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Topic: A poor Man's Little Walter Tube Amp |
Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 1 Oct 2012 6:09 pm |
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It's a start LOL
It's an old PA Amp. I'll try to get it running if the transformers work. If not I'll use it for parts to experiment with.
It even has 6L6's
What can I say the winters are long in Nova Scotia
All I need is one more and I'll have a 50/50 just like Paul Franklin.
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Lee Baucum
From:
McAllen, Texas (Extreme South) The Final Frontier
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Posted 1 Oct 2012 6:16 pm
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That'll never work. It's got too many knobs!  |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 1 Oct 2012 6:24 pm
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@Lee
No problem with too many knobs... I have to take them off to clean it.
Last edited by Bob Lawrence on 1 Oct 2012 7:02 pm; edited 1 time in total |
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Brett Lanier
From:
Hermitage, TN
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Posted 1 Oct 2012 6:40 pm
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| Funny. I heard the original Little Walter (harp player) used to bring around a tube powered PA system to play harmonica through. He's my all time favorite for tone. I wonder if his amp was anything like yours. |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 1 Oct 2012 7:07 pm
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I found one like it on YouTube
Precision Electronics model 30 PA Video
Tubes 2-6L6Gb's,
3-12AX7's
1-5U4Gt
http://www.youtube.com/watch?v=eo4EnQHBQOs
Last edited by Bob Lawrence on 2 Oct 2012 4:50 pm; edited 1 time in total |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 1 Oct 2012 7:12 pm
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Bret,
I would have no idea but it's a Precision Electronics model 30 PA Video . My old time friend Kenny had it in his basement full of antique radios etc. He let me have it and I just wanted something to learn how to work with tubes before I try to make a good tube amp. The transformers maybe shot with all the rust but I'll clean them up and test them. |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 2 Oct 2012 2:47 pm
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Generally, those old shielded transformers are built like a brick, and very little can hurt them. If they are burned out, you'll usually get a very distinctive "burnt plastic" odor from where the leads go in. Other than that, just wire brush off the rust and spray paint them.  |
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Mike Neer
From:
NJ
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Posted 2 Oct 2012 3:23 pm
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Lee Jeffriess told me about this guy, Skip Simmons, who turns the old PAs into guitar amps: http://skipsimmonsamps.com/
_________________
Links to streaming music, websites, YouTube: Links |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 2 Oct 2012 4:34 pm
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@ Donny Hinson
re:, just wire brush off the rust and spray paint them
I think your right. I have a good feeling that some TLC will go a long way. Tonight I'll take of the bottom panel and have a look at the components inside. |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 2 Oct 2012 4:35 pm
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@Mike Neer
Thanks!! for the link. Interesting info there. |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 2 Oct 2012 4:52 pm
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A look at the component side:
I'm impressed, looks very good.
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 2 Oct 2012 5:32 pm Quite a Contrast between Tubes and FPGA Programming
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I been trying to learn the past and the future all at the same time. I spent several hours working on this tube project last night in hopes of learning about the technology for that era (cira 1959). This afternoon I took a course in FPGA programming in Labview (the 2012 release) (note 1)
Note 1 : What Is an FPGA?
Field-programmable gate arrays (FPGAs) are reprogrammable silicon chips.
http://www.ni.com/fpga/
Merging the two I should be able to design a labview program to help with the signal analysis of the tube amp. For example I could take the tube output and feed it through a sound card with a decent ADC(analogue to digital converter) then use a Labview graphical interface to do things like FFT(note2) ans other analysis(note 3)
Note 2: The Fast Fourier Transform (FFT) and the power spectrum are powerful tools for analyzing and measuring signals from plug-in data acquisition (DAQ) devices. For example, you can effectively acquire time-domain signals, measure the frequency content, and convert the results to real-world units and displays as shown on traditional benchtop spectrum and network analyzers. By using plug-in DAQ devices, you can build a lower cost measurement system and avoid the communication overhead of working with a stand-alone instrument. Plus, you have the flexibility of configuring your measurement processing to meet your needs.
Note 3: Other analysis examples(a few examples):
Spectral Measurements
Amplitude
Digital Filters
Distortion Measurements
Distortion
Digital Filter Banks
Tone Measurements
Frequency Domain (Spectral)
Frequency Domain
and Their's more available
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 2 Oct 2012 6:10 pm
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Tubes:(different tube set than the unit I found the picture of, it had 12AX7 * 3)
6EU7
6EU7
6EU7
6L6GC
6L6GC
5U4GB
I'll have to look up the specs via Google:
Should be:
2* 6EU7 should be a preamp tube and a phase inverter. No idea why 3 6EU7 tubes(maybe 1 for a 2 channel system or phono input vrs mic)
2 * 6L6 for power out Push pull @ 30 watts.
