Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: purpletele on December 21, 2018, 02:25:58 am
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I have really been enjoying the 6 v 6 Plexi, in fact I have two of them.
I saw Phil's version of the Dual 50 and really enjoyed his videos and it inspired me to build #2 unless someone beats me to it.
I have a lot of work projects going on but there is nothing wrong with planning and multitasking.
I have a blank standard size chassis that I have been using and a faceplate template so I'll start with the faceplates.
I would like to try the Metro FX Loop with a variable control. I used the Mojotone on my Deluxe and it is not dialed in very well yet.
Steve, do you happen to have a layer from your Visio files for an unloaded turret board? Maybe I have that already stashed away, looking now.
I am anxious to hear how this amp sounds and performs, but it will be a Design Project for a while
BV
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I can make the Visio file available if you want it.
BTW, your power supply drawing is quite messed up.
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I can make the Visio file available if you want it.
BTW, your power supply drawing is quite messed up.
The PS drawing was a confusing, I'm glad you pointed that out.
I would definately like to use your files if that is acceptable.
Thank you
BV
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Cool beans, I just finished mine up this last weekend, as you may have seen, just gotta get the time to double check the wiring, and then I'll fire it up!
~Phil
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If your Power Transformer is 178V/0V/178V @300ma you will need to modify the rectifier and the bias supply just as pompeiisneaks did. Save the mod pic in his video thread so I don't have to redraw it! :wink:
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What like this?
(https://el34world.com/Forum/index.php?action=dlattach;topic=23799.0;attach=73468;image)
~Phil
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No worries, make sure that cap is X2 class, I lucked out and had a few spares because I ordered one for a previous build and I always tend to order x5 instead of just x1
~Phil
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If your Power Transformer is 178V/0V/178V @300ma you will need to modify the rectifier and the bias supply just as pompeiisneaks did. Save the mod pic in his video thread so I don't have to redraw it! :wink:
That seemed like a strange spec for a transformer, but I think I figured out that is the spec for a 100 Watt transformer.
What is the advantage of having the larger capacity transformer? What does that do to the tone and responsiveness? I am assuming that your design is based upon something around 360V @ 150ma like the Heyboer that Doug carries for a 50 Watt.
I think I would just stay within the original design unless there is real magic that I should consider.
BV
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If your Power Transformer is 178V/0V/178V @300ma you will need to modify the rectifier and the bias supply just as pompeiisneaks did. Save the mod pic in his video thread so I don't have to redraw it! :wink:
That seemed like a strange spec for a transformer, but I think I figured out that is the spec for a 100 Watt transformer.
You are the one who posted those specs in your "Marshall PS.pdf" in your original post. I assumed you would be using that PT. If not, then just disregard all the talk about modifying my circuit. And tell us which PT you will actually use.
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If your Power Transformer is 178V/0V/178V @300ma you will need to modify the rectifier and the bias supply just as pompeiisneaks did. Save the mod pic in his video thread so I don't have to redraw it! :wink:
That seemed like a strange spec for a transformer, but I think I figured out that is the spec for a 100 Watt transformer.
You are the one who posted those specs in your "Marshall PS.pdf" in your original post. I assumed you would be using that PT. If not, then just disregard all the talk about modifying my circuit. And tell us which PT you will actually use.
I somehow aquired a some draft work from Phil, or at least I am guessing that was what it was.
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Fun project you have going on.
I would love to build Steve's dual 50 but add a 3rd channel Fender Twin Reverb tone stack for clean!
Would probably be my dream amp or Island amp.
Mark
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Fun project you have going on.
I would love to build Steve's dual 50 but add a 3rd channel Fender Twin Reverb tone stack for clean!
Would probably be my dream amp or Island amp.
Mark
That sort of sounds like the Fridman BE50, I have seen some folks from Italy working on that design.
I have two cool amps on the bucket list, the Sluckey Dual 50 and the Fowler Prowler or whatever you call that beast.
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I definitely don't recognize that PDF, looks like it was made with diy layout creator.
Phil
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Here are the transformers that I am considering.
The OT is from Antique Electronics. I suspect it is manufactured by Classic Tone. When you search the numbers it directs you to the Classic Tone 50 Watt OT.
Thoughts or recommendations?
Thanks,
BV
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Sounds OK to me.
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What I use for my Hot Rod Plexi 50w is:
From Triodstore:
40-18023 PT
40-18025 OT
40-18058 choke 3hy 250mA DC
or
From CEDistribution/AES/others
P-TM-P50 PT
P-TM050 3K6
Hammond 194G 3hy 250mA DC choke
or Mojotone has a good set as well
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What I use for my Hot Rod Plexi 50w is:
From Triodstore:
40-18023 PT
40-18025 OT
40-18058 choke 3hy 250mA DC
or
From CEDistribution/AES/others
P-TM-P50 PT
P-TM050 3K6
Hammond 194G 3hy 250mA DC choke
or Mojotone has a good set as well
Thanks Mark
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https://hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=Transformers&ORDER_ID=859633435
I see Doug has offered more transformers and has some good Marshall 50w transformers PT & OT as well as choke
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https://hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=Transformers&ORDER_ID=859633435
I see Doug has offered more transformers and has some good Marshall 50w transformers PT & OT as well as choke
I see Doug has a transformer with my name on it.
