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The "$250" Amp? - 6LU8 Compactron SE, UL

My suggestion would probably be get the 8ohm ones for a "wider" range of speakers
if you do not have specific speakers in mine, I've tested the 8ohm outputs on 4ohm
and 16ohm loads and the amp performs well on all 3.

If have certain speakers in mind to use there is the "optimum" load here, the amp is
designed with a 5k primary, if you use an 8ohm output with 16ohm speakers you get
a 10k primary, less power and bit better dampening, using 4ohm speakers you will get
a 2.5k primary, about the same power but less dampening and a bit less control.

Sometimes when you have a transformer with multi taps it is not allways the tap that
matches the speakers rated load that actually performs better for your application.

So what I'm saying is in this particular case on this amp, it is not all that sensitive to
the load of speakers presented to it, some amps are more then others in this regard.

Also if someone wanted to spend a bit more money, Edcor does offer outputs with the
multi taps, and they offer ones with more power handling. If you are an experimenter
and want to build or tweak for other amps down the road a larger one with more taps
may not be a bad choice for you.

Basically your looking for a 5K primary, single ended, ultra linear, output that's rated for
at least 15w, I like the Edcors there inexpensive and perform rather well.
 
Thanks for the quick tutorial. Being me, it's a heck of a lot easier to build the amp and then design a set of speakers around it. Sounds like I'll have some leeway with the 8ohm version. I can swap around with the speakers I've got and go above and beyond from there.

Ray
 
I bought a pair of Polk R300's to run on this amp . I only paid 69 bucks for em , and figured i can mess around with the crossovers or just replace the speakers if need be . Cant even buy the materials to make a pair cabinets for 69 bucks . Besides , moving a sheet of MDF isnt gonna work till my back fully heals , if it heals . They have a sensitivity of 89db . So I am guessing they should play plenty loud in a small room .
 
The prototype that everyone's been listening to has had plain jane orange drops in it. I might start there, and then try some of the cheaper audiophile options like Russian PIOs, Russian teflons, maybe those Obligattos caps. Cap rolling is like tube rolling, it's subjective, and can be used to tune an amp to one's particular taste. The nice thing about this amp topology is that you have only a single coupling cap per channel, so that helps keep cost down and quality up.

Other cap tweaks might include bypassing the power supply caps with film caps, and bypassing the power supply cathode bypass cap with films. The cathode bypass caps can be of a lower voltage tolerance, also helps kep cost/physical size down.
 
Sorry, I meant to attach this...Any good Value for a ByPass cap? How about .0068uF ?
 

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I'd go a bit larger. You could go all the way to a 2.2uF film cap for the large val cap (220uF). Some say 10% of the original value. I think 2.2uF in film is pretty decent. You can experiment with any value really, tho. Let your ears decide if it's a worthwhile tweak. As in all things, there are limiting returns once you get past a certain amount.
 
Hey Kegger and Squid, I just emailed you the BOM. Could you take a look and let me know what you think. Cheers.
 
Go djnagle

djnagle said:
Hey Kegger and Squid, I just emailed you the BOM. Could you take a look and let me know what you think. Cheers.
Click to expand...

Go djnagle! Go djnagle! Go djnagle!

It's our birthday, It's our birthday!

Ok, well really, it is the big guys birthday soon here.

My shoulder and arms are aching in various places, Don King decided to give out a buncha dang turkeys and I went to get one since I know the ministry he selected in Jackson.

I asked if they needed some delivery help and there were like, no, we could use you passing them out . . . So I helped pass out 42 pallets of 22 lb turkeys!! O my gosh. Early Santa work.

Then I come here and we have a BOM in it's final throes! :banana::banana:

And my box from Mouser arrived with a buncha different values for this project and 4 others.

So, I am one happy but sore tubehead!

Hope you all have a good Christmas if ya celebrate it and if you don't, drop by someone who does, they might have Turkey :)

http://www.donkingnetwork.tv/
 
I should have a top plate in squidwards hands possibly on Friday.

DSC01131.jpg
 
I've been meaning to ask this question somewhere, and I'm thinking this thread is as good as any...

I have a copy of Multi-Sim, and I'm learning to use it. We use it constantly in the lab section of the electronics courses I'm taking. My question relates to vacuum tube models. Multi-Sim is based on the SPICE (NOT pSPICE) model. Do any of you have a source for tube models based on SPICE or models coded specifically for Multi-Sim? I've found a few on the web, but they're almost all at least 10 years old and specifically for pSPICE.

Also, I have a copy of UltiBoard which works directly with Multi-Sim. If you're not familiar with this, it is a PCB modeling and design tool. You start with the parts layout, drag wires from connection to connection on the screen, and it designs the PCB based on number of specified layers, etc. Pretty cool.

Forgot to mention: I have ikoflexor's model, which is based on ltspice. Will that work?
 
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Fisherdude said:
I've been meaning to ask this question somewhere, and I'm thinking this thread is as good as any...

I have a copy of Multi-Sim, and I'm learning to use it. We use it constantly in the lab section of the electronics courses I'm taking. My question relates to vacuum tube models. Multi-Sim is based on the SPICE (NOT pSPICE) model. Do any of you have a source for tube models based on SPICE or models coded specifically for Multi-Sim? I've found a few on the web, but they're almost all at least 10 years old and specifically for pSPICE.

Also, I have a copy of UltiBoard which works directly with Multi-Sim. If you're not familiar with this, it is a PCB modeling and design tool. You start with the parts layout, drag wires from connection to connection on the screen, and it designs the PCB based on number of specified layers, etc. Pretty cool.

Forgot to mention: I have ikoflexor's model, which is based on ltspice. Will that work?
Click to expand...

Happy New Year everybody!

Most likely the model will work as the spice code in it is pretty generic. An easy way to check, and something I do first for any tube model I find on the net or generate myself is to simulate a very small circuit with a voltage source for B+ and a battery for the bias. Then run a sweeping DC analysis and compare the plot with the curves from the data sheet. I'm not familiar with Multi-Sim but I'd be surprised if it could not do a DC sweep analysis. In ltspice you simply set the two voltage sources to vary between two desired values, in the increments you want. The plot then displays voltage curves just like the data sheet, and it's easy to compare. The shape and consistency of values is most important, not ultimate accuracy, as in reality the tube you use will be slightly different from that shown in the data sheet. Hope this helps. Msg me privately if you'd like to test the thing in ltspice which you can freely download, I can give you this amp model file and you can play with it.
 
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Thanks for the reply! Here's a link to National Instruments Multisim:

http://www.ni.com/multisim/

I'll play with your model and see what I can do with it. As soon as I figure out enough to not look too foolish, I'll drop you a pm!

Thanks again!
 
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