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11-09-2021 10:19 AM
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I'm happy the suggestion I made in the other thread struck a chord... Hopefully a nice jazzy chord
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The route you are going down is a very fun one. And consider me in awe at your work on medical equipment during the pandemic. Bless you!
Regarding the 5e3 build - just remember that it's also totally possible to modify an amp after its built - and many people do. It might be more straightforward to first build it as it came from the kit - get it working, and then start modifying. This also makes it a lot easier to troubleshoot if there are problems, and is also a great way to get a satisfying endorphin rush from having finished a project
If after he is done, he wants to try going with an octal preamp tube - thats doable! It'll take a little bit more reading and messing around, and might require some minor work on the chassis to get the larger sockets to fit - but absolutely.
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And just to get you going - here is a great resource. It is frankly completely possible to build from a kit without even knowing a capacitor from a resistor - but learning a bit about what you are doing makes this that much more useful in the long run.
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PV, I enjoy building amps, I love my son and I thoroughly enjoyed buying him gear when he was young. Back then I came know more about Selmer saxophones than any bassist or guitarist should!
Originally Posted by PentiVarg
That said, your post reads a lot like, "I will spend a lot of time building an amp I don't think he wants because it might help him to figure out what he does want."
My suggestion is to set a figure which you are willing to spend on an amp and bring your son on an amp-hunting trip. If he wants something different he is free to contribute . . . Something tells me that he will find a tool within your budget that is more than satisfactory.
(I bet it's a Fender Princeton Reverb reissue with a 12" speaker, but that's just me.)
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@sys. Yep you planted the idea. Seen the clip you posted, read some books and just built an 5f1 from the schematics with the kid. Easy piecey. From the beginning it was just a question about how to find a good amp for the boy. Now I’m totally hooked and already building a new amp for our record player. The octal delux and Electra amps are >€2000 and I think I can get a similar sounding amp for about half the price (not as good looking though) and also get the fun experience of building and hanging out with the kid.
maybe quit medicine and become an amp builder
. Thanks for all inputs. Next project will become a tweed amp base with the possibility to also have a octal tube preamp as an extra option within the amp as I previously described
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There’s a story there? Originally Posted by PentiVarg
Can’t be that different to build a speaker from modding a respirator or
heart and lung machine
?
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@sys so now it is completed. Took a while but once I started I realised that this was not a “kit” build and needed to learn more about electronics, grounding schematics, tubes, previous amps and so on. Got a lot of help from nice guys with inputs.
The main problem was that I was planning on a switch to be used to change which preamp to be used. A lot of interference made it not to be functional even with a wast variety of different shielded signal wires and different routings.
Due to that the 12ay7 goes to two jacks and the 6SJ7 goes to two different jacks.
will have to use a less aesthetic way of switching. A regular AB pedal. Works fine since the output of the two preamps are almost the same.
then the signal is routed through a 6SCJ7 and finally two 6v6’s.
All built in a 5e3 chassis and had to use a solid state rectifier and a sag resistor to free up a place for the 6SCJ.
To use the switch, that was intended for the preamp switch, I put in a NFB switch. Speaker is a Jensen p12N.
The end result is a 6SJ7 5B3 Deluxe, 12-15W.
Very pleased with the end result. A hum-free amp with a beautiful tone. The sound from the octal tube reminds you of the GA-20 and the triode preamp of a regular clean fender tone.
The cab was made to look like a GA-50 with one speaker.
Now building a smaller, more portable one with a spring reverb. A two channel amp, GA-5 (6SJ7) and a regular Champ (12ay7).Last edited by PentiVarg; 02-22-2022 at 03:34 AM. Reason: Adding info
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OUTSTANDING!!!
I'd buy that.
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Good job !
Congrats !
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Just build one. Fun and you learn ALOT about the amp and how you can affect the “tone”.
If I wasn’t a physician (with a salary that probably exceeds one of an amp builder) I would love to go into amp building. Actually since the wife is a dermatologist I might be able to get her into private practice ?.
Hopefully the GA-5/5F1-reverb amp will be good to. Nice to be able to have less weight to carry around.
After that I’m building a Telecaster with a CC pickup as a training step for an archtop build.
Would be great if one could build an nice sounding archtop by myself. That’s a one year project. Looking for a luthier to go to practice with and am collecting good wood. Harder to build an archtop without a skilled luthiers help and to build an amp I think.
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you are a brave person.
Did you ever tested the GA-50 clone vs. a real vintage one ?
I believe there is a big difference ... I made that experience with a the Filmosound Amps and their repro.
all the best to you, rock on.
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@filmosound 621
no I have not not Done that in a real comparison side by side. There should of course be differences in this case since the schematic is different, especially by the rectifier, and new components and a speaker that’s only been played on for 20-30 h, but for me it is “good enough” close by ear and the sound is really pleasant.
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that is the main thing.
