hot harmonics

[gaussmarkov]

 

[9 volts]

I built the hot harmonic from the above pcb layout and it worked fine! The octave pot can get a little scary when up full, I like the idea of maybe subsituting for a set resistor or maybe a smaller pot. It's got a different sound to the lama.

But wow, I think I'm going to start work on that forty niner really soon!  The sound examples are great at Marks Hammers site and a pcb board design from gaussmarkov to boot! Thats really fantastic.

It looks like there is alot of scope for personalizing the sound of these pedals.
What can I say Thanks again

[gaussmarkov]

i'm glad to hear it worked.     there's always room for a mistake in my version of the schematic.

mark's forty-niner is a much more complicated circuit.  i recommend checking my schematic against his before building.  i could be missing the same mistake each time i check it.   i would really hate to see you build a faulty layout.  and i would really love to see you build something that fires up first time! 

now i am off to hold a spot for the germany-portugal game.   

--gm

[stumper1]

GM-
Thanks for the help!  While I seem to have my head around the series thing I'm still a little confused on the power supply filtering.  Is there a reason that the Hot Harmonics schem shows the power to the IC via the filter while the power for the input/preamp stage is directly from +9v?  Possibly to isolate the 2 sections?  If I were to add the typical 100R/100uf filter to the power supply would this just be redudndant as far as the IC is concerned?  If I add this should I remove the 200R/22uf?  Should I just move the power for the input/preamp stage to the same place the IC gets it's power?  It's a hot day here, should I just open an ice cold beer (it is kind of early though ) and quit thinking too hard?

[Peter Snowberg]

Thanks, gm.  You get this week's "citizenship award"!

+1

[gaussmarkov]

GM-
Thanks for the help!  While I seem to have my head around the series thing I'm still a little confused on the power supply filtering.  Is there a reason that the Hot Harmonics schem shows the power to the IC via the filter while the power for the input/preamp stage is directly from +9v?  Possibly to isolate the 2 sections?  If I were to add the typical 100R/100uf filter to the power supply would this just be redudndant as far as the IC is concerned?  If I add this should I remove the 200R/22uf?  Should I just move the power for the input/preamp stage to the same place the IC gets it's power?  It's a hot day here, should I just open an ice cold beer (it is kind of early though ) and quit thinking too hard?

back from the game--germany won handily and munich is full of celebration.  it's a nice time for germany.  they have hosted a very successful world cup and gone farther in the competition than most of them expected.  it's nice to share it with them.  even though that means i won't be getting any sleep for a while yet. 

my understanding (and i am not the most qualified to speak on this), the transistor might as well get the filtered power, too.  you can see in a previous post that i also noticed this difference between the IC and the transistor in mark hammer's forty-niner schem and moved the power supply for the transistor.  no one has objected, so at least it's not a bad thing to do. 

i picked this approach up from posts by a number of folks.  here's one by martymart.  if you read the thread you will see that the concept was still sinking in for me.    martymart has said at least twice in my presence  that he always sticks a 100uF cap and a 100nF in parallel from the power supply to ground before the circuit.  also, a diode for polarity protection.  the caps put a low pass filter between the power supply and everything else.

also, if you look at lots of circuits (like a tubescreamer) you will see (at least) the 100uF cap sitting there.  and another cap, maybe a 47uF, from the bias voltage to ground.  the small resistor isn't always there.  so the input buffer in a standard tube screamer gets cleaner power.  same thing in the bsiab 2.

one filter seems to be sufficient.  i have never seen two.  so if you are going to filter the supply the the transistor, you might as well just move the connection after the 200R/22uF filter like i did with the forty-niner.  and you might change the filter to 100R/100uF instead of the current values.  the difference is how quickly these two filters roll off as the frequency goes up.

the thread i mentioned above also contains a formula that is often used for comparing two filters like this:  the "cut-off frequency" is F=1/(2*pi*R*C) where R is the value of the resistor in ohms and C is the value of the capacitor in farads.  R.G. explains that the "cut-off frequency is defined as the frequency where the signal being filtered is at half power, 6DBv down or 3db power down" and that "a single RC filter response slopes down at -6db / octave."  so in both cases we are dealing with a single RC filter and we can take their roll-off shapes to be the same.  the respective cut-off frequencies are about 36 Hz for the 200R/22uF and 16 Hz for the 100R/100uF.  Both are well-below the 100 Hz where guitar frequencies apparently start but with only 3db attenuation.  If we go another octave with each that would mean 9db attenuation at 72Hz for the first filter and at 32Hz for the second.  clearly the second filter is killing much more of the stuff you typcially don't want.

so you might decide to just replace the original hot harmonics power supply filter with a 100/100uF filter. 

all that said, it also appears that it doesn't matter to a lot of folks.  we have been happily building the hot harmonics for a while with no complaints (that i can find) about the noise from the power supply.  and there are plenty of circuits with no power supply filtering that have probably also had many satisfied users.  like the triangle big muff pi that some of us were working on last week.  FWIW, i like martymart's approach.  it's easy insurance.  and you don't have to build it onto your circuit board--it can be built separately which is kind of cool because it gives you more flexibility for cramming everything into that 1590B. 

whew!  maybe that was more than you wanted.  but the cars were honking pretty steadily until a moment ago.  now that they have settle down, i'm going to call it quits  ...  but i would still like to hear about that 22uF cap that sits between ground the unused inverters of the 4049.  you don't always see that either.  probably more insurance.

