I just finished a build of HM-2 clone based on the first/upper layout from here: http://tagboardeffects.blogspot.com/2014/05/boss-hm-2-heavy-metal.html (http://tagboardeffects.blogspot.com/2014/05/boss-hm-2-heavy-metal.html).
A first check and all seems to be working except when I turn the Lo (B10k) pot all the way CW, there is a very loud shriek kind of noise.
I asked in the blog, but my question is either lost or being checked, so I took my chances to ask here too.
I planned for it to be a b-day gift on Tuesday for a friend, so that is the reason for my impatience.
Ok, so I'm assuming that this is the schematic:
https://www.hobby-hour.com/electronics/s/hm2-heavy-metal.php (https://www.hobby-hour.com/electronics/s/hm2-heavy-metal.php)
A shriek when the "Lo" is dimed suggests a problem in the 3B op-amp, which acts as a gyrator producing the low frequency response. If the result is a high-pitch squeak, perhaps some component in that section is wrong? It's easy to put 10K where 100K should be, or similar - 10n where 1n should be, etc. After all. the "Low" control should be giving you a *low* frequency control, not a *high* frequency squeak! ???
You'd have to find the relevant components on the stripboard layout. WhyTagboardEffect don't post schematics, I don't understand. It's not like it's illegal, and pretty much everything they post as a stripboard layout is from a schematic which is available somewhere else on the web. So why not post a link to the original schematic?
<edit>link fixed
Thanks!
I did not find any working schematics from that site.
I edited away the trailing "c" from your link, and it goes to what seems to be the "original" traced HM-2. With 10? Transistors. Mine had 3, so not the same schematics.
I found this thread in here though
https://www.diystompboxes.com/smfforum/index.php?topic=123329.0 (https://www.diystompboxes.com/smfforum/index.php?topic=123329.0) and it seems more like it.
But I agree that the Lo was not very "bassy" in its nature. So I might go over that part to spot any mistakes I could gave done.
The layout I used was verified by several so it ought to be ok.
I used other transistors and they all had different pinouts from the layout. And the internet was not consistent. But I have a meter for it and I used pinouts from vendor's site and it makes sound so I am guessing the Qs are correct.
Again thanks for pointing me in a direction.
Quote from: ElectricDruid on May 15, 2022, 05:09:18 PM
WhyTagboardEffect don't post schematics, I don't understand. It's not like it's illegal, and pretty much everything they post as a stripboard layout is from a schematic which is available somewhere else on the web. So why not post a link to the original schematic?
Agree wholeheartedly, Tom. The site is a great resource, but this^^ a thousand times over!
Quote from: bluebunny on May 16, 2022, 03:38:45 AM
Quote from: ElectricDruid on May 15, 2022, 05:09:18 PM
WhyTagboardEffect don't post schematics, I don't understand. It's not like it's illegal, and pretty much everything they post as a stripboard layout is from a schematic which is available somewhere else on the web. So why not post a link to the original schematic?
Agree wholeheartedly, Tom. The site is a great resource, but this^^ a thousand times over!
From my limited experience, I'd say there is often a link to schematics in the blog/chat below. But I agree that there is a sense between the lines to keep low key and not rouse any feathers. Sort of.
Like it a lot and so many nice builds are available plus good discussions about alternatives etc. And the way the moderator listens and adjusts the layout.
Will make a walk-through of the build in my case. Need to flip a few caps to "the other side" to make everything fit.
That seems to be a fine art in itself. Mostly the circuits are discussed there and here, but more often than not the boxing is a bit of a challenge each time with new issues popping up.
At a quick glance it seems like the tagboard effects version has excluded the FET-swiching and the output buffer.
Shriek from the tone controls could also have something to do with the feedback components on op-amp 3a. If I understood the circuit right the tone controls at minimum ground the respective part of the frequency spectrum (at least partially) at the input of 3a when set to minimum. When set to maximum it grounds the feedback on the op-amp 3a for that same frequency range. If you ground too much of the feedback, the gain will go up and it may lead to oscillation.
If the shrieking only happends with the bass pot, I'd inspect stuff around op-amp 3b first too, but if you don't find anything there, check out the parts around 3a too.
is there any reason we can't see what you've built? maybe post some photos, eh. also, what part numbers did you use for your transistors/fet?