"big difference" has been an exageration anyways ...
the original GA-50 ( I sold mine 14 days ago ... ) is one of the greatest vintage amps there is,
more than the sum of its parts ... with the old Jensens, the old red-wood cab ect.
the old circuits have so much harmonics going on, that I smiled about Fender amps and their reverb units
everytime I took out the GA-50.
I believe these amps need no reverb and tremolo at all.
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I agree about the tremolo or reverb but for me it’s all about the project and the practical aspect of it. There is something nice with just a small amp and a guitar and no extra stuff. With the GA-5/5F1-reverb build it’s to have a small 5W amp that has almost all the stuff needed for a good tone with a guitar. The A/B pedal really is a thorn in my side. It would have been better to have the switch integrated. Some day I will have the time and lust to find a solution to the “ugly” A/B switch. But that time is not now. Need to build me another amp.
I might get me one of those original GA-50/GA-20 (octal one) but as of now I don’t feel the need since the one built is better than good enough.
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And how does your son like it?
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Loves it
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This is the final schematic when the triode, 12ay7, is not connected parallel. A NFB is added and have a on-off switch.
There is a half triode tube unused and planning to make it drive a spring reverb sometimes in the future if the GA-5/5F1+reverb circuit works.Last edited by PentiVarg; 02-25-2022 at 02:01 PM. Reason: Forgot to add a schematic
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Your son is lucky to have a dad that encourages and supports his interests. That is a Dad of the Year amp you've built, congrats.
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Now I need to learn how to build an archtop. I’ll think that will be a bigger challenge and take longer time
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Wowza, when you do something, you really do it, eh? Beautiful work. May I ask if you built the cab? Love the nod to the old Gibson's - that suitcase looking baffle has always been a favourite - you might have inspired me to attempt something similar for my current project
(an old geloso g226 conversion to guitar that will need a cab). Either way, a big congratulations, and your son must be one happy camper.
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glad you liked it. It was a pain during part of the process. Especially due to the switch for the preamp placement problem due to that I didn’t want to drill more holes in the 5E3 chassis and the PT interference then made it impossible to use and finding the right sag since it was a solid state rectifier. Got a LOT of help from amp forums experts.
The design is actually a copy of one of Sequels amps
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The cab is made out of pine and covered with burgundy tolex and the front wood painted with a mixture of powder based stain/lye for a mahogany touch.
The handle and corners material can be found on www.tube-town.net
Will use the same material for the GA-5/5F1 reverb amp but will make a different front. Thinking about a round 8 inch front covered with grill cloth milk & honey ?Last edited by PentiVarg; 02-26-2022 at 08:40 AM. Reason: Adding text
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That's a really cool build.
Nice work.
I see you went for a grid leak bias on the 6SJ7 (like GA20) and cathode bias on the 12AY7 (like 5E3).
Did you make any experiments with using a cathode bias on the 6SJ7 like the GA50 has? or grid leak bias on the 12AY7 like some later variants of the GA20 (and 5B3 but they didn't use 12AY7)?
One of the cool things with handwired point to point builds like this, is that these kind of experiments are relatively easy.
This kind of makes me want to build something inspired by this. (I've built 3 valve amps so far and really like it).
You could also have sacrificed an input jack or two for the switch.I didn’t want to drill more holes in the 5E3 chassis
Having multiple inputs on guitar amps today doesn't make that much sense to me today, since they are in most cases only used by one guitar.
But I understand that people want to maintain the look and feel of the original amp and the front panel unchanged.
Also if you connected the inputs like the schematic you posted shows, then you have two identical "hi" inputs. Fender schematics have the 1M hi input resistor on the other side of one of the 68k resistors (which will then act as grid stopper). The 1M resistor is commonly soldered directly on the input jack.
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About the bias I can’t really tell you why one was chosen instead of the other.
When I started the project I knew nothing about tube amp electronics. Due to the nature of the build (experimental) I’d say I have a bit more knowledge since I had to learn stuff along the way.
A great guy helped me since he was interested in this idea and worked with amps. He had wanted to build a Paraphrase Inverted amp with Pentodes and helped me with the schematics.
The idea was to get the “cleaner” tone from the cathode bias on the 12ay7 and the GA-20 sound from the 6SJ7 so when with grid leak bias on the pentode.
I haven’t touched the inside of the amp since I installed the NFB. The son does play on it for 4-5 hours a day and he won’t let me manipulate it anymore since he’s afraid that I’ll ruin the tone. The only adjustment I have done is to remove the parallel coupling on the triode that I had from the beginning due to I had a hard time to not use the whole tube Now the triode gets the full potential and it sounds like a clean Fender amp. A bit of a dull sound when parallel.
As he wrote: “Part of the sound is the Paraphase inverter. It adds some fatness to the sound if a little unbalanced. That and the grid leak bias on the pentode in front (where the cathode is grounded). I think it sounds better for cleaner stuff with a touch of hair than the cathodyne in the 5E3. The 10k as compared to the 5k in the power supply to the screens also gives it a softer sound.”
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