--gm

[Fret Wire]

i picked this approach up from posts by a number of folks.  here's one by martymart.  if you read the thread you will see that the concept was still sinking in for me.    martymart has said at least twice in my presence  that he always sticks a 100uF cap and a 100nF in parallel from the power supply to ground before the circuit.  also, a diode for polarity protection.  the caps put a low pass filter between the power supply and everything else.
--gm

PS supply filtering has been around here awhile. RG's been preaching it for awhile. Phillip Bryant at Fuzz Central was one of the first to start putting it in his layouts, and then it seemed to catch on here with the masses. With a regulated, and filtered wall wart, some ckts are just fine. Then there are some ckts that seem to really need good filtering. I think companies like Boss go complete on ps filtering because they don't know if you'll use the recommended power supply.
The full route is usually
diode
100r
10-220uf
.01uf

If you use a ps, it never hurts to put it in your own layouts.

Here's an example
http://fuzzcentral.tripod.com/liquid.html

[puretube]

http://www.diystompboxes.com/smfforum/index.php?topic=38976.msg277074#msg277074

[stumper1]

Thanks to everyone for the help.  The type of filter described is exactly what I was planning on using.  I built an AMZ Overdrive Pro that worked great w/a batttery but when I put it on my pedal board w/a daisy chained One-Spot it squealed like mad.  Added the filter and it works perfectly quiet now .

The only thing that had me confused was the seperate power supplies for each part of the circuit.  I assumed (I know, I know...) it MUST be done for a reason.  Anyway - THANK YOU to all who helped.

9Volts-
I e-mailed the Hot Harmonics stuff to you and it bounced back.  I deleted the PM w/your e-mail address in it before I noticed.  PM me your address again and I'll make sure you get it.

[gaussmarkov]

one filter seems to be sufficient.  i have never seen two. 

http://www.diystompboxes.com/smfforum/index.php?topic=38976.msg277074#msg277074

ok ... i have seen two.    "never say 'never,'" i guess.

[9 volts]

Hey I added the 22uf cap and it really makes a huge difference to the sound of this pedal.

Mark-  I've also added the .01 cap to the gain pot and it's great. Can i  do the variable midscoop  as well or just do one or the other?

[Mark Hammer]

The variable midscoop can be added withut problem.  The bypass cap is inserted before the gain, where the midscoop occurs after the gain stages, so only the one introduces passive loss. 

The more general concern is with introducing so much passive loss after the gain stages that the only way to get some volume boost, relative to bypass, is by diming everything or by adding a gan recovery stage (as seen in the Big Muff, for those identical reasons). Ideally, one likes to have some "reserve volume capacity" so as to be able to get a volume boost when the effect is on even though the gain is set to something softer.  Many folks like to use this type of pedal to simply push the amp a little harder during solos with a slightly coloured/shaped signal.  If the only way to push the amp is to turn everything on 10 in the pedal, then what you end up hearing is the pedal and not the amp.  I can see where some would want that, but I imagine a great many do not. 

So, if the circuit provides sufficient potential volume boost, even with the gain turned down, and if the tone-altering stages after the gain/clipping stages don't introduce too much passive loss, there should be no problem.  The suggested variable resistor in series with the bypass cap in the midscoop/notch filter will not alter the fact that the signal can simply go by route of the 10k+15k resistors to the output pot, so the amount of passive loss should be acceptable.

[Aharon]

Hey I added the 22uf cap and it really makes a huge difference to the sound of this pedal.

Mark-  I've also added the .01 cap to the gain pot and it's great. Can i  do the variable midscoop  as well or just do one or the other?

[stumper1]

Hey I added the 22uf cap and it really makes a huge difference to the sound of this pedal.

Was this the 22uf power supply cap or the 22uf cap from the unused inverters to ground?

As for the cap on the unused inverters - I'm with gm - why is it there?

[Peter Snowberg]

Could someone please link to the schematic in question with the 22uF from unused inverters to ground?

[stumper1]

Here you go

[Peter Snowberg]

Thanks Stumper. 

The 22uF pictured on the right is the same 22uF in the schematic on the left (the 200 ohm resistor is also repeated on both sides). The line that busses all the unused inverter inputs also connects to pin 1 of the 4049. I think it was illustrated that way to show that the 22uF should be fairly directly accross the Vdd and Vss pins of the 4049 instead of somewhere else connected to the rails.

[stumper1]

Peter-
Thank you!!!!  Now that you point that out it makes some sense.  I was missing the connection to the +9v supply there.  I assumed (there I go again) that unused inverters were being tied to ground - as I did in my layout - not the + supply.  Which leads to one more question....
I've read that you should tie the unused inverters EITHER to ground OR +9v.  Is there any difference between the two methods?

[Peter Snowberg]

No difference.

As long as the inputs are at either Vss or Vdd, the unused inverters will draw the least possible current and they will not oscillate which is the name of the game.

[Aharon]

That's the schem I have.
At the time when this schem was posted (roughly 7 years ago?)I had just begun building.
One of my first projects was the HH.The mystery dude,C Gardel was me,soon after I started using my own name.
I does really sound better this way and Frank thought so too,I never thanked him for crediting me,so here it goes....thanks Frank.
Aharon