Tube Amps / Music Electronics
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|3/3/2005 5:37 AM|
|pierre debs||Re: Completed my 5E3x2 - now modding too|
I hate to bust your bubble, but if you think a CC resistor used in the Paul C. Mod is going to change the tone or lower the distortion you should maybe do some more research on tube electronics before you make amps to sell them.
Do you at least know what the Paul C. mod is actually doing?
good luck, Pierre
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|3/3/2005 7:20 AM|
In had a 5E3x2. Not enough clean headroom. The extra two 6V6 tubes don't clean up the sound, it's just a little louder.
Replaced it with a 5E7 Bandmaster. I'm very happy now.
|3/3/2005 9:30 AM|
yeah, I built the bandmaster too, and am very happy with it. I do like the bandmaster 5E7 just the way it is... Punchy! Great sounding amp.
I want to experiment with the 5E3x2 design because I feel I can learn more about design and eventually have a cool (4) 6V6 amp with a unique sound. I was thinking more like deluxe that breaks up a little later - one that cleans up more nicely than it does now when the volume is rolled back.
I am confident I will get there eventually.
|3/3/2005 9:24 AM|
I did not intend to imply the CC resistor in the paulc mod was going to change things nor do I know all there is to know about phase inverter circuit design. I am learning a lot from the forum.
I feel your other comments uncalled for and don't deserve a reply on a public forum. Feel free to email me directly if you wish to continue this conversation.
|3/3/2005 11:58 AM|
|Bruce /Mission Amps
If and or when you get around to doing the fixed bias mod, I think you "will" hear a little difference between the cathode biased PI and the fixed biased PI mod you made.
After the fixed bias mod you should also lower your power tube's plate voltage a bit as the fixed bias mod increases the plate to cathode voltage of the power tubes by the same amount of the old 6V6's cathode voltage.
Getting the power tubes cooled down a bit with the fixed bias mod will also increase the output a little and clean up the tone a bit.
So would increasing the resistance value of the power tube's cathode biasing resistor. Do not go over 220-250 ohms as it really starts sounding way different then a BIG ASS 12 watt tweed Deluxe.
Using the choke instead of the dropping resistor also adds a little clarity to the amp but again at the expense of increasing the idle current of the power tubes... so adjust the bias so they are idling around 9-10 watts each.
Right now, all four Chinese 6V6s could be running close to their limits in DC bias, closer to 12-14 watts each.
My personal opinion is that if you want it a little cleaner, just use two 12AY7s.
Only one triode of the second preamp tube is running with any gain.
Interestingly, even though the mu of a 12AX7 is 100 and the 12AY7 is around 43, the stage still has enough gain to turn the power tubes inside-out with a 12AY7.
|3/3/2005 12:18 PM|
Spinning a little off of what Bruce said, I have a stock Mission 5E3 (2x6V6, not the 4x6V6). If I use two RCA 12AY7 tubes, I have a lot more clean headroom. In fact, for a small studio pedal steel amp, I use my 5E3 with two 12AY7s and two GE 6L6s and a 15" JBL. I get plenty of clean headroom almost all the way up, even with a VERY powerful Cougar pedal steel single-coil pickup (over 17K and similar to an old Sho-Bud pickup) running full bore without any volume or tone pot to slow it down.
On the other hand, with a standard guitar pickups I do not get "tremendous distortion" with the stock amp on 3 like you are getting. How hot are those Dimarzios and other pickups you are using???
|3/3/2005 1:40 PM|
The pickups are close to "low" (around 8-9K) standard PAF output with the exception being the dimarzio air norton in the bridge position of the dean is hotter, what I would consider a "medium" (13-14K) output humbucker by today's standard (hotter than a PAF). The amp obviousely sounds cleaner with the single coil guitars. I know resistance of the coil does not directly translate into output but most people discuss pickups that way.
I tried a 12AT7 for the V2 and that helped a lot during my lunch hour. But I only had a couple minutes, so had no time. Will try some more combinations tonight and report back.
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