Yes, You can eliminate the capacitor. You adjust the 2SK170 so that when measuring at the input you get as low a value as possible. Should be a mV or less. The output of the 844 will then be around -1.2 mV (typical). This is an easy direct couple. You can get better results as George says by using a BUF03 across the pin 5 TZ resistor. With that setup I get 0.1 mV offset direct coupled all the way. I use a nulling circuit at the BUF03 also. I also have a discrete version of Pedja's circuit up and running. That did require a cap although I am told there are ways around that too.
Hi Torchwood,
Do you mean the discrete Pedja version is better than the one with OP861 I/V and OP861 buffer ? Do you talk about the discrete one after the AYA2 or before the AYA2/3?
stacked 844 (Three for 1541 chip) better the the two op861 according to you ?
Which circuit would you recommend (hmm, simple vs complex) and why? Other?
I just use a two-transistor current source myself, JFETs tend to be more expensive and I can't see what they bring to the table. I do put a ferrite bead on the output of the amp being biassed so that the additional capacitance from the CCS doesn't upset the stability. With the wide bandwidth amps I use, just a few pF can be enough to degrade the stability.
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AD844 Buffer VS BUF03
Hi, In my system the stacked AD844 was really nice, however the BUF03 is on another level altogether. Sadly obsolete. It has excellent output drive and very high input impedance which prevents loading the TZ resistor.
Hi, In my system the stacked AD844 was really nice, however the BUF03 is on another level altogether. Sadly obsolete. It has excellent output drive and very high input impedance which prevents loading the TZ resistor.
Pedja discrete VS OP861
Hi Eldam, I haven't heard the OP861 as I/V so I just don't know. It would be interesting to try. I will have to price out that chip and see how to apply it. The discrete Pedja circuit I have is the later one with the 2SK170 current source jfet. I won't be able to answer the question 3 stack AD844 VS OP861. If someone has tried that I hope they will post.
Hi Eldam, I haven't heard the OP861 as I/V so I just don't know. It would be interesting to try. I will have to price out that chip and see how to apply it. The discrete Pedja circuit I have is the later one with the 2SK170 current source jfet. I won't be able to answer the question 3 stack AD844 VS OP861. If someone has tried that I hope they will post.
Well if the discrete you talk about is NEWER than him own op861 design, I assume the FIRST to be better !
Well the question would be more: is the triple stacked AD844 with BUF634 is better than a design with the OP861 (J. Didden input). The layout, ps, parts are important also, so compare is difficult. But if one is better by a large margin...
Do you try the CEN/SEN... mooded for theTDA1541? Pedja have coming back to discrete then to hybrid design outputstage with him last S DAC.
Well the question would be more: is the triple stacked AD844 with BUF634 is better than a design with the OP861 (J. Didden input). The layout, ps, parts are important also, so compare is difficult. But if one is better by a large margin...
Do you try the CEN/SEN... mooded for theTDA1541? Pedja have coming back to discrete then to hybrid design outputstage with him last S DAC.
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I/V's
Hi Eldam, Send me a link to that OP861 (J. Didden input). I could try building that up. I will also need to try the BUF634 VS BUF03... I read a bit about that CEN/SEN and I'd bet that is good too. Only issue is the TDA1541A needs an I/V resistor of about 12 Ohms to stay in compliance. Jfet's are nice. I have a Pass BA3 preamplifier I really like. I have a number of uncompleted projects I am working on however I could try that OP861 circuit sometime soon....
Hi Eldam, Send me a link to that OP861 (J. Didden input). I could try building that up. I will also need to try the BUF634 VS BUF03... I read a bit about that CEN/SEN and I'd bet that is good too. Only issue is the TDA1541A needs an I/V resistor of about 12 Ohms to stay in compliance. Jfet's are nice. I have a Pass BA3 preamplifier I really like.
