There is also: https://www.jacmusic.com/html/order/!jacmusic-pricelist.pdf no import duties since they are in Germany. If you live in France that is.
My first DIY build was the popular Bugle 45 SET designed by Gordon Rankin. It is highly regarded and well documented. Analog Ethos sells a kit called the "Legendarium" which is essentially the same circuit but uses 2A3s instead of 45s. I know of one person who built that kit with excellent results.
https://www.analogethos.com/legendarium-kit
The instruction manual is very detailed.
Thanks! As this is a precursor and learning experience prior to building my own 45 from scratch, I’m hoping to stay with the basic design and drivers. Just do what I can get the most out of it.
I don’t think ps transformer is big enough to get the kind of voltages on the 6SN7s seen on the 300B and 2A3 circuits.
While, not a perfect , it seems I could get a little more voltage to the 6SN7 by reducing the 20K (and maybe the 33K resistor) coming off the B+? maybe get a little closer to linear. Then increasing the plate resistors values for more voltage swing. I‘m still trying to understand the interplay of changing these resistor values, the resulting voltages the effects on the tube bias. A lot of moving parts for a novice like me.
I don’t want to go completely by trial and error, and was hoping to tap Into the vast experience and knowledge base of those on this form such as yourself as to a good starting point for the resistor values and voltages within the capabilities of the available B+. Any input is greatly appreciated. I may be using some terminology incorrectly, please feel free to correct as this is part of the learning process.
Excellent advice from all! As I already own very nice 2A3 and 300B Elekit amps I am determined to stick with a 45 build.
Modifying the monoblocks on hand is a precursor and learning tool prior to a scratch build and I will be sticking with the original design and drivers.
Getting some great ideas here for my own build—but that is step 2 and I will likely start a new thread for that. For now I am going to stick with improving the circuit at hand.
Bas has provide valuable input on PS mod…open to more. Now looking for some specifics on voltages on the 6SN7s within the capabilities of the power supply
Modifying the monoblocks on hand is a precursor and learning tool prior to a scratch build and I will be sticking with the original design and drivers.
Getting some great ideas here for my own build—but that is step 2 and I will likely start a new thread for that. For now I am going to stick with improving the circuit at hand.
Bas has provide valuable input on PS mod…open to more. Now looking for some specifics on voltages on the 6SN7s within the capabilities of the power supply
Love Skunkie! Her videos have empowered me to proceed with this. Hoping she might chime in on this thread.
I have watched her entire 300 B build series (and the rest). I don’t want to completely redesign these monos as they are a pretty cool looking junk drawer type build. There are some great old salvaged bits in them…along side some pretty cheap crap caps and resistors. I suspect the builder used whatever resistor values readily at hand and must have a large stock of 56uF capacitors! (Also, some have misgivings about the cascode design Skunkie implemented. Still trying to wrap my head around pros and cons of Cascode versus direct couple as they relate to driving SETs)
Having a smaller power transformer, I don’t have the leeway available in her 300b for the voltages on the 6SN7. hoping to get a little closer to a linear operating point with some resistor tweaks. in a nutshell that is the purpose of this thread.
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Thanks again @Bas Horneman !
Unfortunately, no way : for me, the prices are way too high no matter for a project - considering what you would pay for a 300B or 2A3 reissue ! So I'll stay with these more common tubes models - below pictured is my DIY U-300B, using Shuguang 300B :
T
The original poster, rob7 said:
"Yes I have listened to it and it sounds pretty good! but I did buy it to tinker and learn."
Even before the tinkering . . .
Just goes to show you that a design that some do not like, can sound pretty good anyway.
Bas Hornman,
What makes you think an original 45 is cheap?
Especially like the time I purchased 2 pristine NOS 45s for stereo.
I got the amp up and running, and ran for 2 hours of beautiful night time listening, then I turned the amplifier off.
The next morning as soon as I turned it on . . . Bang!
"Yes I have listened to it and it sounds pretty good! but I did buy it to tinker and learn."
Even before the tinkering . . .
Just goes to show you that a design that some do not like, can sound pretty good anyway.
Bas Hornman,
What makes you think an original 45 is cheap?
Especially like the time I purchased 2 pristine NOS 45s for stereo.
I got the amp up and running, and ran for 2 hours of beautiful night time listening, then I turned the amplifier off.
The next morning as soon as I turned it on . . . Bang!
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Rob7,
Good for you, stick with building two 45 Mono Blocks.
I just spotted a major problem with your schematics in Post #1.
Did anybody else spot that, Hello? . . .
There is no bleeder resistor to discharge the B+.
Safety First!
Prevent the "Surviving Spouse Syndrome"
Connect two 25k 5 Watt resistors in series from one end of the choke, and the other end of the series 25k 'bleeder' resistors to ground.
After my first 45 amplifier with the blown NOS tube . . .
. . . I built a less than optimum 1.5 Watt / channel stereo 45 amp, to use at work (with Usher S-520 2-way speakers, and a simple CD player).
Rather than use NOS 45 tubes (New Old Stock), I purchased a few Used 45 tubes, and did a best-match pair with what I had.
Every body at work loved the sound of that amp and Usher speaker combination.
Keep us posted; and Have Fun building and listening!
Good for you, stick with building two 45 Mono Blocks.
I just spotted a major problem with your schematics in Post #1.
Did anybody else spot that, Hello? . . .
