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#1
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
Why is there no gain control on the Adcom GFA-535?
I've used it in between my computer (iMac) and my speakers, and controlling the gain from the computer works, but there's always a noticeable hiss. Wouldn't it be better to have the output of my computer much higher and attenuate the output of the Adcom? Similarly, I've seen many reviews of powered speakers where the reviewers complain that there's a noticeable hiss that can't be attenuated. Why are they designed like that? -- Matt |
#2
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
On 5/06/2018 4:02 PM, Matt Faunce wrote:
Why is there no gain control on the Adcom GFA-535? I've used it in between my computer (iMac) and my speakers, and controlling the gain from the computer works, but there's always a noticeable hiss. Wouldn't it be better to have the output of my computer much higher and attenuate the output of the Adcom? No. Sounds like the computer output has a much higher output level that the Adcom's max input level. Set you computer output level on max and get a passive volume control, adjusting the level down for max Adcom output. That will be the best background hiss level you can achieve using the computer's line output. Or get a better computer, or better audio D-A interface. Similarly, I've seen many reviews of powered speakers where the reviewers complain that there's a noticeable hiss that can't be attenuated. Why are they designed like that? That sounds like artifacts from a crappy implementation of a Class-D poweramp section. Or poor power supply, or both. If a powered speaker has a hiss that can be heard more than 30cm ( a foot ) away, it is a heap of junk. I have some cheap-and-nasty 30W powered speakers beside by computer monitor and can't hear hiss unless I put my ear within a few inches. geoff |
#3
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
geoff wrote:
On 5/06/2018 4:02 PM, Matt Faunce wrote: Why is there no gain control on the Adcom GFA-535? I've used it in between my computer (iMac) and my speakers, and controlling the gain from the computer works, but there's always a noticeable hiss. Wouldn't it be better to have the output of my computer much higher and attenuate the output of the Adcom? No. Sounds like the computer output has a much higher output level that the Adcom's max input level. Set you computer output level on max and get a passive volume control, adjusting the level down for max Adcom output. That will be the best background hiss level you can achieve using the computer's line output. Or get a better computer, or better audio D-A interface. Similarly, I've seen many reviews of powered speakers where the reviewers complain that there's a noticeable hiss that can't be attenuated. Why are they designed like that? That sounds like artifacts from a crappy implementation of a Class-D poweramp section. Or poor power supply, or both. If a powered speaker has a hiss that can be heard more than 30cm ( a foot ) away, it is a heap of junk. I have some cheap-and-nasty 30W powered speakers beside by computer monitor and can't hear hiss unless I put my ear within a few inches. geoff If I remember correctly, the Adcom caused hissing even when nothing was plugged into its input. Tomorrow I'll hook it up again and check that. -- Matt |
#4
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
On 5/06/2018 8:00 PM, Matt Faunce wrote:
geoff wrote: If I remember correctly, the Adcom caused hissing even when nothing was plugged into its input. Tomorrow I'll hook it up again and check that. Could be faulty then ... geoff |
#5
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
geoff wrote:
On 5/06/2018 8:00 PM, Matt Faunce wrote: geoff wrote: If I remember correctly, the Adcom caused hissing even when nothing was plugged into its input. Tomorrow I'll hook it up again and check that. Could be faulty then ... geoff OK. I was wrong about the hiss (or rather a sh sound) being there without an input source. Without a source it is dead quiet. The source of the hiss was my computer, and, I did have to have my ear within 12" of the tweeter to notice it. I hooked my microphones-micpre-reverb unit-recorder-Adcom-speakers, and it was much much quieter. (That chain in my setup was as long as it was only for convenience.) My apologies to everyone for the misinformation--especially to Adcom. -- Matt |
#6
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
Matt Faunce wrote:
OK. I was wrong about the hiss (or rather a sh sound) being there without an input source. Without a source it is dead quiet. The source of the hiss was my computer, and, I did have to have my ear within 12" of the tweeter to notice it. I hooked my microphones-micpre-reverb unit-recorder-Adcom-speakers, and it was much much quieter. Of course. And the level control on the amplifier, if it did have one, would be on the _input_ side before the power amp stage. This would allow you to run your sound card hotter and not notice so much how noisy it is. As I said earlier, a passive attenuator box like that $65 Behringer thing will do the exact same thing, if you're stuck having to do that. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#7
