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Matts Tubelab SEE

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Matts Tubelab SSE

Soldered the board up today. It is a little crammed due to only finding 1000v k40y'S. I have installed the caps in mini binding posts so that they can be easily changed in the
future and the same with the cathode resistor.

If any one could give the picks a look over for issues I would be grateful.

I NEED to order 1 x 3 gang Phoenix screw connection as i was one short, and then the board is finished.

Thanks
 

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Cheers Rob. They are Mills 5w 560 0hm wirewound. I was surprised how small they are though too when they arrived but they are definately 5w.

Thanks for pointing it out though. I have ordered 680 ohm too as l plan to use 6p3s -e too but I have ordered 7w.
 
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I bread boarded it all yesterday and at approx 17:00 had a can of beer that gave me the courage to turn it on. No bangs or smoke!!!!. :)

IT is set in simple triode mode as per Tubelabs instructions.

A lovely sounding amp and plenty of power, even in this mode for my Frugal horns with Alpair 7.3.

A few things I notice.

1) It is chuffing heavy, I am going to have to watch my back on this one.

2) On start up the ecc81 glows very bright, just for a few seconds and then dims down to normal.

3) One of my KT88 / Tungsol 6550's seems to have a hot spot in the middle at the top under the gettering. It moves with the valve though if I swap them so it's not down to my circuit. It's not red though, does this matter.

I now need an enclosure, possibilities are the large Hammond one in walnut, or possibly adapting a 2nd hand LP12 plinth. Any suggestions on this would be appreciated as I am struggling to find one that is large enough and looks nice.

Thanks

Matt
 

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Matt,

You got some big iron there - no wonder it's heavy. Be careful!

Also be careful with the high voltages.

With transformers this size, you will need a large chassis. I think something 17" x 14" would be satisfactory - can you take a few measurements?
 
Hi. I measured up before and I think the minimum size top plate douk be 350mm x 250mm.

Thanks on the high voltages, I have earthed everything metal back to the lec. The kids and cat were not allowed In The room while I was playing it and meter testing was done via croc clips. It has been set aside now until I get to settle some more.

B+ is 445v - 448v 6.6v at heaters but that is without the valves/tubes in place so the 6.3 is about right. I have used the recommended 50k potentiometer but it seems too loud at the low positions sosomething isnt right with it. Either it is faulty or I have it wired wrongly. It is in off (zero volume) in the lowest position but at one click it is bordering on too loud, it does get even louder though as the volume is turned up though. Its had 5 to 10 hrs use over the weekend and it is bedding in nicely sound wise. I have great bass response and am not noticing an issues with high frequencies that some have reported withvtje large Hammond SE opt's. I havecto say itxall sounds nice so far.

Matt
 
Hello. Thanks for the chassis suggestion.

My pot is actually a SMD stepped attenuator bought from ebay, mainly because I read some posts somewhere where people were saying they were good. The ebay description is below.

DACT Type SMD 21 Stepped Attenuator ( Audio Log Type / stereo ).

I am beggining to wonder about this to be honest, i am thinking about buying a cheap log pot and trying it out instead. If it is any good I could change it for an Alps or something better, but of the same values.

Thanks

Matt
 
I have done some experimenting tonight with different sources.


RESULTS ARE.


Homebuilt 834p based phono stage - super loud on click one, even louder on click two, click three would be way too loud for my ears in our room, so i didn't go there. silent in the home position.


Yamaha CD player - The same as above.


Smartphone playing amazon music through a Bluetooth Puck - the source volume is variable so i turned it right down to 1\3rd. This meant i was able to mess around with the Pot on the SSE more. Findings are - the volume is variable over the first 4 or five positions getting louder from position one to 5, position Zero is silent. There is no audible change that I can detect through the 15 or 16 positions after position 5 though. Sound Quality is superb no audible noise or distortion that I can detect anyway.


Any one got any ideas what might be causing this please, I am using Alpair 7.3 speaker drivers that are connected to the 8 Ohm tap. They are approx. 87db sensitivity but some do think that this is a conservative rating.


The hot spot on the valve does definitely move with the valve if you change them over from left to right. I also tried som 6P3S-E's that I have, these had an even glow throughout the hole tube so I am no longer worried about this.


Thanks


Matt
 
Firstly Zman thanks for sticking around. I am glad you are trying to help.

I sketched it out, sorry about the poor quality of the drawing.

Appreciated.
 

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It looks to me from your diagram that you may have a wiring problem. Here's a diagram from the tubelab site. Only the center wire from each connector needs to go thru the pot.
The shields go to signal ground (as do a pair of pins on the pot.) Check that your pot is oriented correctly with the diagram and that you have no solder bridges (a problem I've had.)
 

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