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Messages - QReuCk

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1
Amplifier Discussion / Re: Speaker size increase...is it worth it??
« on: March 20, 2015, 06:46:05 AM »
Of course, I cannot add much than "read again and carefully what these guys said, they are very well versed in all those stuff", but there is some additional thing that always annoyed me regarding all these db and wattage things:
Rating are already not so perfect for 1W. Still all we have is a rating with a 1W program, while we are often feading them with way more than 1W.
And guess what: I see absolutely no reason why a 25W rated speaker would have the exact same efficiency at 1W and at, say, 20W. It's a well known fact that guitar speakers tend to distort when approaching their limits. It's even considered as an interesting effect by some and guitar speakers tend to be made so that this start of distortion is not destructive for the device. On an electro-mechanical device distortion always equates to lower efficiency. It might be a good thing, though: I suspect this lower efficiency at the limits might be partially linked with cone velocity and as such be more pronounced on those pesky high frequencies - especially with a heavier speaker cone.
So I would say the SPL rating should read nnn db AT 1W and not nnn db/W, and the curve itself should be taken with a big pinch of salt if you intend to use the speaker attached to a power amp that can output close to your speakers rating.
The values might be representative enough if you stay well bellow the maximum wattage the speaker can accept though, but I suspect at least the efficiency in highest frequencies is affected way before what most people have in mind.

I might be wrong though, so wait 'till those knowledgeable guys correct me before making your own conclusions.

2
As an owner of a Tech21 Trademark myself, I can confirm what Roly suspects from the design: they get really hot after a good usage. Never had a problem with mine (which actually is a 120 and is monted vertically with a little more vents in it).

anyway, most important thing to do is to LOCATE where the problem lies. Basic trouble shouting for an amp which has such a complete set of connexions on the back panel would be this:
1° try connecting the preamp out (either effect send or Sansamp out) to another power amp/combo amp/whatever amplified thing. Ear if the preamp is good.
2° try feeding the poweramp with any preamp you can find (effect send or preamp out of another guitar amp or even a mp3 player into the effect return of your amp) see if power amp is good
3° try bridging effect send to effect return with a 1/4 cable see if the effect loop switching and connexions are good. Make this try with and without footswitch plugged in.
4° Also try with and without reverb activated.
5° If you have access to an external speaker, also try with one.

Time being a factor, especially on an amp which by design heats a bit more than most others, we can safely thing temperature is a factor. Well temperature is a factor for purposelybuilt thermal cut out, but it is also a factor with bad connexions (connectors OR bad solder joints). You know things tend to move/change dimensions a bit when temperature increases don't you? It isn't that big a stretch to assume a bad connexion may have turned into an unintended thermal cut out. And is the amp farts instead of just going silent, then I would thing an unintended thermal cut out is more likely than a purposely built one. Just saying...

3
Preamps and Effects / Re: Phabbtone
« on: May 14, 2014, 08:42:49 AM »
I use passive Piezzo occasionaly (on a nylon). I found it kinda realistic if you take care of where you put it on the guitar. I would recommand close to the bridge, as this is where the amplitude of the bass content is the greatest.
Anyway, buffering this signal close enough to the guitar itself (beltpack maybe) is the way to go. I do use my GE7 for this purpose also (adding some clean boost + a convenient cut of 200Hz to prevent uncontrolable feedback to happen), but a buffer followed by a good parametric would probably do the trick better.

4
Preamps and Effects / Re: Preamplifier Input Impedance
« on: April 30, 2014, 08:37:22 AM »
I think I understand where you are going with this page. That's very usefull indeed as except for it and this forum, input impedances are often totally overlooked.

Regarding the resonant peak: I do believe frequency response curves doesn't tell the whole story. For me the "enveloppe" of the resonance isn't the same as one of a non-resonant band. i.e.: What happens after you pick your string (how the harmonics develop and fade out is a bit different for the ones in the frequency peak region and the ones that are out of it). Anyway, I find use for a high resonant peak sometimes. But to my liking, tone and volume on 10 on a strat bridge pickup (well I wired mine to tone pot) and into a 1M input impedance is about as much of a resonant peak I like, and I even find that a little less volume (so less load) and tone (peak shifted to lower freq and reduced in value) might be desirable with some levels of drive in some songs.
As a side note: with standard tone control, a new peak appears in the bass/low-mid region when tone pot is close to 0. I did not really checked the maths behind it, but this peak is clearly audible if you pay attention when rolling down your tone (Fender even made a special tone circuit named grease bucket to prevent that as this peak is far from sounding right).

I don't know if that makes sense, but that's what I hear. I know for sure the ear is much less than a good measuring instrument for these stuff (psycho accoustics, etc...), but my ears happen to be the medium between what comes out of the speaker and my pleasure, so I still have to trust them in some way, even if they are probably wrong. That sure isn't to say other people should do just like me. Their ears are not mine and they probably play differently (better) than me. So I encourage them to experiment with these things for themselves and decide what they want.