I have a number of uncompleted projects I am working on however I could try that OP861 circuit sometime soon....Sorry it was not J Didden bu J Rassmussen here :
http://www.diyaudio.com/forums/digital-source/227677-using-ad844-i-v-62.html#post3640844
I was talking about the opa861 stage P. Rodjic offer to the diy communauty here on july 2013 (dowload the pdf for the complete shematic : OPA861 zero-feedback output stage of AYA II - Audial online topic
I surmise some people have already tested it in this thread and can reply to you without you need to make it ?!
It's off topic, but we try to edit a core board for the tda1541 in a thread in the line digital section "any good TDA kit", how do you work yourself ? with a tweaked commercial device like George ?
http://www.diyaudio.com/forums/digital-source/227677-using-ad844-i-v-62.html#post3640844
I was talking about the opa861 stage P. Rodjic offer to the diy communauty here on july 2013 (dowload the pdf for the complete shematic : OPA861 zero-feedback output stage of AYA II - Audial online topic
I surmise some people have already tested it in this thread and can reply to you without you need to make it ?!
It's off topic, but we try to edit a core board for the tda1541 in a thread in the line digital section "any good TDA kit", how do you work yourself ? with a tweaked commercial device like George ?
Hi Jan, from memory I did look at these, but I think a couple of things steered me go the BUF03 way.
I believe the input of the 634 is bi-polar not fet, fet would be more preferable for the very high output impedance of the 844's pin 5 TZ output.
Also from memory it doesn't have dc offset nulling pins, so a bit more complicated to get everything dc coupled. (as I'm not partial to coupling caps).
Cheers George
(It would be nice if they gave the internal schematic of them like they with the AD844)
I've got some of these waiting for me to give them them a try, they also look good, what has delayed me is that they are smd and not as easy to use implement into my cdp. And they are only +-6.5v so power needs to be addressed as well, where the 844 just uses what I had +-15vdc, plus there's no nulling pins on these, but that's no bigee as the BUF03 has in my case.
And the stacked AD844/BUF03 is sounding so good I'm loathed to remove it at the moment because I cannot fault it in any way, hope someone else has the curiosity to compare the two.
Cheers George
OPA861
Hi Eldam, Thank you for that interesting link. It would be worth trying I think. I'd use the 2SK170 current source.... I'll have to ask around about anyone using it. My board... Don't laugh. It started off as the Analogmetric dac. I dumped the output stage (never assembled that). I also removed that bad reclocker design. I use a DIR9001 to CS8412 adapter board for the input receiver. Dumped the SAA7220 for a NPC SM5814 digital filter. Made changes to the decoupling dac caps based on ECDesigns ideas. I have 2 of these one with the triple stack AD844/BUF03. The other with the Pedja Discrete I/V and BUF03 buffer. I use a passive filter based on Cinemag 600/600 transformers. If you want to use the NPC filter you send Sony mode 2's complement, MSB first to the filter from the DIR9001. The 5814 can output I2S.
Hi Eldam, Thank you for that interesting link. It would be worth trying I think. I'd use the 2SK170 current source.... I'll have to ask around about anyone using it. My board... Don't laugh. It started off as the Analogmetric dac. I dumped the output stage (never assembled that). I also removed that bad reclocker design. I use a DIR9001 to CS8412 adapter board for the input receiver. Dumped the SAA7220 for a NPC SM5814 digital filter. Made changes to the decoupling dac caps based on ECDesigns ideas. I have 2 of these one with the triple stack AD844/BUF03. The other with the Pedja Discrete I/V and BUF03 buffer. I use a passive filter based on Cinemag 600/600 transformers. If you want to use the NPC filter you send Sony mode 2's complement, MSB first to the filter from the DIR9001. The 5814 can output I2S.
DAC's
Hi, It's a tough call. The presentation is more laid back and the detail is all there. Almost like headphones the way the details are heard and that is over my MG2.5R Magnepan speakers. The triple stack has a little more you are there especially with the human voice. The detail is there you just notice more the dynamics and slam. It is just a matter of taste. I have compared my OPPO BDP83SE (Sabre) and a CS4398 with Lundahls and to tell the truth I like the 2 TDA1541A S1 crown dacs better. For future high bit I think a dac based around the PCM1704 is the way forward. If I listen to the Delta Sigma dacs then switch to the R2R dac's I am always surprised how smooth the R2R sound. Once I do that I never switch back to DS. All that says is my ear likes R2R better.
