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previous: Terry Jim,I have a Trayno... -- 8/30/1999 11:58 PM

Re: Some quick Marshall Mods...

8/31/1999 12:54 AM

Trace

Re: Some quick Marshall Mods... quote: "I have a Traynor YBA-1 Bassmaster that had a 68K resistor and in my efforts to "Marshallize" the amp I changed it to a 220K. It is my understanding that increasing this resistor value will increase output. Also, I've read others advising to lower the value from 220K to 100k and that would add to the tube's life. BUT, how does either affect tone, etc."         @@@ It does increase the tube life (as I understand it) and it also helps to "brown-up" or "warm-up" the tone of the preamp. If a Marshall has a lot of harsh high end then this helps trim those harsh "highs" I also think that this makes the pre-amp work harder.         q{also, I understand that some people have added a post PI master volume using a dual pot rated at 100k. And I've heard negatives about making the resistors in question the variable type. I'm all ears for someone to clarify this all up.         I've installed these and I have one on one of my own Marshalls. These are simply dual-ganged (two pots back to back so to speak) 100K pots. The "Train Wreck Pages" call for a liner taper but I've use the audio tapers without any problems.     The idea behind this is to keep the phase inverter's tone and in the older 4-input models the phase inverter's tone is pretty important. The phase inverter actually "breaks up" or distorts and if you install a Pre-PI on these models you loose a lot of the tone of the amp (IMHO) When the dual-ganged 100K's are turned to "10" the amp is restored to it's original "fully-cranked" tone (well 220K's would be totally stock but you get the idea         ~~~I don't believe there is much current drawn through these resistors to begin with so am not certain as to the effects on bias. Have not experimented and documented it yet.         @@@ It doesn't really have any grave effects as far as I can tell. Perhapes someone else can elaborate on this more?         ~~~I'd also be interested in hearing more on the 250pf mentioned in item #3.         @@@ I pretty much answered this in the other post but I forget to mention that you can use values between 250pF to 470pF. It really depends on whay you want to hear. I like a 250pF to 330pF in the older Marshalls. I use this on 800's as well but it depends on what someone is looking for.         Another nice touch for the JCM800's (2203/2204)is         1.) Change R6 from the 10K stock value to 4.7K     2.) Place either of the following in parallel to R9 (820ohm cathode resistor)         A.).68uF = very Marshall'esq     b.) 22uF = great for "crunch" or "heavier" tones     c.) 1uF = more Soldano'ish so to speak         If you want a more Soldano-ish tone you might liek to go with C. and replace C1 (.68uF) with a 1uF.             Sorry if I'm rambling...it's been a long day. I hope this helps someone get a little closer to the tone they are looking for. Music is a brotherhood...."Share the knowledge" I always say! (ha, ha)         Hollar back!     Trace