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DIY tube amps - help??

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antpink

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Joined 2005
#1
Right now I have a Meridian CD player, Chinese make valve pre and 2 x power amps (one per channel), that use 4 x EL34 tubes for juice. Proac Studio 125 speakers, apparently 87 dB efficiency (according to website). This setup is lovely, but while researching replacement tubes to cure a bit of an uncontrolled bass - I stumbled across a bunch of info on DIY. So, down to study, downloaded and printed a lot of useful theory and laymans info and read, read, read.

So, I looked at the analog output of the CD player - 2V. Back to the various texts. I found the diytube website thanks to a previous poster, and like the look of the Eiclone. I came to a conclusion that I could probably build a new set of power amps, lose the pre-amp, construct a DIY remote controlled volume pot, and with the money made from sale of unmodified amps, come out on top.

I like this idea, as I have an engineering background (not electrical, but I can learn), have begun to grasp the concepts as presented in some well written (and not so well written) texts available through the marvellous community of diy and tube enthusiasts, and am looking for a hobby to add to my other main one of listening to good music.

So, with the Eiclone, I can see these are constructed as mono power amps, with dedicated PS, transformers etc, and with up to 30-40W on tap, should be able to stir up the Proacs. Question is, I am assuming that it is possible to daisy chain inputs to create a 4 amp, 2-channel bi-amp set-up - am I correct? I wonder if the Chinese amp design, whle extracting some serious juice, might be sacrificing some quality that I could recover by custom building lower power, dedicated section units.

And cosmetically, as well as to possibly reduce grounding interferences, I was considering separate chassis for the transformers and the tube boards, maybe mounting 4xtransformers in a single chassis with power cords between this and the tube boards. That's a longer term idea, as I would start small....😉

So. Am I mad?
 
#2
No, you are not mad. Please forgive this asenine question, but what on earth is an Eiclone?

Also, passive bi-amping is of little use, especially considering you will have to get another amp - you will likely get much better results ditching the passive crossovers altogether for line level active crossovers. There is really no need for the tweeter amp bothering producing bass.
 
#3
An eiclone (I think spelling is correct) is a PCB based design for a monoblock power amp, to be found on diytubes.com. Looks like a neat solution to get 2xEL34's in PP configuration and saving a lot of wiring.

Very good point about the crossover - this could really clean things up I would imagine. I need to go back into the www and do some searching on these. Do you think signal loss would be so great with a passive configuration? I don't suppose you know of active X-overs that are available in schematic form?

Thanks for your help and sage advice.
 
#5
Rod Elliott's site is quite good, but his crossovers contain opamps! 😱

You can find information on valve-based active crossovers on the TubeCad Journal's Tube-Based Crossovers article, and the Active Crossovers and Filters article

There is also a program you can download which calculates the component values for various crossover frequencies and slopes (Butterworth/Bessel/Linkwitz-Riley), but I've forgotten where I downloaded it from. When I find it, I'll post a link.
 
#6
Hi,

Also, passive bi-amping is of little use, especially considering you will have to get another amp
Click to expand...

You can filter passively at the input(s) of the amp(s).
Either way, passive or active, you're always going to need separate amps for the respective speakers.

Actually Planet10 should have info on this somewhere on his website.

Cheers, 😉
 
#8
fdegrove said:
You can filter passively at the input(s) of the amp(s).
Either way, passive or active, you're always going to need separate amps for the respective speakers.

Actually Planet10 should have info on this somewhere on his website.
Click to expand...

Yep, you could just use a passive network at the input of your amps if the amps are sensitive enough and/or your sources have enough voltage swing at the outputs, so you can live with the insertion loss. Here is a link to the information on Dave's website that Frank was referring to.

What I meant before by "passive bi-amping" was connecting the full signal to the inputs of each amp, and attenuating the unwanted frequencies at the output (with the existing passive crossover). In my opinion, this is pretty much a waste of an amp as you get the disadvantages of an actively bi-amped arrangement (the need for another amp) with less of the benefits. There are some very well written articles on bi-amping on Rod Elliot's site: Benefits of Bi-Amping (Not Quite Magic, But Close), and Active Vs. Passive Crossovers.
 
#10
audiousername said:
Yep, you could just use a passive network at the input of your amps if the amps are sensitive enough and/or your sources have enough voltage swing at the outputs, so you can live with the insertion loss. Here is a link to the information on Dave's website that Frank was referring to.
Click to expand...

You beat me to my own link 🙂

If you are DIying your own amps the PLLXOs can be built in-between stages so the issues of gain typically go away. You can also add them between more than one stage to get steeper XOs and more room for tailoring.

dave
 
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