| yldouright |
I've been thinking about a full purpose best bang for the buck integrated amp based on the gainclone for a long time and would like to present some guidelines and a feature set:
Inverted "T" configuration with SuperSymmetry on amplifier section
JFET buffered to achieve maximum current/minimum phase error
unregulated power supply
1 digital input to a five channel DAC
2 general purpose inputs
2 tape (analog) inputs and outputs
1 tuner (analog) input
1 phono input with MM/MC circuits
1 headphone jack and amplifier
Does anyone here see why this project couldn't be completed for less than $250? I think this can all fit in standard 430mm form factor with plenty of room. Please feel free to critique the idea and point out some of the difficulties we are likely to encounter.
Thanks to Dave (planet10) for the use of "frugalphile" |
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| carlosfm |
Why do you need a 5-channel dac?
Is this a 5-channel amp? |
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| yldouright |
carlosfm
Actually, I am undecided. It would be a nice feature to implement with future DVD-A recorded material but it will add some complexity. I suspect, going from a two to five channel DAC will be less trouble than making five amps work well. I think I read that there are some high quality multichannel DAC chips available today but correct me if I'm wrong. |
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| carlosfm |
It depends of what you wanna do.
I don't know any "high-quality" integrated 6-channel (not five) dac.
High quality is single or two-channel dacs.
But this all depends what you want.
You'd better tweak a half-decent DVD-A player and forget about the multi-channel dac inside the amp.
Otherwise what you propose yourself to build is not possible for $250.
Don't forget (ideally) independent trafos and PSUs for everything. |
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| Steve Eddy |
Why complicate things? Get in tough with your frugalphile roots and just go mono.
Transformers by the way make great stereo-to-mono converters. :)
se |
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| Steve Eddy |
| quote: | Originally posted by carlosfm
:D :D :D :D |
Don't laugh too hard. I'm not entirely joking. :)
se |
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| yldouright |
carlosfm
Let's go for the two channel DAC. I'm assuming that you're thinking of three separate power supplies (phono, DAC and integrated amp) but perhaps we can get away with two alone.
Steve Eddy
From your "mono" perspective, the whole thing can be run with a battery supply and a single source supply for recharge. |
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| Steve Eddy |
| quote: | Originally posted by yldouright
Steve Eddy
From your "mono" perspective, the whole thing can be run with a battery supply and a single source supply for recharge. |
Absolutely. Not to mention your speaker budget is cut in half. Or to look at it another way, for the same money, you could make one really mondo speaker. :D
Here's a sneak peek at my latest "chip" endeavor.
I've dubbed it the IPSGTCBPBICA, for Integrated Passive Signal Gain Transformer Coupled Battery Powered Buffered Inverting Chip Amplifier. Also known as the MABTYASTA, for My Acronym's Bigger Than Your Acronym So There Amplifier. :D
Not sure it can rightly be called a "chip amp" though seeing as I'm using the chip as a unity gain buffer. All of the signal (i.e. voltage) gain is accomplished passively using transformers.
Feel free to take any ideas from it if you like.
se |
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| yldouright |
Steve Eddy
That's quite an interesting twist on transformer volume control but I think that your project definitely requires a new thread since it is an active speaker concept :)
The more I think about battery supplies for the amp, phono and DAC section, the more I like it. The whole thing can be arranged with 4 cells but the case requirements will probably increase. The 3875 likes the 12V supply on 4ohm loads but some people may not like the power numbers generated with only 12V on the amp rails. I've heard a battery gainclone with a 12V supply driving a bi-wire 4ohm two way speaker and it sounded pretty good to me and plenty loud too. I suppose it depends on the sensitivity of the speakers used. |
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| BWentler |
This is a wish list for a perfect intergraded amp for my use:
Inverted "T" configuration with SuperSymmetry on amplifier section
JFET buffered to achieve maximum current/minimum phase error
unregulated power supply
1 digital input to a two channel DAC (connected to my PC or a transport.)
2 general purpose inputs
2 tape (analog) inputs and outputs
1 tuner (analog) input
1 phono input with MM/MC circuits
1 headphone jack and amplifier
I could see using Peter's LM3875 amp, DAC, and new phono stage. I do not know were the buffer board would come from. I would also like to see not using battery but a normal power supply. The PS transformers could be housed in a different box to keep RF down and the size of the boxes small.
