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| Romy the Cat's
personal site dedicated to advanced audio and evolved music reproduction
techniques
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[quote user="floobydust"]Running the higher B+ voltage (350 volts) with a 1K cathode bias resistor and the 2.5K load results in higher distortion than the text-book operating point, which is B+ of 300 volts and a 750 ohm cathode biasing resistor and ...
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Hi all ! I thought about this resistor bias idea that Chris proposed , and found some some problems here . One of them discovered Chris himself - it is a big serial resistor in the grid chain , and it can cause not only HF rolloff ( it isn't a big pr...
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Agreed.... ditch the choke... you don't need any additional decoupling. One last model shows the following assuming a 350 volt supply and a 6K load.Useing a 1.21K cathode resistor, it works best to minimize distortion and balances the transfer charac...
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I was playing with new power supply over this weekend, trying to optimize everything. First I got rid of bleeders at all B+ - it has enough critical current with them according to my measurements after the bride. All supplies after the first ...
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[quote user="floobydust"] On a second note, you can also modify this for both adjustable AC and DC balance on seperate potentiometers. Both potentiometers would be in parallel with the filament (and padded) but you use the wipers independantly, ...
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[quote user="ml8"]...but resistor between screen grid and plate, to my hearing, makes sound slightly unnatural, especially in highs.But this may be not true in your case (i didn't try to use this resistor with 6E5P, only with other power tetrodes), s...
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First of all, thanks for additional detail. As mentioned I can speak only for my Fidelity Research XF-1 (30dB). Loading it on secondary as you mentioned, it ALSO damps the trannie - result in my case: less resolution. Primary loading is MUCH more sen...
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[quote user="Ostblock"]Is there any technical reason that you use a 400V transformer to feed the driver tube?The plate voltage on 6E5P is only +200V. Therefore from my point of view, a 220-240V transformer would be enough.[/quote]Ostblock, you need t...
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[quote user="Romy the Cat"]
[/quote] This is a design by quite experience and very rational Russian designer Dmitry Andronikov. http://www.romythecat.com/PDF/se6f5_uo186.pdf He cooks the YO186 at 50mA, at high starting plate voltage, dropping more ...
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Dima and I spent today quite a time experimenting with different operation of the Single-stage Milq. We drove it from my Fluke 409D with resistor bias, loaded with 12.8:1 into 12R. Playing with bias, voltage and current we tried to find an operation ...
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Thanks for your help Romy. Have a look at this (barely legible) sketch so we have a common reference:This is Channel B First Stage bias circuit. All is identical to your published schematic apart from R9 which I had to increase to get the other sta...
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If you study the above, you'll note that the topology involves some compromise, namely, a trade-off between a lower series resistor (for better drive of the following valve) versus a lower current draw through the CCS . This draw has to come through ...
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[quote user="Romy the Cat"] [/quote]I really do not know what is going on and how to explain the phenomena; I just dump it to you “as is”. Because of multiple reasons I decided to drain the Milq’s power supply when the amp shits down. I have a...
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I wish it would be true and I would be busy to build my loudspeakers. Unfortunately it is a lot of work and I did not have even time to look at my site. The r22, the power resistor is not necessary the one which mitigate voltage in your tube....
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[quote user="N-set"]Romy, may I ask you why you've employed an autobias on 6E5Pin Milq's MF rather than your biasing technique (if there is any reason at all)?[/quote]If you look at the page #13 of the Milq DHT thread then you will see that the first...
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[quote user="deemon"]Do you mean a battery bias , Brian ? We didn't try it because of 1 V bias voltage - I don't know if the battery with this voltage does exist . I know only 1,5 V and 1,2 V cells ...... maybe using some chemical reactions we can ob...
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Romy, I did some models using a 400V supply and a 6K OPT load. It's easy to get 4 watts output in this configuration, but using a 2K cathode resistor results in higher distortion and a weak transfer curve. Plate dissipation is around 11 wa...
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Yes, of cause I have experimented with the resistors quality. The way how the resistor
is used in the feedback loop in my view make is less relevant. The feedback resistor
is applied to high impedance source that make less signal to flow other the ...
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[quote user="G"]Should
the grid bias voltage change when I adjust VR1? In my case it does – if I keep
increasing dc on inputs I can get to -1.5v on the grid and around 60v on B+.[/quote]
Nope, it should not, well it is and it is not.
Are you s...
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[quote user="Romy the Cat"]1) Be very careful with use Halco resistors. They were very good 15 years back but they turned south very aggressively. I bought a party of Halco in 2005 and I forced myself to trashed them as they were very noisy. You...
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Domidaw, I am not sure if I will be wrong if I say that this amp was first electrical device I build also. so I went over the same problem as you are going. trust me I made a number of ridiculous mistakes as well and so many times I call to peopl...
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I made experiments running HF filaments from dedicated Hammond 6.3V transformer vs. lifting ground on my 6.3V IDH filaments. I did not listen Sound but rather measure the noise – the result was identical. In the best cases I was able to get 0.63m...
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[quote user="anthony"]Do you have a
“final version” of the schematic anywhere? [/quote] I think that the one you
have might be recognized as final. The Rev2 was without DHT in MF and Rev3 was
with it. I did not do anything else with the amp af...
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Hi Romy,Further to my earlier message, I've measured the bias voltages for the driver tubes in all Channels.A -4.3V not adjustableB -13.82V not adjustableC -4.8V not adjustableD -4.2V (ran out of potentiometer travel...may have to adjust a resistor)E...
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Romy and ClarkeA couple of tips here:To be truly effective, you need at least 3 turns of L+N through the ferrite; more if you can.The "Y" network can be placed either side depending upon where the PP3000 to PP3000 interference is coming from.You may ...
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Hello,Here's an idea - uses a resistor in series with a current source on the negative supply to drop the voltage to the 6c33. Not sure how happy (sonically) the 6C33 will be with a 50k resistor on its grid. It would be huge problem at HF a...
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Pretty clean, Romy (and one hellova tranny at Fundamentals)!Of course, I have questions:I thought you said Vishay metal foils in your earlier response about bias adjustment?If so does that mean steps, or... how, exactly?When you specify "Full" ...
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[quote user="floobydust"]If you do some modeling you're running about 15.5 watts of dissipation on the plate and pushing over 4.5 watts output. Running the higher B+ voltage (350 volts) with a 1K cathode bias resistor and the 2.5K load results in hig...
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Sorry I'm a little late here, but anyway... here's something that may worth trying. Apologies that I can't provide a schematic at the mo - I can sort this out later if you like. In the meantime, you'll need a pen and napkin to help visualise this:The...
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Romy, No easy drawing program available this second (traveling for 3 weeks) but I can send you a simple schematic in PDF if you like via email. In any case, to adapt what you have already have to the split biasing, just remove the cathode bias resis...
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