Remember These?
- Cressy Snr
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#616 Re: Remember These?
Well the next bit of fiddling (sorry Mike) will be ferrites on the 13E1 grid tags. Nick (Jack) gave me a few yesterday, so they’ll end up replacing the grid stoppers at some point.
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#617 Re: Remember These?
A very honest and transparent sound. Very typical in my experience of OTL. I like it that there is one valve per channel. That cleans things up and further exposes the transparency. This was the same take away I had a couple of years ago after Ray demoing his 300B OTL. Speakers were not my cup of tea, but so what? They looked fecking great, were a very tidy professional design and apparently sound wonderful at home. Well done Steve. I know where you are. Finally getting it right at home makes everything else superfluous, and so it should do.
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#618 Re: Remember These?
Cressy Snr wrote: ↑Sun Jun 02, 2019 9:39 pm Well the next bit of fiddling (sorry Mike) will be ferrites on the 13E1 grid tags. Nick (Jack) gave me a few yesterday, so they’ll end up replacing the grid stoppers at some point.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- Cressy Snr
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#619 Re: Remember These?
Tried the ferrites on the 13E1 grid leads instead of grid-stoppers. Cue a swarm of angry wasps.
Remove ferrites and put back 15K carbon comp stoppers; silence once more.
Looks like ferrites are not the answer in this case. Stoppers it is then, but thanks anyway Nick (Jack).
Definitely done fiddling now.
Remove ferrites and put back 15K carbon comp stoppers; silence once more.
Looks like ferrites are not the answer in this case. Stoppers it is then, but thanks anyway Nick (Jack).
Definitely done fiddling now.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- Cressy Snr
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#620 Re: Remember These?
Yep, it’s a great sound. I was talking to Ray on Saturday about these particular OTLs and we both agreed that neither of us would willingly use a valve amp with an OPT any more. Hopelessly inefficient and completely impractical on 99.999% of existing speakers, the single ended, single tube OTL is nevertheless, for me, Wolfgang, and probably Ray (once he finishes his) the ultimate valve amp.Greg wrote: ↑Sun Jun 02, 2019 11:12 pm A very honest and transparent sound. Very typical in my experience of OTL. I like it that there is one valve per channel. That cleans things up and further exposes the transparency. This was the same take away I had a couple of years ago after Ray demoing his 300B OTL. Speakers were not my cup of tea, but so what? They looked fecking great, were a very tidy professional design and apparently sound wonderful at home. Well done Steve. I know where you are. Finally getting it right at home makes everything else superfluous, and so it should do.
The “Fane-Tastic” speakers are by no means perfect, but they do enable me to enjoy a single tube OTL and so, experience its musical transparency and excellence. Power sapping crossover components and impedance flattening Zobel networks are sadly not an option with a single tube OTL. A single wideband driver with a flat impedance characteristic is really the only practical option. 15 Ohms would be ideal, but as we heard 8 is possible, with a 13E1 given a following wind.
Last edited by Cressy Snr on Mon Jun 03, 2019 6:15 pm, edited 1 time in total.
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#621 Re: Remember These?
Oh yeah ?
I've got a bet with myself when the next "fiddle" will occur.
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- Mike H
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#622 Re: Remember These?
Can't see why you couldn't have both. The resistors and the ferrites will be "grid stopping" in different frequency bands. So I'm not surprised if it wants the resistors to still be in there. The ferrites will only work in the RF range, but if you take the resistors out you might end up with very small value tuned grid coils and make an RF oscillator, which sounds like what happened.Cressy Snr wrote: ↑Mon Jun 03, 2019 2:48 pm Tried the ferrites on the 13E1 grid leads instead of grid-stoppers. Cue a swarm of angry wasps.
Remove ferrites and put back 15K carbon comp stoppers; silence once more.
Looks like ferrites are not the answer in this case. Stoppers it is then, but thanks anyway Nick (Jack).
Definitely done fiddling now.
Personally I think I'd want to put the ferrite bead furthest away from the grid, on the opposite lead of the resistor. i'm assuming the grid stopper resistors are right close up to the solder tags?
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- Cressy Snr
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#623 Re: Remember These?
