| GregGC |
Hope I'll get it finished for Christmas.
I was going to call it "Art Sound" but now that it looks like a Christmas tree decoration I'm not sure. |
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| GregGC |
| Unfinished back view. |
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| uvodee |
again gives me ideas to finish it in a non conformistic way
I want it to be small but extremey cool looking
this design is really impressive
J-P |
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| Ropie |
| Well, I'm glad you didn't use that terrible name :D, but it looks great. How does it sound? |
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| GregGC |
| Not ready yet. In a few days. |
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| Ropie |
| Wow - I see you use your TVs as huge day-of-the-week counters in Canada. |
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| Peter Daniel |
| Attention to detail is impeccable. Even the + post is longer than - , so when you connect cables in a dark, you can't make mistake. Very thoughtful. |
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| GregGC |
| quote: | Originally posted by Peter Daniel
Attention to detail is impeccable. Even the + post is longer than - , so when you connect cables in a dark, you can't make mistake. Very thoughtful. |
Praise from you Peter is flattering. :angel:
I don't think I'm worthy. |
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| GregGC |
| quote: | Originally posted by Ropie
Wow - I see you use your TVs as huge day-of-the-week counters in Canada. |
Yes, I might as well use the TV for something usefull.:cool: |
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| ronc |
Geee , now i feel bad.All my amps are spray painted heat resistant flat black, have a powered logo stamped on then are baked in the oven.Looks kinda plain , but functional.
ron |
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| GregGC |
| quote: | Originally posted by ron clarke
Geee , now i feel bad.All my amps are spray painted heat resistant flat black, have a powered logo stamped on then are baked in the oven.Looks kinda plain , but functional.
ron |
Sounds very interesting. Naim like? Pictures? Hints? |
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| ronc |
Yea Gregg i will post some pics. I went with a durable finish, after its baked on it gets very hard and the powdered logo is a bias relief of a lions head which bakes on also.
Simple and durable.
Just got the camera back from the repair shop and will post soon.
ron |
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| JCoffey |
| Nice setup! What speakers are those? I like! |
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| GregGC |
| quote: | Originally posted by JCoffey
Nice setup! What speakers are those? I like! |
Thanks.
The speakers are Yamaha NS-200.
http://www.yamaha.ca/av/speakers/PDMSeries/NS200.asp
Highly praised by What HIFI?. I ordered them based on their review and I don't regret at all. I'm really happy with them.
The weather strip you see there improved the focus of the image tremendously. Actually only one 3 inch strip was enough on the inside of the HF speaker (it made dramatic difference). But that's off topic in this forum. |
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| moe29 |
Greg,
Are those Hammond boxes you are using? If so what part #'s??
Do you find that the box alone is good enough as a heatsink? I'm
assuming that you're mounting the chip to the case.
pictures of the guts please!!!
very nicely done - it's nice to see some color in the projects.
great job :nod: |
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| GregGC |
| quote: | Originally posted by moe29
Greg,
Are those Hammond boxes you are using? If so what part #'s??
Do you find that the box alone is good enough as a heatsink? I'm
assuming that you're mounting the chip to the case.
pictures of the guts please!!!
very nicely done - it's nice to see some color in the projects.
great job :nod: |
Thanks.
The boxes are Hammond 1590C. The guts will go in tommorrow, so I'll give you a better answer in a day or two about the heatsink part. |
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| GregGC |
| The guts of the left ch. |
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| 2Bak |
Beautiful wiring IMHO.
Which resistors and caps do you use?
How does it sound?
/Jan |
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| Ropie |
| Very smart :captain: What are those decoupling caps? |
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| GregGC |
Thanks.
I spent a lot of time to think what the best way for the layout would be in my case, so that I get exact symetry when building the left and the right ch. and the shortest path.
I decided not to use any exotic parts. The power supply caps are Long life High temp. Low ESR United Chemi-Con(equivalent to Pana. FC type if not better). The decoupling cap is Siemens MKT type (4.7uF). The resistors, metal film 1% (I matched them to 0.1%).
