telentubes wrote:Does anyone have experience with the 10" Greenback or any of the Weber 10s?
RJ has my tweed Super somewhere in his house and it has a mixed pair of Webers - alnico and ceramic - that we should try in this build.
RJ Guitars wrote:I have ordered a half dozen head cabinets and another half dozen combo cabinets with a hole for a 10" speaker. If I sell them with this project that's cool, but if I don't I'll use them elsewhere.
Like maybe a KT66 Pocket Rocket???
I'll try to catch up with you off-line for some coffee and some iron chat - I'd like to do this build with either EL34 or KT66 output. Hmmm, maybe I need to do a couple of 'em. Like I said, let's get together as soon as your travel allows.
I was supposed to be on my way elsewhere today but plans change so I'll have a couple unexpected days to work in the shop here... maybe get something done on this project.
I asked for all the heater current that I could get without going up to the giant transformer size... Edcor gave me 2.5 amps which should be adequate to make your EL-34 happy.
oh I almost forgot, there will be 5V @ 2 amps available as well.
RJ Guitars wrote:I asked for all the heater current that I could get without going up to the giant transformer size... Edcor gave me 2.5 amps which should be adequate to make your EL-34 happy.
oh I almost forgot, there will be 5V @ 2 amps available as well.
Good call - that ought to get some (worthy) attention. You've certainly got mine.
Whaddaya think about auditioning the Webers in my Super? Do you have some other 10" candidates in mind?
What is the output Z of the OT? I'm thinking about letting the lil' guy exhale through a certain pair of Celestion Vintage-30s just for (big) grins.
Some of the nicer sounding 10's I have tried in Fender amps are Eminence Legend 1058, Copperhead and the 'Lil Buddy. For Weber I have a 10A125 in my SFPR and it's a great speaker. I have a pair of Weber 8A125's in a cab and boy do those sound nice as well. Hard to go wrong with either brand.
Why is your volume control after the first triode? Why not put a 250k pot where the 220k resistor is like a MasterVolume? What's the advantage of putting it where you did (aside from this is where Fender put it).
Also is R2 68k a grid stop or an input jack resistor to provide load?
If not a grid stop, none of the tubes have a grid stop. Is there a reason Fender/you chose to not have any?
PS: I'm not questioning the quality of the design, just want to learn the reasoning behind the design, that's all. Hope you guys don't mind.
I see the 68k is a gridstop. I guess no others are used because fender felt they arent necessary and/or to prevent additional noise from extra resistors.
I still dont understand wht the pot is btwn v1a and v1b, and not where the 220k is located. What is the reason for that?
surfsup wrote:I still dont understand wht the pot is btwn v1a and v1b, and not where the 220k is located. What is the reason for that?
It's a preamp volume control; it controls how hard V1b is driven, thus not only the volume of the signal, but whether V1b will clip or not. The guitar's volume pot will do that too (with slightly different tone). Since the amp will only put out 4 or 5 watts on a good day, having a master volume would be sort of like putting a speed governor on a stationary exercise bike.
Good discussion - Learning is one of the big drivers for this thread and having knowledgeable folks help explain the basics is great for the new amp builder... and some of us old amp builders too!
I am getting closer to having it all together here. I hope to finish my prototype minimalist amp tonight or in the morning. Despite the CAD drawings and having it sorted out in my mind I seem to end up with a few extra holes in the chassis every time on the first of a kind. It is going well and my education on amp #1 should be adequate to provide you with the right number of holes in the right places on the chassis.
I need to start putting together a list of who wants what. I'll start with asking about the Eagle 100 minimalist version at $99 delivered (US only) vs. the upgraded version at ~$135 Delivered with Edcor trannies. I am still working on shaving down the prices a bit more but have to do a little math and verify I've got all the parts covered. At this point I know the prices could go down and won't go up for round one of this project.
I have a list already started but if you want to save me from sending out a prompt asking you to email me with your preferences, you can send one to me now at info at rj guitars dot net
We've got a few builders signed up. Should be fun.
I finished prototype #1 today using the Allied 6K49VG power tranny and a no-name champ output tranny. The 6K49VG is a Hammond built tranny that apparently is custom wound for Allied. They only had four of them but said if I want more they would get them for me.
I didn't get any info with the OPT so when I first started it up the amp squealed like a pig. I had to reverse the leads to get the correct side of things feeding the negative feedback and all was well. The overall tone was dull so I added a bright cap but it didn't do much. I added a 25uf bypass cap to the 2nd gain stage and it really started to come to life.... but not ideal yet. I think I should have added it to the first gain stage but I'm going to leave it at as is and start prepping some chassis now. I'd like to get a few of these out to you and and let everybody join in the joy of tweaking them into submission.
RJ Guitars wrote:I added a 25uf bypass cap to the 2nd gain stage and it really started to come to life.... but not ideal yet. I think I should have added it to the first gain stage but I'm going to leave it at as is and start prepping some chassis now. I'd like to get a few of these out to you and and let everybody join in the joy of tweaking them into submission.
rj
The published 5F1 schematic shows both triode stages unbypassed, but all the factory-original 5F1s I've seen had a 25uF across the first-stage 1K5 like on the 5E1. I didn't think to keep notes whether they were early or late By putting the cap on the second triode, how much negative feedback do you lose?
By putting the cap on the second triode, how much negative feedback do you lose?