Quote from: duck_arse on May 16, 2022, 11:01:28 AM
is there any reason we can't see what you've built? maybe post some photos, eh. also, what part numbers did you use for your transistors/fet?
So sorry, no reason at all. Just felt it would not be very helpful. An I naïevely thought that "shriek at Lo pot dimes" would be met with some "you probably put C12 polarity the wrong way. Happens all the time." Like a newbie thing.
(https://i.postimg.cc/3yMxFZzW/20220516-170913.jpg) (https://postimg.cc/3yMxFZzW)
(https://i.postimg.cc/7G9PDrhT/20220516-170936.jpg) (https://postimg.cc/7G9PDrhT)
(https://i.postimg.cc/0KNkyXKX/20220516-171331.jpg) (https://postimg.cc/0KNkyXKX)
I made it for my Swedish-Turkish friend. He said he couldn't get any metal tones, and I heard HM-2 would be better ata that than the MT-2 for instance. It's gis B'day tomorrow, but with the shrieky thing I am galling behind schedule a bit.
The text is direct translates except input output which are more of jokes.
I used LM358s for ICs after recommendation on the blogsite.
Ge diodes are D9K as prescribed 1N34A were out for me.
The others 1N4148 and 1N5817 as prescribed.
Q1 is the FET K30A-Y (got a -GR just in case)
Q2 is B549B instead (have 2N5088 in case)
and Q3 is BC559C (with 2N5087 in reserve)
My pre-studies suggest that these options should wotk ok at least. The ICs might even be better than M5216L as the original indicated.
Quote from: Elektrojänis on May 16, 2022, 10:00:51 AM
At a quick glance it seems like the tagboard effects version has excluded the FET-swiching and the output buffer.
Not sure how to tell this, but you think this might be the issue? I tried following the schematics I found in another thread in this forum, and that part has me lost. I find no 10k after the IN on the tagboard. And the 9 volts to 4,5 volts has me lost on the tagboard as well...
Quote
Shriek from the tone controls could also have something to do with the feedback components on op-amp 3a. If I understood the circuit right the tone controls at minimum ground the respective part of the frequency spectrum (at least partially) at the input of 3a when set to minimum. When set to maximum it grounds the feedback on the op-amp 3a for that same frequency range. If you ground too much of the feedback, the gain will go up and it may lead to oscillation.
OK, I think I at least understand the conclusion. But is there any remedial action I can do in the circuit to counter this?
Quote
If the shrieking only happends with the bass pot, I'd inspect stuff around op-amp 3b first too, but if you don't find anything there, check out the parts around 3a too.
I compared the schematics mentioned with the tagboard layout and apart from the ICs numbering and selection of op-amp in respective IC, they seem to match.
I will go through the wiring I made and check for continuity etc.
Or should I probe around to try to detect where the shriek happens?
Thanks
well, here's three bits of bad news. looking at your photo, I can't seee too much detail, but - K30A fet is gate centre pin, layout is for end gate. the two other transistors in the layout are pinned for end base - your BCxxx parts are centre pin base. unless you've done some leg twistings, all three are in
wrong.
QuoteLike a newbie thing.
no sir. the newbie thing is not banging up the photos and the layout and the circuit dia
every time you start a thread, the other stuff is just the usual day to day. don't sweat it.
(https://i.postimg.cc/sQKb6VH1/20220516-174649.jpg) (https://postimg.cc/sQKb6VH1)
The other side. I try to make a habit of checking each leg to not conduct to the neighbour copperlines, but only to its own. Tedious but found a few overflows that way.
Quote from: duck_arse on May 16, 2022, 11:41:25 AM
well, here's three bits of bad news. looking at your photo, I can't seee too much detail, but - K30A fet is gate centre pin, layout is for end gate. the two other transistors in the layout are pinned for end base - your BCxxx parts are centre pin base. unless you've done some leg twistings, all three are in wrong.
QuoteLike a newbie thing.
no sir. the newbie thing is not banging up the photos and the layout and the circuit dia every time you start a thread, the other stuff is just the usual day to day. don't sweat it.