Regarding your Gronk-O-Matik: That's too much of a layout for me to fully understand, but I like the idea.

5
Preamps and Effects / Re: Preamplifier Input Impedance
« on: April 29, 2014, 07:19:14 AM »
If Roly checks that topic, I would be very interested in a confirmation that all these diagrams are made without a passive volume and tone circuit in the guitar (straight from pickup to jack). These circuits in guitars will have an impact on these curves so while we are at it, I'll try to explain my thoughts about it (and hope more knowledgeable people than me will either confirm or correct me if I'm wrong).

Regarding the volume pot of your guitar:
Let's assume you have no tone circuit for now or a no load tone pot on 10. With volume on 10, you effectively have the pot value in parallel with the input resistance of the amp. If your volume pot is a 500K, then you have 500K in parallel with whatever input impedance your amp has.
Aside from custom wiring, and other trebble bleed, 2 arrangements are most common:
1° gibson volume pots have the hot from pickup on an outer lug, ground on the ather outer lug and wiper to guitar plug or switch. When the wiper is at half resistance, your pickup is loaded with 250k in series with 250K of the other half of your pot which is in parallel with your amp input. So that's 250K + 1 / (1/250+1/Z)
2° "indonesian wiring": pickup hot to the wiper and guitar plug to one outer lug. When at half resitance, you have 250K in parallel with your amp input which is in series with 250K. So that's
1/(1/250K + 1/(250K+Z)).

Your volume knob doesn't only reduce the amplitude of the signal, it also changes the load of the pickup.

As a side note, I have a guitar without a tone pot. I wired the volume so that it's just a variable bypass to ground (wiper to guitar plug, one outer lug to ground). Then the variable value is in parallel with the amp input and the only thing it does is changing the load. This has a pretty dramatic effect on frequency content in addition to volume (remember electricity loves the path of least resistance), which I happen to like for that guitar because I often need more trebble when the signal needs to be hotter. I think I need to change the pot value though cause the usable tones are more in the lowest half of the range than anywhere else.

Then you enter in the equation what your passive tone circuit does and it's actually another can of worm alltogether. Base line for now is that it also modifies the load in addition to letting a cap bleed some frequencies to ground.

Now back to your concern. By experience, I would say that a too low input impedance will sound lifeless and that a too high one might sound just unmanageable (pretty much what Phatt said really). I would say that combined with the passive volume and tone circuitry, 1M is just fine. That's the value most guitar manufacturers have in mind when selecting what volume and tone pots they put in guitars anyway and we have to assume some of them know their stuff.

6
I don't know for the regulars, but I haven't been visiting in quite some time and enjoyed the read.
If you want both the 3 amp setup and taking it a bit easyer on the back, consider the Envoy 110 instead of the bandit (maybe refit your existing one in a ply cab, and run an envoy in parallel with it).
Tip: Envoy 110's clean chanel does really benefit from either a clean boost or a boosted EQ in front of them in my opinion. The drive chanel will be hissy especially if you use the more gain switch, but you already stated you don't need that.
I know I'm not the only one over here to boost the clean chanel of a transtube.
Some other options that I saw recently would include the H&K edition blue, a Tech21 trademark 60 and if price isn't a problem, then have a look a DV Mark: they make a 120W 12' combo which weight almost nothing. More options are available on the used market (older Fenders, Roland cube 60 blue or JC60, Yamaha GA112...) and as they aren't tube amps, you can have them at reasonable prices.

7
Amplifier Discussion / Re: amps
« on: July 31, 2013, 09:41:24 AM »
In my experience, you can pretty well use an electric guitar amp for amplifying an accoustic, but you'll have to deal with some issues:
1° Electric guitar amps are designed to reproduce well frequencies up to 6KHz. Higher frequencies are highly disregarded in this context. For a metal stringed accoustic, you need up to 12 KHz if you want to hear all the complexity of the harmonics. That's more caused by the speakers than the amp itself, but amps are designed knowing that they won't have to reproduce frequencies higher than 6KHz, and some designer like to purposedly restrain the range in order to give an easier job for the amp. If you have a nylon stringed accoustic, you will barely hear this limitation.
2° Usually, Accoustic amps have a pretty usefull feature to control feedback and prevent it being turned into larsen. These are phase inversion switches or specific narrow Q band-cut filters to cut the larsen frequency. You won't have that on an electric guitar amp. Knowing how to position yourself and your guitar in relation to the speakers and/or inserting an multiband EQ (or parametric if you find one) in your chain can go a long way to not need these features, but these are workarounds.

