Post by thetragichero on Oct 19, 2020 17:52:28 GMT -5
working on another one of these builds for a guy, this time using a more normal (ie non voltage doubler) bias circuit. power transformer from a traybor yba4 (biiiiig horkin Hammond), output transformer from an evh 5150 50w (schumacher), 2xel34 (with ability to run 6l6 or 6550) trying to make this purtier so the majority of the preamp (save for volume, tone controls) and phase inverter are on this here eyelet board i made
Post by thetragichero on Oct 23, 2020 3:42:54 GMT -5
all power supply nodes in. power and standby switches. whatever tech removed the output transformer cut the leads to within an inch of their lives so i removed the bells and spliced my own on. plates and screens on. need another terminal strip for the phase inverter plates
Post by pasqualino on Oct 23, 2020 17:37:03 GMT -5
WOW!!! That is a thing of beauty!
I too prefer the 6l6 to the EL34 tube amps (Fender vs. Marshall for the most part, not limited too of course.) My tube chops are real rusty, I need help with this for sure and am so psyched that guitarnuts.com exists so we can help each other out. When I was in the Navy I gained great familiarity with tubes as ALL of the "contingency" stock was tube based. Gotta love the way the use the word contingency here. The military uses it as an abbreviation for nuclear contingency plan. So tubes are still taught in the electronic training classes. Not in a design sense, just enough to know how it works so you can fix it.
I bought the ckt cards for a Sloclone and will be experimenting with that. How do you get transformers for these things? I remember some Russian guy had videos of winding his own, that would be a trip. I want low relatively low power so maybe I'll try 6V6.
Post by thetragichero on Oct 23, 2020 18:39:05 GMT -5
i use a lot of transformers pulled from old Hammond/Thomas/Baldwin organs. also scour eBay and reverb for transformers either pulled from working amps to "upgrade" or purchased for projects that never materialized for new transformers i prefer classic tone (although they appear to have gone out of business due to the pandemic), usually had for a good price from tube depot. antique electronic supply carries, along others, a wide selection of Hammond and magnetic components (parent company of classic tone) transformers i stay away from mercury magnetics because they're overpriced and don't seem to post datasheets for their iron. that's a big no in my book, as i want to make sure it's going to work before i purchase
Yeah, the particular flavor of output tube will affect the character of an amp. But I think there are bigger differences between Fender and Marshall because of things like the size of the cathode bypass caps and the structure and values used in the tonestacks. And of course when we're talking about the whole system, speakers play a big role. Jensen > Celestion as far as I'm concerned. YMMV.
I want low relatively low power so maybe I'll try 6V6.
I would. Unless you need more power, 6V6s are very nice and the iron for a medium-power amp can be easier on the wallet. And your ears will have less tendency to bleed when you crank it. But a 20w amp isn't that much quieter than a 40w amp. So you will still annoy your neighbors.
You might even consider 6BQ5s (EL84s). Somewhat similar characteristics as the 6V6s but in a noval envelope instead of octal.
Post by thetragichero on Oct 28, 2020 2:55:59 GMT -5
i work super duper slow. added the bias test points, offboard wiring for the phase inverter (and connected to its b+ node), finished the power tube wiring. wired up the input jacks, volume, and bright switch. next up is depth and tone controls
Post by thetragichero on Oct 30, 2020 0:56:42 GMT -5
wired up the output jacks and line out. this is a weeeeird output transformer where the 8 ohm tap is paralleled to the 16 ohm tap so there's a shunt tip jack for the 16 ohm jack. since global negative feedback is taken off the 8 ohm that means this'll be a bit dirtier when played through a single 16 ohm cab. i'm okay with that. also completed the bias circuit
Post by thetragichero on Nov 3, 2020 1:37:49 GMT -5
didn't take a picture before knocking off for the night but the presence and effects loop jacks are done, b+ nodes for the preamp are on a terminal strip on that side of the chassis, started attaching leads to the tube sockets. guess tomorrow will finish up and install the preamp board. then tubes go in!
Post by thetragichero on Nov 8, 2020 1:27:06 GMT -5
finally back at it. preamp board wired in. just need to attach a few leads to the phase inverter and the ground from the preamp board to the volume pot (which attaches the isolated jacks and pot grounds to the preamp stage filter caps in hopes of cutting out noise. trying new things with each build to find things to make em better. besides the awful wiring at church my vibrochamp build is remarkably quiet, amazing me as the cramped chassis forced me to float the preamp board over the tube sockets with wires everywhere)
Post by thetragichero on Nov 9, 2020 15:10:59 GMT -5
last night night the pi wired up, tested on lightbulb limiter (in the event of shorts). popped tubes in and wasn't able to bias both power tubes evenly. didn't have the patience for troubleshooting (first order would be swapping the power tubes to see if it followed the tube or remained in the socket. earlier in the week noticed that my 1k (red third band) and 100k (yellow third band) resistor bins were swapped so i had originally installed 2k2 bias feed resistors instead of 220k so those have already been corrected. errors happen so I'll double check my work). it does pass signal though (had the amp on the scope with a dummy load) so we're getting there