Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Madison on August 28, 2011, 12:56:41 am
-
Here it is.
The "PLXSE"
Little gain monster!
I don't think I would want any more gain.
It's over the top with a LP;have to turn down the preamp a bit.
With a Strat or Tele it's just about right.
Really sounds good with my old Charvelle metal beast guitar.
It's got a 8" speaker in it to make it compact.I think a 10" could fit with some finagling.
VVR is surprisingly good!
Thanks for all the tips, ideas, and sharing your wealth of knowledge.
I'm not worthy :worthy1:
-
NICE :thumbsup:
-
Nice looking amp!
-
Absolutely beautiful! I love your wood cab. Very very nice job with it. I'm impressed!
With respect, Tubenit
-
Nice. I'm just a little curious about part of your circuit. The fourth tube sections grid leak resistor is connected to the third tubes cathode. What does this do? I'm used to seeing that 470K resistor going to ground. Doesn't this put a positive voltage on the forth tubes grid? What's the voltage on the forth tubes grid and forth tubes cathode?
-
Nice! I'm humbled by the woodwork!
-
Very, very clean, nice build! Impressive woodworking there. Well done!
-
Great work! The circuit looks interesting, thank you for sharing that.
/Leevi
-
:m11 :m11
-
Love the cabinet, beautiful!
-
WOW!!! some great talent on this forum. Beautiful job.
-
:headbang:
Nice job!
-
Well done!
I bet that would sound awesome through a 4x12 cab.
-
Madison, how did you make that tube chart? Punky
-
Really nice work! Just the cab looks great. Any gut shots?
Nice. I'm just a little curious about part of your circuit. The fourth tube sections grid leak resistor is connected to the third tubes cathode. What does this do? I'm used to seeing that 470K resistor going to ground. Doesn't this put a positive voltage on the forth tubes grid? What's the voltage on the forth tubes grid and forth tubes cathode?
IRRC what you're looking at actually is local feedback around the 3rd gain stage. Depending on voltages, the 4th stage probably is biased relatively "hot". Madison, can you post voltages? Especially the 3rd stage cathode & plate, and cathode and grid of 4th stage?
Jeff - I can tell you that Madison faithfully followed a proven circuit.
Madison - is your feedback resistor really 1.5K, not 15K? Seems like a much larger percentage of NFB than the circuit you started with. Also, how did you come up with 56K for the power tube's grid return resistor? The base circuit had a 250K Master Volume pot there. I understand why VVR replaces the MV, just wondering about the relatively low value for the grid return resistor.
Most importantly - does this meet the customer's needs/wants?
Thanks for sharing your work,
Chip
-
Nice woodworking Madison! You might consider a cover if you pack it around any; nice woodwork like that gets dinged up much easier and often than you might think (I know this!). Regards
dennis
-
Madison, how did you make that tube chart? Punky
Punky, I used Visio to make these old Fender style tube charts. These are totally made inside Visio but you can easily put any image onto the chart.
-
Good stuff Madison! You got this done pretty fast!
-
That looks killer! Very nice work!
Any chance we could see the guts?
-
Would you be so kind as to explain how the chassis is mounted? :dontknow:
-
1st off, thanks!
Seriously, this would not be possible without Mr. Hoffman's generosity and the gang.
>> how did you make that tube chart?
I found a few on the net and I think Steve was nice enough to share his with me way back.
Then I went into Fireworks (like Photoshop) and decided to make my own to get really clean hi rez to manipulate.
>>The fourth tube sections grid leak resistor is connected to the third tubes cathode. What does this do?
Chip covered it, thank goodness!
I kind of get the concept but not skilled technically enough to explain it as eloquently as he did!
>>Madison, can you post voltages? Especially the 3rd stage cathode & plate, and cathode and grid of 4th stage?
No time to.It's gone.
Dumb, I know all about it.
>> is your feedback resistor really 1.5K, not 15K?
1.5K was a happy medium for me
YMMV.
>>how did you come up with 56K for the power tube's grid return resistor?
Circuit didn't like going above that level.
>>meet the customer's needs/wants?
Me thinks so.No news is good news round these parts.
>>Any chance we could see the guts?
This thing went though a bunch of changes.Flat out odd bizarre layout in some places.
But, it sounded great!(for that sort of sound)
It was also dead quiet.
I have enough stuff laying around,I think I will make a 6v6 head for myself.
That one will be perfect and I'll share.
>>explain how the chassis is mounted?
I rolled my own chassis on this one.(I don't recommend it but I did it for kicks).
The front, bottom, and,rear 1 piece of aluminum bent to a "U".
The sides are wood.
The 4 cab cleats support the underside of the chassis.
The speaker baffle has a lip to keep the chassis from falling out the front.
The rear panel is about 1/2 inch thick and the top 2 screws thread into the chassis.
The tolerances are tight!
It's a lot of work.
I''d suggest chassis straps if you are in a hurry and plan REALLY well where to drill.
Miller time.
Peace all.