The Other 13E1 SE-OTL

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Wolfgang
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#181 Re: The Other 13E1 SE-OTL

Post by Wolfgang »

Great results Ray. It always feels good if listening results are comparable. I had the same impression with the 6C33 OTL and it says something about multi tube and single output tube OTLs IMO.

J. Broskie has mentioned somewhere that 6 and more output tubes connected in parallel would actually sound better if the quiescent current is not the same and may fluctuate in each tube compared to the rest. So I was wondering what about OTLs with up to 4 tubes in parallel like the 300B? B. Rosenblit said the same about the current but in general which would also include TS amps with 4 output tubes tied together.
My efforts to tame the current in each tube in the 300B OTLs (SE and PP) and make it the same for each tube resulted in deeper and more powerful bass and a more serene overall presentation of the music, moving more in the direction of how the 6C33 OTL sounds. This was not so much audible with the PP which in general didn't respond much to anything I tried like less NFB, different NFB resistors, precisely matching tubes/currents but was very obvious with the SE. But nothing compared to the 6C33. Interesting.

I wonder what could be the source of the hum?
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#182 Re: The Other 13E1 SE-OTL

Post by Cressy Snr »

Ray P wrote: Sat Jun 20, 2020 3:15 pm
  • There's a tiny amount of hum but only really audible if you're close to the speakers
Ray, if you are running AC heaters on the 13E1s, I’ve noticed you have nothing connected to pin 2 on the valve bases, in which case your heaters are floating.

If you have a single 25V winding powering both heaters, ground pin 2 on one of the valve bases only; doesn’t matter which. If you have two 25V windings, one going to each valve, then each pin 2 should be grounded. I had the same issue.
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Ray P
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#183 Re: The Other 13E1 SE-OTL

Post by Ray P »

I rewarded myself with a 35mile turn on the bike - space is good, otherwise I would have probably ended up fiddling all afternoon.

Steve, yes, AC heaters on the 13E1s. The heater transformer is 120VA toroid with two 12V secondaries connected in series, grounded at the 'centre-tap'. The 13E1s are in parallel. I will explore alternative grounding arrangements later, easy enough to do with a croc. lead and screwdriver.
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#184 Re: The Other 13E1 SE-OTL

Post by Ray P »

Apart from some fettling to sort out the hum and explore how changing the feedback and cathode current affect the sound I just need to fit the base plate and make the Olive wood front panel when the material arrives.

I've got a spare 2pole 11way switch and I've been wondering about using it to have selectable feedback resistor control on the front panel to accomodate different speakers and perhaps tweak' the sound for different scenarios - thoughts?
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Ray P
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#185 Re: The Other 13E1 SE-OTL

Post by Ray P »

Incidentally, grounding arrangements consist of a star of stars with the centre of the star connected to chassis ground via a Broskie arrangement of Cap, resistor and bridge in parallel. Each input/driver PCB has a star grounding layout and those stars are taken to the central star along with the other grounds (power supplies, loudspeaker out, etc.). The input connectors are twisted pairs with the ground taken to the PCB star. I think that should be pretty optimal.

I have noticed that I have forgotton to ground the 6H30Pi filament supplies - they're floating.
Last edited by Ray P on Sat Jun 20, 2020 9:19 pm, edited 1 time in total.
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#186 Re: The Other 13E1 SE-OTL

Post by Cressy Snr »

Ray P wrote: Sat Jun 20, 2020 7:23 pm
...I have noticed that I have forgotton to ground the 6H30Pi filament suppliess - they're floating.
That’d do it.
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Paul Barker
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#187 Re: The Other 13E1 SE-OTL

Post by Paul Barker »

Ray P wrote: Sat Jun 20, 2020 7:23 pm
I have noticed that I have forgotton to ground the 6H30Pi filament supplies - they're floating.
you can get some hum not referencing it somewhere. Dependingon circuit levelled with an eye on cathode heater voltage or ground where appropriate.
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Ray P
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#188 Re: The Other 13E1 SE-OTL

Post by Ray P »

I've actually made up the wires to ground the 6H30pi supplies to the central star, just neglected the installation in my enthusiasm - tomorrow mornings first job!
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#189 Re: The Other 13E1 SE-OTL

Post by Ray P »

I've installed the forgotten wire links to ground the 6H30pi filaments and the hum/buzz has gone and the amplifier is now all but silent, just a tiny bit of hiss if you put your ear up against the speaker driver - result.

