New Eiclone

a DIY, modified Mullard 5-20 monoblock design

New Eiclone

Postby WA4SWJ » Wed Mar 30, 2005 6:39 pm

Hi Everyone,

Here's a link to a couple of pictures of my first Eiclone.

http://community.webshots.com/album/354063825LZnHlO

Hope the link works OK. I used Uncle Ned's transformers and they're beautiful and beefy. I have not fired it up yet but will do so later this evening and I can't wait to hear it. All resistance checks are fine so I've got to set the bias and then go from there. I still have to hook up the center tap fuse once the RTV dries.

I'm building three of these for a tube style home theater system just for the fun of it. I'm using the ST-35 I built earlier for listening now and it just gets better and better. I'm loving it. It will eventually be used for the rear channels. Of course, I'll pull it out from time to time to do some more suitable duty than rear channels. I have a Sony DVD player with a built-in Dolby Digital decoder. Not audiophile, but it sounds pretty darn good. It also does DTS. It will feed all these amps direct. Lots of knobs to tweak! I'll work on that problem later. Others have already suggested a multiple unit pot on the same shaft.

I'll post some more pictures when I get the other two done but it might be a while. At least a couple of weeks. Thanks Shannon for some really great amps and projects. After I finish all of this the next project will be an off-the-wall 832 transmitting tube stereo amp - again just for the fun of it and for something unusual to put in my office. I have a pile of 832's and have ordered some transformers already.

Regards to all those on the forum. Hope you're having as much fun as I am! Yellow_Light_Colorz_PDT_12

More later,[url][/url]
Last edited by WA4SWJ on Sun Jun 05, 2005 6:27 pm, edited 2 times in total.
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Postby pro_crip » Wed Mar 30, 2005 6:48 pm

The link doesn't work, it says something about me not being the owner of the album and advises me to log in.
Why don't you go upstairs and play with the beaver?
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Postby WA4SWJ » Wed Mar 30, 2005 7:08 pm

Aw, heck. I was hoping it would work. Well, I don't have a web page and don't know how to post pictures here. Try this - go to webshots.com and do a member search for longea. You don't have to be a member to do that. I have a lot of pics there on a variety of subjects. The amp pics are in my New York folder and you should be able to see them there.

Sorry - I thought this might work but I guess not.

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pix

Postby Shannon Parks » Wed Mar 30, 2005 8:53 pm

How about these:
http://image30.webshots.com/30/0/45/37/ ... Pek_ph.jpg
http://image30.webshots.com/30/0/47/5/3 ... gsU_ph.jpg
http://image32.webshots.com/33/5/33/32/ ... Ece_ph.jpg

BTW, when using outputs where you are sure about the phase, leave the negative feedback disconnected at first. I will sometimes then have a couple test jumpers where I can momentarily connect the negative feedback to see if she oscillates - you can have a DMM hooked up to the B+ and it will drop, as the current flows free. If so, swap the output primary halves.

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Postby WA4SWJ » Wed Mar 30, 2005 10:22 pm

Shannon,

Thanks for posting the links. I'll take some more pictures tomorrow. I was too eager to fire it up to take more this evening.

I checked the feedback polarity prior to power up according to Ned's transformer drawing. It worked fine with the feedback connected. I tried reversing the primary halves just for grins and it oscillated right away. So, I got them right according to the drawing the first time.

When I first fired it up it was quite noisy. I grounded the input jack to the chassis and totally eliminated that. However, it does have some moderate hum that is independent of the volume control. I'll look at that tomorrow. It's late now. I'll play around with the grounds and see what I can find.

The amp sounds great. I'm playing a Sting DVD audio disk and using it for the center channel right now. Sounds really good with a lot of punch. I'm using Electro-Harmonix EL34's as well as the 6SN7 and 12AX7. I set the bias slightly higher at 57 ma.

So far, so good!

Thanks again. More tomorrow.

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Hmmmmmmmmm ..........

Postby WA4SWJ » Fri Apr 22, 2005 6:50 pm

Hi Gang,

I finally had time to get back to my first eiclone and work on the hum. My ST-35 is silent but this eiclone is not. I have about 4.7mV of AC hum across an 8 ohm speaker with the input shorted and the volume control turned to 0. The hum is not volume control dependent. I've installed shielded cable on the input (shield grounded only at the board) with no change.

Checked the bias again and set it for 55 mA on each tube. That's well balanced.

Checked the diodes - both are good.

Tried reorienting the choke - no difference.

Had to ground the center tap of the 6.3V winding to get rid of volume control dependent hum of high order. Did that first to get rid of really bad hum.

Curious if anyone has suggestions. Links to pictures are in this thread.

