I bought 4 lundahl LL1539 on ebay for 50€ and i'am testing them on the out of my buffalo24.
I attach two measures of frequency response and THD done with RMAA, the first is with the lundahl directly connected to the out + and - of the buffalo and the second is with the lundahl connected to the balanced out of the IVY (the I/V conversion unit from TP).
For now i have had little time to listen the two configurations and cannot say which i like more, one strange thing is that also when the lundahl are connected directly to the buffalo i have really pleasing sound even if we have high values of THD on low frequencies. Maybe i like distortion 🙂.
Ciao
Andrea
(on the left buffalo -> ll1539, on the right buffalo -> ivy -> ll1539)
I attach two measures of frequency response and THD done with RMAA, the first is with the lundahl directly connected to the out + and - of the buffalo and the second is with the lundahl connected to the balanced out of the IVY (the I/V conversion unit from TP).
For now i have had little time to listen the two configurations and cannot say which i like more, one strange thing is that also when the lundahl are connected directly to the buffalo i have really pleasing sound even if we have high values of THD on low frequencies. Maybe i like distortion 🙂.
Ciao
Andrea
(on the left buffalo -> ll1539, on the right buffalo -> ivy -> ll1539)
Attachments
No wonder you get distortion with the 1539 as they are not perfectly suited to the task. The low RDC is probably the problem together with a low primary inductance.
As you like it so far, I am sure you can imagine how good it would sound with the optimal direct-connected transformer😉.
As you like it so far, I am sure you can imagine how good it would sound with the optimal direct-connected transformer😉.
Hi revintage,
thanks for your comment, there is something i can do to improve the performance of LL1539 without the IVY?
Some R in series with the primary?
Anyway the solution with buffalo -> IVY balanced out -> LL1539 is a really good sounding one.
Ciao
Andrea
thanks for your comment, there is something i can do to improve the performance of LL1539 without the IVY?
Some R in series with the primary?
Anyway the solution with buffalo -> IVY balanced out -> LL1539 is a really good sounding one.
Ciao
Andrea
I see rising bass distortion like that when the transformer is too small. Looking at the specs you linked to, that doesn't seem to be the problem. But maybe - as Lars says.
Interesting.....
Interesting.....
This is not the first time that it has been reported that the Sabre DAC sounds better working directly to a transformer in Vout (even though the DAC datasheet says there is lower distortion in Iout mode) - maybe it has something to do with slew rate distortion?. I find on the few DACs I've tried transformers, that it's a more natural & relaxed sound.
Don't think you like distortion. But rather the sound is good despite the distortion. THD is pretty useless as an indicator of the pleasure of the listener. Furthermore in your case. The distortion is 'only' in the low frequencies probably because of the small core of the transformer. Your brain does not care that much apparently about distortion in the low frequencies. (I don't think anyone's brain does) But I have no proof that distortion in the low freqs is hardly audible.
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current output dac
Did someone try transformers with current output dacs like pcm1794 (or 1798) other than Lundahl or Sowter? Maybe Cinemag CMQEE-3440A, other step up or input micro trafos? old or custom stuff?
Did someone try transformers with current output dacs like pcm1794 (or 1798) other than Lundahl or Sowter? Maybe Cinemag CMQEE-3440A, other step up or input micro trafos? old or custom stuff?
BTW, guys, I have modded a Squeezebox Receiver which has a WM8051 Vout DAC doing the analogue output duties. This DAC has a 2.5V DC bias on the Vout which is blocked by a electro cap. I bypassed this cap & have used my Sescom MI97 transformers with one primary leg connected to a 2.5V supply & the other leg to the Vout - wonderful, clean, natural sound.
This DAC sounds good & is interesting in that it will drive headphones directly with a slightly reduced volume 1Vrms when driving 16ohm load as opposed to 1.7Vrms when driving 10K load.
Just thought I'd post.
This DAC sounds good & is interesting in that it will drive headphones directly with a slightly reduced volume 1Vrms when driving 16ohm load as opposed to 1.7Vrms when driving 10K load.
Just thought I'd post.
The important components are those on the secondary. Don't use the primary components - they are not needed, and may harm performance with this DAC.
thanks for the help
one more question ....
Resistance values (13kohm) and capacitor (680pf) to be inserted on the secondary, must be precise, or through a resistor (8kohm - 15kohm) with a capacitor (1000pF), which are in the house?
these resistors and capacitor on the secondary I use it when I try other transformer?
one more question ....
Resistance values (13kohm) and capacitor (680pf) to be inserted on the secondary, must be precise, or through a resistor (8kohm - 15kohm) with a capacitor (1000pF), which are in the house?
these resistors and capacitor on the secondary I use it when I try other transformer?
