New SE With Triode Mode KT120/150

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simon
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#46 Re: New SE With Triode Mode KT120/150

Post by simon »

Interesting. My only experience of 6N1P was in a 6N1P/6N6P Aikido and it wasn't very nice, all mid and no extremes. I changed to all E88CC just because I had some and it was so much better. I always presumed my 6N1Ps and 6N6Ps must have been bad ones though.
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#47 Re: New SE With Triode Mode KT120/150

Post by Paul Barker »

Could Have been anything at the time, not worth trying to find out what long afterwards.

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#48 Re: New SE With Triode Mode KT120/150

Post by Cressy Snr »

Yesterday I had the Rocky (now more of a test mule) amp on for about 4 hours and the radiant heat effect of the KT120s on the output transformers became rather silly. So it was with heavy heart that I had to make the decision to drop the HT and put in my KT88s.

These lasted for one listening session last night. It’s not that they were bad, just that in comparison to KT120 they sounded flat and weedy. One word springs to mind about KT120 in comparison to the KT88s - “authority.” Iron fists and velvet gloves etc. is the appropriate over-used cliché that can be applied I think. So back went the KT120s this morning. However, for now they’ll remain on the lower HT voltage, of 300V a-k, so that the amount of radiant heat hitting the output transformers can be kept manageable.

When I build the new amp, the HT volts can go back up to their previous level, as there will be plenty of room for the valves and the output transformers to happily co-exist.
Last edited by Cressy Snr on Mon Jun 15, 2020 12:30 pm, edited 1 time in total.
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#49 Re: New SE With Triode Mode KT120/150

Post by Cressy Snr »

The wood frame from the Super Rocky will be recycled again and will become the chassis for the valve phono stage. I’m going to build it eventually honest. :D
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#50 Re: New SE With Triode Mode KT120/150

Post by izzy wizzy »

Cressy Snr wrote: Mon Jun 15, 2020 12:27 pm The wood frame from the Super Rocky will be recycled again and will become the chassis for the valve phono stage. I’m going to build it eventually honest. :D
When you finally finish rebuilding Rocky ... maybe. Look forward to it as long as you don't use ECC83s ;)
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#51 Re: New SE With Triode Mode KT120/150

Post by Cressy Snr »

izzy wizzy wrote: Mon Jun 15, 2020 12:32 pm
When you finally finish rebuilding Rocky ... maybe. Look forward to it as long as you don't use ECC83s ;)
Nah, it’ll be 833As :lol:
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#52 Re: New SE With Triode Mode KT120/150

Post by JamesD »

Simon said
Interesting. My only experience of 6N1P was in a 6N1P/6N6P Aikido and it wasn't very nice, all mid and no extremes. I changed to all E88CC just because I had some and it was so much better. I always presumed my 6N1Ps and 6N6Ps must have been bad ones though.
Looking into this a little more I came across this piece byJRB - Heater Madness about half way down the page https://www.tubecad.com/2018/02/blog0411.htm

Really interesting that heater voltage might be behind our different experiences...
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#53 Re: New SE With Triode Mode KT120/150

Post by pre65 »

Interesting. When I raised the subject of starved filaments recently I detected some "resistance",suggestions that what's written on the internet is not always correct. But, of course, we all know that to be true.
Last edited by pre65 on Mon Jun 15, 2020 1:16 pm, edited 1 time in total.
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#54 Re: New SE With Triode Mode KT120/150

Post by IslandPink »

Wow, he's a mine of great information.
I did experiment with filament voltage on the KR 300B's and they sound better at 4.9 than 5.0V. I had heard one other comment about this in the context of IDHT's, can remember when or with what valve, but I do slightly under-run them anyway, with hope of increasing lifespan.
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#55 Re: New SE With Triode Mode KT120/150

Post by Nick »

Interesting. When I raised the subject of starved filaments recently I detected some "resistance",suggestions that what's written on the internet is not always correct. But, of course, we all know that to be true.
My point was as it always is that taking the several hundred words in that link about why and when lower heater voltages can be a good thing (and when not) and turning it into an single sentence about something being better is always likely to be wrong.

Lowering the heater voltage will change the characteristics of the valve, it may be that the new characterises work better in that application, it may not. If there are batter then its a pointer that they were not optimum in the first place for the normal voltage.
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#56 Re: New SE With Triode Mode KT120/150

Post by steve s »

I read somewhere that under running valves by more than 25% could lead to the cathode being spoilt.. in the days when they where relatively expensive this could have been a big deal. Not so much today unless you are running rare valves.
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#57 Re: New SE With Triode Mode KT120/150

Post by IslandPink »

Yes, certainly heard that about DHT's.
I remember now it was 6C45pi's where someone said the full filament voltage is only required for the highest Gm, you can reduce higher-order distortion by dropping the filament voltage a bit.
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#58 Re: New SE With Triode Mode KT120/150

Post by izzy wizzy »

Nick wrote: Mon Jun 15, 2020 1:35 pm
My point was as it always is that taking the several hundred words in that link about why and when lower heater voltages can be a good thing (and when not) and turning it into an single sentence about something being better is always likely to be wrong.

Lowering the heater voltage will change the characteristics of the valve, it may be that the new characterises work better in that application, it may not. If there are batter then its a pointer that they were not optimum in the first place for the normal voltage.
Well indeed as those 12B4 are running on fresh air just about. No wonder a lower heater V might make things a bit better. I mean, where are all those hot electrons gonna go with such a low anode.
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Paul Barker
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#59 Re: New SE With Triode Mode KT120/150

Post by Paul Barker »

Steve on Dht (note not approved by Stephie for Idht )filament starvation you hear too many modern voices . Stephie wrote the only paper you’ll ever need to refer to. Read that and make up you’re own mind, you can Trust Stephies opinion.
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simon
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#60 Re: New SE With Triode Mode KT120/150

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JamesD wrote: Mon Jun 15, 2020 1:01 pm Simon said
Interesting. My only experience of 6N1P was in a 6N1P/6N6P Aikido and it wasn't very nice, all mid and no extremes. I changed to all E88CC just because I had some and it was so much better. I always presumed my 6N1Ps and 6N6Ps must have been bad ones though.
Looking into this a little more I came across this piece byJRB - Heater Madness about half way down the page https://www.tubecad.com/2018/02/blog0411.htm

Really interesting that heater voltage might be behind our different experiences...
I'm racking my brains to remember how I heated them - it was probably 14 years ago. It was the second stage of a phono and they could have been heated by a voltage reg, but I've a feeling they were AC heaters.

The current draw of E88CC is 300mA, 6N1P 600mA, and 6N6P 750mA. So if they were AC heated wouldn't it be more likely that the E88CCs had a nominally higher voltage?
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