The PS is not ready yet. Hoping for tomorrow.
Greg |
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| Pedja |
Hi Greg,
Really nice, I like it.
My experience with Siemens MKT says that they can sound harsh and thin though, you might try some other coupling caps. Btw, what series are exactly those Chemi-cons?
Pedja |
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| GregGC |
Pedja,
Thanks for the tip. I have also some non-polar electrolytics (10.0uF), but I thought of trying the MKT first. Do you think the non-polar electrolitics would be better in general?
The big caps are LXY type. Compared them to the FC's and they have the same parameters but a bit longer life. |
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| sandro600 |
Excellent job..........once youve fired up
could you report on noise levels ?
Is the shielded coax cable to stop noise ?
Ive made 4 iterations of gainclone 2 inverted
and 2 NI. All produce buzzes and the last
i could faintly hear a commercial radio station.
I didnt have a 220pf cap to put on the rca plugs
as suggested in a previous post to silence this hash.
It wont stop me from experimenting till I get something
that sounds as decent as others have reported. |
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| Pedja |
| quote: | Originally posted by GregGC
I have also some non-polar electrolytics (10.0uF), but I thought of trying the MKT first. Do you think the non-polar electrolitics would be better in general? |
Hi Greg,
Generally not unless they are Black Gate NX. I use them for some time now and my findings are positive. But in my opinion it is not any hard to find better caps than those Siemens, I guess any MKP will perform better (there are many low priced good MKPs nowadays). Anyway, I think you can easily swap the caps in your amp and check what is it you like.
Pedja |
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| GregGC |
Pedja, thanks. I'll try the MKP's.
Sandro, thanks. The coaxial is to decrease outpu/input coupling within the box because the lenght of the wires happpened to be kind of long. As far as RF, the housing is connected (should be) to Star-GND, so the whole assembly is shielded, and as you mentioned, I have the RC in filters at the RCA's.
I should get it done today and will report back. |
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| GregGC |
Reporting on the completed NIGC.
Everything is just fine. No oscillations, it doesn't even worm-up at the levels I listen to it. The speakers are 90dB/w/m.
It sounds like one eager to run boy. Fast and detailed, not harsh (to me at least). Base is plenty. Again it will depend on the listening level, but at any reasonable (higher than I could ever listen to) level sounded fine in the base section.
So far I've listen to the type of music like Diana Krall, James Taylor, Sting, Classical. Everything as I said sounds very vibrant. I'll check it on Destiny’s child and see how it goes with more complex music.
Output offset is 2.5 mV on one and -12mV on the other one. I guess I didn't pick well matching IC's but it's not a big deal at all. The noise level is very low. You ear has to be at the speaker to hear tiny hisss.
So far very pleased with the results.
More updates later.
Greg |
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| moe29 |
I'll check it on Destiny’s child and see how it goes with more complex music.
...Greg, for some reason i think you'd be better off listening to
some Bob Marley on this setup :nod:
jammin' music for a jammin' amp ;) ...congrats again. |
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| SimontY |
Brilliant! Congratulations, I'm feeling inspired!!
-Simon |
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| GregGC |
Thanks guys!
Yes, Destiny's child is quite fine. Enough base as I reported before. A lot of mid and high detail. Crispy clean. I'm sure if you feed it with a bad signal though it'll expose it badly.
Greg |
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| rick57 |
If you have Peter Daniel’s box making/ craftwork skills, ignore:
I have zero metalwork experience, but am soon to build two ‘gainclones’ (one 3886, one TDA 7293).
With Christmas here, the number of tins for lollies, chocaltes, coffee, biscuits etc is about 5+ times normal. Here in Oz, I found a great range at K-Mart. I got a large one for the PS, and a small one for the amp.
Only 15 shopping days to go . .
Anyone else done this? Strike any problems??