What is everyone thoughts on this? |
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| Steve Eddy |
| quote: | Originally posted by BWentler
I would also like to see not using battery but a normal power supply. |
I would argue that batteries are the "normal" supply. :)
se |
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| BWentler |
| quote: | Originally posted by Steve Eddy
I would argue that batteries are the "normal" supply. :)
se |
I aggree, battery supplies are the "purest" power you can get. The issue with batteries I see are the size of the battery(s), the extra charging supply for the battery, and the need to fill landfills with piles of dead batteries. We can all recycle but does 100% of the batteries get recycle or not?
I use a great power conditioner so the "need" to isolate the phono/DAC/pre-amp/amp power supplies from the AC power lines have been removed.
I would be insterested in seeing a test between battery/off line power supplies and transformer/on line power supplies. The test would include the overall size of the power supplies, amount of head room, flexability of the power supplies, sound quality the devices, and to finish this off, the total cost of each.
Bruce |
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| yldouright |
| If we assume a 12V rail system for the amp, DAC and phono stage, the part count for the power with batteries and recharge circuit will provide at least 2X the bang for buck (probably more) over making three separate quiet supplies. As I mentioned earlier, the major inconvenience is the space required. |
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| Steve Eddy |
| quote: | Originally posted by BWentler
I aggree, battery supplies are the "purest" power you can get. |
Yeah, that's rather the perspective I'm coming from here.
Batteries are DC from the start. Otherwise, you have to take a 120 or 240 volt sinewave, run it through a transformer to step down the voltage, rectify it into 100 or 120 Hz pulses (and their harmonics), then into some reservoir capacitors to make it look a little more like DC and if you want to reduce the ripple more, some form of voltage regulation.
And that's not counting upstream stuff like line filters, power conditioners, etc.
Just gets insane after a while. For me anyway. :)
| quote: | | The issue with batteries I see are the size of the battery(s),... |
Yeah, that can be an issue if you need a lot of juice. But if you've got high sensitivity loudspeakers and are using something as relatively efficient as the power opamp chips, you don't need to use huge batteries. With the right speakers, you probably wouldn't need any more than 7Ah batteries for any typical listening session.
| quote: | | ...the extra charging supply for the battery... |
Yeah. But hey, the charging can also be done via solar, wind and/or human power. How 'bout an audio system that's completely off the grid? That's my goal anyway.
| quote: | ...and the need to fill landfills with piles of dead batteries.
We can all recycle but does 100% of the batteries get recycle or not? |
So, just because some idiots will toss batteries into the landfill they should be disregarded?
Lead acids depending on how much you abuse them can last upwards of 5 years. And there's already a mature recyling system in place for lead acid batteries, thanks to the automobile industry. There's no excuse for any batteries to be dumped into the landfill in pursuit of audio.
| quote: | | I would be insterested in seeing a test between battery/off line power supplies and transformer/on line power supplies. The test would include the overall size of the power supplies, amount of head room, flexability of the power supplies, sound quality the devices, and to finish this off, the total cost of each. |
Don't hold your breath on that one. :)
se |
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| carlosfm |
| quote: | Originally posted by Steve Eddy
But hey, the charging can also be done via solar, wind and/or human power. |
Human power?:usd:
Someone's gotta work hard and have strong arms to make my amp sing some hours every day.:D |
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| Steve Eddy |
| quote: | Originally posted by carlosfm
Human power?:usd:
Someone's gotta work hard and have strong arms to make my amp sing some hours every day.:D |
No wife or kids, eh? :D
se |
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| yldouright |
Let's get serious please. This isn't Gilligan's Island and noone here is going to fashion a bamboo bicycle to generate power for a gainclone. I will be generating a parts list and budget as we move along on the undisputed items. The inputs described are numerous and noone seems to object to the ten sets of RCA jacks that will be required (or nine if we decide to use another connector for the DAC input) so I submit:
$15-ten RCA Gold female input jacks
$20-ten position switch (or two switches making 12 positions)
Does anyone here have a problem with single ended inputs for this project? Given the fact that we will be running an "X" type amp, would we be better off with balanced inputs? |
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| matjans |
well, yes, but since most people don;t have balanced/differential sources... :xeye:
steve eddy
a very nice plan indeed, the transformer based amp. what chipamp will you be using that is unity gain stable and can still deliver the current you need? |
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| yldouright |
matjans
Your reply brings up an interesting point. Since the sources are more than likely to be single ended, do we need to bother implementing supersymmentry in the amp? Some of the folks here have modded their sources to run balanced but I will leave this to the readers of this thread if the benefits of noise cancellation outweigh the additional parts and the inconvenience of modding our sources. Is there anyone who has built the GCSS and the TGC who can tell us what to expect with single ended sources? Metalman? carlosfm? Nuke? |
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| Steve Eddy |
| quote: | Originally posted by matjans
steve eddy
a very nice plan indeed, the transformer based amp. what chipamp will you be using that is unity gain stable and can still deliver the current you need? |
Thanks.