Also, I worked through a turret board for the Fowler HRM!
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Did you get the file?
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This looks like a really cool project. I always thought a switchable Plexi/JCM 800 preamp would make for an all-around great amp.
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Did you get the file?
Steve,
It appears that the only file that is saved is the first page of the schematic. That is what I received when I imported the drawing, and it is the same page that is in the zip file.
I tried it a couple of times and it does appear to be one page only.
Thanks for trying, I worked through the turret board last night, so that is loaded up waiting for Doug to shovel his way to his shop.
I really don't need the drawing, I'll just do my standard layout and have the circuit board be a rectangular shape. Please save your energy, I may need help somewhere else :huh:
Once I get the faceplate done then I can just reference your drawing, the amp chassis layout will be very similar to Single Channel Deluxe (That amp has been on the local circuit, my friends dig it)
I am going to try to perfect the MV on this amp, I have been 70% successful with MV installation.
BV
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This looks like a really cool project. I always thought a switchable Plexi/JCM 800 preamp would make for an all-around great amp.
Mike, I laid out a turret board last night. I'll let you know how that turns out as far as spacing and such. If it's accurate then I'll send you the file code if you wish.
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It appears that the only file that is saved is the first page of the schematic.
There is only ONE file. It is a multi-page Visio file and you must have Visio to open it correctly. How are you trying to open the file?
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It appears that the only file that is saved is the first page of the schematic.
There is only ONE file. It is a multi-page Visio file and you must have Visio to open it correctly. How are you trying to open the file?
User Error!! It's all there, thank you. I haven't used Visio for quite a while and didn't recognize the tabs.
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use a bassman PT and forgo the crappy cap coupled neg. bias ckt. presuming you'd be using 450-ish volts to the plates?
http://www.classictone.net/40-18094.pdf
--pete
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use a bassman PT and forgo the crappy cap coupled neg. bias ckt. presuming you'd be using 450-ish volts to the plates?
http://www.classictone.net/40-18094.pdf
--pete
Thanks Pete, its probably best if I color within the lines, I get into trouble when I try to do something slick.
I'm not sure what it would look like to forgo the crappy cap coupled neg bias ckt, but it sounds interesting.
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graft in the fender deluxe reverb ab763 bias ckt and PS. e.g., use the JCM 800 PS and add a bias supply that uses a bias tap.
however, if you're not comfortable making those changes, then please disregard the suggestions.
thanks!
--pete
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graft in the fender deluxe reverb ab763 bias ckt and PS. e.g., use the JCM 800 PS and add a bias supply that uses a bias tap.
however, if you're not comfortable making those changes, then please disregard the suggestions.
thanks!
--pete
Pete,
Thanks for the suggestion, I am going to stick with the plan as it exists at this time.
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Master Volume Advice
A continuation of Ed's discussion on MV implementation.
I am working on the faceplates for the Dual 50 amp and I am going to designing a MV on the back panel.
The MV is really important on this amp, whereas the MV on the 18 watt Plexi was not as important.
I am planning on starting with a 250K Dual Pot by PEC utilizing the PPIMV.
If anyone thinks I should try a different value and the Lar Mar method I would welcome the input.
Starting to gain some momentum.
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Metropolous uses the Rich Mod II with a dual 500K pot from PEC. Supposedly, that's the gold standard for PPIMV on a 50 watt Plexi. I have read that it sounds better at low volume than the LarMar, but I have not done a comparison.
What chassis are you going to use?
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Metropolous uses the Rich Mod II with a dual 500K pot from PEC. Supposedly, that's the gold standard for PPIMV on a 50 watt Plexi. I have read that it sounds better at low volume than the LarMar, but I have not done a comparison.
What chassis are you going to use?
Mike,
I have the Metropolous instructions for MV so that is a good call.
I am using a chassis that I have made as my standard, primarily because I like the cabinet that I use to fit it out. The chassis is a blank with the IEC cut out, I get it from a fellow on Reverb, his shop is called Synaptic Amplification, he does nice work.
I attched a photo of my Single Channel Deluxe Reverb in the cradle. I will be using a very similar layout for the Dual 50.
I just finished the first pass at the Faceplate and the Backplate and sent it off to Sandy Henry. I pay her whatever it takes to clean up the alignment issues that I can't figure out.
I am using Adobe Illustrator so I can communicate with Sandy. She uses a different program, but she can read .eps files. She'll send me a pdf of the her corrections and I print it off full size at a Architects office. I cut out the prints and make sure it looks correct. The only critical holes are the IEC and the FX Loop.
That's my method for my standard chassis.
BV
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Sandy Henry Rocks at Faceplates!
It takes quite a bit of design on your own part, but the service and final product make this a fun hobby.