Re: When ground is not ground....
Whatever my reply was previously, I went down to my cave and re-run the input ground: I conected it directly to noninverting input (which is connected to common point). The result? No improvement at all, if not degradation.
Tube Dude was so certain however that it makes a difference, like if he's been working on those type of amps every day. Which makes me wonder if he has the same type of conviction on every issue (like DBT and null testing for instance.
).
I did one additional change though, after checking grounds. I installed the 50k pot at the input and now the amp reminds me much more the sonic signature of my other gainclones. Which is another issue, either the pot has such a big influence on sonics, or the amp simply needs a sort of resistor at input to the ground?
Tube_Dude said:
Whatever my reply was previously, I went down to my cave and re-run the input ground: I conected it directly to noninverting input (which is connected to common point). The result? No improvement at all, if not degradation.
Tube Dude was so certain however that it makes a difference, like if he's been working on those type of amps every day. Which makes me wonder if he has the same type of conviction on every issue (like DBT and null testing for instance.
).I did one additional change though, after checking grounds. I installed the 50k pot at the input and now the amp reminds me much more the sonic signature of my other gainclones. Which is another issue, either the pot has such a big influence on sonics, or the amp simply needs a sort of resistor at input to the ground?
Steve Eddy said:
When I started figuring the design of this in my head, I had only the transformers at hand and I was looking for nice heatsinks to implement them here. I found those at local surplus store, anodised. This is pretty common extrusion and I saw it in local stores on more than one occasion over the years.
Re: Re: When ground is not ground....
Koinichiwa,
Well, if the source is reliably connected and low DRC/ACR you need no resistor (but that is easy to try).
BTW, I forgot to congratulate on your excellence of implementation. If I could, I'd make you an honarable German.
I rather suspect these Alps plastic pots are to blame. They have a very "manipulative" influence on sound in my experience. I'm afraid I still adhere to the "straight wire" ideas and hence (for example) after much testing no IT coupling in my SE Amp, instead LCL coupling, all IT's I tried where to "manipulative", though thoroughly decent, enjoyable and musical. And hence a preference for $1 Alps carbon trac pots from RS over black beauty or alps blue.
BTW, take the gold BG out and replace the bootstrap with a minimum of BG-N, better BG-NX or best MKT or film & foil (just kidding - I'd use an ERO MKT 22uF anyway).
I'm interested in more comments on the mosfet output TDA Chips. I know they where rejected elsewhere and why and agree from parallel experience, but I have enough "ominous Valve Work" to do to get involved deeply with the SS....
Sayonara
Koinichiwa,
Peter Daniel said:
Well, if the source is reliably connected and low DRC/ACR you need no resistor (but that is easy to try).
BTW, I forgot to congratulate on your excellence of implementation. If I could, I'd make you an honarable German.
I rather suspect these Alps plastic pots are to blame. They have a very "manipulative" influence on sound in my experience. I'm afraid I still adhere to the "straight wire" ideas and hence (for example) after much testing no IT coupling in my SE Amp, instead LCL coupling, all IT's I tried where to "manipulative", though thoroughly decent, enjoyable and musical. And hence a preference for $1 Alps carbon trac pots from RS over black beauty or alps blue.
BTW, take the gold BG out and replace the bootstrap with a minimum of BG-N, better BG-NX or best MKT or film & foil (just kidding - I'd use an ERO MKT 22uF anyway).
I'm interested in more comments on the mosfet output TDA Chips. I know they where rejected elsewhere and why and agree from parallel experience, but I have enough "ominous Valve Work" to do to get involved deeply with the SS....
Sayonara
Peter Daniel said:
Ah. Have you (or the local store) any left? If so, I might be interested in buying a couple. Currently I'm just using samples I got from Accel and they've already been plated (gold). I'll be buying a whole 9 foot bar from them sometime later but I've got some Bolivian rosewood left and thought it'd be nice to build just one pair in black/rosewood (I'm going to stop using tropical hardwoods once my stock of rosewood is gone).
se
The amp with a new grounding technic...
So ...maybe your system doesn't have enough resolution...
So you think that your amp need grounding technics that viole the grunding principles that are comum to any amplifier design...and only you know the way it must be grounded... Fine!!
If you are so sure why you go to the cave to try it???
PS:you never see me to defend the DBT...if so point it!!!
For me not all amps sound the same...but the ones that have a better null...sound allways better...
And if for you the null teste is so complicated...for me is logical and intuitive...
So ...maybe your system doesn't have enough resolution...
So you think that your amp need grounding technics that viole the grunding principles that are comum to any amplifier design...and only you know the way it must be grounded... Fine!!
If you are so sure why you go to the cave to try it???
PS:you never see me to defend the DBT...if so point it!!!
For me not all amps sound the same...but the ones that have a better null...sound allways better...
And if for you the null teste is so complicated...for me is logical and intuitive...
Re: The amp with a new grounding technic...
Although I might give the impression that I was sure, in reality I wasn't, that's why I decided to check it. But now I am sure that it doesn't affect anything, at least in that type of layout
Tube_Dude said:
If you are so sure why you go to the cave to try it???
Although I might give the impression that I was sure, in reality I wasn't, that's why I decided to check it. But now I am sure that it doesn't affect anything, at least in that type of layout
Steve Eddy said:
steve - at the risk of hijacking the thread...
...how do you go about getting samples from accel - just ask them? or do you have to have a tax ID or something? ....also, do you happen to have a price list for their profiles?ObTopic: nice lookin' monoblocks!
it looks like you really have fun with your amp-making. salut!
So far I tried LM3875, OPA549 and today TDA7294.
I've seen grading on a forum of the gainclone chips, where TDA was listed as best sounding, others claimed that OPA was better than LM chip, but my feeling is that LM sounds better than the other two chips mentioned.
