New SDA-2Bs and Adcom GFA 555
TheRealSpinner
Posts: 30
Long story, but here goes...
I've been lurking around for the past week or so because I've been looking for speakers for ths shop (I pull late nights fairly often and wanted some speakers I could really crank and the speakers in there really sucked). While searching Craigslist, I came across a pair of SDA-2B (no interconnect) for $200 and a pair of Technics for $150. At this point, I had no idea what I was looking for, and started to do some research. (This site came up a lot for the SDAs, but I couldn't find any information on the specific Technics). I decided I would audition both pairs. First I listened to the Technics , and really liked the sound of them... then I listened to the SDAs.
Even playing off of a crappy all-in-one AIWA, the SDAs sounded pretty darn good. I jumped on it and talked the guy down to $175.
I took them to the shop and hooked them up to my Onkyo TX-SV727 and started bumping. I was not impressed. I thought, "Where is all the bass I heard earlier, I know my home speakers (JBL CF120s that I have always thought were fantastic since I bought them new in 1997) sound how I like, so maybe I'll bring them to the shop and see which speakers work better."
I brought my JBLs in and set up both pairs using A and B outputs. I couldn't believe how much better my JBLs sounded at the shop, compared to the SDAs. Not quality-wise, but the JBLs put out the quantity and bass I needed at the shop, and thought that I could enjoy quality of the SDAs better at home. I have to say that putting the two sets next to each other, I couldn't understand why I had ever liked the sound coming out of the JBLs.
So, I brought the SDAs home.and hooked them up to my Marantz SR880 receiver. Again, I was disappointed. I was getting very little bass, and I had to turn the receiver up much more than for the JBLs. And, on top of that, the amp was shutting off after 20 or 30 minutes of play. I couldn't figure out what was happening.
I started my research again. It seemed that my Marantz was not happy playing 4 ohm speakers, so I started researching amplifiers. I was between Parasound HCA 1200 and an Adcom GFA 555. I found an HCA 1200mkii locally on Craigslist, but the guy never responded, so j kept looking. Then I found a few GFA 555s on eBay (both the original and second model). I pulled the trigger on a slightly scratched $300 original (with pictures of a clean inside).
So, I'm waiting for the Adcom now, and decided to try a little speaker positioning. (I've read about how important that is with theae speakers.) I tried everything, against the wall, 3" out, 6" out, closer to each other, further apart. I would walk around the room, angle the speakers toward the center, away, it just never sounded good. I sat on the couch again, feeling defeated and ready to just wait for the amp, hoping it would fix it, I noticed that when I leaned to one side, bass would suddenly appear. Then I intentionally tried leaning, yep there it was.
It got me thinking. I remembered that somebody responded to a similar list about missing bass, saying that polarity might be reversed, so I checked... Yep, that was the problem.
So as the night rolled on, ithe wife and I decided to put in a movie. Since the speakers were working correctly, I needed to set up individual levels through.the Marantz menu (it plays white (or pink) noise through individual speakers so you can adjust the kegs to each other). When I did so, I noticed that the left speaker seemed to be noticably quieter and a much less highs. Now I'm worried that I've blown something in the tweeter.
So now, I'm sitting here, listening to my SDAs with a $300 amp on its way to my house. I'm not at all upset about the purchase, in fact, I'm still eager to try it out, but I might have waited a bit longer to buy one if I had known this was the problem, and now I'm wondering if I should have spent the amp money elsewhere, but I know that once its here, I'll never look back. I'm even considering getting another one and running a sub off it. (Can you tell I enjoy bass.)
I know this was a long post, but what the heck, its my first post, and I've gotten so much information from you all, I'd share my reason for finally joining.
I've been lurking around for the past week or so because I've been looking for speakers for ths shop (I pull late nights fairly often and wanted some speakers I could really crank and the speakers in there really sucked). While searching Craigslist, I came across a pair of SDA-2B (no interconnect) for $200 and a pair of Technics for $150. At this point, I had no idea what I was looking for, and started to do some research. (This site came up a lot for the SDAs, but I couldn't find any information on the specific Technics). I decided I would audition both pairs. First I listened to the Technics , and really liked the sound of them... then I listened to the SDAs.
Even playing off of a crappy all-in-one AIWA, the SDAs sounded pretty darn good. I jumped on it and talked the guy down to $175.
I took them to the shop and hooked them up to my Onkyo TX-SV727 and started bumping. I was not impressed. I thought, "Where is all the bass I heard earlier, I know my home speakers (JBL CF120s that I have always thought were fantastic since I bought them new in 1997) sound how I like, so maybe I'll bring them to the shop and see which speakers work better."
