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Single Ended EL-34 build


henry4841
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I have decided this is what I am going to build next. I already have all the big iron and tubes so why not improve the old built EL-34 amplifier I have. It may be a KT-77 tube amplifier or possible an EL-34 built around the EL-34 tubes I recently bought on Ebay. The circuit for either one is the same with possible some changes in the cathode resistor biasing the tube at it's best spot. Right now I am favoring the Tubelab SSE circuit. I like it for it's simplicity and easy build. Other than a constant current circuit added to the input tube the design is a very simple one. There have been many builds done with this design by George Anderson. Started on the wood chassis with cherry wood and plate aluminum in my woodworking shop yesterday. Pictures are forth coming.  

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For the last 2 nights I have been listening to my class A/B 150 watt SS amplifier. The first night just with a buffer pre only hearing the amp itself. Buffer contributes very little to the sound if any. Very quick and clinical sounding. The sound many enjoy and prefer but just not my favorite form of sound. The amplifier was built by myself and it uses all the good circuits a well designed SS A/B amplifier should have. Last night I decided the sound needed some tube flavor and added and installed a 12AU7 tube preamplifier designed by Maynard into the mix and it became my favorite kind of sound then. Without some 2nd harmonics the kind of music I enjoy just does not have as pleasant sound to my ears. Especially when it comes to vocals. This is a trick anyone can do with their SS PP amplifier. Install a good tube preamp and take a listen.  

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I listened to my modified Hafler 500 for years with a tube pre using NOS Mullard CV4003'S. I do believe an amplifier's only job is to amplify the level of the input signal faithfully without adding coloration. Of course we love tubes and what they can do to season the sound. That being said I like a tube pre in front of both my solid state and tube amps for how it "seasons" the incoming signal at the amp.

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I decided to buy some Hammond 125ESE's for this build. Bigger than the ones used in the Sweetie. They were 125DSE's. Order placed with Tubedepot this morning. Tubedepot has a very detailed data sheet for this transformer. Notice the chart at full power at 5,000K. Looks really good and that is at full power. Much better at the lower power level using Klipsch speakers. I bet they beat Edcor's spec sheet, that is if Edcor provided one which they do not. 

 

https://s3.amazonaws.com/tubedepot-com-production/spree/attached_files/125ESE.pdf?1659103176

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21 hours ago, henry4841 said:

Some progress, about an hours worth. My GF and I decided to sit on the front porch together for awhile this morning limiting my time in the wood working shop. 

You have to prioritize your time. And that was a good choice. I could be better at it myself, but my wife knows that I love to tinker. 

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10 minutes ago, Shakeydeal said:

I prefer a passive pre on the front end of a good tube amp. We all like what we like.......

Me as well. Well not exactly, I use an active buffer with no gain. A tube pre with a tube amp is just too much of a good thing for me. I say it's your system use what pleases you in your house. You are the only one you have to please. It is really that simple. 

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I should have started this thread by saying this is a well documented design where a complete build guide and parts list is available. 

 

http://tubelab.com/designs/tubelab-sse/

 

Hundreds if not a thousand or more have been built on diyaudio by members there. I built mine I'm guessing 6 or more years ago. George Anderson of Tubelab is a well respected information source on tube design and info. 

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Did not get any work done on this project yesterday. My granddaughter was visiting and my GF and I were busy enjoying her company and keeping her entertained. I did get my new, for me, old Marshall EL-34 tubes I bought on Ebay and installed them in my working amplifier I am going to rebuild. Before putting them in I listened to 2 songs of an album with my Gold Lion KT-77's first where I could do somewhat of a comparison. To my ears the sound was very similar with maybe a touch better bass. Mids and vocals were pretty much the same. I am happy with the purchase of the Marshall tubes. I paid $45 for the pair as tested excellent by the seller. I am going to build this amplifier around those tubes. The were made by a Russian company called Svetlana who made tubes for Russians for many years. Old company who had a good reputation making tubes. I am going to assume that USA or western European tubes were not available to the people or Russia. Russia still used tube electronic gear long after the USA started using SS gear. Marshall using them in their guitar amplifiers says a lot. 

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1 hour ago, henry4841 said:

 I paid $45 for the pair as tested excellent by the seller. I am going to build this amplifier around those tubes. The were made by a Russian company called Svetlana who made tubes for Russians for many years. Old company who had a good reputation making tubes. I am going to assume that USA or western European tubes were not available to the people or Russia. Russia still used tube electronic gear long after the USA started using SS gear. Marshall using them in their guitar amplifiers says a lot. 

Since Mullard/Philips was a European company, any equipment manufacturer in Europe who needed an EL-34 type tube in their equipment used one. Although they were a good tube, they were also very inexpensive and that is why they were so prevalent at first, not because of their sound, reliability or other attributes. 

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Spent some time in my woodworking shop yesterday making some progress on the wood chassis. Also ordered parts and tube for this build at Tubedepot. Some of this wood has been exposed to the sun in wood storage area in my garage and has already taken on the nice cherry wood color. After applying some oil and more exposure to light the color differences should blend together nicely. This chassis is taller and a little bit larger than the last build. The OPT's I have chosen will have to be installed under the chassis much like the last build and they are larger. Also need the extra room for the choke in the PS section to be installed underneath as well. 

 

 

P1040088.JPG

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You think it could use a skirt, trim, at the bottom. I really have not thought about it. Good idea, let me give it some thought. I do have some rubber feet ready on my Mouser order. As far as square, it is a rectangle but getting close to being a square. 

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I forgot to mention this morning with the picture that it is just the picture of the initial glue up stage. I am not sure the size of round over bit I use for the top but off hand I am going to say more than a 1/4" round over. That and I have to do a lot of sanding to get the dovetails looking good. And some wood filler. I make my own from the dust collected in my sander and wood glue. Best color match I have found. 

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