Well first off, I'm really very new to the whole DIY amp thing, and I've been told I have enough knowledge to be dangerous.
Recently, my dad was cleaning out his basment, and he found an old Webcor reel-to-reel, a HAM radio reciever, and a CB set that he was going to get rid of. Being unemployed at the moment, I have a bunch of time on my hands. So I snagged those and started doing some research.
From the components I pulled out, I came up with a 12AX7A, a 7025, and a 6UE7 (which according to my searches at nj7p.org all have the same characteristics). I also got a 6X5GT rectifier, 2 6V6GTs and a 6AQ5A. And of course the power and output transformers from each, which I am going to have to get a multimeter to test as none of them have manufacturers listed and it's not that easy to find information based on the numbers on the sides of them.
So, looking at various amp schematics to find something with a similar tube configuration, I came across the Fender Bassman 20. It has one 7025 in the preamp and another one feeding 2 6V6s in push-pull.
Now, being that this is my first attempt at anything like this...it would make a lot of sense to just try and recreate the Bassman 20 circuit and deal with the 18w it's supposed to produce.
Unfortunately, I've always had a bit of a mad scientist streak. (I blame my dad's family). So what I'm looking to do is add in another 7025/12AX7 gain stage, use my tube rectifier instead of the SS one in the schematic, and convert the power stage from 2 6V6s in PP to the 6AQ5A in SE class A into the 6V6s in PP class B. Plus I'd like to add an effects loop so I can use this 31band EQ i've had sitting around since my church upgraded their PA.
So any thoughts, comments, suggestions are appreciated, but you don't have to tell me I'm crazy...I'm already well aware of that. From my research I know that what I'm looking to do is reasonably possible. I just need an assessment of the feasability. Whether modifying this schematic will work or if there's something better, or if, the worst option, starting completely from scratch would be the easiest.
Thanks in advance for any help.
PS, the schematic for the Bassman 20 that I've been working from.
http://www.schematicheaven.com/fenderamps/fender_bassman20.pdf
Recently, my dad was cleaning out his basment, and he found an old Webcor reel-to-reel, a HAM radio reciever, and a CB set that he was going to get rid of. Being unemployed at the moment, I have a bunch of time on my hands. So I snagged those and started doing some research.
From the components I pulled out, I came up with a 12AX7A, a 7025, and a 6UE7 (which according to my searches at nj7p.org all have the same characteristics). I also got a 6X5GT rectifier, 2 6V6GTs and a 6AQ5A. And of course the power and output transformers from each, which I am going to have to get a multimeter to test as none of them have manufacturers listed and it's not that easy to find information based on the numbers on the sides of them.
So, looking at various amp schematics to find something with a similar tube configuration, I came across the Fender Bassman 20. It has one 7025 in the preamp and another one feeding 2 6V6s in push-pull.
Now, being that this is my first attempt at anything like this...it would make a lot of sense to just try and recreate the Bassman 20 circuit and deal with the 18w it's supposed to produce.
Unfortunately, I've always had a bit of a mad scientist streak. (I blame my dad's family). So what I'm looking to do is add in another 7025/12AX7 gain stage, use my tube rectifier instead of the SS one in the schematic, and convert the power stage from 2 6V6s in PP to the 6AQ5A in SE class A into the 6V6s in PP class B. Plus I'd like to add an effects loop so I can use this 31band EQ i've had sitting around since my church upgraded their PA.
So any thoughts, comments, suggestions are appreciated, but you don't have to tell me I'm crazy...I'm already well aware of that. From my research I know that what I'm looking to do is reasonably possible. I just need an assessment of the feasability. Whether modifying this schematic will work or if there's something better, or if, the worst option, starting completely from scratch would be the easiest.
Thanks in advance for any help.