I'm currently using an LM-675. It's made unity gain stable by way of noise gain compensation. That's what the RC network across its + and - inputs is for. It's set so that it has a gain of 10 at around 500kHz, but a gain of 1 (or techincally, -1 since it's inverting) at DC and throughout the audio band.
The same technique can be used for other chip amps.
se |
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| Steve Eddy |
| quote: | Originally posted by yldouright
Your reply brings up an interesting point. Since the sources are more than likely to be single ended, do we need to bother implementing supersymmentry in the amp? Some of the folks here have modded their sources to run balanced but I will leave this to the readers of this thread if the benefits of noise cancellation outweigh the additional parts and the inconvenience of modding our sources. Is there anyone who has built the GCSS and the TGC who can tell us what to expect with single ended sources? Metalman? carlosfm? Nuke? |
Actually, you can have your cake and eat it too.
One of the neat properties of a good input transformer is that it can give you exceedingly high noise rejection even when fed from a wholly unbalanced source.
The Jensen JT-11P-1 for example can give you 100dB of common-mode noise rejection when fed from an unbalanced source (compared to 107dB from a balanced source). And because its input is floating, it can readily accept either unbalanced or balanced inputs
So, you don't need to use a balanced amplifier scheme and you don't have to mess with your sources.
And if you don't want to pay for something like a Jensen JT-11P-1 or a CineMag CMLI-15/15B, I've heard some people report good results using the less expensive Edcor transformers.
se |
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| yldouright |
Steve Eddy
I hear noise reduction figures used all the time without the accompanying applicable bandwidth. Foe example, the LM3875 has 120dB of noise rejection but only at the lower frequencies so I'm not so sure your cake will satisfy as a complete meal. I've just been introduced to Mauro Penesa's gainclone circuit and am still reading about it. This presents yet another amp section candidate for this project. |
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| Steve Eddy |
| quote: | Originally posted by yldouright
I hear noise reduction figures used all the time without the accompanying applicable bandwidth. Foe example, the LM3875 has 120dB of noise rejection but only at the lower frequencies so I'm not so sure your cake will satisfy as a complete meal. |
First, those 120dB figures are with the two inputs shorted together and driven from a single source impedance. In a realworld scenario, the line impedances don't balance nearly so precisely and for electronically balanced inputs, the CMRR figure degrades quite rapidly with greater impedance imbalances.
To get that kind of figure in the real world, you'd have to hand trim the line impedances to within a fraction of a percent.
And yeah, the figures are typically given for lower frequencies, but then it's the lower frequencies, i.e. power line frequencies, that are the most prevalent source of noise in the audio band which couples into the line via loop inductance.
But transformers also provide galvanic isolation which can eliminate noise from ground loops and chassis leakage currents.
| quote: | | I've just been introduced to Mauro Penesa's gainclone circuit and am still reading about it. This presents yet another amp section candidate for this project. |
Can't say I'm familiar with that one. Got a URL?
se |
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| Steve Eddy |
Thanks, Russ!
se |
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| yldouright |
Steve Eddy
You elaborated my point perfectly. The specification only tells a part of the story, to know anything useful you have to read how they came up with the number. Building the integrated gainclone as I described it here will give us the opportunity to address the line impedence issues you disclosed in your post. |
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| yldouright |
| Two new candidates for the amp section of this project are available courtesy of mauropenasa. The 'reference' amp which has a group buy currently under the management of Russ White and the 'NIGCWIPC' which has an active volume control. |
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| yldouright |
Steve Eddy
Did you get a chance to look over Mauro's circuits? |
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| Steve Eddy |
| quote: | Originally posted by yldouright
Steve Eddy
Did you get a chance to look over Mauro's circuits? |
No. I haven't had a chance to see him without his clothes on.
se |
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| Steve Eddy |
OH!! THOSE circuits! :D
Yeah. Interesting design. But just way too much uh, "stuff" for my tastes. But that's just me.
se |
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| carlosfm |
| quote: | Originally posted by Steve Eddy
OH!! THOSE circuits! :D
Yeah. Interesting design. But just way too much uh, "stuff" for my tastes. But that's just me.
se |
:D |
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| yldouright |
| If you figure the additional parts for a separate preamp, the Mauro designs are actually sparse. I think carlosfm has stated many times that all the gainclones he has tested so far need a separate preamp. From reading his posts, I don't think he has decided which pre is his favorite yet but please correct me carlosfm if you have finally settled on the perfect match for all the gainclones. |
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| carlosfm |
| quote: | Originally posted by yldouright
From reading his posts, I don't think he has decided which pre is his favorite yet but please correct me carlosfm if you have finally settled on the perfect match for all the gainclones. |
Of course I have a favourite pre.