I personaly use my Peavey Envoy110 when playing my nylon and I am very happy with it. It sure isn't a perfect solution, but it's what I've been using for a few years now and I even had compliments about how "real" it sounded.
I had one of my friend playing through it with is folk electro accoustic and found it didn't sound bad at all. Maybe not all of the chiming top end, but still good enough to not be ashamed playing for an audiance.

You have to remember that a lot of commercially available SS amps for electric guitar are just a power amp and a very transparent preamp (at least for their clean chanels).

But if you want to build something, listen to other guys here, they are super knowledgeable, which I am not. I just like lurking here to learn one thing or two from them and share my very little experience when I think I can help.

8
Tubes and Hybrids / Re: Another cool but dangerous antique
« on: July 31, 2013, 08:53:23 AM »
Found this on the interweb:
http://www.guitar-museum.com/guitar-39483-VINTAGE-TEISCO-AUDITION-GUITAR-AMP-BATTERY-OPERATED

Looks like Audition is/was a local brand of Teisco. Maybe a good start for your searches.

9
Amplifier Discussion / Re: Serious Blocking Distortion
« on: July 09, 2013, 04:56:19 AM »
I'm with stormbringer there:
If you think about it, the real point of SS amps aside from the price and maintenability is the scalability. If for some reason you have your power amp distort, then you miss the biggest tonal advantage of SS amps: they sound almost as good at low level as at near-full volume. The only difference is introduced by psychoaccoustics (our ears do not compress bass and trebbles the same way depending on volume), room reverb (I meen "real" room reverb, you know sound wave bouncing on the walls and the ceilling) and feedback (sound waves from the amplifier exciting guitar strings).
Tube amps sound better at high volume because tube power amps are push-pull stages clipping slowly and symetrically while tube preamps are single-ended triodes clipping kinda slowly and asymetrically (which can sound good to an extent, but doesn't sound quite the same).
Fortunately enough, you can build a fairly pleasing soft symetric clipping into a solid state preamp. You can also put some asymetric clipping if you need it and even design the possibility to mix them together. So there is really no point in trying deliberately to have a solid state power amp sound different depending on the outup volume.

10
The Newcomer's Forum / Re: Peavy Session 400 Problems
« on: June 26, 2013, 04:25:36 AM »
Well, my top on list suspect in that case would have been input jack, but if it does it with both input jacks, that reduces the likelyness of it.
Next suspect would be the connexion between power amp and speaker, especially as the speaker has been replaced: the speaker wires are exposed in an open style combo and the connexion could have been mechanically stressed easyly (as for the input jacks).
So really thoroughly check these connexions (input jacks to preamp board and power amp to speakers).

If preamp and power amp are on different boards, I would also check meticulously the connexion between them.

As it happens after some playing, next suspects on the list would be any solder or connexion near some place where there is heat (probably near transformers, power amp chips, etc...). So check for places on the circuitry that are a bit warm after some playing. The fault could be located not to far from here.

So basically follow Enzo's advice but maybe start with these connexions rather than checking every trace in the circuit. At least that's what I would do.

Pots sometimes crackle and function intermitantly, but dirty pots are usually pretty obvious to spot without even openning the amp, and usually they do their thing either at powering up or just when you turn them up or down.

11
Well, depending on where you measure the original harmonic content, this could very well also be used to prevent intermodulation distortion, not only harshness. But you have to know the more you manipulate the distortion content to remove "undesired" things, the less it sounds like a real guitar through a real amp. Think about the early Metallica layering two harmonized distorted guitars, each of them playing single notes. It has some usability, but it doesn't sound at all like one guitar playing both parts at the same time.

I would fear also the risk of loosing some of the character of the instrument and playing style. This risk could be lowered if the harmonic content you put back comes from the harmonic structure you record from the actual instrument and you keep a lot of information about the transients, but I'm not sure it will sound true.
For fun I watched a video with a guy comparing different guitar tone caps. Not here to debate wether or not caps material make a difference or if this kind of video proves anything, but the video showed some instant bar graph of frequencies amplitude. This gave me the opportunity to see that the enveloppe of each harmonic doesn't follow the same patern: some harmonics will be more compressed or will fade quicker than others. This is really instrument dependant and playing style (right hand technique) dependant. I would fear your compression method could somehow neglect that effect and as a consequence substract some of the character.

Could definitely have a use as a cool effect you activate sparsly though but I'm not sure I would want to base my core tone on that.

12
Preamps and Effects / Re: Clipping theory - a nice find this week
« on: June 04, 2013, 11:56:13 AM »
You know what's funny about it? I too tend to scan forward when I see equations. I noticed the diagrams and thought these where interesting by their own merit because the curves were not what I expected them to be (more precisely, they are not what the typical guitar forum -not this one but you know what I mean - consensus assume them to be).