Cheers |
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| GregGC |
The boxes for the power supply are very thin. The transformers are quite heavy. That’s the only think to consider when buying the boxes. Second is the fact that you’ll have to attach the IC to something a bit stiffer than just a tin box to have a good thermal contact and low thermal resistance. And the last the cables are quite heavy so you’ll need some wall stiffness where the connectors are installed.
That's all I can think of right now. |
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| matjans |
hi greg,
what kind of speaker cable are you using? on the pic it seems like normal multiple-thin-copper-strands. May i humbly suggest trying a( thin) tnt-audiocat5 cable ?
You'll be surprised with the results. |
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| GregGC |
Hi Mat,
It is the normal speacker cable. I was thinking of trying a single pare of a network cable. I have to see what the cable you sugest looks like.
Thanks for the suggestion. |
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| sandro600 |
excellent news regarding the very low level of noise of any kind.
Is the schematic the one you posted under the "Ultimate Gainclone" post two or three weeks ago ? Actually under that post there were about three schematics > Did you choose one of them ? |
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| GregGC |
| quote: | Originally posted by sandro600
excellent news regarding the very low level of noise of any kind.
Is the schematic the one you posted under the "Ultimate Gainclone" post two or three weeks ago ? Actually under that post there were about three schematics > Did you choose one of them ? |
This is the sch. of it. Haven't made any changes so far. Have been listening to it and don't feel like taking it a part yet. Mind you I don't see why I would've. The clarity is amazing. |
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| sandro600 |
| very good .......thanks greg |
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| sandro600 |
Greg is the gainclone still performing to your expectations ?
Reason for asking is , my colleague and I have just completed a bass reflex box for a pair of Fostex 206 E
Powered by our existing amp the highs were too prominent, there was a lack of bass. Not nice.
We then added a notch filter as suggested by
http://home.hetnet.nl/~geenius/Solo206.html
Major and pleasing improvement But we know speakers and amps have to be matched.
So the next step is a gainclone, but it doesnt have to be a super minimalist design so we were thinking of using your schematic.
Cheers |
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| GregGC |
| quote: | Originally posted by sandro600
Greg is the gainclone still performing to your expectations ?
Reason for asking is , my colleague and I have just completed a bass reflex box for a pair of Fostex 206 E
Powered by our existing amp the highs were too prominent, there was a lack of bass. Not nice.
We then added a notch filter as suggested by
http://home.hetnet.nl/~geenius/Solo206.html
Major and pleasing improvement But we know speakers and amps have to be matched.
So the next step is a gainclone, but it doesnt have to be a super minimalist design so we were thinking of using your schematic.
Cheers |
Sandro,
No complains so far. Nothing has changed in the way it sounds. I like it. It has very clear highs, and mids and the base is just fine. I’ve been listening to it since and not planing to even tweak it.
You can use the sch. I have there, so far no problems at all.
Tell us how it sounds.
Nice speackers!
Have fun! |
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| ronc |
As a horn designer and builder , IMHO the 206e is really built for rear horn loading.The Qts is really too low to be effecive in a BR.
ron |
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| Optical |
I have recently completed GregGC's design too, my first impressions were that it lacked bass, but i changed the input cap to a 6.8uF 100V one and it improved the bass responce to a satisfactory level and level everything out, i think the circuit sounds ok but might might need tweaking to individual taste?
Im using Cerwin vega E312's so they tell me loud and clear if theres bass or not..
I honestly have to say that i think the inverted GC i built once to test sounded a little bit breighter than this one, but i havent done an A/B comparison..
Also there is -13mV dc offset on both outputs :) |
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| uvodee |
A few weeks ago I followed te schematics of the 'ultimate gainclonce'. It turned out to be a hit and no no 'nasty side effects'.
I could not measure any dc anywhere and the thingies (insulated on an apexjr. heatsink, that was it) played for weeks.
So when my brother in law came by yesterday he took them home after leaving behind some hard earned dollaaaars.
I made one last night, I started well after midnight till about 3 pm.