There is no bleeder resistor to discharge the B+.
Safety First!
Prevent the "Surviving Spouse Syndrome"
Connect two 25k 5 Watt resistors in series from one end of the choke, and the other end of the series 25k 'bleeder' resistors to ground.
After my first 45 amplifier with the blown NOS tube . . .
. . . I built a less than optimum 1.5 Watt / channel stereo 45 amp, to use at work (with Usher S-520 2-way speakers, and a simple CD player).
Rather than use NOS 45 tubes (New Old Stock), I purchased a few Used 45 tubes, and did a best-match pair with what I had.
Every body at work loved the sound of that amp and Usher speaker combination.
Keep us posted; and Have Fun building and listening!
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Thanks! any thoughts on upping the voltage to the 6SN7s? Again, looks like a junk drawer build using what was onhand. Possibly not the optimum resistor values.
Thanks @eduard !
Yes, I built them in 2013 and the tubes are still the same today... The circuit supply offers two modes : Hi=8WRMS with B+=400V and Lo=4WRMS with B+=300V. Most of the time I use it in the Lo mode, hence the long life of the tubes.
T
More voltage for the 6SN7 tubes? . . . Sure.
The 6AX5 drops 50V at 125mA load. Perhaps it drops 45V at 50mA load.
1. Get a couple of 1.5kV rectifier diodes (yes, solid state diodes, I use SS diodes all the time for the B+).
With a 1V drop or so, you get perhaps 44V more B+.
Connect their Anodes to the same place as the 6AX5 plates.
But . . . you need real estate to add two filter caps, and a resistor between them. You are building a second power supply that runs off the power transformer.
2. Or use the existing caps and choke, and throw out that 6AX5 and replace it with those 1.5kV rectifier diodes (additional real estate is not needed)
Not anything else I can suggest if you uses the same power transformer.
Do not forget to wire in the bleeder resistors.
The 6AX5 drops 50V at 125mA load. Perhaps it drops 45V at 50mA load.
1. Get a couple of 1.5kV rectifier diodes (yes, solid state diodes, I use SS diodes all the time for the B+).
With a 1V drop or so, you get perhaps 44V more B+.
Connect their Anodes to the same place as the 6AX5 plates.
But . . . you need real estate to add two filter caps, and a resistor between them. You are building a second power supply that runs off the power transformer.
2. Or use the existing caps and choke, and throw out that 6AX5 and replace it with those 1.5kV rectifier diodes (additional real estate is not needed)
Not anything else I can suggest if you uses the same power transformer.
Do not forget to wire in the bleeder resistors.
Thanks. To clarify, this would only be used to power the 6SN7s and the current rectifier and filter would still be used for the 45 tubes? This is a mono block design and the 45 filaments are on a sperate transformer so not too much strain on the transformer as is however, it is only rated for 60 milliamps Would this be a problem?
Not ruling this out and it is a good mental exercise for me. As stated, I am still learning. I was hoping for something simpler to stay somewhat close to the original design. Seems I could gain some voltage on driver by replacing the 33K resistor where it splits off from the B+ by using a lower resistance or removing it. Then adjust the plate resistors. I have no idea the full ramifications of this, or if it’s even viable. More of a question.
I guess I’m just trying to optimize the circuit as is.
The capacitors are no name Chinese crap and I was going to upgrade them and while in there I might as well replace the resistors which also appear to be of dubious quality. I could just use all the original values, but if I’m going through this effort I would like to make the best use of the circuit. Again, I’m not sure how much care went into optimizing the voltages in this amplifier. Maybe there is no room for improvement, but if there is, I would like to attempt...even if the change is negligible, no reason not to while I’m changing out the resistors and caps anyhow.
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Simplest and most straightforward would be to make the second stage a duplicate of the first stage, with a coupling capacitor in-between. Should have been that way to begin with - a very silly original circuit.
All good fortune,
Chris
An option I am considering. Still curious to see what can be rung out of this circuit… and maybe learn anything or two. In the end, there’s a good chance I will end up doing as you suggest.
Curious, why so little love for the 6SN7? Seems fairly linear, capable of enough swing for a 45 tube, readily available. I know there’s much more to it than this. Hoping somebody can Provide some specifics to a newbie. Maybe even suggest some current production alternatives, and specifically why they might be better? I see a lot of banter about “this driver being better than that”… But never an explanation as to why.
Kind of derailing my own thread… But I enjoy the banter here.
Still looking for some suggestions as to optimal voltages and resistor values in the monos as built.
Kind of derailing my own thread… But I enjoy the banter here.
Still looking for some suggestions as to optimal voltages and resistor values in the monos as built.
It's just a first, obvious, step. Evolution would take you to optimizing each of the driver stages for its location, attempts to remove the low voltage electrolytic cathode bypass caps, and possibly a combination of positive feedback, cathode to cathode, and negative feedback, 2nd stage anode to first stage cathode, to minimize impedance at 2nd stage anode driving output valve Miller C.
new post: 6SN7 is a very linear valve, but needs (like everything) to be operated in its best region. Throwing away lots of B+ like the JC Morrison circuit is foolish, but fashion-forward in the 1990s.
All good fortune,
Chris
new post: 6SN7 is a very linear valve, but needs (like everything) to be operated in its best region. Throwing away lots of B+ like the JC Morrison circuit is foolish, but fashion-forward in the 1990s.
All good fortune,
Chris