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Post by warmstrat on Dec 1, 2007 15:13:56 GMT -5
This is so far a purely theoretical question, but i might cram it into my strat at some stage (if there's space after doing JohnH's "Dual-Sound" mod...)
But here's the question... What is there to be gained (awful pun) from installing some sort of active buffer or preamp (is there a difference??) in the guts of my guitar?
I have heard many things about this, including that it will: 1) enable me to drive the input stage of an amp harder 2) boost high-end signal lost in cabling and wires 3) reduce hum and interference
How much of this is true/possible/desirable? What options are there?
Thanking the fellow 'nutz in advance...
Sir Thomas "Warmstrat" the Fearsome, esq.
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Post by JohnH on Dec 1, 2007 16:25:21 GMT -5
Have you seen this thread:? guitarnuts2.proboards45.com/index.cgi?board=schem&action=display&thread=1159677238&page=1Ive built several buffers with and without gain, into guitars and also into cables. Some of my guitars sound beter with and some without. Id recomend the cable buffer project to try it. Its cheap and low risk and gives you all the same benefits of enhanced treble response, before comitting to a built-in. As to buffers with gain - Ive done this too, but have come to the conclusion that unless you have very weak pups, Id rather have the gain built into a stomp box where I can hit it without missing a beat. John
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Post by warmstrat on Dec 1, 2007 17:07:13 GMT -5
As to buffers with gain - Ive done this too, but have come to the conclusion that unless you have very weak pups, Id rather have the gain built into a stomp box where I can hit it without missing a beat. As in a "booster" pedal?
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Post by JohnH on Dec 1, 2007 17:10:37 GMT -5
yup J
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Post by warmstrat on Dec 1, 2007 17:16:42 GMT -5
I listened to your sound samples... and i like it.. I figure you can alwys nuke some of that treble with your tone knob if you like, whereas to add treble after the fact is quite tricky... Your cable version also looks pretty neat - can we include an LED to show that its all working on the inside? (remember, this is all still theory - I have no _immediate_ intentions of building one of these...) And my list of "benefits"? Are they valid? Besides the treble gain , which I now have heard for myself...
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Post by JohnH on Dec 1, 2007 19:07:43 GMT -5
You can add an LED to the buffer cable battery box. But even a small LED will take 20x the current draw of the circuit. Still not much though. The circuit uses of the order of 0.1mA while and LED needs about 2mA. The blue ones do look cool though, and the power is all engaged when the cord to the amp is plugged to the box.
Your benefits are right - noises can be reduced a bit, particularly 'microphónic' thumps and bumps when you move the cord. Hum reduction is probably not so much, except if you use a bad cord.
John
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Post by warmstrat on Dec 2, 2007 20:27:51 GMT -5
Hmmm... It looks simple enough to maybe just give it a go, whether or not i end up using it....
>Does the box at the end require any sort of shielding? >Can we switch it on and off, if, say, one wanted a muddier "vintage" sound?
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Post by JohnH on Dec 3, 2007 0:28:49 GMT -5
The one I currently have is built into a plastic box. Theres no noticeable interference, so long as the cord is shielded (two core plus shield, usually used for microphones), since the whole signal is low impedance. and has enough grunt to squash induced noise.
The active component is in the guitar-end jack plug, so to switch it off youd have to get something there. Easier just to change to a normal cord. Alternatively, if in the guitar, you can switch it about a 1nF cap between jack hot and ground before the buffer, it will replicate about a 25' cord capacitance.
John
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Post by warmstrat on Dec 3, 2007 7:49:01 GMT -5
Or i could just use this here tone knob that Mr. Fender so kindly gave me...
yeah?
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Post by warmstrat on Dec 3, 2007 7:54:20 GMT -5
I thought i had a handle on the situation here... but now i'm confused...