(https://i.postimg.cc/56JFqfd8/16527162686963105993982375851882.jpg) (https://postimg.cc/56JFqfd8)
Not easy to see, but I did twist and isolated all three. Gate/Base are the colored ones
I tried probing, but felt the shriek was everywhere sort of.
But observed that Dist. needed to be quite high for the Lo pot to shriek. Seemed Hi pot was not without contribution either but it only happens when almost diming the Lo and high "enough" on the Dist.
Those kind of high gain circuits on strip board with lots of wires are notoriously sensitive, but usually it is the treble pot that sets them shrieking. Have you tried moving the pots and wires, around, separating them from the board and each other?
Even the footswitch can be a site for mischief. Better to test before you wire those up!
(https://i.postimg.cc/v4TWLQZj/boss-hm2-heavymetal-distortion-pdf-1.png) (https://postimg.cc/v4TWLQZj)
Note that the two opamps are "swapped" from the schematic and layout. In the Schematic the low gyrator uses pins 5,6,7, in the layout it's 1,2,3.
The components you should check if the lows gyrator is the problem:
1.5uf electro attached to low 2
330 ohm R between 1.5uf cap and IC pin 1 and 2
68nf cap between 330 ohm and pin 3
100k between pin 3 and VB.
And hey, you haven't posted voltages yet.
did you get the "cut" between that cap and the IC? It is hiding under that 100k R next to it. There are two cuts under that R but that's the treble control side...probably not your problem.
Quote from: idy on May 16, 2022, 12:51:04 PM
(https://i.postimg.cc/v4TWLQZj/boss-hm2-heavymetal-distortion-pdf-1.png) (https://postimg.cc/v4TWLQZj)
Thanks, yes that's the one I compare tagboard with
Seems the posted schematics and tagboard order match with 1 further up on the board an 3 connected to Level 1. I noticed that 1,2,3 vs 5,6,7 are swapped in some place(s).
So I will number as they are on the board, so possibly not the same numbering as the schematic.
Here goes
IC1
4.42 4.42 4.39 0.0
4.11 4.12 4.12 8.9
IC2
4.42 4.42 4.42 0.0
4.39 4.42 4.42 8.9
IC3
4.43 4.43 4.22 0.0
4.38 4.40 4.43 8.9
Quote from: idy on May 16, 2022, 12:48:25 PM
Those kind of high gain circuits on strip board with lots of wires are notoriously sensitive, but usually it is the treble pot that sets them shrieking. Have you tried moving the pots and wires, around, separating them from the board and each other?
Even the footswitch can be a site for mischief. Better to test before you wire those up!
Thanks, yes enough cable to keep them away from each other.
And yes I agree, it sparkles when you touch wires and move about so quite sensitive.
Quote from: idy on May 16, 2022, 01:08:18 PM
Note that the two opamps are "swapped" from the schematic and layout. In the Schematic the low gyrator uses pins 5,6,7, in the layout it's 1,2,3.
The components you should check if the lows gyrator is the problem:
1.5uf electro attached to low 2
330 ohm R between 1.5uf cap and IC pin 1 and 2
68nf cap between 330 ohm and pin 3
100k between pin 3 and VB.
And hey, you haven't posted voltages yet.
did you get the "cut" between that cap and the IC? It is hiding under that 100k R next to it. There are two cuts under that R but that's the treble control side...probably not your problem.
I forgot to mention: I could not find electrolyte 1.5uF so I got a tantalum polarized 1.5uF instead.
By check I assume you mean connectivity, glitch free etc. I feel I had done it during building. And seems none of them are not as they should be.
I had another problem fitting it in the box and the "Inpüt" and "Ütpüt" jacks just ran into some caps. Among them the 68nF you mentioned. So to fix
that problem, I relocated them to the other side of the board. With a few cable plastics as protectors I got 4 of them relocated.
And lo and behold, the shriek is no longer there.
If I max some pots around I do get a shriekish noise but that seems very much more like feedback. It is a powerful circuit as far as boost goes.
So, all fingers and other things crossed, I now consider it solved enough to box it properly. In my experience some noise goes away when you finally put everything in place.
Should the problem pop up again, I have some good ideas where to check.
Many thanks!