Same config, same hardware (I have stock for 5 stereo's) same toroid etc...
and every. let's say 45 seconds to one minute i get a non defined noise accompaning the music. Something i would describe as oscillating and sometomes a very present HUMM.
What did I do wrong??? I thought I did exactly the same thing. I use the simple schematic-ultimate gainclone with very few components (2 caps 1000uf, 2 resistors 680 & 22k and one pot 22k)
when there is no disturbing noise, the sound itself is fantastic, even when connected to a portable cd player. hi, mid and bass are, I think, very much perfectly combined...
Jean-Pierre |
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| GregGC |
| I would think that that might be external HF noise. Put your DSS cordless phone or the cell phone when it rings next to the amp and listen. I would put an input RC LF filter to cut all the HF nastiness that comes from the input. If your IC is well shielded and the caps are of a low ESR type and close to the IC you should be fine. Didi you change the speaker cable? Is your grounding done the same way as before? Check the wiring again. |
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| uvodee |
again..
the same caps (digikey's) panasonics
i will check it in a few minutes
the LM3875 are all TF's so all insulated and mounted on the 8 by 5 by 1/2 heatsinks they are not even close to getting warm!
Let me see and tryg to find out what it is!
thanks!
Jean-Pierre |
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| uvodee |
i checked everything and remembered that the caps WERE indeed different!
I though I had used panasonics but they were nichicon 1000 uf 50 volts
now I used nichicon again and the problem seems to be less .there
but still after a while I get distortion when the sound gets dynamic....
and once in a while i get some oscillation
must have something to do with the shielding you think?
OK, I keep looking!
Jean-Pierre |
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| GregGC |
Jean-Pierre,
Check the PS also. Measure all the voltages of the PS. Is the shielding as good as the previous one?
Greg |
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| uvodee |
too nervous!
I am going to look at every thing, every connection and the shielding of the ps tonight!
I tried the panasonics as well as the nichicon's and when there is no distortion or any other noise, I like the nichicons more.
Jean-Pierre |
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| GregGC |
Jean-Pierre,
Did you try adding a low-pass RC filter at the input. Just to see if that is/isn’t HF coming from the input/source? |
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| uvodee |
I tinker a lot (made my own video projector and other stuff) I am rather inexperienced in electronics so I have no basic knowledge how to make a filter like that, however I think that that could solve the problem, but.....
could exterior factors start interfering after a minute or so.... would they not start messing things up right away?
Jean-Pierre |
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| GregGC |
http://www.diyaudio.com/forums/show...9023#post279023
Take a look at R1/C1. That is LF Filter. Use 10k/100pF. Connect them directly ont the RCA connector of the amp.
My concern is that that interference signal was not present before, or if it was, the housing of the amp you had before was doing better job shielding the amp. So if you have different type of housing now, that very well can be the problem.
Try adding R1/C1 to your amp and see if you get some improvement. Another thing to try would be to bypass the 1000uF caps with 47nF. On each 1000uF connect 47nFcap in parallel.
Let see if you get any improvement. |
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| uvodee |
very last option the bypassing
still the same,
the time of clean music seems to reach about 3 to 5 minutes then it starts to slightly crack and then the louder humm comes forward and pushes all the other sound to the back...... |
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| uvodee |
turn the power off and on the sound is back to perfect for 3 to 5 minutes.....
it truly drives me crazy
J-P |
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| GregGC |
| quote: | Originally posted by uvodee
turn the power off and on the sound is back to perfect for 3 to 5 minutes.....
it truly drives me crazy
J-P |
Sounds like a capacitor that's bad or backwards. Check if any of them gets warm. Is the problem evident in both chanels at the same time? Do you have input cap?
Does it hapen if there is no input signal. Turn it on donCan you show me the exact sch. of the amp?'t play any music and see an see if the noiseigoing to appear.
Did you mesure the powersupply voltages when no input signal is present (when you first tun the amp on and after it starts making all the noise?
It could be a bad solder joint too.
