Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Ed_Chambley on February 20, 2012, 10:43:25 am
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Is here a reason why Doug has never made a layout for a 18 watt TMB. Does the tonestack take too much away from the amp? I have never played an 18 watter, but is a single tone preferred by most. What are the advantages/disadvantages? Anyone ever used El-34's instead of the EL-84? I know a different OT would be needed have a 25 watt, EL-34 Deluxe Ab763 with an OT primary 5200 at 8 ohms. Doesn't sound like I thought it would, so I am converting it to 6v6 and adding another OT. Weber has a TMB layout for an 18 watt, but it has 2 inputs. Does anyone have a layout for a TMB using Dougs board?
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http://www.18watt.com/storage/18_Watt_TMB.pdf (http://www.18watt.com/storage/18_Watt_TMB.pdf)
There is a board built specifically for that layout but I can't tell you where. hint...hint...
Or you could roll your own. I think there's even a TMB Lite out there. Lot's of info at 18watt.com.
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http://www.18watt.com/storage/18_Watt_TMB.pdf (http://www.18watt.com/storage/18_Watt_TMB.pdf)
There is a board built specifically for that layout but I can't tell you where. hint...hint...
Or you could roll your own. I think there's even a TMB Lite out there. Lot's of info at 18watt.com.
I am going to roll my own. The Layout you posted is all I need. Thanks. What do you think of the EL-34 idea? I got very lucky a few years ago and bought a box of tubes and there were over 50 Mullards fx2 and about 70 Seimens (sp?) All in the box. I love these things, but don't know what a 18 Watt circuit will do with them.
I have seen the boards and I know where to get one, but I an really enjoying making my own.
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http://www.18watt.com/storage/18_Watt_TMB.pdf (http://www.18watt.com/storage/18_Watt_TMB.pdf)
There is a board built specifically for that layout but I can't tell you where. hint...hint...
Or you could roll your own. I think there's even a TMB Lite out there. Lot's of info at 18watt.com.
You cannot say? I know where and you can get them, in different colors as well. There is still much fun for me in making my own boards. Makes me feel like the amp is more my own.
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What do you think of the EL-34 idea?
That will kinda make it a Plexi. The TMB preamp was modeled after a Plexi or JMT45.
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That is what I was thinking, but I want to do a low voltage version, say 225-0-225 with 6.3 @ 5a and 5v @ 3a. I think I can still use a 5y3 rectifier, but I don't know what voltage I will get at the B+ prior to filtration. I do have a frankenamp with el-34's that is low voltage and El-34's sound really nice. I think this one is about 15 watts, but is more fenderish in the preamp and cap and resister values.
This will be cathode bias I assume. I looked at the layout and it looks like it is.
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On the layout that Slucky posted, there is an ecap value of 500uf/50v. What is a suitable replacement? Also, there is a dual cap can with 32/16uf. Is 32/32uj a good replacement?
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there is an ecap value of 500uf/50v. What is a suitable replacement?
Anything between 50µF and 500µF
there is a dual cap can with 32/16uf. Is 32/32uj a good replacement?
Huh??? Where do you see a 32/16 can on the layout I linked to?
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there is a dual cap can with 32/16uf. Is 32/32uj a good replacement?
Huh??? Where do you see a 32/16 can on the layout I linked to?
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Between the rectifier tube and the power tube. It has a 1k/5watt connected between. What is it if not a cap.
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See c20 on this layout
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That ain't what I posted and it ain't a TMB.
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I understand that, but it is still on the layout, it just has no reference to it. Do you simply leave it out and if so what do you do with the OT wires connected and the resistor?
The reason I looked at the tremolo layout is so I could figure out what it is and what it is for.
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Here's the schematic that goes with the layout I posted. Maybe it will help.
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Steve - in your schematic and layout are the 32uf and 16uf high voltage filter caps NOT in a cap can?
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The TMB schematic I posted clearly shows two cans. One can has 2 each 32µF caps. The other can has 2 each 16µF caps.
The TMB layout I posted shows a can with 2 caps of UNKNOWN values. And there are two each single axial 16µF caps on the board.
Both drawings came from 18watt.com. I know the layout and schematic do not exactly agree. I didn't draw either. I don't know why they are different. Maybe the good folks over at 18watt.com can clear this up. I was just trying to give Ed some info about the TMB. Sorry for all the confusion.