A huge thanks all who helped out with tips and ideas! I really appreciate it. :D :icon_biggrin:
I think my friend will get his present tomorrow if the coating will dry fast enough. ;)
Quote from: matopotato on May 16, 2022, 01:45:18 PM
A huge thanks all who helped out with tips and ideas! I really appreciate it. :D :icon_biggrin:
I think my friend will get his present tomorrow if the coating will dry fast enough. ;)
Don't rush it!
I once did a pedal in hurry like this for a friend's birthday, and it finished up having fingerprints in the clearcoat because it was still a bit soft!! I should have baked it or something! It would have been better to have waited a couple more days and done a better job.
Thanks.
I usually wait a few hours after print. At least overnight and some after coating. Then at least half or a day for the water to get out. Cut holes and last coating overnight or a bit more.
I think I have previously rushed most stages at some point so I try leave it some time.
But thanks for the warning. Very valid point.
(https://i.postimg.cc/0KmNW2K7/20220517-111830.jpg) (https://postimg.cc/0KmNW2K7)
I works! Not as chainsaw as I had hoped, but tons of output, and no shriek.
(https://i.postimg.cc/HVgWWm7P/16527791927842292713226236323696.jpg) (https://postimg.cc/HVgWWm7P)
A bit tight, but I could improve planning for sure.
Quote from: matopotato on May 16, 2022, 01:33:37 PM
Quote from: idy on May 16, 2022, 12:48:25 PM
Those kind of high gain circuits on strip board with lots of wires are notoriously sensitive, but usually it is the treble pot that sets them shrieking. Have you tried moving the pots and wires, around, separating them from the board and each other?
Even the footswitch can be a site for mischief. Better to test before you wire those up!
Thanks, yes enough cable to keep them away from each other.
And yes I agree, it sparkles when you touch wires and move about so quite sensitive.
can I ask - whatchoo mean when you say
sparkles? flashes of light or sound?
Quote from: matopotato on May 16, 2022, 11:24:44 AM
I used LM358s for ICs after recommendation on the blogsite.
...
My pre-studies suggest that these options should wotk ok at least. The ICs might even be better than M5216L as the original indicated.
my heart skipped a beat when i read this, for 99 out of 100 pedal designs, the LM358 is specifically awful, as it produces crossover distortion... but this pedal generates additional crossover distortion on purpose anyway, so adding more doesn't ''ruin'' the tone.
cheers
Quote from: duck_arse on May 17, 2022, 10:37:55 AM
Quote from: matopotato on May 16, 2022, 01:33:37 PM
Quote from: idy on May 16, 2022, 12:48:25 PM
Those kind of high gain circuits on strip board with lots of wires are notoriously sensitive, but usually it is the treble pot that sets them shrieking. Have you tried moving the pots and wires, around, separating them from the board and each other?
Even the footswitch can be a site for mischief. Better to test before you wire those up!
Thanks, yes enough cable to keep them away from each other.
And yes I agree, it sparkles when you touch wires and move about so quite sensitive.
can I ask - whatchoo mean when you say sparkles? flashes of light or sound?
Sound. Sorry, English not my mother tongue. Sometimes I sort of direct translate. And this happens
Quote from: iainpunk on May 17, 2022, 11:19:28 AM
Quote from: matopotato on May 16, 2022, 11:24:44 AM
I used LM358s for ICs after recommendation on the blogsite.
...
My pre-studies suggest that these options should wotk ok at least. The ICs might even be better than M5216L as the original indicated.
my heart skipped a beat when i read this, for 99 out of 100 pedal designs, the LM358 is specifically awful, as it produces crossover distortion... but this pedal generates additional crossover distortion on purpose anyway, so adding more doesn't ''ruin'' the tone.
cheers
;D :icon_biggrin:
Ok, I went by the discussion on the tagboard blog page where the LM solved problems of noise. At least that sounded as the consensus. I suppose TL072 would be more noisless, but the M5216L were considered the worse option.
Who knows, maybe even Metalheads have a distinction between chugg and noise? We'll have to ask Ola Englund ;)
Quote from: iainpunk on May 17, 2022, 11:19:28 AM...the LM358 is specifically awful, as it produces crossover distortion...
