Single-Ended Pentode Redux

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Nick
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#106 Re: Single-Ended Pentode Redux

Post by Nick »

Leave secondary open.
I would put them in series, get the phase right and you have a free bit more inductance.
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#107 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

Tried out the New Sensor, Tung Sol EL34 with Mullard GZ34 rectifier in the amp today. I slightly reduced the feedback level, by increasing the value of the anode resistor on the driver tube from 22K to 27K.
With the EL34 running around 45mA and the drivers at 5mA, I'm on the 50mA limit of the 20H choke feeding each channel.

This configuration sounds beautiful. I've once again fallen in love with the EL34. Over the years I've tried all sorts of valves, but I keep coming back to this ubiquitous pentode. It sounds absolutely superb in SE ultra-linear mode with a bit of additional feedback.
The only other valve out of the ones I've tried that gives me the same emotional response is the 45. It's a highly personal thing and others certainly will not share this viewpoint, but those two (EL34 and 45) do it for me.
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Paul Barker
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#108 Re: Single-Ended Pentode Redux

Post by Paul Barker »

I get that. My first experience was Mullard el34 se triode. Hook line and sinker!
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#109 Re: Single-Ended Pentode Redux

Post by Paul Barker »

I think it was Mike can’t remember what he trades as or did if he’s finished. I think he’s the son of Langrex owner but not same business. He said someone visited in a van offered him Mullard EL34’s up to a van full. He said to me, how many do you expect I took. 2!
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#110 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

Yikes!
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#111 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

Just a small change to the diagram. The position of the ultra-linear tap on the OPT was annoying me.
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#112 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

The SS amp with NVA boards is back on the system now. Work on the breadboard is done, so now it needs building into a box. I’ve got about a week to make the migration as there is a huge list of other things to be doing that can’t be put off for much longer ie a huge decorating job.
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#113 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

Cressy Snr wrote: Sun Feb 06, 2022 11:01 am The SS amp with NVA boards is back on the system now. Work on the breadboard is done, so now it needs building into a box. I’ve got about a week to make the migration as there is a huge list of other things to be doing that can’t be put off for much longer ie a huge decorating job.
Not done a great deal. Four holes, a bit of perforated steel, four valve sockets mounted. Never mind. It'll get done eventually. It's another chopping board job, this time portrait rather than landscape. Mains TX, choke and rectifier will occupy the back row. Output transformers on middle row and input and power valves on front.
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#114 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

I’ve lost interest in this chassis. This ‘portrait’ layout means that I can’t be sure the thing won’t hum unless the inputs are fitted at the front. I’m not having that I’m afraid, so I have five Poundland £2 chopping boards stacked and glued up as a translam construction, as with the 45 amp.

Unlike the 45 amp, the 6th (top) board will be detachable and fixed with brass screws in cups at each corner. This means I can get the jigsaw into the other five, all at the same time, thus making a far neater, more uniform job of the inner faces of the sides, front and back than I did before.
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#115 Re: Single-Ended Pentode Redux

Post by Paul Barker »

Did you know Ongaku had phono inputs on the sides of the monoblocks?
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#116 Re: Single-Ended Pentode Redux

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Paul Barker wrote: Sun Feb 20, 2022 9:12 am Did you know Ongaku had phono inputs on the sides of the monoblocks?
Aye, I’ve seen all sorts of uncompromising amps with inputs at the sides and even on the front panel. I’m not sure what advantages they have, apart from the avoidance of noise pickup caused by having the portrait orientation with the dirty region across the the back and the low level leads passing beneath the said dirty region. It’s certainly not aesthetically pleasing to have plugs stuck out sideways. Some portrait amps I’ve seen even have the speaker cables out the sides too.

The landscape orientation with transformers rectifiers off to one side, avoids this ugliness, because you can keep the inputs well away from the dirty end by running them down the opposite side, but then you may get the channel nearest the dirty side being slightly noisier than the one furthest away, as I have experienced, but only with AC heated DHTs. :?
Indirect heated stuff is usually silent with a landscape orientation as was the E-Linear in breadboard form.

From a DIY perspective,I suppose it all comes down to what kind of visuals you are prepared put up with to get the ultimate sound quality. And compared to an Ongaku or similar, your average EL34 amp would pale into insignificance, no matter how you built it.
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#117 Re: Single-Ended Pentode Redux

Post by Paul Barker »

Dont forget the benefit of changing sources without disconnecting everything, pulling amp out , puting other source in, reconnect everything on youre way back in with amp.

Ongaku style suits monoblocks I should say.
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#118 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

Paul Barker wrote: Mon Feb 21, 2022 11:34 am Dont forget the benefit of changing sources without disconnecting everything, pulling amp out , puting other source in, reconnect everything on youre way back in with amp…
Aye there’s that.
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#119 Re: Single-Ended Pentode Redux

Post by Cressy Snr »

Chassis so far with a few parts dry fitted:
E8DBE599-7FAE-42AB-A2B5-3A7754B8B71A.jpeg
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There is still a LOT of work to do. I’d estimate another week of sanding, finishing and fitting the big bits before I can even think about wiring it up. The top is not yet attached. On this one, the controls are actually in line with the valve sockets. :lol:
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Ray P
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#120 Re: Single-Ended Pentode Redux

Post by Ray P »

Looking good Steve.
Sorry, I couldn't resist!
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