Nothing better on my side ...
Well you seem liking more the discrete + buf03
Hi, It's a tough call. The presentation is more laid back and the detail is all there. Almost like headphones the way the details are heard and that is over my MG2.5R Magnepan speakers. The triple stack has a little more you are there especially with the human voice. The detail is there you just notice more the dynamics and slam. It is just a matter of taste. I have compared my OPPO BDP83SE (Sabre) and a CS4398 with Lundahls and to tell the truth I like the 2 TDA1541A S1 crown dacs better. For future high bit I think a dac based around the PCM1704 is the way forward. If I listen to the Delta Sigma dacs then switch to the R2R dac's I am always surprised how smooth the R2R sound. Once I do that I never switch back to DS. All that says is my ear likes R2R better.
yeap, it's very hard sometimes to say which is the best device when close...
Tastes matter, room, tonal equilibrium of speakers... it's here individual !
Sometimes some music help me to choose: like piano, harmonica (very cruel for the speakers and devices : we have often too brighty and too trebled dac !), Andine Flut, female voices, cello !
thanks for the input, I'm OT, let's go back to the stacked AD844 and fast OAP...
Tastes matter, room, tonal equilibrium of speakers... it's here individual !
Sometimes some music help me to choose: like piano, harmonica (very cruel for the speakers and devices
: we have often too brighty and too trebled dac !), Andine Flut, female voices, cello ! thanks for the input, I'm OT, let's go back to the stacked AD844 and fast OAP...
Interresting, is Telefunken E180F not the first tube of the latest gnome shematic T. Loesch use for TDA1541 ?
Did you compare both with the double opa860 shematic given last years (look at above in this thread) by Pedja Rojic ?
All your tests was maid with the same DC outputs caps each time ?
Did you compare both with the double opa860 shematic given last years (look at above in this thread) by Pedja Rojic ?
All your tests was maid with the same DC outputs caps each time ?
I'm using this schematic with 33R as I/V and Sowter 1:1 transformer
I did'n try OPA860 I/V from Pedja
On tube stage I have ordinary Mundorf Mcap as output capacitor and on the AD844 stage I'm using Sowter 1:1 transformer instead of DC cap ( which was great improvement instead of DC cap)
An externally hosted image should be here but it was not working when we last tested it.
I did'n try OPA860 I/V from Pedja
On tube stage I have ordinary Mundorf Mcap as output capacitor and on the AD844 stage I'm using Sowter 1:1 transformer instead of DC cap ( which was great improvement instead of DC cap)
TDA1541 VS TDA1541A with triple stack
Hi guys, I am doing an experiment. So I stuck an old TDA1541 (plain) dac into my triple stack rig. I wasn't expecting any difference. It was a bit of a shock. The "A" an S1 crown chip had a black velvety background and the plain chip is really out of know where. Imaging is different. Laid back. Detail is really the best I have heard. Now it has a ruthlessly revealing ability. Still very musical just bad stuff can be very bad especially in the upper mid range into the treble. Good stuff really nice. MP3's are revealed as bad in the treble region.... I once tried a SRPP with an I/V around 35 Ohms. It was real nice just I could clearly hear the dac go out of compliance range in the bass. I can't recall which tube at the moment. Dave
Hi guys, I am doing an experiment. So I stuck an old TDA1541 (plain) dac into my triple stack rig. I wasn't expecting any difference. It was a bit of a shock. The "A" an S1 crown chip had a black velvety background and the plain chip is really out of know where. Imaging is different. Laid back. Detail is really the best I have heard. Now it has a ruthlessly revealing ability. Still very musical just bad stuff can be very bad especially in the upper mid range into the treble. Good stuff really nice. MP3's are revealed as bad in the treble region.... I once tried a SRPP with an I/V around 35 Ohms. It was real nice just I could clearly hear the dac go out of compliance range in the bass. I can't recall which tube at the moment. Dave