The OPA549, IMO, produces the sound that is very clean, completely free of any discernible aberration, but unfortunately also free of too much emotion for my taste. While very clean and taut, the sound lackes involvement, as if the op amps were doing their jobs very professionally, but without emotion - all business, nothing personal. This is not a very big difference over LM chip, and sometimes, depending on listening material, I couldn't decide which chip I prefer, but this is the bias I have.
The TDA chip, although today is the first day I listen to it, seems somewhat lacking coherence (if this is best description). It's very dynamic, with lots of bass, but somewhat bloomy midbass and the midrange seems to be out of phase (for lacking better words). It's sort of bothering and whenever I try to listen, it makes me restless. There is detail, but highs seem a bit edgy also.
It offers somewhat thick and veiled sound, as if I were looking for something through a thin mist, more like a haze. Obviously, it lacks involvement and I really don't know if this can improve after burn in time.
I also understand that the construction of this amp is different than the other clones I made so far. This is the first amp that is using parallel 1000u caps, and my feeling is that a single cap works better. I'm not sure about the bootstrap cap as well. Maybe placing better one would improve things.
I've seen grading on a forum of the gainclone chips, where TDA was listed as best sounding, others claimed that OPA was better than LM chip, but my feeling is that LM sounds better than the other two chips mentioned.
The OPA549, IMO, produces the sound that is very clean, completely free of any discernible aberration, but unfortunately also free of too much emotion for my taste. While very clean and taut, the sound lackes involvement, as if the op amps were doing their jobs very professionally, but without emotion - all business, nothing personal. This is not a very big difference over LM chip, and sometimes, depending on listening material, I couldn't decide which chip I prefer, but this is the bias I have.
The TDA chip, although today is the first day I listen to it, seems somewhat lacking coherence (if this is best description). It's very dynamic, with lots of bass, but somewhat bloomy midbass and the midrange seems to be out of phase (for lacking better words). It's sort of bothering and whenever I try to listen, it makes me restless. There is detail, but highs seem a bit edgy also.
It offers somewhat thick and veiled sound, as if I were looking for something through a thin mist, more like a haze. Obviously, it lacks involvement and I really don't know if this can improve after burn in time.
I also understand that the construction of this amp is different than the other clones I made so far. This is the first amp that is using parallel 1000u caps, and my feeling is that a single cap works better. I'm not sure about the bootstrap cap as well. Maybe placing better one would improve things.
Re: Re: The amp with a new grounding technic...
Well, it does have an effect. Whether the effect is audible or not is another matter.
The effect is that the voltage drop across the resistance of that wire you have running between the speaker post and ground (due to the current flowing through the loudspeaker) is added to your input signal seen at the input of the opamp as a small amount of positive feedback.
se
Peter Daniel said:Although I might give the impression that I was sure, in reality I wasn't, that's why I decided to check it. But now I am sure that it doesn't affect anything, at least in that type of layout
Well, it does have an effect. Whether the effect is audible or not is another matter.
The effect is that the voltage drop across the resistance of that wire you have running between the speaker post and ground (due to the current flowing through the loudspeaker) is added to your input signal seen at the input of the opamp as a small amount of positive feedback.
se
faustian bargin said:steve - at the risk of hijacking the thread...
Well, they don't normally send samples. At least not free samples unless perhaps you've spent a gob of money with them in the past.
Here's what happened in my case.
Before they were purchased, I could get samples at the per foot price plus a nominal charge for cutting and deburring. I hadn't purchased anything from them in some years and that was prior to the company being sold.
So when I recently wanted to get a couple of 4-1/4" lengths for prototyping this amplifier, the salesman quoted me something on the order of $75. And this was for an extrusion that sells for just under $90 for an entire nine foot bar.
I politely declined and told the salesman I'd just take my business elsewhere. I wasn't trying to be a hard-*** or anything. I simply wasn't prepared to pay nearly as much for two small pieces as I'd pay for an entire bar.
If I'd have known ahead of time that this extrusion would work out for me the way I was hoping, I'd have just bought a bar. I knew it would work thermally, but wasn't sure how it would work out aesthetically for the design I had in mind (the extrusion would be an integral part of nearly the entire front face of the amplifier).
Anyway, a little while later, the secretary called me back and asked me what was wrong. I explained to her how I'd purchased sample quantities under the previous ownership and she said she'd see what she could do.
Two days later, I received two 4-1/4" pieces. No charge.
Oh, and no, I don't have a price list for their profiles. Just this particular one. And the prices I'd been quoted in the past for several others are long gone from my memory I'm afraid.
se
Peter Daniel said:I don't remember the price (less than $20 CAD if not mistaken), but it should be peanuts with a current CAD exchange rate.
Yeah, I could probably just dig that up from a week's worth of lost change under my sofa cushions.
I'd only want two. But my plate's so full now I'm thinking I may not be able to get around to using them before I get that full bar from Accel which in that case I could just toss a couple from that in with a batch of Coda faceplates and have 'em anodized black.
Hmmmm. Decisions, decisions...
se
There is no really any schematic, only the info collected from some posts. I used 2000u BG per rail and additionally bypassed signal supply with 4.7 BG N. You see 33u bootstrap cap in my pics, but this is what I had available.
The amp seems to be improving and maybe it's not that bad after all. But still, I'm missing a bit of air and more resolution in the trebles.
The amp seems to be improving and maybe it's not that bad after all. But still, I'm missing a bit of air and more resolution in the trebles.
Attachments
Check the post 882 and 883 of this thread
http://www.diyaudio.com/forums/showthread.php?s=&threadid=9112&perpage=15&pagenumber=59 for instructions and
schematic.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=9112&perpage=15&pagenumber=59 for instructions and
schematic.
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