My AD815.
Btw, Mauro's design doesn't need a pre, it already has it. |
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| Russ White |
| quote: | Originally posted by carlosfm
Btw, Mauro's design doesn't need a pre, it already has it. |
Well, yes you can build it that way, but otherwise its really just a buffer. ;)
Listening to one right now. :)
With my non-bufferd 627 preamp. :up: |
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| yldouright |
carlosfm
The point of my last post was to highlight the fact that the Mauro design saves you the parts you will need with a separate preamp. Have you also tried the AD811 and other video amps? When you compare the preamp to the OPA627 buffered gainclone, do you find a great difference? I believe I read that you couldn't decide between the buffer and a dedicated pre for some time. What characteristic finally made you decide on the AD815 pre?
Russ White
I am leaning toward the NIGCWIPC as my solution because of its greater simplicity. I think your post refers to the "my reference" design you are currently offering in a group buy. The point of this thread is to come up with a best bang for buck integrated. |
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| carlosfm |
| quote: | Originally posted by yldouright
carlosfm
The point of my last post was to highlight the fact that the Mauro design saves you the parts you will need with a separate preamp. Have you also tried the AD811 and other video amps? When you compare the preamp to the OPA627 buffered gainclone, do you find a great difference? I believe I read that you couldn't decide between the buffer and a dedicated pre for some time. What characteristic finally made you decide on the AD815 pre? |
I have always use a standalone pre, because I prefer to have short speaker cables, and the power amp in a central position between the speakers.
I have used a buffered power amp because it was inverting topology, and it worked better that way.
The AD815 is superior to the OPA627 (even biased to class-A) and to my previous OPA627+BUF634 pre.
The AD815, besides very detailed, is very clean.
The cymbals are impressive, the treble is gorgeously clean, no blurring, no tizzzzz, no grain.
An experienced drummer would recognize a Zildjan cymbal.:D
Bass is very tight too, midband very open and natural. |
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| filholder |
This AD815 thing has got me interested Carlos, what circuit are you using? Go on cheer me up, had a bloody awful day here in london.
Fil |
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| carlosfm |
| quote: | Originally posted by filholder
This AD815 thing has got me interested Carlos, what circuit are you using? Go on cheer me up, had a bloody awful day here in london.
Fil |
When will those guys stop?:bawling:
I hope this will cheer you up:
http://www.diyaudio.com/forums/show...0783&highlight=
Most of the thread talking alone...:D |
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| filholder |
Thanks Carlos,
Very interesting read, might have to try it some time.
Looks very interesting if I could just get the pot wired up right :D
Need to go to bed now, like i said exhausting day physicaly and mentally. I guess most of us here on this fourm are lucky enough to live in stable democracies where this **** is extremely rare. Still my worse day since living in london these last 10 years. Mustn't grumble though too many poor sods wont have a tomorrow to look foward too.
Fil |
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| yldouright |
carlosfm
Thanks for the link. It answered two of the questions I asked above. I agree that a good preamp is more convenient than tuning up a buffer for those of us that have uncooperative living spaces but I still believe the best bang for the buck comes from an integrated gainclone with a buffer and phono stage in the same box so the selection list for the amp section is listed:
the inverted "T" Clone
the "X" Clone
the NIGCWIPC or
one of the discreet buffered gainclones (Nuuk, help us decide here)
The X Clone seems the darkhorse here simply because of the questionable benefits of this design without balanced sources. The inverted T has been discredited by some but I think that with a little more tweaking and a buffer this might surprise us all. The NIGCWIPC has been tested by at least one member and he has found it robust and sounding quite well. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by yldouright
I still believe the best bang for the buck comes from an integrated gainclone with a buffer and phono stage in the same box so the selection list for the amp section is listed |
Hmmm, my OWN take would probably be an UNBUFFERED inverting gainclone, which uses the "lead/lag compensation" trick to fix the stability issue (in other words 220pF in series with 10K between inverting & noniverting input).