Measure the voltages please. |
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| uvodee |
Sounds like a capacitor that's bad or backwards. Check if any of them gets warm.
Checked them = nothing gets warm, even the LM feels cold!
Is the problem evident in both chanels at the same time?
I started with only one channel this time, so I h cannot answer that one
Do you have input cap?
I used " the ultimate gainclone schematic, second time.
Does it happen if there is no input signal. yes and no, as long as there is no signal everything stays quiet but when the music arrives then after 3 to 5 minutes i get the crackling followed by hummmmmm...
Turn it on donCan you show me the exact sch. of the amp?
sure, here it is...
't play any music and see an see if the noiseigoing to appear.
Did you mesure the powersupply voltages when no input signal is present (when you first tun the amp on and after it starts making all the noise?
toroid power ingoing is 41 volts , after the bridge it is 60.5 volts
It could be a bad solder joint too.
I checked them so many times i had to replace the LM because I broke off some tips.....
\
Measure the voltages please.
I will do so and I will also measure the dc offset. now that I found out how to do it ( with a 10 ohm R)
Gee, I must have been very very lucky with the first amp 2 channels, I built it, connected it and it played right away. This time it seems like climbing the Kilimanjaro!
Jean-Pierre |
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| uvodee |
Sounds like a capacitor that's bad or backwards. Check if any of them gets warm.
Checked them = nothing gets warm, even the LM feels cold!
Is the problem evident in both chanels at the same time?
I started with only one channel this time, so I h cannot answer that one
Do you have input cap?
I used " the ultimate gainclone schematic, second time.
Does it happen if there is no input signal. yes and no, as long as there is no signal everything stays quiet but when the music arrives then after 3 to 5 minutes i get the crackling followed by hummmmmm...
Turn it on donCan you show me the exact sch. of the amp?
sure, here it is...
't play any music and see an see if the noiseigoing to appear.
Did you mesure the powersupply voltages when no input signal is present (when you first tun the amp on and after it starts making all the noise?
toroid power ingoing is 41 volts , after the bridge it is 60.5 volts
It could be a bad solder joint too.
I checked them so many times i had to replace the LM because I broke off some tips.....
\
Measure the voltages please.
I will do so and I will also measure the dc offset. now that I found out how to do it ( with a 10 ohm R)
Gee, I must have been very very lucky with the first amp 2 channels, I built it, connected it and it played right away. This time it seems like climbing the Kilimanjaro!
Jean-Pierre |
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| uvodee |
sorry, here it is..
the only thing I changed (from the very beginning) is the pot. The value I use is 25 K.
For making the ground stars I use very small copper washers where every wire (cap etc..) is safely soldered onto. I make 2 stars and they are connected to each other.
I have used 3 different sources to test now : 1) portable cd player, 2) Pioneer cd player (25 disc changer) and 3) a very very cheap dvd player
the best sound comes from the cheap dvd player but the result after a few minutes is always the same whatever source it comes from .... crackling followed by Hummmmmmmmm |
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| GregGC |
Thanks for the sch.
Let see what you measure as a DC output and rail voltages as the amp starts making noise.
Does the pot position afect the noise in any way? I'd put a 22k to 47k resistor from +in (pin 7 to gnd) just to make sure that the pot is OK and it provides constant gnd path for +in. |
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| uvodee |
the pot position does not make any difference.
I replaced the pot with a 50 k R ... no difference.
I can do this because all the sources come with a volume pot
I have to start all over again cause I ruined 2 LM's in the last 36 hours due to pin breakage....
J-P. |
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| GregGC |
Today decided to do some experimenting with values and sch. changes.
Found that removing the cap and keeping the gain just above 20 gave the best results (base and HF balance). More base and the highs are more refined.
The 1k resistor keeps the DC offset at the output to a nice low level when the attenuator is at low levels. With the shown res. values (had to decrease them to 3.3k/68k to keep the offset low) the DC offset is in single digits at all levels but the highest volume setting (it's around 25mV at max. volume).