Yes they are. Now you’re gonna have me fiddling again.Mike H wrote: ↑Mon Jun 03, 2019 9:12 pmCan't see why you couldn't have both. The resistors and the ferrites will be "grid stopping" in different frequency bands. So I'm not surprised if it wants the resistors to still be in there. The ferrites will only work in the RF range, but if you take the resistors out you might end up with very small value tuned grid coils and make an RF oscillator, which sounds like what happened.Cressy Snr wrote: ↑Mon Jun 03, 2019 2:48 pm Tried the ferrites on the 13E1 grid leads instead of grid-stoppers. Cue a swarm of angry wasps.
Remove ferrites and put back 15K carbon comp stoppers; silence once more.
Looks like ferrites are not the answer in this case. Stoppers it is then, but thanks anyway Nick (Jack).
Definitely done fiddling now.
Personally I think I'd want to put the ferrite bead furthest away from the grid, on the opposite lead of the resistor. i'm assuming the grid stopper resistors are right close up to the solder tags?
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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#624 Re: Remember These?
Worth a sperrymint, if only to tick that off as having been tried. Only 3 things can happen, A. nothing, B. it makes it worse, C. it makes it better. You might need an oscilloscope to detect what's going on though, if not audibly obvious.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- Cressy Snr
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#625 Re: Remember These?
OK
So what I did is this:
Grid stopper up against tag as normal
ferrite placed on grid feed wire
feed wire soldered to other end of resistor as close to resistor body as possible
any protruding wire cut off with flush cutting pliers.
Ferrite slid up wire until it is as close to resistor body as possible with a kink to keep it from sliding back along wire.
Resistor and ferrite end up at 90 degrees to each other
Result!
13E1 that was vibrating internally is now not doing it.
Treble clarity improved, imaging improved, soundscape larger, depth goes further back. I thought it couldn’t get any better but it clearly has.
So with the 13E1, we need highish value carbon comp grid stoppers, with a ferrite bead placed before each stopper, as close to resistor body as possible, and low value anode stoppers soldered up against anode tags.
The 13E1 does take a bit of taming, but it sounds fab once whipped into line.
Wolfgang is correct; small component changes are extremely audible with these single tube OTLs
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#626 Re: Remember These?
Glad there's a result. I'll look up the Farnell p/n for them ferrites...
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- Cressy Snr
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#627 Re: Remember These?
Oh and RF is a bloody insidious little pest. I’ve discovered, albeit a bit late in the day, that getting a clean signal throughput is far from straightforward and the detrimental effect on sound quality from subtly intrusive hash is cumulative.
I’ve learned something really useful from this little outing and would argue that all the expensive audiophile components in the the world, come to nought if the signal path itself is full of unwanted shite. Not that there are any expensive bits in my amp, but if there had been any, they would almost certainly have been wasted.
I’ve learned something really useful from this little outing and would argue that all the expensive audiophile components in the the world, come to nought if the signal path itself is full of unwanted shite. Not that there are any expensive bits in my amp, but if there had been any, they would almost certainly have been wasted.
Last edited by Cressy Snr on Mon Jun 03, 2019 11:46 pm, edited 1 time in total.
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#628 Re: Remember These?
Yes please Nick - it looks as though I'll need to get hold of some for my project.
Sorry, I couldn't resist!
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#629 Re: Remember These?
The ferrite beads are https://uk.farnell.com/wurth-elektronik ... dp/1635667
These are the same ferrites that I use on my uTracer (and other valve projects) to suppress RF. Always found them to be good (but not cheap).
HTH
EDIT: When I say "not cheap", in small quantities, they're ok, but the uTracer used nearly 100.
These are the same ferrites that I use on my uTracer (and other valve projects) to suppress RF. Always found them to be good (but not cheap).
HTH
EDIT: When I say "not cheap", in small quantities, they're ok, but the uTracer used nearly 100.
Vivitur ingenio, caetera mortis erunt
- Cressy Snr
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#630 Re: Remember These?
Aye, the ferrites finish off very nicely, the overall performance of this single tube OTL.
It’s taken me nearly 15 years to understand that RF isn’t just about rectifier switching spikes
Anyway I’ve enjoyed being the guinea pig for SEOTLs using this particular tube. Can’t really complain about how it’s turned out.
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