The 100K...220K linear track potentiometer (PEC Carbon?, alternatively generic tandem carbon track) together with the 10K input impedance of the IGC manage fine to give a proper "log" volume control.
A 330k/10K feedback circuit makes sure with an 18V transformer that around 0.5V will clip the amplifier if the volume is all the way up, way enough for any modern source, output probablky in the 25W ballpark.
Then add a "Analogue Addicts" Phonostage (also often called "El Cheapo") internally which has been covered elsewhere here many times and in detail and use up a pair of OPA637 for that if you can, if MC stepup is needed the single 2SK170 (et al) per channel is fine.
The resultant "integrated" amp is minimal, will sound pretty good, has an excellent MM (MC option) phono which equally sounds pretty good and will probably do for a lot of people.
I personally would probably limit any Solid State work to that kind of thing (it is worth doing more when doing commercial gear) but the result will take some beating, on a shoestring budget too.
Sayonara |
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| yldouright |
We can always count on herr Loesch to shed some light on a darkened thread and make alight the darkened fiber of our thoughts. Welcome Kuei Yang Wang to my humble thread. The phono stage would indeed be and El Cheapo type circuit with some form of AD video op-amp. CarlosFM has been very happy with with AD815 pre so there is corroboration of your now three year old suggestions to use these AD video chips. Like you, I generally like less parts but so many members have agreed that a buffer is mandatory to get the most out the LM chips that I have been convinced the additional complexity is warranted. Two points I would like to make:
The rail voltage decided upon should really be a function of the builders planned speaker system. In my own case, I have some 4 ohm speaker drivers so I would use 12V rails if I were to build the amp section with LM3875s and 16V rails with the LM3886s.
Using a lower rail voltage necessitates a smaller multiplier so I thought a buffer would help add some gain. Obviously, I'm not the authority here but that is my opinion based on what I have read so far.
Have you had a chance to look at Mauro's two circuits? |
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| carlosfm |
| quote: | Originally posted by yldouright
The phono stage would indeed be and El Cheapo type circuit with some form of AD video op-amp. CarlosFM has been very happy with with AD815 pre so there is corroboration of your now three year old suggestions to use these AD video chips. |
There's some confusion here.
You can't use a current-feedback op-amp on a phono stage:att'n: |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by yldouright
The phono stage would indeed be and El Cheapo type circuit with some form of AD video op-amp. |
Video Op_Amp's are not very suited for the job, you will find them rather noisy.
The OPA637 is the best compromise between noise, speed and sound for MM Pickups.
For MC Pickups, you may consider a AD811 in inverting configuration on the input for that, Bipolar CFB Video op-amp's are good in very low impedance circuit and some have low noise there, but for MM Pickups and MC with stepup, low noise Fet input Op-Amp's tend to be quite good for that kind of job and sound great there.
| quote: | Originally posted by yldouright
so many members have agreed that a buffer is mandatory to get the most out the LM chips |
Buffers are in fashion now, BUT practically non of them have ever implemented the ACTUAL configuration I recommended. By now we have buffered, T-Network IGC's with regulated supplies and all that jazz. No doubt all these items have merit and are interesting to try and all, but there is also merrit in doing things simple.
| quote: | Originally posted by yldouright
The rail voltage decided upon should really be a function of the builders planned speaker system. In my own case, I have some 4 ohm speaker drivers so I would use 12V rails if I were to build the amp section with LM3875s and 16V rails with the LM3886s. |
Well, yes, this depends somewhat, but if the "soft" PSU derived from the original Gaincard is kept, then much higher rail voltages are actually needed.
| quote: | Originally posted by yldouright
Using a lower rail voltage necessitates a smaller multiplier so I thought a buffer would help add some gain. Obviously, I'm not the authority here but that is my opinion based on what I have read so far. |
I am not sure I follow, what are you refering to?
| quote: | Originally posted by yldouright
Have you had a chance to look at Mauro's two circuits? |
Yes, don't much care for that way of doing things myself, otherwise quite smart circuitry, but the multiple feedback loops can get out of hand and can result in poorer transient behaviour. If tuned right this may very well be better than the chip on its own, but it can equally be worse very easily... One would have to build and test the thing.
Sayonara |
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| metalman |
Sorry to be late for the party, but somehow this thread escaped my notice. Damn job keeps interfering with my hobbies.
