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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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29th Dec 2017, 2:13 pm | #1 |
Pentode
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A pair of Leak TL12s
First TL12+ finished and working, took me most of the day.
This one had chosen components which were a little more expensive, they were chosen to try and keep the original look and to see if they somehow perform better. The next TL12+ will have cheaper off the shelf components and different resistors and capacitors. My goal is to see which performs and sounds better (if components really do make a difference) After that I'll start doing a few more tweaks and modifications. |
29th Dec 2017, 6:13 pm | #2 |
Dekatron
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Re: A pair of Leak TL12s
Many of us will bw interested if you can tell any difference! However comparing 2 amps this way, even if the components have been changed so that one has "basic" components and one has "Audio Karma" components, is not a fair test as there could be multiple other factors affecting the sonic performance....valves, wiring, shielding, trannys et al.
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30th Dec 2017, 12:52 am | #3 |
Nonode
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Re: A pair of Leak TL12s
Really nice work and a pleasure to see! You might have to wait a while before you hear any differences however. If I understand the philosophy of people like Arthur Radford at all, it was about consistency rather than quality of manufacture - eg, all the .01 uF capacitors used in the manufacture of an amp came from the same batch. In other words, he couldn't control the quality of component supply, but he could insist upon a supply of (as far as possible) identical components. I hope that makes sense
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30th Dec 2017, 1:17 am | #4 | ||
Pentode
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Re: A pair of Leak TL12s
Quote:
I intend to use one speaker in the same location with the same speaker cable, choose around 8 songs i know really well and compare from there. I also intend to use do a frequency sweep in some way and measure the results. The main factor here really is the internal components, thats the major change, i'm hoping the trannys (like most leak products) are built well and relatively the same. Quote:
I've read that components need to be burnt in or allowed to settle in to get the best from it (breaking in). I don't really have 100 hours to kill listening to music! i just about make time to do this hobby. |
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30th Dec 2017, 5:24 am | #5 |
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Re: A pair of Leak TL12s
The problem with reading things is that you then have to choose what to believe. There is no escaping this issue because if you look around you will find contradictory things written. If you try to handle this by looking for a majority vote then you are susceptible to the infectiousness of folklore... anyone who believes something feels better if they can convince others to believe in the same things, and will try to combat the spread of any different view. Children (of all ages) shout at each other because they think louder is more convincing and they fear not being believed.
With all this human-created spin and noise going on, it is very difficult to listen with a pair of unbiased ears, free from other people's expectations. Ears are made from meat, plus a couple of bones. They vary from person to person, they vary with physical parameters, the age, they change with exposure to sound. They are most certainly not precision transducers. The precision you get comes from processing in the brain, where sounds are compared to recently heard things used as a reference. Ears of themselves are not absolute, and the perception of a sound is a function of the environment and history it appears in. So take care. We can be fooled in all sorts of ways, and we can fool ourselves. The only way to be certain that you can really hear a difference is when you can prove beyond reasonable doubt that you can reliably recognise each amplifier when you have no other clues as to which one you are listening to on each occasion. Statiistically-demonstrable success would then leave you having to decide which you preferred. trying to decide which is 'better' opens a whole new can of worms. It is an interesting observation that so many people are happy to believe all sorts of explanations for the causes of differences in reproduced sounds, but absolutely oppose any suggestion that there may be limits and variability in their hearing and perception of sound. Comparing your two amplifiers should be a lot of fun, it will certainly be a lot of work David
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30th Dec 2017, 10:56 am | #6 | |
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Re: A pair of Leak TL12s
Quote:
EDIT: You may well need to do rather careful matching of the output volumes. The two amps should have much the same gain, but small variations will arise particularly if the resistors in the feedback circuitry aren't exactly the same. Our ears are (unconsciously) quite sensitive to volume with a general preference for higher volumes. A well-known trick among the more scurrilous hi-fi salesmen was to play the system that they wanted you to buy at a slightly higher volume than the one that you were comparing it against. You might not notice the volume change, or think it mattered, but you would notice the sound quality 'improvement'. Cheers, GJ
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31st Dec 2017, 12:43 am | #7 |
Pentode
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Re: A pair of Leak TL12s
I've started work on the next TL12+, what was different is that surprisingly many of the components were still within range.
For example the Original TOC Metal Pack 0.25uf measured around 0.38uf with an ESR of 1.2ohms The Metalmite 0.1uf measured around 0.12uf with en ESR 2.1 ohms. Which is pretty good right? My question to you guys is it still useable? Even the Smoothing cap (16uf and 8uf) measured to value! I have bought brand new poly types, just wondering if its worth trying these out for sound test. Thanks |
31st Dec 2017, 1:10 am | #8 |
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Re: A pair of Leak TL12s
ESR is only applicable to electrolytic capacitors.
Capacitors with paper dielectric degrade by becoming electrically leaky. This needs to be checked at the full working voltage.
