I disagree. You do know that one of the most famous guitar amps is Fender's The Champ and it's 6V6 SE, right?
I don't see how just because guitar amps using certain tubes that they automatically monopolize the usage. It's like saying just because PA speakers use horns then they can't be used in home audio. It's really about how the tube is being used in the circuit if implemented correctly.
.....Amps from 50s use 6V6 for guitar trad. jazz, soul music etc....with very nice sound. Not like 6L6, EL84 /Beatles's VOX/, EL34, 6L6 /Led Zeppelin's Orange, AC-DC's Marshall...../ IMO, these tubes with sharp sound aren't for really true sounding...again IMO. If You have interest to make the difference, You can make similar amps with different tubes of them....I made more than 50 SE /I also think PP doesn't sound real like from live jazz, classical instrumental concerts/ for a more of 10 years....https://picasaweb.google.com/109570777566485968551/Amplifiers
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Tubes don't have a "sound". Circuits do... especially if you operate them outside their most linear working range...
I have to disagree! Why does the sound of my amp change when I roll tubes? I'm not circuit rolling..
Tubes, caps, resistors, OTs, wires, speakers, magn. heads and bands, phono needles, records, Ge and Si transistors...... .....have own "sound".....
A circuit intentionally designed to create distortion (such as many guitar amps) become dependant on tube parameters.
Tubes have a roughly +/-20% manufacturer tolerance.
Roll tubes and you change teh relative loading of stages by as much as +/-20% if the subsequent load (eg.Grid resistor) approaches the rp of the tube rolled (RP ~=rp).
Designe a circuit with RP >> rp and you wont see much difference while rolling tubes (so long as the same number type is used, ie no 12AU7 swapped for 12AX7).
Tubes have a roughly +/-20% manufacturer tolerance.
Roll tubes and you change teh relative loading of stages by as much as +/-20% if the subsequent load (eg.Grid resistor) approaches the rp of the tube rolled (RP ~=rp).
Designe a circuit with RP >> rp and you wont see much difference while rolling tubes (so long as the same number type is used, ie no 12AU7 swapped for 12AX7).
I decided to try this schema:
And at VERY low levels it sound as it should but when I raise the volume a little the sound get distorted.
When messauring the current at the cathode,it is at idle 35mA and if I raise the volume it goes down to zero...
Any one can help on this?
And at VERY low levels it sound as it should but when I raise the volume a little the sound get distorted.
When messauring the current at the cathode,it is at idle 35mA and if I raise the volume it goes down to zero...
Any one can help on this?
I soldered a Rk and an elyt over it and injekted the signal in G1,with an 6C45P and have listened some,the Va is about 300v and it sounds quite good...
Guitar amps are designed, intentionally or accidentally, to be very sensitive to the parameters of each valve. For example, they typically use very high value grid stoppers so the HF rolloff of the circuit is not determined by intentional filters or the OPT but by the combination of grid stopper and Miller capacitance. Miller capacitance is set by grid-anode capacitance and voltage gain, both of which vary somewhat from valve sample to valve sample. This would be very bad design for hi-fi but is accepted as the norm for guitar amps. Why such large grid stoppers? Either deliberate (to encourage tube rolling), or accidental (didn't realise what would happen), or unavoidable (poor layout wth long unscreened wires leads to HF instability without them).
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I read in a book (who does that anymore...) that a guitar amplifer design was published with the use of largish (68k) grid stoppers and everyone else in the industry copied the 'error' -
The 'classic' guitar amps had two inputs per channel, separated by 68k stoppers. One of them has a 1M grid leak to ground that gets shorted when not plugged in, effectively turning the 68k grid stopper into a grid leak to ground. In others words, a high (1M) impedance input for passive guitar/bass pickups and a low (68k) input for low impedance sources like organs. These amps were made for the whole band, not just for the guitar player.
What do you do when you make an amp just for guitar? Leave out one input (and leave the other 68k stopper...).
I must admit that I kept the 68k grid stopper in my single input amps as well 🙄
What do you do when you make an amp just for guitar? Leave out one input (and leave the other 68k stopper...).
I must admit that I kept the 68k grid stopper in my single input amps as well 🙄
Dunno. The AX84 HI-octane has 220k grid stoppers. Nothing like reffing an engine with the brakes on. 🙂
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