To answer one question, after we got the last of the stability problems worked out, the GCSS will work nicely with a single ended input (just ground the negative input to maintain the gain). Compared to the more standard GC variants, driven single ended it compares quite well, but keep in mind I never did build a totally tricked out fully tweaked basic or GCSS version. Single ended it didn't really present a significant advantage over the basic version, at least to my ears. Balanced input was another story, where it kept the clarity but added more body to the presentation. The one advantage of the GCSS, independant of input configuration, is that the sound of the amp seems less dependant on the power supply configuration, probably primarily due to the cancellation effect of the balanced topology. To the GCSS the difference between capacitance only, regulated, capacitance snubbered, and regulated snubbered was a lot less noticeable, whereas with the basic GC I could hear distinctive differences. I keep hoping that Peter Daniel or Carlosfm might take a wander into GCSS land so I could find out their opinions, but no luck so far (hint, hint).
My opinion, for what it's worth. If your using single-ended input, your efforts are better spent on getting the power supply right than adding the complexity of the SuSy. I'd also vote for the 3886 over the 3875 now that I've had a chance to work with both.
I'll try to pay attention here from now on.
Cheer, Terry |
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| yldouright |
carlosfm
What is reason you wouldn't use a current feedback op-amp on a phono stage?
Kuei Yang Wang
I thought I remembered reading that the video op-amps had the best noise to gain ratio and was very well suited as a phono stage gain device. Is there a way to use one of these video op-amps for both the MM and MC? I thought we might switch in a MM circuit that would throw away the gain without leaving a greater noise floor. There have been reports of some people having success with the T-Clones by throwing away the gain and thereby also reducing noise. I'm still researching exactly how this was done but if you know what I'm talking about and can elaborate I would be thankful. I mentiion the T-Clones because they were also reported to be noisy by some members but some members have successfully implemented the "T" layout presumably by throwing away gain. This technique is also mentioned in the X-Clone thread and endorsed by Nelson Pass as a way to get a better sounding gainclone. Speak of the devil :)
Terry, you must have sensed that I was thinking of you when I wrote that last comment. |
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| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by yldouright
I thought I remembered reading that the video op-amps had the best noise to gain ratio and was very well suited as a phono stage gain device. |
Nope, just not true. Check the datasheets.
OPA627/637 has around 5nV|/Hz and practically no current noise. The MM Cartrige is usually an inductor around 0.5-1H so across a lot of the audio range the noise of the Op-Amp is comparable to that generated by Cartridge & load resistor. Add any bipolar input op-amp and you add a lot of current noise, and your low noise goes to hell.
The AD815 due to current noise has a net Ein of around 3uV+ for 100Hz - 20KHz while the OPA637 manages < 0.8uV under the same conditions, or respectively -64db and -76db below 5mV respectively.
| quote: | Originally posted by yldouright
Is there a way to use one of these video op-amps for both the MM and MC? |
Not easily, the AD815 will be marginal and it appears to be indeed one of the best....
Sayonara |
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| yldouright |
Kuei Yang Wang
The OPA627/637 is good for a gain of 10x according to what I've read before its noise starts increasing geometrically, the video op-amps we are discussing hold their noise value up to a gain of 60x and higher so if you take that into consideration, how am I incorrect when I say that they have superior gain to noise ratios? |
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| carlosfm |
| quote: | Originally posted by yldouright
carlosfm
What is reason you wouldn't use a current feedback op-amp on a phono stage? |
With current-feedback op-amps you should use feedback resistors values recommended by the manufacturer, or close to that.
Also, you can't use caps on the feedback loop.
To help even more, they have have high(er) input dc-offset, which you would really need to protect with input coupling caps if you don't want to destroy your cartridge.
As Kuei says, the OPA637 is very good for the job, has low noise, and sounds amazing biased to class-A at around 10ma.
The 'El Cheapo' is a very good phono stage.
I made one a couple of years ago (MM), with OPA637 biased to class-A.
I compared that to a Linn Linto (connected to a full-spec LP12 / Linn Akiva) and the 'El Cheapo' was better.
The 'El Cheapo' doesn't sound cheapo.:D |
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| Peter Daniel |
| quote: | Originally posted by metalman
Balanced input was another story, where it kept the clarity but added more body to the presentation. The one advantage of the GCSS, independant of input configuration, is that the sound of the amp seems less dependant on the power supply configuration, probably primarily due to the cancellation effect of the balanced topology. To the GCSS the difference between capacitance only, regulated, capacitance snubbered, and regulated snubbered was a lot less noticeable, whereas with the basic GC I could hear distinctive differences. I keep hoping that Peter Daniel or Carlosfm might take a wander into GCSS land so I could find out their opinions, but no luck so far (hint, hint).
