Alguien escribió:I would start with some things like this
Change the 10K resistor on V1B. The more you lower the value, the more of an increase in gain you will get. 4.7K seems to be what the amp likes best, but you can go as low as 1.8K(more SLOish). You could use a switch to flip between a few different values, or have the tech add a small 10k trim pot and you can make it variable to find what you like best! (When prototyping amps, that is the method I use. Rotate the pot til it gives you what you want, measure the value, then just remove the pot and add the fixed resistor. Awesome way to work!)
You could add a bypass cap on that resistor also. Try a 1uf. Also try throwing a bypass cap on V2A's cathode resistor.
Ditch the tone stack slope resistor and go with a Soldano value(47k). This can also be put as a pot on the amp and tweaked for a variable midrange!
Change the value of V1A cathode bypass cap from .68uF to 1uF.
Change the resistor between V1B and V2A that goes to ground (470K) to a 1 meg. Change the bypassed resistor in the same area to a 220K or 100k. This will let a ton more level go to the next stages, instant gain increase.
Also, you can remove that cap bypassing the resistor, and see if you like it(or add a switch).
All of these mods(other than the tone stack mod) should be done one at a time. If you do everything at once you may not like the results. Start slow and work your way up.
Válvulas de previo en un JCM800 para tener mas ganancia
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¿compañero lo modificaste? yo he hecho dos de estos y he estado recopilando info, todas las mod que he visto apuntan siempre al segundo triodo, resistencia de su catodo de 10k bajarla de valor, hasta un maximo de 1k8, o incluso, poner un condensador en paralelo con este de 220nF o ir probando otros valores.
llevo dos meses recopilando info sobre este preamp en el cuartito del diyer que hay verdaderos crack, en esto los argentinos nos superan jajaja, hay muchas formas de subir el gain, todas parten de achicar la resistencia de grilla de las etapas o achicar resistencias de catodos o, poner condensadores en serie, a mi la que mas me tienta es la del segundo triodo, pero tengo que desmontarlo para probarlo.
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