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PostPosted: 10 Apr 2016, 07:19 
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wdecho wrote:
Thanks for sharing your build. My first thought looking at the underside was "sure is busy under there." Great job.


LOL yes it looks busy but on closer inspection its not.. :D

By industrial standards is quite open. Its dead silent with my ear inside the speaker cone and cool inside. I drive the venting with the warmth of the choke by the vent (hole in the top of the chassis) which pulls the air into the underneath of the chassis on the EL34se.

On the RH the vent is driven by the tube rectifier and the driver uses Electron stream triode on EF86.
The EL34 spends most of the time in ES. The RH in pentode but is switchable.

I'm not a fan of Ultra linear and prefer ES, triode or pentode. However its each to his own I don't like global FB either :D.
Each to their own I guess.

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M. Gregg

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PostPosted: 14 Apr 2016, 13:43 
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Just for interest,

The Potentiometer is a Ko-On TKD not the stepped version (you know when one position is just not quite right and the next isn't either) sounds a bit like baby bears porridge :D, however the Tocos carbon are also very good. I'm not a fan of Alps many are :)

The EL34's tube sockets/bases are mounted as shown because I like to see the heater running full length of the tube at the front and the heat fins inside the tubes shield the glow from the heater at the top of the tube which can be to bright when watching films in a dark room.

The lamp is 12V running on the 6.3V heater supply to give a glow under the chassis it can be done with LED's but you need to put a blob of hot glue on the led to diffuse it and stop the single bright spot under the chassis, I'm a fan of cruise lights again you can see the amps on but its not in your face which direct on indicators can tend to do. So I fit most "Power on" lighting with consideration to not point direct at you when you are sat in front of the system.

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M. Gregg

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PostPosted: 18 Apr 2016, 14:47 
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Ferrite bead option.
For those that like to try things. :)
NB don't let the ferrite touch the metal conductor. Fit over the insulation about 20mm from the 220 Ohm.
Interesting exercise to try.

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M. Gregg


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PostPosted: 18 Apr 2016, 15:47 
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M. Gregg wrote:
Ferrite bead option.
For those that like to try things. :)
NB don't let the ferrite touch the metal conductor. Fit over the insulation about 20mm from the 220 Ohm.
Interesting exercise to try.

Regards
M. Gregg


I'm ok with this. Generally ferrite is non conductive.

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PostPosted: 18 Apr 2016, 15:54 
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mwhouston wrote:

I'm ok with this. Generally ferrite is non conductive.


I think the contact with the conductor has an effect not the conductive nature of the ferrite. :)
I.e. even spacing around the conductor it could be an air gap but the wire insulation is just easier. However each to their own.

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M. Gregg

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PostPosted: 10 May 2016, 15:21 
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I always liked the PYE badge,
And its a PYE-stream so I thought why not fit one.. :D (next to the power switch)

NB the cathode bypass caps are now Kaisei I quite like them YMMV..


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M. Gregg


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PostPosted: 03 Jul 2016, 03:34 
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Just thought it worth a mention,

Just for interest. :)

Regards the driver tube you can also run 5751 and 7025 ect.
Its worth trying the 390K anode load as well, I'm running magnetic tantalum at the moment after listening to the 150K for some time the 390K is interesting.


I am trying a clarity cap in the 10uF film cap position its a bit bigger than the previous cap but it fits OK. You can also see the Kaisei caps in the pic. The 47K PSU feeds to the 15uF have also ben changed to Kiwame to see if it adds anymore depth to the sound just running them in at the moment.

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M. Gregg


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PostPosted: 03 Jul 2016, 04:46 
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Looking busy in there.

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PostPosted: 03 Jul 2016, 05:33 
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mwhouston wrote:
Looking busy in there.


Yes,
But its still cool as a cucumber LOL.
I like to try a few different things this is the first Clarity Cap in the PSU.
I'm still trying to work out how much impact the Clarity Cap has had, I'm not convinced at the moment but its early days.

Just a reflection on the cathode resistors the Ayrton-perry winding gives a less warm sound and I prefer the warmer sounding resistors in this position. You can go to far and end up with a sterile sounding amp often referred to as skeletal sound in the Audiophool groups.
LMAO skeletal sound :D what next..

Just for interest,
I have been drying out some Allen Bradley 1Watt carbon resistors checking the value is as close to 1K as possible.
I just used the heat from the sun and rotated them every few hours.
Then sealing them with epoxy resin to prevent moisture ingress. (pic) Just for a test.
I know some people that keep the Allen Bradley resistors in a sealed polly bag with silica jell packets.
OK as non signal grid stoppers.


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M. Gregg


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PostPosted: 03 Jul 2016, 09:59 
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M. Gregg wrote:
OK as non signal grid stoppers.
It has been my experience that the Allen Bradley CC resistors are incredibly noisy. In low signal conditions it is mostly the characteristic hiss, but it is very prevalent.

A few years ago i measured some "Allen Bradley" resistors (some were probably not brand resistors but from other suppliers) from several sources and they were mostly the same. All very typical old style CC resistors with typical noise profiles. When compared against several different metal films, noise levels were typically about 30dBv higher in the CC types.

I know that there are articles all over the web about how "awesome" AB resistors are supposed to be, but frankly I would never use them in a high fidelity system in any location. Maybe in a guitar amp if I was looking for a retro sound, but for the most part, I leave them for others.

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