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I'm presently using a bridged version of LM4780 with (only) a balanced input. After trying that, I don't think I will go back to single ended LM3875 (unless I try it in bridged version).
As you noted, a bridged version seems to give more body to the presentation without loosing any clarity. Also spaciousness and dynamics increase.
Just today, I replaced ML380S preamp with S&B102 line stage in a completely balanced configuration and I really like what I hear now. There is a certain coherence and ease of presentation I didn't experience in a long while. I will be soon trying a new silver version. ;)
But this was only possible with a new DAC I got yesterday (that has low impedance balance outputs).
I tried similar configuration with TDA1543 passive stage and S&B102 used as single ended to balanced converter didn't work well at all. Using it in fully balanced setup is another story.
As to the SuSy, this would require another active stage in front of the amp, and I'm not sure if the trade off is worth that. But considering the simplicity of such circuit, I might try it one day ;)
IMO, the future of GCloning is in fully balanced topologies. |
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| metalman |
| quote: | Originally posted by Peter Daniel
But this was only possible with a new DAC I got yesterday (that has low impedance balance outputs). |
Care to share which DAC it is and how it compares to your TDA1543?
| quote: | Originally posted by Peter Daniel
As you noted, a bridged version seems to give more body to the presentation without loosing any clarity. Also spaciousness and dynamics increase. |
Yes! We seem to have the same opinions exactly on the sound of the bridged topology. |
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| carlosfm |
| quote: | Originally posted by Peter Daniel
I tried similar configuration with TDA1543 passive stage and S&B102 used as single ended to balanced converter didn't work well at all. Using it in fully balanced setup is another story. |
Passive stage... sure.:rolleyes:
The source is the most important component on any system.
It makes everything after it sound good or bad, it rules.
Single-ended or balanced, the difference is not night and day, if well done.
You can't compare amps when you also change the source component. |
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| Peter Daniel |
| quote: | Originally posted by carlosfm
You can't compare amps when you also change the source component. |
I have no idea what are you trying to say here. |
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| Peter Daniel |
| quote: | Originally posted by metalman
Care to share which DAC it is and how it compares to your TDA1543?
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Well, somebody suggested that I should try different things than my "beloved" TDA1543 DAC, so I purchased recently some other DACs for comparison purposes. I have now Benchmark DAC-1. Having seen all those good reviews, I couldn't resist not to try it. Well, I tried it and tomorrow it goes back on Audiogon.;)
I also found a very good deal on ML360S and bought it. I didn't really like it that much, when it replaced TDA1543. Although sort of refined and well behaved, it was lacking immediacy and energy the smaller, (beloved) DAC shows. It is almost like those quotes, I found on AA, perfectly apply here:
"Many reviewers harp on such descriptions as 'smooth, analog-like', etc. I would rather make my comparisons to the effect of live music....which is neither necessarily smooth, or analog-like! But it IS emotional, driving, very present, and full-range (airy highs AND taught, very deep bass). One is simply moved by the music, the intent of the artist, and dazzled by the notes, the beat, the emotion of the singer, the life of the recording. CDs played through (such) components will grab your atention. Take John Hammonds' latest cd, Ready For Love. I happen to know John personally, and when I say that it is erie to hear his music on my system, I mean it. His voice is so real and alive, all that is missing is the cigarette smoke. This cd sounds like John and the band were having fun. That is the kind of energy that comes across; it's more than just the notes.
... and it has the best bass I have heard (by that I mean tightness and impact, not just 'boom') and it delivers the energy of music, the emotion, the reason why an artist has bothered to put the music to disc in the first place. This is not just a matter of good sound, which I realize now is what I used to be into: nice, warm, lovely sound. No, this is direct music like you will get live. Not colored, syrupy 'sound'. It is not for the faint of heart. But it is for those of us who want to get into the essence of what is on the disc."