Then reading this discussion highlighting the non memoryless non-linearity, I finally grasped what you are saying (or what you didn't intend to say but my limitted english made me believe you did :duh ) with your Z-plane and that perfectly makes sense. We always (knowingly so or not) use some sort of fourrier analysis in our understanding of filters, but capacitors do pass intensity based on voltage drop, so they can act a bit different treating complex guitar signals (especially distorted ones containing lots of harmonics) than as pure gain reducer of each individual band.
I yet again cannot make use of that knowledge in practical circuits, but I find it interesting anyway.

13
Preamps and Effects / Clipping theory - a nice find this week
« on: May 31, 2013, 03:33:59 AM »
Hi guys!

I stumbled across this article earlier this week:
https://ccrma.stanford.edu/~dtyeh/papers/yeh07_dafx_distortion.pdf
So I though that was somewhat enlightening and I would share the link here.
It is more of a numeric modelisation project, but the approch they used to understand the behaviour of real life analog devices is interesting, me think.

For instance, look at the sine wave signal response they obtain for the Boss DS1 and for the Tube Screamer.
Typically, pieces of information you find on the interweb tell you that the diode arangement of the DS1 is hard clipping, which is often represented with a perfectly truncated sine wave where it hits the voltage limitation of the diodes. They measured the real device through oscilloscope + fourier analysis and what did they found? Both the OP amp and the diodes are distorting the signal, and both these devices do have a different real life behaviour than the typical representation. The resulting wave form is nowhere near what people usually asume for such devices, and the tone setting parts do not explain such behaviour if you model them as pure linear filters.

I don't exactly know if it really fits in there as the electrical behaviour of each component and arrangement is pretty blured in this "block box" approach. But as it deals with stompboxes, I might be in the correct forum to gather your thoughts about "real life" devices vs "how we assume it should work".

Thoughts anyone?

14
Sometimes I start typing, end up with an indigest page covered with words, and someone comes in, and manage to say the same thing in 2 lines, being far more understandable than my long text.

Maybe I should work on my boss's main recommandation: "learn to be more synthetic in your reports".
 :lmao:

15
Of those amps, the only one I have used is the Fender FM212R.
As far as I know, it is pretty much as reliable as you could get. The one I played on belongs to a music school and has been used and abused not only by guitar teachers and their students, but also by bands who signed a contract for using the music school rehearsal room. I recently someone play bass guitar on this (far from recommanded), and I know this thing has served to amplify voice, keyboards, etc... for years without any problem. Its clean chanel is pretty good once understood the right amount of tone knob on the guitar and EQ settings on the amp and its output volume is more than enough to gig.
The drive chanel can sound decent, but you will probably want to stay away of the "more drive" switch. So consider a good overdrive/distortion stompox to complement it if you need overdriven tones.
Overall and with the exception of high gain settings (more drive + a lot of gain), It is pretty respectfull of the character of your guitar and playing style and does react to playing dynamics, volume and tone knobs variations. But even for rehearsing with 2 drumers I like my Peavey Envoy 110 (40W, single 10' speaker) far better than this one, especially if I put an EQ in front of the Peavey.
In case of problems, a FM212R is on the "don't repair" list for Fender dealers, so if it brakes under waranty they will simply give you another one. When not under waranty, depending on who you speak to, they might not want to spend time on it, although it is pretty simple and as such not that hard to fix (just not economically realistic).


DSP based units such as the mustang IV are, guess what? DSP based. This is a completely different world. When testing them, you should be carefull to test how it reacts to playing dynamics, guitar knobs and pickup configuration, because that's the main weak point of entry-level DSP based units.
If they brake, they won't be repaired and that's not just an economicall decision. Repairing the DSP part is just not feasible by a regular tech. Repairing the power amp, powerinput or jack connectors usually are, but that's pretty much all about it.

My preference goes to analogic SS amps. If you search a good used one, my recommandation would be to seek Tech21 TM120 (discontinued and maybe a bit complicated preamp, but built like a tank and very good sounding - have one myself, which costed me 290€ used, and really like it, especially for live usage thanks to the 3 independant preamps it features and wonderfull tones you can get from it), Peavey Bandit (also on the advanced-circuitry side of the SS type and would require a 12' additional cab to be turned into a 2x12, but steal analog and sounding great). I've also heard good things about Hiwatt Maxwatt 100's and Randalls.

Another option would be to buy a FM212R anyway as it may be the cheapest 100W poweramp with 2 12' speaker you can find, begin with it and if you feel you need something different tonally, you just have to focus on the preamp part (some good analog preamps are available on the market for just a handfull of $ more than a distortion stompbox) and maybe the speakers, but that's not even sure you'll need a change here.

Oh, and if you go to a music store, prepare for the vendor not understanding you, cause they usually are not aware that you can sound good with SS gear too...

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