I brought my JBLs in and set up both pairs using A and B outputs. I couldn't believe how much better my JBLs sounded at the shop, compared to the SDAs. Not quality-wise, but the JBLs put out the quantity and bass I needed at the shop, and thought that I could enjoy quality of the SDAs better at home. I have to say that putting the two sets next to each other, I couldn't understand why I had ever liked the sound coming out of the JBLs.
So, I brought the SDAs home.and hooked them up to my Marantz SR880 receiver. Again, I was disappointed. I was getting very little bass, and I had to turn the receiver up much more than for the JBLs. And, on top of that, the amp was shutting off after 20 or 30 minutes of play. I couldn't figure out what was happening.
I started my research again. It seemed that my Marantz was not happy playing 4 ohm speakers, so I started researching amplifiers. I was between Parasound HCA 1200 and an Adcom GFA 555. I found an HCA 1200mkii locally on Craigslist, but the guy never responded, so j kept looking. Then I found a few GFA 555s on eBay (both the original and second model). I pulled the trigger on a slightly scratched $300 original (with pictures of a clean inside).
So, I'm waiting for the Adcom now, and decided to try a little speaker positioning. (I've read about how important that is with theae speakers.) I tried everything, against the wall, 3" out, 6" out, closer to each other, further apart. I would walk around the room, angle the speakers toward the center, away, it just never sounded good. I sat on the couch again, feeling defeated and ready to just wait for the amp, hoping it would fix it, I noticed that when I leaned to one side, bass would suddenly appear. Then I intentionally tried leaning, yep there it was.
It got me thinking. I remembered that somebody responded to a similar list about missing bass, saying that polarity might be reversed, so I checked... Yep, that was the problem.
So as the night rolled on, ithe wife and I decided to put in a movie. Since the speakers were working correctly, I needed to set up individual levels through.the Marantz menu (it plays white (or pink) noise through individual speakers so you can adjust the kegs to each other). When I did so, I noticed that the left speaker seemed to be noticably quieter and a much less highs. Now I'm worried that I've blown something in the tweeter.
So now, I'm sitting here, listening to my SDAs with a $300 amp on its way to my house. I'm not at all upset about the purchase, in fact, I'm still eager to try it out, but I might have waited a bit longer to buy one if I had known this was the problem, and now I'm wondering if I should have spent the amp money elsewhere, but I know that once its here, I'll never look back. I'm even considering getting another one and running a sub off it. (Can you tell I enjoy bass.)
I know this was a long post, but what the heck, its my first post, and I've gotten so much information from you all, I'd share my reason for finally joining.
-SPINNER-
SDA-2b
Adcom GFA 555
Marantz SR880
JBL CF120
Onkyo TX-SV727
Other Junk
SDA-2b
Adcom GFA 555
Marantz SR880
JBL CF120
Onkyo TX-SV727
Other Junk
Post edited by TheRealSpinner on
Comments
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Welcome to the SDA world. If you search the forum there is a nice little modification you can perform on the 2Bs that will take them to another level. Search 2BTL. It consists of changing out the old capacitors, resistor, removing the polyswitch, and adding/replacing other components. Well worth it.
Also as soon as the 555 arrives check the DC offset. It needs to be under 35mvdc. Replace the 4 electrolytic capacitors on the input ASAP to avoid any leakage of them on the board. It is cheap insurance.
Holler back on the forum if you have any questions as I am sure some of the others will chime in also.SDA2BTL
Marantz CD5004
Adcom GFA-545
Bottlehead Quickie Tube Preamp -
Congrats and welcome to the forum, and the world of SDA!"Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills/jantzen inductors, Gimpod's boards, Lg Solen SDA inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR BP's, upgraded IC Cable, Black Hole Damping Sheet strips, interior of cabinets sealed with Loctite Power Grab, AI-1 interface with 1000VA A-L transformer
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You need the interconnect between the two speakers, you will need to get your read on about proper SDA set-up, (no toe in) and yes, they are right/left specific. You will need to update the x-overs to gain their full potential.
Also, check any amps. that you may use, as they NEED to be a common ground variety.
Welcome to CP -
Replace the 4 electrolytic capacitors on the input ASAP to avoid any leakage of them on the board. It is cheap insurance..
Not necessary as they aren't prone to leakage.
To the OP, you need the inteconnect cable for the speakers to perform as intended.