PS, the schematic for the Bassman 20 that I've been working from.
http://www.schematicheaven.com/fenderamps/fender_bassman20.pdf
Re: Re: Bass amp from spare parts
The reel-to-reel is a Webcor EP2712-1
It had 6EU7 and the 7025, the 6X5GT and the two 6V6GTs
there is no manufacturer information on the power transformer but the numbers on it read "68P028-5 596603"
The CB is an Eico Sentinel Pro, the numbers on the transformer read "30079 10976645"
The HAM reciever is a Knight Star Roamer
Of course, duct tape fixes everything
Wavebourn said:
The reel-to-reel is a Webcor EP2712-1
It had 6EU7 and the 7025, the 6X5GT and the two 6V6GTs
there is no manufacturer information on the power transformer but the numbers on it read "68P028-5 596603"
The CB is an Eico Sentinel Pro, the numbers on the transformer read "30079 10976645"
The HAM reciever is a Knight Star Roamer
leadbelly said:
Hope you've got lots of duct tape!
Of course, duct tape fixes everything
This isn't the greatest pic ever...it was too washed out with the flash and just too dark without it, but all of the secondary lines coming off the transformer went right to the socket for the rectifier.
The pic is too big to attach and the resolutions a little high to just include it in the post, but it's at http://www.resilienceguild.net/files/Darthin/secondaries.jpg
The pic is too big to attach and the resolutions a little high to just include it in the post, but it's at http://www.resilienceguild.net/files/Darthin/secondaries.jpg
Whoa,
I'm liking this discussion! First of all, Chaos5522 - I like your attitude! Rip it up, your project is definitely possible.
Secondly, my bass rig is a Hi-Fi? I guess I should be listening to it more than my "other" Hi-Fi then! Only I like the music coming out of the "other" Hi-Fi better, so until Les Claypool or Marcus Miller want to come over and play on my bass rig, I'm afraid the "other" Hi-Fi will be getting more play. My chops ain't all that...
But my bass rig is all-tube FWIW.
I'm liking this discussion! First of all, Chaos5522 - I like your attitude! Rip it up, your project is definitely possible.
Secondly, my bass rig is a Hi-Fi? I guess I should be listening to it more than my "other" Hi-Fi then! Only I like the music coming out of the "other" Hi-Fi better, so until Les Claypool or Marcus Miller want to come over and play on my bass rig, I'm afraid the "other" Hi-Fi will be getting more play. My chops ain't all that...
But my bass rig is all-tube FWIW.
No, I did not mean your rig.
That mass production they sell in GC for bass guitars is not a real Hi-fi, but approach to bass guitar amps' design is more like hi-fi amp design rather than a lead-guitar amp design.
You can add some parametric or graphic EQ to shape your tone, but a power amp must be clean, and even better with anti-clipping compressor like my amps have.
That mass production they sell in GC for bass guitars is not a real Hi-fi, but approach to bass guitar amps' design is more like hi-fi amp design rather than a lead-guitar amp design.
You can add some parametric or graphic EQ to shape your tone, but a power amp must be clean, and even better with anti-clipping compressor like my amps have.
I guess I should also note that:
I am using an all-tube stereo reel-to-reel Roberts (Akai) as a preamp for my Peavey AlphaBass (6-6L6s) actually in a quite perverse way.
I run my bass into the line input (or is it mic?) of one channel and then from Speaker Out (xformer) directly into the line input of the second channel. Then Speaker Out again into the Power Amp In of the Peavey.
Ummm... people here will yell at me for such abuse, but if you use a very light touch on the controls, you can get a whole range of clean to massively overdriven sounds and feedback just by twiddling the vol & tone knobs on the bass. Yes, this setup has the potential to damage gear if care is not taken. I love the sound though.
This ree-to-reel has, I would say, about 2-4W total output anyway. I don't even know what tubes it's running, I base that on trying to play through a 1-12 cabinet on it's own. I like it better adding in the 185W tube power of the Peavey
I am using an all-tube stereo reel-to-reel Roberts (Akai) as a preamp for my Peavey AlphaBass (6-6L6s) actually in a quite perverse way.
I run my bass into the line input (or is it mic?) of one channel and then from Speaker Out (xformer) directly into the line input of the second channel. Then Speaker Out again into the Power Amp In of the Peavey.
Ummm... people here will yell at me for such abuse, but if you use a very light touch on the controls, you can get a whole range of clean to massively overdriven sounds and feedback just by twiddling the vol & tone knobs on the bass. Yes, this setup has the potential to damage gear if care is not taken. I love the sound though.
