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 Post subject: EL84 Monoblock project
PostPosted: 01 Jul 2017, 01:11 
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Joined: 25 Jun 2017, 21:52
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Hello,

New to the forum and new to tubes. I am a tube convert after refurbishing a pair of Magnavox AMP 169 BB monoblocks and a Victor stereo pull from a console. My oh my, the revelation. I had always heard that tubes sounded different but really never paid attention. Until now.

My thought was that I can keep on getting old consoles and removing the chassis, incur cost and time and then try to make them beautiful. Or, I can just start from scratch and build what I want and make it beautiful as I go. So, I would like to build this or something similar to this project. I tried to find a thread on this project but could not find any. Still learning this forum stuff I guess.

http://diyaudioprojects.com/Tubes/EL84-Mini-Block-Amps/

I have the schematic and understand most of it.

I wonder if anyone has a parts list? I will go on over to the chassis forum and see what I can figure out for a chassis too.

Thanks in advance.

I have attached what I did with my dusty dirty pair of Maggie monos to this post. I put a fuse and switch in and ran the wires underneath a black walnut plank. I changed numerous coupling capacitors and it cleaned up the sound a lot.

James


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PostPosted: 03 Jul 2017, 13:44 
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Joined: 29 Apr 2017, 15:14
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You still have not mentioned, what your objective is.


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PostPosted: 03 Jul 2017, 16:19 
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Joined: 25 Jun 2017, 21:52
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Hi,

I guess I was unclear. I want to build the project at the link I provided in the first post. Here it is again:

http://diyaudioprojects.com/Tubes/EL84-Mini-Block-Amps/

The two EL84 based mini mono blocks intrigue me and I think I can make it look cool too.

Thanks,

James


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PostPosted: 03 Jul 2017, 16:39 
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Joined: 01 Jun 2013, 09:05
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Just for interest,

Why do you need a parts list? (the parts are on the circuit diagram just make a list..)
Remember that resistors /Capacitors have a working voltage<<so choose the working voltage and wattage to suite the situation.

However if the idea is to make a tube amp to sound like a Magnavox I think you may find it a bit different.
You say you like tube sound<<I guess you mean old Magnavox sound (that's not the same thing)
You need to be aware that just making a chassis that looks good and building the circuit might not work out so well, because the layout can effect the operation of the circuit. eg transformer cross talk and pick up is one.
NB tubes in my experience don't have a sound the same tube can sound different in different circuits with different components etc.
Old output transformers don't sound like new transformers if that's what you are after.
If you intend to build the project as shown in the link go for it..but be aware that its not a Magnavox.

Just a few thoughts.
Regards
M. Gregg

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PostPosted: 03 Jul 2017, 21:49 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, Yes this amp is not a vintage device. Yes it uses tubes, but it has a much cleaner sound than most vintage stuff like the Magnavox. Designs like that one from that era seldom had much in the way of response below 50 HZ or above 10KHZ. Distortion was usually much higher as well. Yes I know that there were numerous ones that were better, but now we can easily surpass their performance. The EL84 mono blocks and their cousins the Poddwatt DMBs and bigger brothers are premium sounding amps full range response and low distortion. They will sound similar to the ones you fixed up, just IMO much better. And yes they do sound different from solid state amps. I won't get into a discussion on which is better and why, just different. BTW the actual cost difference between building the EL84 amp and the EL34 version is not much. You might consider them as well.

Good listening
Bruce

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PostPosted: 04 Jul 2017, 02:19 
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Joined: 25 Jun 2017, 21:52
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Hello,

Thank you folks for the replies. I am looking forward to building this and to what it sounds like. I actually hope it is different than the Magnavox sound out of curiosity and because I already have a pair of Magnavox monos.

I note that the design calls for .33uf PIO (which I figured out to mean Paper In Oil - thank you Google). How critical is it that they are PIO style?

James


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PostPosted: 04 Jul 2017, 11:05 
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Location: Arizona, USA
Hi, I used the K40Y9 PIO caps because they are consistently good sounding and not costly. Really any 0.33uf will work. But....it will alter the sound. Others I like are WIMA MKS, Panasonic, Auricaps, Jantzen Cross caps and Silver Z caps and lately Audyn Caps Plus (Parts Express has them). They are inexpensive....but huge in size. IMO one of the nicest sounding caps at any reasonable cost. Still huge. The Audyn True Copper Caps are the ones I like best but they are both huge and costly. Russian Teflon FT-4 caps (in 0.22uf or larger) are also quite good, but they are huge and may be hard to obtain.

Good listening
Bruce

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PostPosted: 05 Jul 2017, 10:09 
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Hello,

Thank you for the thoughtful and complete response. You prompted me to do some actual reading on the subject of capacitors and why they sound different in comparison to others. It was enlightening for me.

To me, though capacitors work in a magicky mystical electronics arena there is a physicality that enters into the equation and bears on a capacitors effectiveness in doing its job. By physicality I mean the material that they are made of has a real-world physical impact on how the capacitor performs. At some finite point there are electrons being transferrred, agitated, excited and flowing around.

The differences in material impact performance and in turn impact audibility depending on where the capacitor is in the circuit. Are my old ears capable of hearing the difference? Perhaps not but I do know that I will never hear the difference unless I put in good ones from the start.

Thanks again.


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PostPosted: 05 Jul 2017, 12:58 
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There is nothing magic about capacitors they all sound rubbish,

however on a brighter note some are less rubbish than others.. :D
Just for fun>> http://www.humblehomemadehifi.com/Cap.html


Regards
M. Gregg

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Last edited by M. Gregg on 05 Jul 2017, 13:06, edited 1 time in total.

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PostPosted: 05 Jul 2017, 13:06 
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M. Gregg wrote:
There is nothing magic about capacitors they all sound rubbish...


In your opinion ;)

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* Ratings are for transistors - tubes have guidelines*
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