H9"Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul! -
Take a look at this diagram:SDA2BTL
Marantz CD5004
Adcom GFA-545
Bottlehead Quickie Tube Preamp -
I apologize to the OP for coming at you with those things you did not inquire about. As soon as I hear Adcom 555 and SDA2B in the same post I get excited.
Heiney9 is correct about the leakage problem not being prominent in the original 555s. It was more of a problem in the 555II and 565 mono blocks. However if you are handy with a solder iron and have the necessary tools I would replace the 4 on the input board. Me, I would replace 25 year old caps such as these but do agree with Heiney9 about the leakage issue and the original 555s.
Again sorry if I got the thread off course and now back to the original programing still in progress.Not necessary as they aren't prone to leakage.
To the OP, you need the inteconnect cable for the speakers to perform as intended.
H9SDA2BTL
Marantz CD5004
Adcom GFA-545
Bottlehead Quickie Tube Preamp -
great combo! i've been running sda2b's (tl'd) with an adcom gfa555, for a few years now..your 1st priority should be the i/c....then watch out!
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When I did so, I noticed that the left speaker seemed to be noticably quieter and a much less highs. Now I'm worried that I've blown something in the tweeter.
It very well might have a bad tweeter, but it also could be that the polyswitch (tweeter protection) has completely gone south. An easy way to test, swap the left and right tweeters. If the problem follows the tweeter, it's bad. If the problem stays in the left speaker, it's the polyswitch on the crossover board.
As others have stated, you NEED the SDA cable to hear what they are capable of. I also agree that the TL upgrade takes these speakers to an entirely different level. Just do it.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Thanks for all the responses. I will say that I did know about these speakers needing a common ground amp (thanks to this board) and checked my amps before I purchased the SDAs. And even though I don't have the Adcom in hand, I have read that several members here use it successfully.
As far as the interconnect, I also read that it works to jam speaker wire into the pin/blade receivers. I noticed that when I did so, it seemed to affect the Marantz's safety shut-off (it came on much sooner). That got me thinking. I checked the resistance of the SDAs and they measure in at about 3.7 ohms, with no inputs. When I connected the i/c, it dropped to 3.4 or lower. Since the Marantz isn't spect'd at anything below 8 ohms, I left it disconnected.
PreCd, I'm grateful for the suggestion on the Adcom in its way, but i don't know how to check the DC Offset, or what it does. Would you mind elaborating?
And about speaker placement, I had read (on this forum) about changing the distance from the wall affected the bass, which is why I tried moving it all around, and that toe-in was a no-no for these speakers, but I thought is try it out anyway. And there is a similar diagram on the back of the SDAs about distances, but I'm glad to see more details to the description, WITH explanation, thanks.
I must say that, for the time being, I don't think I will be replacing any parts on the speakers or amp (unless the DC offset is a problem). I'm just going to enjoy them for a while so that I can get used to what I am listening to, and then go ahead with modifications. That way, I should actually be able to hear the changes I make.
Any other suggestions about what to check on the GFA when it arrives? I do have a VOM, and the necessary tools to do repairs, I just don't know what I am looking FOR or even what I am looking AT once I open it up.
Thanks again for the replies I'm looking forward to receiving the amp, and hope it was a worthwhile investent.-SPINNER-
SDA-2b
Adcom GFA 555
Marantz SR880
JBL CF120
Onkyo TX-SV727
Other Junk -
To check DC offset set your volt meter to DCmV. Leave the speaker leads disconnected. Turn the 555 on and let it idle to warm up. Say 5 minutes or so. Take your voltmeter and check each channel at the output of the 555, measuring across them. This will give you the DC offset for each channel.
You can check offset with the preamp connected but you will get a different reading. Try both and record those readings.
Give me a yell if you want when the amp comes in if you need help.SDA2BTL
Marantz CD5004
Adcom GFA-545
Bottlehead Quickie Tube Preamp -
When you say "accross them", do you mean plus to plus, minus to minus? Or plus to minus?
Just reread your post. You said check each channel, so I guess that means plus to minus.-SPINNER-
SDA-2b
Adcom GFA 555
Marantz SR880
JBL CF120
Onkyo TX-SV727
Other Junk -
To check DC offset set your volt meter to DCmV. Leave the speaker leads disconnected. Turn the 555 on and let it idle to warm up. Say 5 minutes or so. Take your voltmeter and check each channel at the output of the 555, measuring across them. This will give you the DC offset for each channel.
You can check offset with the preamp connected but you will get a different reading. Try both and record those readings.
Give me a yell if you want when the amp comes in if you need help.TheRealSpinner wrote: »When you say "accross them", do you mean plus to plus, minus to minus? Or plus to minus?