5U4B (never heard of this one ) it should be a rectifier tube,.
Physically they look Ok but have to be tested . |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 3 Oct 2012 6:12 pm First cleaning attempt
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This is going to take time but it's starting to shape up:
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Tim Marcus
From:
San Francisco, CA
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Posted 4 Oct 2012 7:41 am
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are you going to stick with point to point?
that looks like a great project - I bet that thing will sound amazing with those old tubes and original transformers!
_________________
Milkmansound.com |
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Lee Baucum
From:
McAllen, Texas (Extreme South) The Final Frontier
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Posted 4 Oct 2012 9:14 am
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Will you have a fancy wooden cabinet built, to hold the chassis?  |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 4 Oct 2012 5:19 pm
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@Tim,
re: are you going to stick with point to point?
Yes at least for now but it won't look as neat and tidy as your amps. I am not restoring this amp, to me it's just a inexpensive experimental platform for me to play with. I will try to get it going in it's current form and then possible change the pre-amp sockets to support Octal tubes, beef up the base response ,play with the frequency response on the front end add some modern by-pass caps etc and then hopefully I'll get a decent clean tone. In addition I'll design some computer software to do several types of analysis , maybe reports etc. |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 4 Oct 2012 5:28 pm
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@Lee
re: Will you have a fancy wooden cabinet built, to hold the chassis?
No not likely for this version however, if I am successful with what I'm attempting to do with this experimental version then I will build another homebrew version with a new aluminum chassis and all new parts (not a kit). It will be a while before I can get to that stage and at that time I will consider a nice wood cabinet if I can find someone that can help with that part. A carpenter I am not |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 4 Oct 2012 6:21 pm Tube Check
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Testing a 6L6 Power output tube.
Tested Great!
I think that the tube checker needs as much TLC as the amp but it seems to work fine. |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 6 Oct 2012 4:48 am Tube Test
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Tube 1 - 6L6 - Tested very good
Tube 2 - 6L6 - Tested very good
Tube 3 - 5U4B - No setup info for tube checker
Tube4 - 6EU7 - No setup info for tube checker
Tube5 - 6EU7 - No setup info for tube checker
Tube6 - 6EU7 - No setup info for tube checker |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 6 Oct 2012 5:07 am
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From this Article:
http://www.guitarplayer.com/article/first-impression-little-walter-tube-amplifiers-15-watt/8189
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** 15 Watt Version **
"Phil Bradbury has designed his point-to-point wired product primarily for guitarists. The Little Walter ($1,500 direct)
is based on the 1946 5C3 tweed Fender Deluxe amp. As in that rare vintage piece,
PREAMP:
the preamp driver and phase inverter are a pair of 8-pin 6SC7 octal (8 pin) tubes, rather than the more common 9-pin 12AX7 or 12AT7 employed in the majority of tube amplifiers. Bradbury feels that what the 6SC7s lack in gain, they make up in touch sensitivity.
POWER OUTPUT:
Two 6V6 power tubes
RECTIFIER:
a 5Y3 rectifier
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Changes required to MAKE A 50 WATT VERSION
- point-to-point wired (Stays the same)
- PREAMP:the preamp driver and phase inverter are a pair of 8-pin 6SC7 octal (8 pin) tubes(stays the same)
- Power Output:
Change from a pair of 6V6's to 6L6's
- RECTIFIER:
a 5Y3 rectifier (mostly likely upgrade to a 5AR4/GZ34s or 5U4 or use a solid state rectifier) |
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Bob Lawrence
From:
Beaver Bank, Nova Scotia, Canada
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Posted 6 Oct 2012 5:22 am Schematic - Fender Deluxe 5C3
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Fender Deluxe 5C3
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James Quackenbush
From:
Pomona, New York, USA
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Posted 6 Oct 2012 9:14 am
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Hi Bob,
The 5C3 ciruit that you show the schematic for was introduced into the Wide Panel Tweed Deluxe back between 1953-1955 ....I have this circuit in a Deluxe that was made by Rob Hudson of Blues Pearl fame back in the day ......It's a GREAT sounding amp !!......The problem with the 6SC7 tubes are that most of them are microphonic .... There is another tube that is very similar in characteristics that is just as old , that will only need a slight modifation to the pin outs that has less microphonics .....I would have to go thru some of my notes to find this tube ....I have had a lot of Tweed Deluxes , but this one is my favorite circuit ......Jim
PS ...I also have some old PA amps that have been modded for guitar use .....They are DRIPPING with tone and character !!......Now to see how they sound for Pedal Steel !!.......Jim |
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