Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Cris_mas on December 05, 2024, 07:26:32 pm
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Hello, Cris here, first post (well, technically the second) so I'm hopping I'm not infringing any norm on the forum.
So yep, pretty much got bored of digital setups and want to build a clone of this beautiful device, i can source many parts but 2 are my main concern right now:
-Rack cabinet (will have to import it, i live outside USA)
-Power transformer (can't see clearly the values i need for secondary in the schematic i have)
Another point is i don't know if all resistors for example should be 1/2 watt or more (or less) some tolerances are absent on the schematics and I'm a bit spoiled with BOM, which is a thing that usually don't happen in tube world (I've been more time on pedal world lately).
For the rest i think i can manage, well i will avoid going the pcb route (haven't found any layout of the pre) so maybe will go veroboard or point to point, what works best for me i guess.
If I'm missing something just let me know, I'm only calculating costs and budget for now.
Greetings earthlings
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Is it the first amp ( pre amp ) you'll build ?
If it is the case, you should study how tubes amps work before.
Most resistors are 1/2 watt, 10 % There are no tolerance on schematic 'cause any amp tech know what to use when amp are in the shop.
Schematic are not for a build purpose.
For power supply 5 to 25 watts.
Where will you buy the optocouplers ?
Schematic ;
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More here:
https://el34world.com/Forum/index.php?topic=23669.0
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Is it the first amp ( pre amp ) you'll build ?
If it is the case, you should study how tubes amps work before.
Most resistors are 1/2 watt, 10 % There are no tolerance on schematic 'cause any amp tech know what to use when amp are in the shop.
Schematic are not for a build purpose.
For power supply 5 to 25 watts.
Where will you buy the optocouplers ?
Schematic ;
Thanks for the insight.
I built (assisted) a 1987 Plexi and moded a few of my own amps, but never built from scratch. Also, my skills with tubes are a bit rusty since I’ve ditched my tube amps a few years ago. I’ve ensambled a tube pre in pedal format but with nixie power supply so I haven’t dealed with heavy irons in a while. I will have to re school myself for this project, I must recognize. I can ask for assistance tho, so I will first buy all the components. I was asking about the power supply because I’ve read very different voltages on the secondary (from 270volts to 300 and beyond!) Also don’t know how much current I need and I get confused on the heater tap. I’ve seen the optos on amp parts page or something like that. They are the new xvive reissue of the Vactrols.
Thanks for the link, I will check it out
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260 volts DC for preamp tube are often see on amps.
Power transformer AC at secondary ; 230 volts c.t. may work ?
Current ; look tubes specs sheet ; 12AX7 ; 300 ma each X4 tubes =
Scroll down in the middle ;https://robrobinette.com/How_Amps_Work.htm#Power_Supply
You also need secondary winding for the solid sate :BangHead:
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260 volts DC for preamp tube are often see on amps.
Power transformer AC at secondary ; 230 volts c.t. may work ?
Current ; look tubes specs sheet ; 12AX7 ; 300 ma each X4 tubes =
Scroll down in the middle ;https://robrobinette.com/How_Amps_Work.htm#Power_Supply
You also need secondary winding for the solid sate :BangHead:
thank very much for the info @Latole, i will study the basics before putting together this beast. In the meantime i will collect the parts and see were i can obtain the PT, Toroid hopefully.
As far as voltage, i know that the more voltage the more the headroom but in this case i have a misunderstanding about the "output voltage" of the secondary vs the so called "cold clipper" of Soldano topology, but i guess i will have to read the Robinette web to learn more about it.
About the heaters, people does increase to 12 volts for reducing current consumption, but is it worth it?
Lastly, the last line about the " Solid state winding", i was considering putting an analogue Power Amp analog sim circuit in parallel to the normal out, so i can feed an Impulse Response loader-module, so i guess i need to calculate how much current i need to that and the voltage to make that.
again, many thanks Latole!
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Here's another drawing.. https://www.prowessamplifiers.com/schematics/images/Soldano%20SP77%20redrawn.pdf
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" About the heaters, people does increase to 12 volts for reducing current consumption, but is it worth it ? "
Answer ; Yes it is.
Power transformer with more current = bigger and more expensive $$ PT than PT with more voltage ( 6 to 12.6 volts) less current .
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at the end i'm leaning towards a kit build I've found on a german website, although its not a soldano sp77, its based on a Soldano pre (x88 i guess??).
https://www.musikding.de/Anvil-Tube-Preamp-Kit (https://www.musikding.de/Anvil-Tube-Preamp-Kit)
I opted for this because of costs, and supply of parts, but im not so sure about how it sounds (its too metal for me on the sound samples i found) so i will have to mod it anyway :BangHead:
thanks for the info BTW, i will tell more details in a new post
(https://www.musikding.de/media/image/product/3262/lg/anvil-tube-preamp-kit~2.jpg)
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Not a good idea to try and start doing mods on a PCB.