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
On Tue, 5 Jun 2018 08:00:04 -0000 (UTC), Matt Faunce
wrote: geoff wrote: On 5/06/2018 4:02 PM, Matt Faunce wrote: Why is there no gain control on the Adcom GFA-535? I've used it in between my computer (iMac) and my speakers, and controlling the gain from the computer works, but there's always a noticeable hiss. Wouldn't it be better to have the output of my computer much higher and attenuate the output of the Adcom? No. Sounds like the computer output has a much higher output level that the Adcom's max input level. Set you computer output level on max and get a passive volume control, adjusting the level down for max Adcom output. That will be the best background hiss level you can achieve using the computer's line output. Or get a better computer, or better audio D-A interface. Similarly, I've seen many reviews of powered speakers where the reviewers complain that there's a noticeable hiss that can't be attenuated. Why are they designed like that? That sounds like artifacts from a crappy implementation of a Class-D poweramp section. Or poor power supply, or both. If a powered speaker has a hiss that can be heard more than 30cm ( a foot ) away, it is a heap of junk. I have some cheap-and-nasty 30W powered speakers beside by computer monitor and can't hear hiss unless I put my ear within a few inches. geoff If I remember correctly, the Adcom caused hissing even when nothing was plugged into its input. Tomorrow I'll hook it up again and check that. Unless you are running Klipsch Horns, the GFA-535 should be pretty quiet with no input. They were so reliable, we used them in professional installations where their failure rate was almost nil. |
#8
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
On 05/06/2018 05:02, Matt Faunce wrote:
Why is there no gain control on the Adcom GFA-535? The short answer is that it saved the makers a few cents, and cut down the number of support calls about not enough volume when the Luser forgot to turn it up. -- Tciao for Now! John. |
#9
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
On 5/06/2018 10:04 PM, John Williamson wrote:
On 05/06/2018 05:02, Matt Faunce wrote: Why is there no gain control on the Adcom GFA-535? The short answer is that it saved the makers a few cents, and cut down the number of support calls about not enough volume when the Luser forgot to turn it up. Or Adcom were on a puritanical 'power amp' kick. That being said, I have at least fout power amps with no level control. Make that 5 . Quad 405, home-built mega-Quad 405, Hafler DH-220, NAD 2200, old Perraux something-or-other, home-built early 75W mosfet (Maplin kit ?). OK that's six. Probably a few more too. Never a problem with noise or gain-staging with any of them. geoff |
#10
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
geoff wrote:
Quad 405, home-built mega-Quad 405, ** A Kiwi service tech working in Sydney ( Brain someone ) told me how popular it was to build your own Quad 405 if you lived in NZ. Good copies of the original PCBs were available and clones of metalwork & other parts too. This was in the early/mid 80s when buying a genuine example was impossible or crazy expensive. Like to know some details of you "mega-Quad 405". .... Phil |
#11
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
On 6/06/2018 2:46 PM, Phil Allison wrote:
geoff wrote: Quad 405, home-built mega-Quad 405, ** A Kiwi service tech working in Sydney ( Brain someone ) told me how popular it was to build your own Quad 405 if you lived in NZ. Good copies of the original PCBs were available and clones of metalwork & other parts too. This was in the early/mid 80s when buying a genuine example was impossible or crazy expensive. Started (not by me) at NZ Railways where I was a comms tech . The main enthusiast even went to the extent of getting heatsinks cast ! Later on NZ Broadcasting techs also did something similar (not the heatsinks though). Like to know some details of you "mega-Quad 405". Twin c-core transformers, larger reservoir caps, MJ15003 outputs, TIP42(?)C drivers and 55VDC rails. Better electro's and poplyprop caps throughout where appropriate. geoff |
#12
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
geoff wrote:
Phil Allison wrote: Quad 405, home-built mega-Quad 405, ** A Kiwi service tech working in Sydney ( Brain someone ) told me how popular it was to build your own Quad 405 if you lived in NZ. Good copies of the original PCBs were available and clones of metalwork & other parts too. This was in the early/mid 80s when buying a genuine example was impossible or crazy expensive. Started (not by me) at NZ Railways where I was a comms tech . The main enthusiast even went to the extent of getting heatsinks cast ! ** That is very much like what Brian was telling me. Like to know some details of you "mega-Quad 405". Twin c-core transformers, larger reservoir caps, MJ15003 outputs, TIP42(?)C drivers and 55VDC rails. Better electro's and poplyprop caps throughout where appropriate. ** So about 150W @ 8 ohms per channel ? The Quad 405 must be the most cloned, modified and re-engineered home hi-fi amp ever. I recapped one for a friend a few years ago, new main and PCB electros, ( all the Roederstein ones had gone high ESR ) plus a few other bits that looked ratty. Fitted gold RCA inputs and binding posts for outputs. ..... Phil |
#13
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
Matt Faunce wrote:
Why is there no gain control on the Adcom GFA-535? Because you didn't order it with that option. If you want the level control, you want the GFA-535L. I've used it in between my computer (iMac) and my speakers, and controlling the gain from the computer works, but there's always a noticeable hiss. Wouldn't it be better to have the output of my computer much higher and attenuate the output of the Adcom? Yes, if you are stuck with a noisy interface, you may need to do that. You might just be able to put a fixed attenuator in front, though, rather than bother with a full gain control. Similarly, I've seen many reviews of powered speakers where the reviewers complain that there's a noticeable hiss that can't be attenuated. Why are they designed like that? Because the designers are expecting them to be used with sources where this isn't a problem. Consider investing in the Behringer Monitor1 passive attenuator or something similar if you're stuck having to structure gain this way. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#14
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
Scott Dorsey wrote:
Matt Faunce wrote: Why is there no gain control on the Adcom GFA-535? Because you didn't order it with that option. If you want the level control, you want the GFA-535L. I have the GFA-535L. For me the level control wasn't convenient enough to be worth it. The left and right channels are controlled separately. Trying to match them every time you change the volume is a hassle. So is using a dime or a screwdriver to turn them. A lot of people make their own volume controls, but I don't have any experience with that kind of thing, so I ended up getting one of these passive attenuators: https://www.tisburyaudio.co.uk/mini-...e-preamplifier Lately I came across this volume control from Nelson Pass that is buffered but has no gain. Sounds like a good idea, but I haven't had the opportunity to try one: http://www.firs****t.com/b1.html https://www.passdiy.com/project/prea...-buffer-preamp |
#15
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
On 8/17/2018 1:29 PM, Tatonik wrote:
I have the GFA-535L. For me the level control wasn't convenient enough to be worth it. The left and right channels are controlled separately. A lot of people make their own volume controls, but I don't have any experience with that kind of thing, so I ended up getting one of these passive attenuators: https://www.tisburyaudio.co.uk/mini-...e-preamplifier That's pretty classy for a "pot-in-a-box" but the fact that they use precision resistors for the gain steps means that they might have taken care that each step of both channels has equal attenuation. Even a good quality dual pot can have a variable difference of as much as 1 dB of attenuation between channels over its range. Lately I came across this volume control from Nelson Pass that is buffered but has no gain. Sounds like a good idea, but I haven't had the opportunity to try one Those Nelson Pass designs have separate level controls for the left and right channels, something that you decided against when you bought the amplifier without them. You really don't need the buffer unless you're feeding it from a tube preamp with a high impedance output. : -- For a good time, call http://mikeriversaudio.wordpress.com |
#16
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
In an ideal world, all final stages should have
volume con-AHEM! - attenuators. Beause you never know what people are going to be combining and running up-line from that amp. |
#17
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
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#18
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
geoff wrote: "
On the other hand some people know what they are doing, how, and why. geoff " I also know how to gain stage, keeping stuff both out of multiple cellars and from multiple distortion points, but I view the final attenuator as an added safety point. |
#19
Posted to rec.audio.pro
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Why No Gain Control on Adcom Amp?
Theckhhhmah gibbered ...
My question concerns where to set the volume coming out of the boombox before setting input gain on the board. Quarter-way? Half- way up? And then he made the ridiculous claim ... I also know how to gain stage QED, DF. |
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