This ree-to-reel has, I would say, about 2-4W total output anyway. I don't even know what tubes it's running, I base that on trying to play through a 1-12 cabinet on it's own. I like it better adding in the 185W tube power of the Peavey
Wavebourn,
This is an unusual Peavey. They didn't make a lot of all-tube bass heads. This one is called an AlphaBass, built for only 1-2 years around 1991, has 3-12AX7, 1-12AT7 and 6-6L6 output tubes. I know for sure their TNT line of SS amps used comp, but I'm fairly certain mine does not...
This is an unusual Peavey. They didn't make a lot of all-tube bass heads. This one is called an AlphaBass, built for only 1-2 years around 1991, has 3-12AX7, 1-12AT7 and 6-6L6 output tubes. I know for sure their TNT line of SS amps used comp, but I'm fairly certain mine does not...
A bass amp will need a strong OP Tranny if it is to be used for clean bass at any significant volume. 2 6v6s may not suffice if you are looking to use the amp for clean bass in a band situation.
Of course the "Bassman" series was not used for playing bass by most guitarists and is known for it's good distortion for normal guitar instead.
I'm confused on where the output tranny is coming from. I don't know if reel-to-reels had powerful outputs. (I didn't know they had speaker outputs.)
Of course the "Bassman" series was not used for playing bass by most guitarists and is known for it's good distortion for normal guitar instead.
I'm confused on where the output tranny is coming from. I don't know if reel-to-reels had powerful outputs. (I didn't know they had speaker outputs.)
Well in the long run this is meant to be more of a practice amp, since I don't actually own one myself...The amp i'm using now is a piece of crap SS 25 watt no-name that distorts when I turn it up lound enough to TRY to keep up with an acoustic guitar player. And it's on loan to me from a friend.
SO in the long run, all i really need is a practice amp, and given the parts I have I could reproduce something like the bassman 20 or one of the projects from ax84. But that's just not the kind of person I am. I really want to squeeze as much power as I can out of the components I have. Granted, at the moment, the limiting factor on that is what the transformers are capable of. This will be known as soon as I can get my hands on a multimeter and some equipment to test them. Right now I'm trying to configure an amp that I would like, that will do what I need and satisfy my uncontrolable urge to tinker with things. Once I know what the transformers are capable of, I'll adjust the design based on that new information.
SO in the long run, all i really need is a practice amp, and given the parts I have I could reproduce something like the bassman 20 or one of the projects from ax84. But that's just not the kind of person I am. I really want to squeeze as much power as I can out of the components I have. Granted, at the moment, the limiting factor on that is what the transformers are capable of. This will be known as soon as I can get my hands on a multimeter and some equipment to test them. Right now I'm trying to configure an amp that I would like, that will do what I need and satisfy my uncontrolable urge to tinker with things. Once I know what the transformers are capable of, I'll adjust the design based on that new information.
This sounds similar to the recipie that was written inside the first Chicago Transit Authority's first album (1969). It describes the setup used on the song Free Form Guitar as a Strat played through a Showman using a Bogen PA as a preamp.
I didn't own a Showman and I was using a Stromberg Carlson PA with a home made input section (Bandmaster circuit) for my guitar amp, but of course I had to try it. I dug up an old Bogen PA and stuck it between my guitar and the amp. It sounded absolutely wicked, but had so much gain that it hummed and picked up the local AM radio station. A friend tried it but his guitar amp was a solid state Kustom. The result two fried amps. NEVER try this with solid state amps! They really don't like 50 volts of signal on their inputs.
You want to try something absolutely wild? You need a stereo wired guitar or bass (two pickups to two different output jacks). Plug one pickup into your usual amp. Daisy chain (or Y cord) that amp into a smaller practice amp. Plug the speaker output of the practice amp into the second pickup. What you get is controllable feedback. Play a note or chord, the sound gets amplified and fed back into the string through a second pickup. With proper adjustment and a little luck you can get infinite sustain. The effect is similar to an Ebow.
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