Does this buffer circuit add or remove anything from my signal at all? In a nutshell, does it EQ at all or anything to boost treble? Or does it merely counteract the treble-sucking effects of guitar cables? I thought it was the latter, but now i'm not so sure...
*feels stupid*
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Post by JohnH on Dec 3, 2007 14:24:45 GMT -5
You have it right - the buffer adds no colouration, it just stops the cord capacitance from affecting the signal anywhere downstream of the buffer (and the buffer is effectively at the guitar, for both built-in and buffer-cable types). So if you want to have the buffer in place, but alos have it sound as if there is a cable present, you have to switch in a cap upstream of the buffer, ie at the guitar, or just change to a non-buffered cable.
Johh
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Post by ashcatlt on Dec 3, 2007 16:45:34 GMT -5
The DC blocking caps on either end of the circuit (the only caps in john's schem) will roll off some low frequencies, but I'm sure john has chosen values well outside the range of desirable guitar frequencies. Question is, would it have a noticeable impact if used on a bass?
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Post by JohnH on Dec 3, 2007 20:45:51 GMT -5
The input and output caps on the buffer and buffer cable were intended to be reasonably generous, to have a negligible effect on bass.
For the buffer, with its 22nF input cap and 390nF output cap, I reckon the loss is about 1db below about 20Hz, when driving a load of 50k. More typically, amp input impedances would be more than this, so would lose less bass.
If however, one wanted a buffer to drive bass into say, a line input of 10k, then I’d want an output cap increased to about 2uF and the output source resistor decreased to about 15k.
John
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Post by warmstrat on Dec 5, 2007 13:46:41 GMT -5
The site that JohnH credits in the original thread on this topic states that
"Another advantage of a preamp is that the famous "loss of highs when you turn down the volume control" effect goes away. This is the effect that folks attempt to compensate for with a small capacitor across the volume control. "
Is it therefore worth omitting the treble bleed resistor/cap combo in "strat dual-sound" if I do want to use this cable? I wouldn't want to turn the volume down and inadvertently boost the treble to insane levels (and yes, I do a fair amount of "violining" and volume swells without a volume pedal, so it is important).
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Post by JohnH on Dec 5, 2007 14:51:58 GMT -5
If you were always going to use a buffer, then the treble bleed is not needed, But having both does not go insane, it is a fairly small effect giving just a bit more 'cut' to the sound. I might do a few tests with my Dual sound (which has the bleed) and the buffer cable, at reduced volume. At full volume, the treble bleed has no effect.
John
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Post by warmstrat on Dec 6, 2007 16:02:39 GMT -5
Ok.. sounds good, seeing as i'm rapidly becoming a JohnH fan Let me know how they sound, if you do go ahead...
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Post by JohnH on Dec 7, 2007 7:35:33 GMT -5
Well I had a go at that, so cop an earful of this: www.soundclick.com/player/single_player.cfm?songid=6049634&q=hiIt features the 'Dual sound' Ibanez Roadstar 'Strat', through a buffer cable. The first part is full volume, with bridge/middle in parallel, followed by bridge. middle and some neck in series. Then its the same again at reduced volume, and hence the treble bleed is working. It was interesting - I really like the sound of the buffer with this guitar, particularly the series sound which is not as clear without the buffer. The reduced volume part is a little thin, with treble bleed and buffer together. It makes me think Imight take the treble bleed out and do a built in buffer. One useful comparison is to boost the playback volume for the second part, so you can hear the tone differences without the volume difference. This recording has somewhat better technical content than my earlier ones. It is miced from my DSL401 using a Shure PG58 mic into a mixer and then the PC. The amp is set very clean, which is an unusual state for my amp. cheers John MMMV with the buffers - I prefer them in most of my guitars, except for my Les Paul which sounds better without one IMO.
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Post by warmstrat on Dec 9, 2007 14:46:52 GMT -5
I see. (hear)
It's not too horrific, though... i could just tweak the tone knob down a bit, then i'd be fine with that. Thank you for your efforts!!
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