I'd use values as close as possible to those recommended. It'll work with others, but you'll get frequency response anomalies. Different transformers will need different terminations. Also, it's important to keep capacitance as low as possible on the output - this transformer won't drive long leads.
any of you guys try out jung's mixed feedback output circuit with a transformer in the feedback loop?
http://waltjung.org/PDFs/ADI_2002_Seminar_Ch6_Audio_Drivers_I.pdf
from figure 6-61 onwards, but there are some great circuits as usual through tyhe whole article. of particular interest to me is 6-64, but I would like to somehow incorporate a discrete buffer to up the current; allowing me to drive low impedance headphones directly if I choose.
havent seen any circuits around here using a transformer in the feedback loop for dac I/V. I think it could be quite interesting indeed.
got some O-Netics made by BudP from a member on the forum; interested in trying this circuit on the output of the ackodac using OPA1632, a pair of discrete buffers and a transformer per channel
http://waltjung.org/PDFs/ADI_2002_Seminar_Ch6_Audio_Drivers_I.pdf
from figure 6-61 onwards, but there are some great circuits as usual through tyhe whole article. of particular interest to me is 6-64, but I would like to somehow incorporate a discrete buffer to up the current; allowing me to drive low impedance headphones directly if I choose.
havent seen any circuits around here using a transformer in the feedback loop for dac I/V. I think it could be quite interesting indeed.
got some O-Netics made by BudP from a member on the forum; interested in trying this circuit on the output of the ackodac using OPA1632, a pair of discrete buffers and a transformer per channel
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I have some LL1517 transformers which I might get around to incorporating as per fig 6-64 in that article
Well done with the O-netics - I would try them directly on the DAC outputs first, they may not require the impedance management that the LL1517 needs!
oh for sure i'll try them direct for driving my amps and active monitors, this is only one of the output stages I have planned for the ackodac, but 6-64 (plus buffer in the loop) also provides and opportunity to add enough current to drive the headphones. its a novel circuit that I would really like to try and I doubt very much that the output of the sabre direct will have near enough current to drive JH13
Funny you should mention headphones - I'm currently looking at balanced drive of balanced headphones. I will be using two ES9022 DACS with an I2S splitter before them so one DAC handles R+/L+ & other one handles R-/L-. I just got some really nice Superlux HD681 headphone for next to nothing which I will be re-wiring for balanced operation.
I will be going a completely different route to this - I'll be using a Beam Deflection Tube based pre-amp ala John Swenson if I need more drive for the headphones. I'll be using this pre-amp anyway as part of my main rig balanced input & balanced output into a Susan Parker balanced amplifier or Gary Pimm Solid State Tabor balanced amplifier.
yeah all my headphone gear and monitor setup is balanced also; except my portable amps. but i'm making my own portable balanced dac/amp instead of buying one of the IMO could be done better soon to be released balanced drive portables. just researching split battery supplies at the moment actually. got any tips or links for a bipolar battery supply? I mean theres the obvious of using 2 battery packs with a centertap and then a decent undercharge circuit, but anything on google relating to bipolar batteries points to patents. best solution i've got at the moment is using more battery than I actually need and running the +/-vdc through a positive and negative jung type discrete SMD reg, to account for the slightly differing demands on the different polarities
anyway nuff OT there, so yeah waiting for the O-Netics to get here to play around with on my PCM1794A dac for a bit first, then if I really like those, to simplify matters for the home rig I was thinking I might get Bud to build me a custom output trannie with a small amount of gain
anyway nuff OT there, so yeah waiting for the O-Netics to get here to play around with on my PCM1794A dac for a bit first, then if I really like those, to simplify matters for the home rig I was thinking I might get Bud to build me a custom output trannie with a small amount of gain
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I have been using for a while Lundahl 1674, with AKM DAC AK4396 and have been very happy. I had them in my Behringer DCX2496 configured as 1+1 : 2+2 and in the output I had XBOSOZ. Than I decided to replace XBOOZ for jFet buffer. In order to keep needed gain I configured Lundahls 1+1 : 4+4. I am trilled with the results and now I am going forward with board configuration. I have to mention I would not be here without my friends Zen Mod who designed the circuit and Cviller who is making the PC board design. I am making this board for 6 channels since I am planning to use it with my Behringer, but if there are some of you guys interested to participate and would like to order boards than I might be willing to create scored boards where they are divided in three - two channels per section.
Here is the schematic. Please let me know before I go into fabrication:
Here is the schematic. Please let me know before I go into fabrication:
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