But, I thought that I can somehow improve things and since ML has exactly the same output stage as the preamp (6 ohm output impedance), I decided to remove preamp completely and use passive, S&B102 based, line stage. Well, it was a right move and the sound is pretty good now, different in character from what I was getting with NOS DAC and ML380S preamp, but at least comparable;)
PS: To be completely clear, the TDA1543 DAC I'm using presently is not exactly the same version that I offer as a kit. It has some parts upgraded: 4 x BG N 1000/50 caps are used in main filtering stage (replacing BG NX 25/50), Caddock TF020 replace Rikens and V-Cap TFTF replace BG N in coupling. Those parts alone add about $600 to the price tag though |
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| carlosfm |
| quote: | Originally posted by Peter Daniel
I have no idea what are you trying to say here. |
You can't change two components at once and compare.
It's not conclusive.
Make a single-ended TDA1541A NOS dac with Sin(x)/x compensation and active stage and compare again with that balanced output dac.
Also, read below.
| quote: | Originally posted by Peter Daniel
"Many reviewers harp on such descriptions as 'smooth, analog-like', etc. I would rather make my comparisons to the effect of live music....which is neither necessarily smooth, or analog-like! But it IS emotional, driving, very present, and full-range (airy highs AND taught, very deep bass). One is simply moved by the music, the intent of the artist, and dazzled by the notes, the beat, the emotion of the singer, the life of the recording. CDs played through (such) components will grab your atention." |
Right, agreed.
You will never hear this out of a NOS dac with passive output. |
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| Peter Daniel |
| quote: | Originally posted by carlosfm
You can't change two components at once and compare.
It's not conclusive.
Make a single-ended TDA1541A NOS dac with Sin(x)/x compensation and active stage and compare again with that balanced output dac.
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I was using balanced amp in all cases, as the preamp has balanced output. And I was using single ended outputs from both DACs, What is your point then as I still don'tt get it.
And this is exactly what you are getting from NOS DAC with passive output:
"...to the effect of live music....which is neither necessarily smooth, or analog-like! But it IS emotional, driving, very present, and full-range (airy highs AND taught, very deep bass). One is simply moved by the music, the intent of the artist, and dazzled by the notes, the beat, the emotion of the singer, the life of the recording. CDs played through (such) components will grab your atention."
If you claim it's not the case, you simply didn't make it right. But I'm not really surprised, observing your conclusions in other areas. |
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| carlosfm |
| quote: | Originally posted by Peter Daniel
If you claim it's not the case, you simply didn't make it right. But I'm not really surprised, observing your conclusions in other areas. |
Well, some deaf people out there?:confused:
A NOS dac without Sin(x)/x compensation has a marked high frequency roll-off.
Passive stage has high output impedance, of course it doesn't work with a passive pre.
I don't know how some can't clearly detect this on a listening test, because it's very clear.
Maybe my standards are higher than normal?
Oh well... |
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| Peter Daniel |
| Go back and read again what I wrote here. Maybe then we can have civilized discussion. |
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| Steve Eddy |
| quote: | Originally posted by Peter Daniel
IMO, the future of GCloning is in fully balanced topologies. |
Balanced? Bah! Humbug! :D
se |
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| yldouright |
I really hate having two of this forums most prominent members have misunderstandings so I have tried to see what caused it in an effort to resolve it.
carlosfm
You had stated that a passive stage must have high output impedence which will cause a high frequency roll off and that is generally correct but Peter stated that his output impedence was a very low 6 ohms because of the new DAC which enabled him to take advantage of the passive configuration with the S&B part.
Peter Daniel
You had stated that you were able to drive the passive line stage without any sacrifice in immediacy, air and presentation but since we were (and still are) looking for a single ended source solution, carlosfm may have missed the fact that you were using a balanced source. I don't know if we can make a best bang for buck audio solution in this thread with balanced sources but that is the point of this thread: To discuss how to get closest to the sound spending the least amount of money. The 102 is an expensive part so it would have to make a really tremendous improvement to warrant its use given the aim of this thread.
BTW, I am not immune to misunderstanding my fellow member posts so if I have misinterpreted either of you please tell me if my analysis was not accurate and correct me accordingly. I understand that both of you were acting in good faith in guiding this thread but please be more attentive to the text of the posts and the intent of the thread before being critical of each other in the future. |
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| carlosfm |
| quote: | Originally posted by yldouright
carlosfm
You had stated that a passive stage must have high output impedence which will cause a high frequency roll off and that is generally correct but Peter stated that his output impedence was a very low 6 ohms because of the new DAC which enabled him to take advantage of the passive configuration with the S&B part. |
It's not a question of "must have", it's in fact unavoidable.
The marked treble roll-off is unavoidable with a non-oversampling dac, you must compensate for that on the output stage.
Sorry, I don't want to discuss the obvious anymore. |
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