Easy way to cure a scratchy voice coil in a guitar speaker

Posted on 2 CommentsPosted in Amps

I recently had a problem with a Music Man HD130 amp (the one Mark Knopfler used in the early days of Dire Straits). One speaker was creating a scratchy, distorted sound, surprisingly only at very low volume while it was fine at medium or high volume. I managed to cure it with an easy trick, nothing too special or secret but nevertheless something I want to share in case someone runs into similar problems with his amp.

When I removed the speaker to have a closer look at what might be wrong with it, I immediately noticed that infamous scratchiness when moving the cone carefull with two fingers. It was worse when pushing more on particular places while it disappeared when doing so at some other spots. I quickly came to the suspect that the problem came from “standing” upright for decades (it was a 1976 amp with original speakers). The voice coil is not really a heavy part but still it has some small weight, and after years this weight can deform the cone slightly so that the voice coil scratches on one side. For the same reason you should always store speakers horizontally but who stores a combo amp or a speaker cabinet this way?

mm-amp-speakers
The speakers after turning and swapping – the two ‘Music Men’ on those stickers with their heads down now – but the speakers feel happy again

The solution was very easy and inexpensive, even without any costs at all: all I had to do was turning the speaker for 180 degrees, so that what pointed to the top became the bottom end. I did the same with the second speaker, not only to prevent similar problems with it in the future but also to make the connectors of both speakers look to the middle between the speakers again, which means I also swapped the left and the right speakers. Hopefully it will work fine for the next 41 years now 🙂

Of course this easy fix does not always work, if the cone or the voice coil is damaged only a recone job will help. But before doing so you should give it a try.

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Strange guitar sound on the Werchter 1981 recording – Did Mark mix direct out and microphone?

Posted on 5 CommentsPosted in Amps, Dire Straits/ Mark Knopfler live pictures and videos, Mark Knopfler gear

On July 5, 1981, Dire Straits played on the Werchter festival in Belgium. The concert was broadcasted on the radio and on TV and is one of the very few soundboard recordings from the 1980/81 On Location tour.

There is one thing that always strikes me about that recording: Mark’s guitar sound was what I’d call ‘strange’, and completely different from all other recordings of the same tour we have (and there are many…). It had a very different, harsh kind of treble. To my ears it sounds like a direct out of the amp, and not like the mic’ed guitar speaker you would expect here.

You will probably know that a typical guitar speaker is a ‘woofer’, a loudspeaker aimed mainly at low and midrange frequencies. It has a pronounced treble roll off, which means it hardly produces high treble frequencies over maybe 6 kHz. For this reason it strongly colours the sound; it automatically filters out unwanted harsh, crisp frequencies. Without the guitar speaker especially a distorted guitar would not sound as we all expect it to sound. For this reason there are – unlike in a PA system – no tweeters (high frequency speakers) in a guitar cabinet.

celestion-graph
Typical frequency response of a guitar speaker

What is strange about the Werchter guitar sound is that I feel to hear exactly these frequencies that should not be there. How is this possible, as we know that Mark of course used guitar speakers on this tour, Marshall 4 x 12″ cabinets to be precise? And on all other recordings from the tour the sound is not like on this one.

It seems unlikely to me that they had a completely different setup for this day – especially as Mark’s live sound required a full effect rack that is not easy to substitute. And even if a guitar speaker suddenly fails, you can simply put the microphone in front of another one – there are four of them in each cabinet! The only theory that makes sense to me is that there was a second signal path involved, one without the guitar speakers. This ‘direct out’ was blended with the signal from the microphones/speakers. One possible reason to do so might be that this way you have more high end and low end to enrich the ‘normal’ sound of the speakers to a desired extend.

I guess for the radio/TV broadcast the concert was mixed separatedly from the PA mix, most likely by engineers of the broadcasters . This is not unusual, you normally want to mix to a much wider stereo signal than you’d do for a PA system. And the sound guys responsible for this mix simply used the direct signal rather than the mic’ed speakers signal, they maybe did simply not know why there were two different sources and what to do with these.

Interestingly the youtube video of this concert includes a few songs that were missing on the radio/TV broadcast. These came from an audience recording in bad quality (see video description), but you can clearly hear that on these songs the sound is very much as it is on all other recordings from the tour, not as thin and trebly as on the radio mix!

Of course this is speculation but if I am right indeed it tells us something about the way Mark created his stage sound on this tour (or even on others, too ??) .

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The Peavey Deuce VT – David Knopfler’s amp with Dire Straits

Posted on 19 CommentsPosted in Mark Knopfler gear

This blog post is not about a Mark Knopfler amp but still has a clear connection to Dire Straits: the Peavey Deuce VT was the amp that David Knopfler played on stage with the band between 1978 and 1979, and thus contributed to the band’s unique sound.

Note the red light which shows that the effects channel is activated

 

The Peavey Deuce VT was built from 1978 to the early eighties. Before, a similar model called Deuce (without the VT) was available that had – besides various other technical differences – a tremolo effect instead of the phaser.  As a combo with two 12″ speakers, it has similar dimensions as the Fender Twin Reverb or the Music Man HD 130 212 that Mark played at the same time. In fact David started to play the Peavey at the same time as the Music Man appeared for the first time, in late 1978. Before (mid 1978) both Mark and David were seen with Fender Twin Reverbs on stage. I assume both were bought together when they felt they needed to upgrade their equipment for the following tours.

The Peavey Deuce is – just like the Music Man – a hybrid amp which means the pre-amp stage is solid state, while the power amp has four 6L6 tubes. Today solid-state is considered to be inferior because of the harsher distortion compared to a tube, but back then it was almost high-tech, considered to be more reliable than an all tube design – no crackling noises, no whistling pre-amp tubes, less danger for a failing tube in the middle of a performance. The amp is bulit like a tank, solid and heavy, suited for professional usage on big stages.

While Mark’s Music Man is basically an upgraded Fender Twin Reverb, with the same controls, the Peavey Deuce VT has its own layout: two channels (Effects and Normal) , built in reverb (works on both channels) and the phaser effect (effects channel only). On the left we find four input  jacks, two for the effects channel, one for the normal channel, and one to use both channels (together or switchable with a foot switch).

The Normal channel has a control for pre gain (gain before the EQ section), bass, treble,  and post gain (after the EQ section), the Effects channel has controls for pre gain,bass, middle, treble, post gain, and color and rate for the phaser. The phaser of the Deuce VT is said to be really good sounding. The phaser we hear live on the songs Down to the Waterline or Once Upon a Time in the West might be from the Deuce, but some sources also claim that a MXR stomp box was used for this matter. However, many pictures from this time seem to prove that David’s guitar cable went directly into the Peavey,  so live it should come from the Deuce.

Finally we have  a Master section on the amp that has only one control for the reverb which affected both channels.

The four 6L6 tubes creates an output power of 120 watts. Most amplifiers in the pre-amp section are ICs (TL 072 or 478).

The amp was optionally available with heavy-duty speakers called Black Widow. These are much heavier, more solid and can handle more power  than the stock speakers. I know from David himself that his amp had  these.

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