Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: guntherbuffalo on March 12, 2014, 05:47:13 pm
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Hi, Has anyone build an Atlas Tweed? I am told it is just like a Matchless spitfire but with 6v6 power tubes. I have a schem but was wondering if anyone knew of a layout?
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Are you referring to the old Gibson Atlas amps? If so, never seen a layout. Can you share your schematic?
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Maybe this one? :dontknow: (http://www.tdpri.com/forum/attachments/shock-brothers-diy-amps/21509-anybody-ever-build-atlas-tweed-atlastweed-jpg)
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That's the one!
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Alternatively, how much would need to be changed to build a spitfire with 6v6 power tubes.
The Spitfire layout I have been looking at is the Ken Watts one:
http://www.turretboards.com/layouts_schematics/matchless/spitfire_watts_layout_current.jpg (http://www.turretboards.com/layouts_schematics/matchless/spitfire_watts_layout_current.jpg)
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Hi, Has anyone build an Atlas Tweed? I am told it is just like a Matchless spitfire but with 6v6 power tubes. I have a schem but was wondering if anyone knew of a layout?
Never see a layout for Gibson amp.
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Doug has a HUGE Library of Schematics!
http://www.el34world.com/charts/Schematics1.php (http://www.el34world.com/charts/Schematics1.php)
schematic and layout here: http://www.el34world.com/charts/Schematics/files/matchless/matchless_spitfire.pdf (http://www.el34world.com/charts/Schematics/files/matchless/matchless_spitfire.pdf)
with respect, Tubenit
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As I said I do have a layout for the spitfire, but not one implementing 6v6 tubes instead of el84 tubes like the above schematic.
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If all you're doing is using different tubes, the layout (how you arrange the components) should be pretty much the same.
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Cool thanks. Would I need to change some components to optimise the circuit to the new tubes? Would a pair of 6v6s push out more than a pair of el84? Cheers guys :-)
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Would I need to change some components to optimise the circuit to the new tubes? Would a pair of 6v6s push out more than a pair of el84?
Compare the two schematics to see what component values need to be changed. Power will be about the same for either tube type.
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Looks as the voltages will be quite a bit higher on the Gibson than the Spitfire. So much that if the desire to use EL84's in the future may not be possible. I do like the fat switch on the Spitfire, but the old Gibsons do really sound great to me. Especially the lower wattage tweeds. I really dig the gibson tremolo as well. I have played the Atlas before and really like it.
Keep us posted on you progress if you do decide to build it.
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Will do. To be honest I am not sure how much this schem has to do with the gibson atlas. I have been told that this schem is just a spitfire with 6v6's and a few other tweaks.
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Consider using a 270R/10w cathode resistor for the 6V6's. Other than that, I personally probably wouldn't change anything else. I'd play it like that and see if I liked it.
Change 9 pin socket to 8 pin.
Wire correctly for 6V6
Change shared power tube resistor.
With respect, Tubenit
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Here is the layout for the spitfire. It is similar, but has a Master. Never played a spitfire. The Phase Inverter resistors on both amps are 100k. It does look like the inspiration for the spitfire may have came from this. The Gibson OT states 10K for the primaries and looks like it was edited to this figure. I might go with 8k if I were purchasing a new one.
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Thanks, I will be using the Ken Watts Layout as it is most straightforward to me.
Thanks for the info Tubenit - what affect would using a 270R/10w cathode resistor for the 6V6's compared with sticking with the 130/5w that is used with the EL84 tubes?
Cheers,
Paul
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what affect would using a 270R/10w cathode resistor for the 6V6's compared with sticking with the 130/5w that is used with the EL84 tubes?
It'll save you having to replace the 6V6s every time you play the amp.
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Haha fair enough!
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Will there be any likely difference in volume?
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what affect would using a 270R/10w cathode resistor for the 6V6's compared with sticking with the 130/5w that is used with the EL84 tubes?
It'll save you having to replace the 6V6s every time you play the amp.
:laugh:
Gunther, not much, if any, difference in volume. 6V6 and EL84 have similar/equal plate dissipation rating, I think they're rated at 12 watts dissipation per tube. Differences in volume come more from speakers than anything else, IMO. A 5 watt amp can be surprisingly loud.
Without looking it up, I think 6V6's can handle more plate voltage than the 84's. But there again, it's the current you have to watch more than the voltage.
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Thanks, I will be using the Ken Watts Layout as it is most straightforward to me.
Thanks for the info Tubenit - what affect would using a 270R/10w cathode resistor for the 6V6's compared with sticking with the 130/5w that is used with the EL84 tubes?
