plexi 800 [goop-alarm] [traced]