The amp sounds great but I want it to be silent at idle like my ST-35. Perhaps I should have mounted the power transformer away from the signal end of the board like Shannon's prototype. My next two will be built like that and if that works, I'll buy another chassis and rebuild this one eventually.

Comments anyone? How much hum voltage do you have at the speaker terminals at idle?

BTW - I have not had so much fun in a long time. Even with the hum in this amp I am enjoying it.

Thanks!!!
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Re: Hmmmmmmmmm ..........

Postby Shannon Parks » Fri Apr 22, 2005 7:25 pm

WA4SWJ wrote:Comments anyone? How much hum voltage do you have at the speaker terminals at idle?

BTW - I have not had so much fun in a long time. Even with the hum in this amp I am enjoying it.

Thanks!!!


I'll check mine tomorrow and post back.

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Re: Hmmmmmmmmm ..........

Postby Shannon Parks » Fri Apr 22, 2005 7:52 pm

separks wrote:
WA4SWJ wrote:Comments anyone? How much hum voltage do you have at the speaker terminals at idle?

BTW - I have not had so much fun in a long time. Even with the hum in this amp I am enjoying it.

Thanks!!!


I'll check mine tomorrow and post back.

Shannon


BTW, Ed, I did some extensive noise/hum testing on the Ike a few weeks back, but hoped to do some more before posting. But:

1) The input signal wiring seemed real critical. Moving the location of these wires could really improve the noise floor. Trial and error at this point - no hard pointers.

2) My original open loop gain tests were faulty as they were taken before I learned to 'cal out' any low level input signal error. I just discovered this error a couple weeks back and am still a little confused how it happened. In a nutshell, the amp can happily use another 8dB of negative feedback due to the fairly high sensitivty of the Eico power amps. This is probably a good idea for those with efficient speakers. The mod is simple: remove R8 and replace with a 2K resistor paralleled with a 1000pF cap. Nothing else needs changed. This can be done using a surface mount technique for testing and listening. I did have a chance to do extensive stability tests with this mod and it looks good.

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eiclone in put lead

Postby audioray » Sat Apr 23, 2005 9:18 am

looking at your photo it seems that your input wire is not shielded to board.
allso what does the cap/resistor do on small term. block do. i allso have annoying humm in both amps. must send photos when son is available.
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Re: Hmmmmmmmmm ..........

Postby Shannon Parks » Sat Apr 23, 2005 1:42 pm

separks wrote:BTW, Ed, I did some extensive noise/hum testing on the Ike a few weeks back, but hoped to do some more before posting. But:

1) The input signal wiring seemed real critical. Moving the location of these wires could really improve the noise floor. Trial and error at this point - no hard pointers.

2) My original open loop gain tests were faulty as they were taken before I learned to 'cal out' any low level input signal error. I just discovered this error a couple weeks back and am still a little confused how it happened. In a nutshell, the amp can happily use another 8dB of negative feedback due to the fairly high sensitivty of the Eico power amps. This is probably a good idea for those with efficient speakers. The mod is simple: remove R8 and replace with a 2K resistor paralleled with a 1000pF cap. Nothing else needs changed. This can be done using a surface mount technique for testing and listening. I did have a chance to do extensive stability tests with this mod and it looks good.

Shannon


Good grief, I'm an idiot sometimes! Yellow_Light_Colorz_PDT_10

I had a 6189 (aka 12AU7 sub) in there for some reason when I did my open loop tests two weeks ago. Anyhow, I just noticed it after 'finishing' noise tests a few minutes ago. Thermion is coming over to sweep his linestage and ST70 so it will have to wait until tomorrow. I will report back then with <proper> information. So don't do the R8 mod I mentioned yesterday unless you plan on using a 12AU7 at V1. Who knows? This might end up being a great mod.

FWIW, the grounding scheme all looks solid. I did tests with a jumper across J1-1 and J1-2 to eliminate any noise from input wiring. This is a good test for anyone to make.

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Postby WA4SWJ » Sat Apr 23, 2005 6:18 pm

Shannon,

OK - no problem on the mod. I don't have the parts to do it right now anyway. I'll continue messing around with it. As I mentioned I'll build my other two with different chassis arrangements and see what difference that makes.

The hum is not objectionable now but you can just hear it across the room. Up close you can definitely hear it. Grounding the center tap of the 6.3 volt winding was a must for this amp.

Always enjoy your comments. Thanks!
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Mods and Rockers....

Postby Shannon Parks » Sun Apr 24, 2005 6:57 pm

WA4SWJ wrote:Shannon,

OK - no problem on the mod. I don't have the parts to do it right now anyway. I'll continue messing around with it. As I mentioned I'll build my other two with different chassis arrangements and see what difference that makes.

