Hi Hanze,
Of course, it's aDIY forum
18R or 25R (for 2xTDA1541A) to Jensen MC 1:8 (configurable 1:4) to choke loaded 46. Pls take a look at the attachment to my previous post. The output impedance of the tube is quite high but my amp can take it with 50k input impedance and short (<1m) cables in between.
That's interesting, thanks for suggesting. Tube needs about -8V bias, with 4mA DC from 2xTDA1541 would mean 2k I/V?? PLus the gain is only about 5. I guess not with this tube.
Thanks again HK!
Of course, it's aDIY forum
18R or 25R (for 2xTDA1541A) to Jensen MC 1:8 (configurable 1:4) to choke loaded 46. Pls take a look at the attachment to my previous post. The output impedance of the tube is quite high but my amp can take it with 50k input impedance and short (<1m) cables in between.That's interesting, thanks for suggesting. Tube needs about -8V bias, with 4mA DC from 2xTDA1541 would mean 2k I/V?? PLus the gain is only about 5. I guess not with this tube.
Thanks again HK!
Hey Diyiggy,
Well I played around with some film caps though not of such high values but I just did not like what I heard but when I tested the line output transformer it was a different world all together. You hear everything in the music & it comes through very naturally no etching sound or whatsoever. As to how I get the bass from, it's my self developed recipe.
Im unsure why but many diyers just think that stepping up the voltage using using a trafo will do a good job. 2 crucial points on hand here, output impedance of the trafo & to me most important current drive. Without enough current music will just sound un-dynamic.
Cheers
Well I played around with some film caps though not of such high values but I just did not like what I heard but when I tested the line output transformer it was a different world all together. You hear everything in the music & it comes through very naturally no etching sound or whatsoever. As to how I get the bass from, it's my self developed recipe.
Im unsure why but many diyers just think that stepping up the voltage using using a trafo will do a good job. 2 crucial points on hand here, output impedance of the trafo & to me most important current drive. Without enough current music will just sound un-dynamic.
Cheers
Sumotan, gives me your Martin Logans and I will tell you then
When I build & finish my still learning Horn speakers ya but you have to pay for shipping.
Not much between us both itchy finger guys that we've not tested ya. Lol
I have to improve my swim in order to avoid the planes, boats, trains or put my bath tube on the sea and construct a diy wind... then maybe I could take it back, lol ! Long road from Europe than your country side guys, long time I didn't went there and it should last because this 5 microns monster ! (bass and snap, I told you, it's about C5&C6 and gnd behavior...this chip is very special with its three V rails )
)
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@ diyiggy: yes and same to you, my regards to Leia.
@ sumotan: yes too much hassle, all of it
@ phixphi: yes, needs tube that is happy to bias near 0V and with higher gain. I like your approach, I bet it sounds great.
HK
Hi Hanz
If one uses a step up trafo at the I/V stage output impedance would be high & after that you add a tube stage which would have to have high RP right ?
So why not use just passive I/V into tube stage & output via opt, that way you kill two birds with 1 stone not needing a signal cap there & reducing output impedance as well.
Yep thats what I like to do, too. Mu 70 Rp 2k2 33R I/V 2:1 OPT.
But there are other ways and certainly interesting method with type 46 as per the other poster, and if driving 50k input impedance, Rp 2 to 3k is no problem.
HK
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Hi Sumotan,
Unsure what you mean, I use direct -2mADC offset through 33R I/V to bias grid of mu 70 triode (p), Rk 10R, Ip 15mA, Rp 2k2, plate load 45H 2:1 OPT.
If I didnt need a low output impedance 1:1 would be very much my preference.
You can add more pieces if you want, I dont mind
HK
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To sink the unbalanced current, there must be a DC path from the chip output to...somewhere
... if I understand correctly to +5V. That's why I'm not sure how to implement @ecdesign idea of sinking 2mA to tube's B+. There must be a return path to the chip somewhere. In my case tube and DAC are galvanically separated by the OT. Secondary loading vs. primary loading the OT is a subject on its own. With my MC cartridges I prefer primary loading. Some great info here: :: View topic - SUT Selection The experimentation will show but I think my OT wants to see a well defined driving impedance to preform best.@diyiggy
Yes, I know Pedja's PDF. Apart from two led lights that I don't think I need, his implementation of 8414 differs from the datasheet only in a 3.3nF cap shorting the RC filter circuit. And a bit changed RC values.
@sumotan
Transformers are good on paper but v difficult to make them right in real life. Each introduces apart from nonlinear also phase errors. I went for LC coupled tube with a massive (compared to the tube Rp) choke and a cap as easier solution.
@Hanze thanks
What is yuor tube if I may ask?@ Hanze sorry miss understood your post, noted
@ phixphi For now I'm using 600:600 ohm line out on my AyA dac makes a world of difference in SQ when compared to caps. Hope to test out a wacky tube solution in a couple of months time. Good thing about the trafo that I have is that it can handle 60 ma of dc offset.
@ phixphi For now I'm using 600:600 ohm line out on my AyA dac makes a world of difference in SQ when compared to caps. Hope to test out a wacky tube solution in a couple of months time. Good thing about the trafo that I have is that it can handle 60 ma of dc offset.
@Hanze thanks
6688, 7721, 7722
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You sink the 2 mA from the chip through a resistor to 155V. So actually this resistor should not be 39 Kohm , if you move the I/V resistor to the secondary side of the transformator but 77,5 Kohm. I would make it 75 Kohm resistor and a 10 Kohm trimmer in series.To sink the unbalanced current, there must be a DC path from the chip output to...somewhere
I sink 4mA (2xTDA1541), but actually I think what I drew is not sinking anything since there is no connection from +155V supply to the chip. It must not be what John had in mind. The DC unbalanced current must have a path back to the chip. I think to +5V, the experts pls correct me if I'm wrong.
@sumotan What caps did you use? They are a b*tch. I've spend on the caps and the choke same as for a pair of good outputs...
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If the two grounds are not connected, you are right. No sinking anywhere.
You can use the +5V (and a 1,25 Kohm resistor ) or any other positive supply with ground common to the chip (and of course a properly scaled resistor)