Not if the load is over maybe 50k.
My first project with the quad LM324 worked fine into a hi-Z input, obviously nasty into a 500 Ohm equalizer. I hacked a fix on tight deadline and moved on. But later I saw other people using the LM324 without complaint. I realized that many of these were real lightly loaded. (The others were, as you say, distortion boxes.)
Quote from: PRR on May 17, 2022, 09:17:48 PM
Quote from: iainpunk on May 17, 2022, 11:19:28 AM...the LM358 is specifically awful, as it produces crossover distortion...
Not if the load is over maybe 50k.
My first project with the quad LM324 worked fine into a hi-Z input, obviously nasty into a 500 Ohm equalizer. I hacked a fix on tight deadline and moved on. But later I saw other people using the LM324 without complaint. I realized that many of these were real lightly loaded. (The others were, as you say, distortion boxes.)
Is there some way to measure the actual input and oitput impedance of a pedal. I have a DMM pretty standard, and I think impedance and resistance are possibly 2 different things. Impedance relate to AC and resistance to DC roughly. And more than resistors have influence in AC.
Quote from: matopotato on May 18, 2022, 03:19:43 AM
I think impedance and resistance are possibly 2 different things. Impedance relate to AC and resistance to DC roughly. And more than resistors have influence in AC.
Resistors exhibit the same constant resistance both for DC and AC.. :icon_wink:
(at least, for frequencies where not modeled as series inductor and parallel capascitor besides their natural resistance..)
https://resources.system-analysis.cadence.com/blog/msa2021-understanding-resistor-behavior-at-high-frequencies
Quote from: matopotato on May 18, 2022, 03:19:43 AM
Is there some way to measure the actual input and oitput impedance of a pedal. I have a DMM pretty standard
A brute (but easy and convenient) way is to place a high value pot, wired as variable resistor) between signal source and impedance for measurement..
When signal's amplitude is halved, take pot out of circuit and measure its resistance..
The result reflects input impedance at question..
Of course, you can obtain the same with just a single series resistor of value about equal to estimated impedance (or any other value) but you'll have to deal with voltage divider Thevenin equivalent calculation.. :icon_wink:
Quote from: antonis on May 18, 2022, 06:55:12 AM
Quote from: matopotato on May 18, 2022, 03:19:43 AM
I think impedance and resistance are possibly 2 different things. Impedance relate to AC and resistance to DC roughly. And more than resistors have influence in AC.
Resistors exhibit the same constant resistance both for DC and AC.. :icon_wink:
(at least, for frequencies where not modeled as series inductor and parallel capascitor besides their natural resistance..)
https://resources.system-analysis.cadence.com/blog/msa2021-understanding-resistor-behavior-at-high-frequencies
Quote from: matopotato on May 18, 2022, 03:19:43 AM
Is there some way to measure the actual input and oitput impedance of a pedal. I have a DMM pretty standard
A brute (but easy and convenient) way is to place a high value pot, wired as variable resistor) between signal source and impedance for measurement..
When signal's amplitude is halved, take pot out of circuit and measure its resistance..
The result reflects input impedance at question..
Of course, you can obtain the same with just a single series resistor of value about equal to estimated impedance (or any other value) but you'll have to deal with voltage divider Thevenin equivalent calculation.. :icon_wink:
Thanks, I think I will have a problem knowing "half"volume. Especially since I thought it being logarithmic.
Quote from: matopotato on May 18, 2022, 06:57:44 AM
Thanks, I think I will have a problem knowing "half"volume. Especially since I thought it being logarithmic.
Volume is considered signal's amplitude (voltage..!!) :icon_wink:
You don't have to "translate" it at dBs 'cause you don't address to engineers..
Just measure AC voltage at signal source output and effect input..
Quote from: antonis on May 18, 2022, 07:23:16 AM
Quote from: matopotato on May 18, 2022, 06:57:44 AM
Thanks, I think I will have a problem knowing "half"volume. Especially since I thought it being logarithmic.
Volume is considered signal's amplitude (voltage..!!) :icon_wink:
You don't have to "translate" it at dBs 'cause you don't address to engineers..
Just measure AC voltage at signal source output and effect input..