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I think I can still use a 5y3 rectifier
http://www.nj7p.org/Tube4.php?tube=5Y3GT (http://www.nj7p.org/Tube4.php?tube=5Y3GT)
I am not sure that you want to use a 5Y3 if you use EL34's. Maybe consider a 5V4?
With respect, Tubenit
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The TMB schematic I posted clearly shows two cans. One can has 2 each 32µF caps. The other can has 2 each 16µF caps.
The TMB layout I posted shows a can with 2 caps of UNKNOWN values. And there are two each single axial 16µF caps on the board.
Both drawings came from 18watt.com. I know the layout and schematic do not exactly agree. I didn't draw either. I don't know why they are different. Maybe the good folks over at 18watt.com can clear this up. I was just trying to give Ed some info about the TMB. Sorry for all the confusion.
Steve, no confusion. When you posted the schematic it cleared things up. I was having trouble finding a can with 32/16uf. The schematic has 32/32 and the 16's are on the board. No problem. Thanks for your help. I know you did not draw either, but from the 2 I can decipher the build. It is not really a difficult build, but there are some strange values in the layout listed in the tremolo layout which is the only place I can find the value of the cap can.
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I think I can still use a 5y3 rectifier
http://www.nj7p.org/Tube4.php?tube=5Y3GT (http://www.nj7p.org/Tube4.php?tube=5Y3GT)
I am not sure that you want to use a 5Y3 if you use EL34's. Maybe consider a 5V4?
With respect, Tubenit
Yep, already realized that. I was thinking 5u4gb. Kindly tell me about the 5v4 if you would.
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I built the original 18 Watt Trem into an old Ampeg cab with a 15" Big Ben. It's one of my favorite amps.
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I built the original 18 Watt Trem into an old Ampeg cab with a 15" Big Ben. It's one of my favorite amps.
Never had any luck using 15's. I just sold my last jensen 15. What layout did you use? I'll bet looking at your builds you did not use any multi cap cans. I have heard conflicting info on this topic and I know what Merlin writes, but I have built many marshall type builds using cans and I cannot tell any difference. I must not have the ears to hear things such as this.
I love the look of the old Ampeg. Been trying for years to get a reverbrocket from a friend. He never plays it, but I borrow it from time to time.
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I used my own layout on everything I built. I'm also a huge fan of cap cans, especially those blue 32x32s. I prefer to use the cans if space permits. Better look again. The cans are in most of the stuff I built and also most of the stuff I restored.
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I used my own layout on everything I built. I'm also a huge fan of cap cans, especially those blue 32x32s. I prefer to use the cans if space permits. Better look again. The cans are in most of the stuff I built and also most of the stuff I restored.
Me too. I prefer the look. Also it is very easy to place them where your wires can be short. Something about the cans sitting on top of the chassis looks cool to me. I usually use the blue FT caps unless I am building a marshall type amp. I use solen caps in marshall builds, so I use the black JJ's. In this project I am going way different. Sozo sent me some free blue caps. Suppose to be like the like 60's mallery's. Everything is going to be blue. I have even got some blue leather from a friend who has an upholstery shop to cover the head cabinet.
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I am getting ready to punch the chassis for El-34's. Other than the difference in wiring up the sockets between EL-84 and EL-34's, the screen resistors for 84 on the schematic I am using the grid resistors are 8.5K and 34's are usually 5.6k. Will it make much difference? Also, the OT is 8 Ohms at 4900 and an 18 watter has no NFB. The layout Slucky posted above is the general layout I am using. If I wanted to add NFB, how would I go about this? I attached the layout again and as you can see the grid resistors are on the board and I thought it best to place them directly on the tube.
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Great layout, but I'm interested in the same TMB layout but WITHOUT the Master Volume... If one of you has it that's great! I've just received a friend's 18w TMB and he has a high squeal on the treble and mid pots... It starts above 2/10 on those pots and the more I go up the less volume the amp puts out. Never seen such an issue on an amp...
So a good layout would be good, and I could probably better his grounding scheme and stuff. He did some poor wiring work on this one... :embarrassed:
Thanks!
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I built this layout without the master and used EL-34. Now it has KT-66, cathode biased. Removing the. master is no big deal. Look at it close and you will see how.
If you do build it, use a large chassis. It will help with a food ground scheme. My first one squealed. I took it apart and rebuilt it in a full size marshall JTM-45.