The hum is not objectionable now but you can just hear it across the room. Up close you can definitely hear it. Grounding the center tap of the 6.3 volt winding was a must for this amp.

Always enjoy your comments. Thanks!


Hi Ed,

I spent a lot of time on the Ike today. I have been meaning to get back to the ST35 and Ike after my ST70 driver project. Basically, my ST70 driver grew out of the Ike and now it looks like it will pay some dividends back to the Ike.

While I was able to a few tweaks on the Eiclone circuit noise-wise, the main culprit is the high gain from the original circuit. The Dynaco numbers for power amp gain seem much more reasonable at ~23dB, while the Eico is ~30dB. I am in the process right now of reverting one of my test Ikes to completely stock and at that point will try to implement gain and negative feedback numbers very similiar to my ST70 driver project. That's where that 2K and 1000pF figure came from. That only worked - mistakenly with a 12AU7 - since that Ike was AC-coupled with a CCS.

Long story short, I'll post a sticky message soon with the mod which will be as simple as possible. Don't worry about getting any parts - I'll send out mod packs free of charge to any Ike customer that wants one.

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Postby WA4SWJ » Sun Apr 24, 2005 8:13 pm

Shannon,

I'll look forward to seeing the info. I am in the process of building the second eiclone now. I'll send some pictures tomorrow evening. I have the chassis drilled and most of the hardware mounted. I'll have to build the PC board tomorrow evening. This one has the transformers mounted at the chassis back with the cores 90 degrees to each other.

I did notice some oscillation in my first eiclone that was not due to incorrect transformer half connections. It appeared to me to be way too much gain. It was also very noisy that also appeared to be oscillation. I don't have an oscilloscope so I couldn't check. By grounding the center tap of the heater winding all that went away.

I do have a couple of 12AU7's lying around I can try out if that's one step of the solution. BTW, I have Uncle Ned's transformers. They are very nicely made.

Thanks for the info. Good luck with the study.
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Ike

Postby Shannon Parks » Mon Apr 25, 2005 6:41 am

WA4SWJ wrote:I did notice some oscillation in my first eiclone that was not due to incorrect transformer half connections. It appeared to me to be way too much gain. It was also very noisy that also appeared to be oscillation. I don't have an oscilloscope so I couldn't check. By grounding the center tap of the heater winding all that went away.


Hi Ed,

Something sounds wrong here. The board already has the two 100 ohm resistors for a DC reference on the filaments. Removing these and switching to the filament CT should show no difference.

Either way, there shouldn't have been any oscillation - the stability network on the Ike is quite stout. Did you have the negative feedback hooked up at this time and the input loaded?

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Postby WA4SWJ » Mon Apr 25, 2005 8:59 am

Shannon,

Yes, the feedback was connected and it was connected properly. It also had the same behavior without the feedback connected. As I mentioned above, I tried reversing the primary halves and it oscillated right away so they were correct to start with. I connected them in accordance with the polarity as shown on Ned's drawings. So all is well there.

I have a 50K pot on the input that loads the input to zero ohms when set at minimum level. When I turned the volume control up even slightly, 60 Hz hum began and was progressively louder as I increased it. The input connections are made with 2-conductor shielded wire with the ground at the board end only. All of this stuff ceased when I grounded the filament CT to the chassis (oscillations too). Now it just has hum that is not volume control specific. I have not tried the test you mentioned a couple of posts above. I'll try that tonight. I also have not tried running a bond wire from the board to the chassis. I'll try that too.

I also tried lifting the chassis ground with no effect. Interesting problem, huh? As I mentioned, the amp sounds great but has that 4.8MV of hum that I'd like to get rid of. The amp is operating fine in all other regards.

I might try a 12AU7 this evening but I want to complete my second amp to see how it does. I'm busy building right now and will experiment more as soon as I'm done with this one. You mentioned perhaps some more room for higher negative feedback. Why not connect to the 16 ohm tap?

BTW - all the resistance checks were perfect so I am sure I haven't swapped a part anywhere. I double checked that.

Also BTW - I'm a EE so I'm pretty familiar with all this. I just don't have any test equipment other than a digital VOM! All my good stuff is in my house in Arizona. I might buy an oscilloscope at the Dayton Hamvention in a few weeks. That would help me determine if it's power supply filtering or a ground loop somewhere.

Still more BTW - my ST-35 oscillated too on both channels until I installed the small capacitors on the grids of the 12AX7 to ground as shown in your schematic. Once I installed those that problem went away completely. (I didn't have them at first - they were backordered and I was anxious to fire it up!) I have not tried this on my eiclone. My ST-35 sounds absolutely great and is quiet. That's a fabulous little amp.

More pictures tonight. I'm progressing well with the second one and it has a different layout as I mentioned.

Regards,
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