I've just had another hour or so listening, flitting around different tracks, and it ain't arf good! It's one of those 're-explore the music collection' periods. Currently using the DSD decoder but will also try my Buffalo 3SE and the Soekris/300B DAC/HPA at some point.

It is pretty toastie though and hopelessly inefficient. The chassis get's warm, though nowhere is it uncomfortable to touch so it looks like my venting and heatsinking arrangements are about right. Obviously the main heat source is the pair of 13E1s and there's little I can do about that, the 68W for the filaments is fixed and reducing the cathode current by a few tens of milliamps isn't going to make a big difference.

It's a keeper so it's time to move/retire the 300Bs and start exploring feedback and current tweaking (the 300Bs are currently on the floor in front of the rack so reduced to 'being in the way'!).
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#190 Re: The Other 13E1 SE-OTL

Post by Cressy Snr »

Told you, you were in for a treat. :D
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izzy wizzy
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#191 Re: The Other 13E1 SE-OTL

Post by izzy wizzy »

Ray P wrote: Sun Jun 21, 2020 11:09 am It's a keeper so it's time to move/retire the 300Bs and start exploring feedback and current tweaking (the 300Bs are currently on the floor in front of the rack so reduced to 'being in the way'!).
Gosh. How many times does a 300B amp get labelled that! A new music collection is a wonderful upgrade.
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#192 Re: The Other 13E1 SE-OTL

Post by steve s »

Nothing wrong with the 300b in the right context, but paralleling them takes alot away.. I had the luxury of hearing that 300b otl kit at home and also heard steves 13e1, the transformer less sound is there with them both but the resultion as at a different level.
In fact it showed to me that a good transformer easily beats parrallel otl valves as far as resultion is concerned.
Good result ray
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Ray P
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#193 Re: The Other 13E1 SE-OTL

Post by Ray P »

izzy wizzy wrote: Sun Jun 21, 2020 11:24 am Gosh. How many times does a 300B amp get labelled that! A new music collection is a wonderful upgrade.
Another advantage of the 13E1 over the 300Bs is that the reduced valve count means I've gone from three boxes to one.

I've started to wonder what to do with the 300B amps, I don't think there's much of a market for them so I may just sell on the 300Bs and dismantle/recycle the rest. I don't have the room or the finances to just leave them 'in storage'. I feel the need to have a purge of other excess projects too.
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#194 Re: The Other 13E1 SE-OTL

Post by pre65 »

Ray P wrote: Sun Jun 21, 2020 11:45 am I feel the need to have a purge of other excess projects too.
It's always sad to dispose of unwanted projects, when one thinks of the time and money that have been invested. :(
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#195 Re: The Other 13E1 SE-OTL

Post by Ant »

I've been having similar thoughts re projects since I completed the eds1000 deck, similarly centred on resolution.
At the moment I'm listening to a record on Emma's jvc deck that I listened to 2 days ago on the new one, and the resolution just isn't in the same league.
The jvc is no slouch and has the Hana cart on it which is very very good indeed. The graham slee phono stage is also very good. But the linear arm and dd deck just seems to dig so much further in and extract so much more. And it's so coherent in the way it serves it up
The jvc will stay because she won't use anything else, the jbe will stay because I have a strong attachment to it, but the big lenco is now sat gathering dust. So is the jbe.
I'm seriously tempted to store the jbe and sell off some of the arms, decks and carts I have.
In some ways it's abit galling to have trod a path for so long then suddenly taken a sharp left that you could have taken years ago, but I suppose that's part of the fun
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