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31st Dec 2017, 1:27 am | #9 |
Pentode
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Re: A pair of Leak TL12s
Thanks Station X! I think ill stick to just using brand new ones.
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31st Dec 2017, 7:13 am | #10 |
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Re: A pair of Leak TL12s
Most capacitance meters are fooled into reading high when confronted by a leaky capacitor. So a 0.25uF part showing 0.38uF is rather suspicious.
David
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5th Jan 2018, 12:47 am | #11 |
Pentode
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Re: A pair of Leak TL12s
Side by side
Amplifier 1 Amplifier 1 Leaks with valves in Ok so i finally managed to finish putting in the components! Looking at both of them i prefer amplifier 2 with the PIO and bigger resistors. It just looks so much better. Anyway i have an issue with Amplifier one that i just rebuilt and its annoying me, every component has been replaced. When i switch on the amplifier with just the gz34 in i get a healthy voltage of 363V across c13 & c14. All my heater voltages measure 6.3v which is all great. So then i place the ef86 and the ecc81 valves in and again the voltages across the caps and the valves are all stable. Heres my issue now, as soon as i place the power valves EL84s in, everything goes hectic. All the voltages start jumping around and not stable across the anodes? I thought it could the smoothing cap so i changed it, made no difference. Now it's late and i have to go work tomorrow! I'll have another go tomorrow, any tips and what to look out for please let me know! Thanks |
5th Jan 2018, 12:59 am | #12 |
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Re: A pair of Leak TL12s
Reversed feedback connections?
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5th Jan 2018, 1:42 am | #13 |
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Re: A pair of Leak TL12s
Interchanged anode connections at the output pair?
ditto grid 1's ditto anodes of te phase splitter or all three? :-0 David
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5th Jan 2018, 3:46 am | #14 |
Heptode
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Re: A pair of Leak TL12s
If you have only replaced components on the tag boards it is very unlikely there are any reversed or interchanged connections... unless it's something you did but didn't consider important to mention.
More likely that there is a component connected between the wrong tags, or incorrect value... kohms instead of megohms, or uF instead of Pf etc. or vice-versa. Sadly, we (well, I) can't read the values from your photos. Some of them look incorrect. Does the tiny ceramic capacitor used in the step network have adequate voltage rating? (The tiny yellow one between the electrolytic and the 1 meg). Is it ceramic? If so it's inappropriate as it will add unwanted distortion at least. Did you use 100Kohm for both phase splitter anode loads? These will work but will increase distortion. One should be 91kohm as per the Leak diagram. |
5th Jan 2018, 2:25 pm | #15 |
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Re: A pair of Leak TL12s
Neat work. Can't add much apart from recheck and recheck your work ( check resistor values, it's easy to mistake 100 ohm for a 10k for instance) and scope one of the EL84 anodes through a 0.1u high voltage cap to protect your scope input.
Andy.
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5th Jan 2018, 4:50 pm | #16 | |
Pentode
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Re: A pair of Leak TL12s
Nope none of the wiring was altered, just components replaced.
Quote:
Checked every component again and it's all fine, i even changed a few of the capacitors and resistors to make sure, my scope unfortunately fell and broke today so cant use it! |
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5th Jan 2018, 4:58 pm | #17 | |
Pentode
Join Date: Aug 2017
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Re: A pair of Leak TL12s
Quote:
What made a difference was the 16ohm tap on the output transformer, this seemed to stabilise it all. Or just using one output valve, soon as i put both EL84's in it went crazy again. Thinking that probably my output transformer maybe the issue (hoping not) |
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5th Jan 2018, 5:14 pm | #18 |
Dekatron
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Re: A pair of Leak TL12s
The plug and sockets which select the output transformer secondary tappings can easily develop poor contacts and I guess it's possible that there's a wiring issue (open circuit or short circuit) associated with the sockets. You'd need to undo the securing screws (both the ones through the transformer laminations and the ones which secure the shroud to the chassis) and remove the shroud to check - it's not really difficult to do, but do keep track of any insulating washers, if fitted, on the screws through the lams.
In general it's not a good idea to run a valve amplifier without a load on the OP transformer secondary. Have you been using a load ? If it was a speaker was there any sound when the amplifier was acting up ? Cheers, GJ
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5th Jan 2018, 5:39 pm | #19 | |
Pentode
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Re: A pair of Leak TL12s
Quote:
Always attach a load, use an arcol 8ohm 50 watt resistor, i also have 4ohm and 16ohm. There was still sound coming through even when it was acting up (i checked with a speaker, although the output was very low. |
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5th Jan 2018, 6:04 pm | #20 |
Heptode
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Re: A pair of Leak TL12s
Did you make any voltage checks on the amplifier?
Anode and cathode voltages for the EF86 and ECC81 should be enough to basically confirm their correct operation and might show up for example any broken pin in a valveholder (which is not unknown). Likewise, cathode voltages for the EL84's would confirm correct DC conditions there. |