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Old 14th December 2012, 03:37 PM   #401
rolls is offline rolls  Switzerland
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Quote:
Originally Posted by chaos View Post
so you think it would make sense to use the transformer in 1:20 and just take a wirewrap wire which would give me around 0,25R with a lenght of about 2,5"?
at least the transformer was made for voltages like this

cheers,klaus
My S&B 1:20 works very well, you have more output and still reasonably low output impedance. I take a thin copper or silver wire (see my post above). About 25cm of a 0.07 wire makes a resistance of about 1Ohm. Exact lenght is not important, but both wires must measure exactly the same, must have an exact mid point, measure with a ruler. The thinner the wire, the better the sound.

Last edited by rolls; 14th December 2012 at 03:41 PM.
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Old 18th December 2012, 02:29 PM   #402
RollE2k is offline RollE2k  Sweden
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I'll probably be looking at 2,2R from each phase to gnd, and then put a LL9226 afterwards in 1:20 mode, transformer would have internal DCR of 1:260R, so with this config i'll have an output impedance of approx 2K, which sounds reasonable. According to Lundahl this transformer does work with up to 40mV on the primary.
A 1:25 would be even better for me, but i haven't found anybody that does have any AM-transformer with such low internal resistance as these Lundahls. The LL1943 would probably also work in 1:32 but would yield much higher output R, since the impedance ratio would be 1:1024.
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Old 20th January 2013, 02:08 PM   #403
RollE2k is offline RollE2k  Sweden
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Have ANYBODY tried running dual mono Buffalo/ES9018's with step-up transformers?
I'm thinking this would be the best of two worlds. since you would have approx 32mA per channel it would be possible to load each phase <1R, and since the output impedance would be so low, it would be possible to run 1:32 transformer.

With output loaded with 0,9R on each phase, and with LL1941 i calculated output impedance of approx 2460R. With ~0,92V on the secondary. and since i myself have 3,75x gain thereafter, i would get approx 2,4vRMS out thereafter. It would even be possible to run even lower loading.

So - have anybody tried anything similar this?
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Old 21st January 2013, 04:56 PM   #404
chaos is offline chaos  Austria
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this is exactly my plan! i have a second buff IIIse at home and will try it soon. but at first i want to fine-tune my tube output stage, modified it last weekend. playing right now: I/V resistor 1R tx2352(no tx2575 with low values like this:-( , s&b tx 103 stepup 1:5, choke loaded 5842. at first with 100r cathode resistor, 135v on the plate, unbypassed. now i have a battery in series with the grid, cathode directly to ground. clearly better, but i will play a little with the voltages. 10k on the input of the 5842 is also a little high i think, will get a pot and set it when i run dual mono. in dual mono i will put a second 1R resistor in parallel. in my system i could decrease this value even further....vitavox horns...
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Old 21st January 2013, 05:54 PM   #405
RollE2k is offline RollE2k  Sweden
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I take it you already have the transformer, otherwise - wouldn't it be better getting a transformer with lower internal impedance, since the primary is 17ohms , you could load the dac even lower (0,5R?) with another transformer. LL9226 seems like a candidate for you, if running in 1:20 you get approx 1,25R primary. But then again, if you already have a transformer, try it!

Also, please let me know how it sounds for you, because i'm really interested to hear :-)

EDIT: i see S&B transformer is possible to run in 1:10 and 1:20 also, why not try that and lower load? :-)

Last edited by RollE2k; 21st January 2013 at 05:56 PM.
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Old 21st January 2013, 08:24 PM   #406
chaos is offline chaos  Austria
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right now i run it with 1R in 1:5. sounds extremly good(secondary on the stepup is 10k, a little bit to high, played around with a pot,i think around 9k would be ok. but hard to say if you compare the tx2575 10k with a pot.will decide when it is dual mono.)...but there is always room for improvement
dual mono i will run it with 0,5R.
i also thought about 1:20, 0,125R on the primary. like a low output mc cartridge(the voltage). would i be worth it?
i plan do make a small pcb for connecting the buff to dual mono(soldered to the bottom), 0,125R should be possible without resistor(pcb will be around 25x 90mm, space for resistors and connecting stepup.)
what i dont know: noise pickup? double layer? ground plane? and what is the tolerance of a resistor etched on a pcb? is there a point of dimishing results?
i think it would be possible to make a pcb with 2 0,125R resistors but....my budget is limited
anyway, i will get another set of plate chokes this week(lundahl 1667, 270H, 15ma, my bartoluccis are only 80H), will try this first. i want a perfect tube output before i go dual mono.

cheers,klaus
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Old 21st January 2013, 08:57 PM   #407
RollE2k is offline RollE2k  Sweden
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Have you tried with cascode DN2540's instead of plate choke? of course you'll need a little higher (not much) B+, but it will give you very nice PSRR, and channel separation.
Many perfer it to choke loading.

Are you running SE or BAL tube output-stage? have Balanced line-stage/power amp after, so i will run balanced all the way. Myself i will need to buy a quite high step-up ratio, since i have 6h30p-dr tubes in the line stage (mu=15) and then output transformer wired in 8:1 (to not have to much gain from the analogue inputs.)

Well, you could always try many different ways of connecting the transformer 1:5/1:10/1:20 and report back on results. Even if you have tube-stage thereafter it will still be interesting to hear your reports with really low loading and high step-up ratio. I'm most interested to hear what you think about dual-mono and 1:20 step-up :-)
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Old 21st January 2013, 08:57 PM   #408
chaos is offline chaos  Austria
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btw, just talked to a friend, was not shure which step up he has, we compared it in my system, the s&b was simply much better.(phono, benz ruby)

cheers,klaus
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Old 21st January 2013, 09:02 PM   #409
rolls is offline rolls  Switzerland
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Quote:
Originally Posted by chaos View Post
right now i run it with 1R in 1:5. sounds extremly good(secondary on the stepup is 10k, a little bit to high, played around with a pot,i think around 9k would be ok. but hard to say if you compare the tx2575 10k with a pot.will decide when it is dual mono.)...but there is always room for improvement
dual mono i will run it with 0,5R.
i also thought about 1:20, 0,125R on the primary. like a low output mc cartridge(the voltage). would i be worth it?
i plan do make a small pcb for connecting the buff to dual mono(soldered to the bottom), 0,125R should be possible without resistor(pcb will be around 25x 90mm, space for resistors and connecting stepup.)
what i dont know: noise pickup? double layer? ground plane? and what is the tolerance of a resistor etched on a pcb? is there a point of dimishing results?
i think it would be possible to make a pcb with 2 0,125R resistors but....my budget is limited
anyway, i will get another set of plate chokes this week(lundahl 1667, 270H, 15ma, my bartoluccis are only 80H), will try this first. i want a perfect tube output before i go dual mono.

cheers,klaus
Take a piece of wire!
best sound, better than any resistor you can buy!
I have copper at the moment, but will buy silver, if I can get a piece.
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Old 21st January 2013, 09:14 PM   #410
chaos is offline chaos  Austria
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hm, im a tube guy
i never heard a transistor of any kind sound as good as a tube. does not work for me. its even desturbing in the regulator. right now i run the whole thing with allen wrights super reg. valve rectifier, lclclc sounds better to me. but i ordered the salas hv reg, 2 of them
haha, i sold my phono because i thought i will do the equalisation on my pc....not so shure right now!
the buff with the exa sounds really good, but any dsp .....maybe some years later, right now it does not work for me.
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