Cheers,
Paul
What I posted is the donotlinktothiswebsite Ken Watts Layout. Look at the bottom of it. Attached is the PDF.
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Ah cool! Thanks!
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Gunterbuffalo,
IF you are going to be involved in amp building .................... then I would advise saving this document and learning also how to read the data sheets.
http://tdsl.duncanamps.com/tubesearch.php (http://tdsl.duncanamps.com/tubesearch.php)
And don't be hesitant to look at what other people have done. Example: is a cathode biased 6V6 amp is the 5E3 Deluxe. What is the value of the cathode resistor on that amp? That can be a starting place to thing about stuff like that.
Then look at the data sheet for the 6V6 tube ........................ then look at the "tube data cheat sheet". Doing all three of those steps can help narrow down how you are approaching a build.
With respect, Tubenit
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Here are some examples of a cathode biased 6V6 amps.
http://www.el34world.com/charts/Schematics/files/gibson/Gibson_GA-19RVT.pdf (http://www.el34world.com/charts/Schematics/files/gibson/Gibson_GA-19RVT.pdf)
http://www.el34world.com/charts/Schematics/files/fender/Fender_DELUXE_5E3.pdf (http://www.el34world.com/charts/Schematics/files/fender/Fender_DELUXE_5E3.pdf)
http://www.el34world.com/charts/Schematics/files/ampeg/Ampeg_12B_JET.pdf (http://www.el34world.com/charts/Schematics/files/ampeg/Ampeg_12B_JET.pdf)
http://www.el34world.com/charts/Schematics/files/danelectro/danelectro_centurian_275.pdf (http://www.el34world.com/charts/Schematics/files/danelectro/danelectro_centurian_275.pdf)
http://www.el34world.com/charts/Schematics/files/top_hat/tophat_clubdeluxe.pdf (http://www.el34world.com/charts/Schematics/files/top_hat/tophat_clubdeluxe.pdf)
http://www.el34world.com/charts/Schematics/files/bogen/bogen_cha-20.pdf (http://www.el34world.com/charts/Schematics/files/bogen/bogen_cha-20.pdf)
All of these are from different amp companies. What are the ranges of power tube (shared) cathode resistors? It appears to be somewhere between 250 ohm and 325 ohm. So that would be a starting place to think about these.
How did I know to look for these? Occasionally when I had time over lunch breaks at work, I looked over schematics to see what people did. That gave me a starting place.
You can figure this stuff out! It just takes some time and persistence.
Hope some of that helps. With respect, Tubenit
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Thanks for this Tubenit,
It's all stuff that will get me more independent at this! As it's still all pretty new. I will have a look through all those schems.
Paul
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The big problem that was not addressed when I started doing this was tube data sheets. I could look at them, but the stuff made no sense to me at all.
I also did not know circuits were designed around this data and I thought it was a guessing game since I had no experience with building amps, just repairing. Replacing tubes, caps, pots, bias and a few mods.
On the forum we speak of them and even refer to specific items from the data sheets. If I would have known I would have started a thread for each item on the tube data sheet as it is that important. You cannot know what you do not know.
As you look at schematics, you will notice a lot of the same resistor values for the same tube type. This is no accident.
Since to me preamp and tone stacks were and are the most difficult to understand, I would suggest top begin there. The preamp is everything up to the Phase Inverter.
I wish we could start a thread and go over all the items on a data sheet in a specific tube, starting with a triode because it is the most simple to understand IMO. The problem is it gets very difficult to understand quickly and it is not necessary to understand all of it to build amps.
When you begin to understand, ask questions and keep asking the same one till it sinks in. I spent days trying to understand load lines and thought the guys here would get tired of my questions. Some did, but others kept helping me. One day Hot Blue Plates took the time to go over it many times in great detail. I finally understood it.
I see where one member who builds a lot of amps did not understand we mentally convert mv to ma when biasing with a 1 ohm resistor and I have a hard time flipping ohms law and lack knowledge about current. I can still build an amp tho. And I am reading and learning about current.
Why was this so important? I can now design amps of my own and when I want something to sound different I know how to do that.
What Tubenit is telling you is the straight dope.
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Awesome cheers! Like I say I have only built a champ so far so have a lot to learn, but just from building that I can see how this can get addictive! I definitely have the passion!
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I found this on my internet travels. Might be useful to some other people. Has all the tube data and also a bit of a key identifying each pin for tubes:
http://www.ampage.org/td/ (http://www.ampage.org/td/)
Paul
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Grab the attached pdf. You will dig it.
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Sweet thanks!