Ok, I have a tonegenerator. So I can measure AC voltage from that machine?
And measure at pedal input. But with cable, so open box I guess. And then I an calculate impedance?
I actually have a strobe, but only 1 channel.
Sorry for my ignorance. I could probably ha e googled as well...
I found this link which should be useful for the details
https://www.diystompboxes.com/smfforum/index.php?topic=57305.0 (https://www.diystompboxes.com/smfforum/index.php?topic=57305.0)
Quote from: matopotato on May 18, 2022, 08:05:15 AM
I found this link which should be useful for the details
https://www.diystompboxes.com/smfforum/index.php?topic=57305.0 (https://www.diystompboxes.com/smfforum/index.php?topic=57305.0)
Just do what R.G. says in his 1
st post.. :icon_wink:
(https://i.imgur.com/Lxg5mC5.png)
Quote from: matopotato on May 18, 2022, 06:57:44 AM....I think I will have a problem knowing "half"volume. ....
Trust your ears. There's two main zones: >90% of volume, and <10% of volume. "Down a little, not a lot." You never need to know with great accuracy. It WILL be different bass and treble so your musical brain is needed to judge the effect.
Quote from: antonis on May 18, 2022, 08:52:08 AM
Quote from: matopotato on May 18, 2022, 08:05:15 AM
I found this link which should be useful for the details
https://www.diystompboxes.com/smfforum/index.php?topic=57305.0 (https://www.diystompboxes.com/smfforum/index.php?topic=57305.0)
Just do what R.G. says in his 1st post.. :icon_wink:
(https://i.imgur.com/Lxg5mC5.png)
Is Vs AC i.e. tonegenerator signal
Or DC, like 9V?
I thought Vin would be 9V with +/- and the Vs be an AC signal of sorts with varying frequencies to get some spectral view.
Forget all about DC here.. :icon_wink:
Impedance hates DC 'cause it neutralizes reactive components..
(caps turn into open circuit and inductors to short circuit.. - resistors, frankly, don't give a damn..)
Vs is signal amplitude and Vin is a portion of Vs, according to above mentioned formula..
About spectral view: IMHO, 3 measuremets at lower, higher and mid-band frequencies of interest should be adequate..
Quote from: antonis on May 18, 2022, 03:49:49 PM
Forget all about DC here.. :icon_wink:
Impedance hates DC 'cause it neutralizes reactive components..
(caps turn into open circuit and inductors to short circuit.. - resistors, frankly, don't give a damn..)
Vs is signal amplitude and Vin is a portion of Vs, according to above mentioned formula..
About spectral view: IMHO, 3 measuremets at lower, higher and mid-band frequencies of interest should be adequate..
Thanks. It's the + and - that is confusing. AC don't really have any constant polarity in a specific location over long time. I thought. Of course momentarily there is a polarity unless "0", but not as connections would go.
So I didn't understand how to interpret the figure.
But if I scrach the polarities and think ~ instead, it should be ok. Or I misunderstood completely. (Again ;-) )
Yes, for our purposes scratch the polarity and think AC source fro signal.
The example schematic shows the simplest example, with a series R and a shunt R. In real life a signal encounters R, C and L. L is usually left out because its so small. But in a power supply or wah-wah pedal, it becomes important.
Really we mostly deal with R and C. Those two values, Zs and Zl, stand for impedance in series with the signal and impedance loading the signal. That impedance can come from a resistance, capacitance or inductance. Or (in real life) all together. But we measure impedance in ohms, like R, but it changes with frequency.
The way a cap works we can think like this: at some high frequency it has no impedance to the signal. At some low frequency the cap treats it like DC. You can make that reactance into an ohm value. With a simple tone control type filter we are putting a C in one direction and an R in the other. At the frequency where the signal sees equal "resistance" (really impedance) in both directions you have 1/2 the voltage, 6db less signal.
Quote from: matopotato on May 18, 2022, 04:42:19 PM
Or I misunderstood completely. (Again ;-) )
:icon_lol: :icon_lol: :icon_lol:
No, you've got it absolutely right.. :icon_wink:
P.S.
It's a matter of convension for AC voltage sourses to be depicted with positive and negative poles for been distinguished the current send and return paths inside a closed loop (network)