Just reread your post. You said check each channel, so I guess that means plus to minus.
You only need to do this if the 555 in question is the first series. If you have a 555II (MKII) it uses a dc servo to prevent dc offset at the output. I know in your OP you stated GFA555 not GFA555II so I'm just throwing it out there for general consumption.
You will measure each channel independantly. The + probe of the DMM to the + of the speaker output and the - probe to the - of the speaker output. Do this for the L and R channels and report back. Be sure the scale on your DMM is set properly.
H9"Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul! -
OK, Adcom arrived, checking DC output.
Since there are no labels on the output, what I believe to be the right channel output gives me .023 Volts (23 MB) DC. Good.
Here's the kicker.
Left output gives me -.057 Volts (-57 mV).
I'm confused here. I've got plus to positive to red, negative to black. I'm assuming the negative sign means I have the leads backward, but I don't think thats the case. I haven't hooked the amp up to speakers yet, does this mean I should NOT?-SPINNER-
SDA-2b
Adcom GFA 555
Marantz SR880
JBL CF120
Onkyo TX-SV727
Other Junk -
Don't worry about the negative. 57 mV while higher than ideal is not surprising for an amp of its age. This should not cause any problems with the sound of the amp and will be fine to use as long as it stays below 100mV.
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the sign for dc offset doesn't mean anything, it's the number that's important.
See this thread, especially the first post
http://www.audiokarma.org/forums/showthread.php?t=5634
The left is a little on the high side at 57mV, but not terrible, IMO."Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul! -
+1..Don't worry about the negative. 57 mV while higher than ideal is not surprising for an amp of its age. This should not cause any problems with the sound of the amp and will be fine to use as long as it stays below 100mV. -
As long as I won't damage anything, I think it's safe to say that I won't notice anything.
Like everything else, I'm sure it is something that will bug me just to know, though. So, is this something I can fix? I checked the link that was posted about DC offset and it looks like it can be fixed, but does anybody know which parts to replace, and how much they cost?
I know I should be searching the site by now, or start a new thread, but... since you are listening and I've spilled my whole setup. :redface:-SPINNER-
SDA-2b
Adcom GFA 555
Marantz SR880
JBL CF120
Onkyo TX-SV727
Other Junk -
If you want to try to lower the offset, I would check out http://www.diyaudio.com/. There are a few threads in the forums about DC offset on this amp. Nelson Pass comments on the forum sometimes.
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get yourself a service manual....i might have a pdf...not sure if it will go thru email...i found mine for free on the net somewhere...the manual lets you know how to make the offset and idle adjustments...it also gives you a schematic
mike -
That amount of offset is not going to be an issue.You will always have some offset but you could lower it by installing a tighter matched pair of transistors on the diff. input stage.However it would'nt be worth the effort and is a project only for an experienced tech IMO.
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get yourself a service manual....i might have a pdf...not sure if it will go thru email...i found mine for free on the net somewhere...the manual lets you know how to make the offset and idle adjustments...it also gives you a schematic
mike
One really shouldn't mess with the internals of electronics unless one is very familiar with doing those things."Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul! -
As FGTV stated replacing the diff trans would lower the offset. I got mine to lower quite a bit by replacing the filter caps also. It went from 35mv to 9mv after they were replaced. I have never seen that mentioned anywhere but it had that effect on mine. The overall consensus is to change out the diff trans. though. And again as FGTV stated it is a for a higher level tech as they must be matched and need to be thermally coupled.
Send me a picture of the back of your 555 and lets see if we can determine which version of 555 you have. Even the MKIs were made in 3 or 4 different configurations. At the least after we determine the config of 555 you have we can walk you through adjusting the bias. That is not too complicated and will benefit the overall sound of the amp.
I think you are safe to run it though.TheRealSpinner wrote: »As long as I won't damage anything, I think it's safe to say that I won't notice anything.
Like everything else, I'm sure it is something that will bug me just to know, though. So, is this something I can fix? I checked the link that was posted about DC offset and it looks like it can be fixed, but does anybody know which parts to replace, and how much they cost?
I know I should be searching the site by now, or start a new thread, but... since you are listening and I've spilled my whole setup. :redface:SDA2BTL
Marantz CD5004
Adcom GFA-545
Bottlehead Quickie Tube Preamp -
One really shouldn't mess with the internals of electronics unless one is very familiar with doing those things.
abso-effin-routley!!! but, if you're set on doing research, due-diligience asking questions, etc...don't pop the top without the manual!