Found that gain at just above 20 gives more refined highs and deeper base than gain of 30.
C6 was never installed on the first place. Didn't needed. So, the less parts the better.
So, I think, for my taste this is a better performing version of the amp. No DC should be present at the input of the amp though. |
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| uvodee |
wow, and I already find the design I was workingon with very very competitive, exluding the humm factor that is.
I am ordering some more parts tomorrow including 6 LM385
some of the R's you used are not in my stack-on cabinet.....
I found another design (from decdun) today.
If the ultimate schematic causes me anymore trouble the following days I think i will try the decdun design. seems pretty simple as well.
Jean-Pierre |
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| GregGC |
| quote: | Originally posted by uvodee
wow, and I already find the design I was workingon with very very competitive, exluding the humm factor that is.
I am ordering some more parts tomorrow including 6 LM385
some of the R's you used are not in my stack-on cabinet.....
I found another design (from decdun) today.
If the ultimate schematic causes me anymore trouble the following days I think i will try the decdun design. seems pretty simple as well.
Jean-Pierre |
Jean-Pierre,
I'm afraid that it's not the type of sch. you use, that causes the noise problem.
Good luck with the new build though.
Greg |
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| uvodee |
going to try "the ultimate schematic"
then I will try your schematic
and if those do not work , I will change to Decdun's...
J-P |
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| GregGC |
| quote: | Originally posted by uvodee
going to try "the ultimate schematic"
then I will try your schematic
and if those do not work , I will change to Decdun's...
J-P |
J-P,
Try this one, please. It's very close to the "Ultimate" but with beter DC offset. The pot can be 50k if you want. R* can be anything between 330 Ohm and 1K (keeps DC offset from changing too much at lowest volume levels). R5 I changed to 1K to get the gain down to 22. As per my observations it sounded beter to me. It's your call at the end. |
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| uvodee |
will try this one...
and I truly hope that crackling and humm will be gone
J-P |
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| uvodee |
i made the schematic you have on top of here
I did not have a 100 k pot
so i used a new 25 k
same thing crackling followed by hum
this time i could almost swear i could hear radio conversations while the hum was present
i added for fun a 2000 uf 35 volts cap paralel to the 1000 uf from the V+ (c1)
result is a little les volume but crakling much less and there is no more hum??????? not sny other interference
i measured the dc offset ( i used a 9 ohm R}
offset was 35 mv without load and between 0 (or -0) and 28 mv fluctuatung, with music
Greg what do you suggest?
J-P |
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| GregGC |
It looks like powersupply (PS) related.
First, add a 100pF cap between +in and -in of the amp (pin 7 and 8) and see if you'll stop hearing the radio. Do that first please.
Second (if the above doesn't help) I looks like the 1000uF cap didn't work very well (maybe a bad cap). What hapenes if you replace that cap with another 1000uF cap? remove the old one and put a new one in place. Also the volume shoudn't depend on that cap at all.
What kind of transformer do you use? Is it possible to be too small for the porpose and not be able give you enough power.
What type of PS caps do you use? One or two transformers per chanel. one or two bridges per chanel.
Important!!!
I reread your previous messages and couldn't find any PS details. You said 60V after the bridge. Can you tell me what voltage do you have between pin1 and GND and between pin4 and GND.
I realy need those voltages.
Thanks! |
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| uvodee |
the more I thought about going another schematic, the more I started doubting my components....
and guess what, the IEC receptacle (with some kind of filter in, did not let ground go through, I have a few (recycled from old pc's and I guess that a)it had a default when it came here or I used too much heat when desoldering the original wiring - for that I use a 100Watt gun....
I used another (recycled) receptacle (after testing the ground and..........................
everything is PURRRRRRFECT now!!
It sounds perfect, no crackling, no humm....
and i use the setup of the original Ultimate Schematic of the Gainclone
exactly like the first duo I made...
Thanks for standing by me!!!!!
J-P |
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| GregGC |
Glad to be of help and to hear everithing is fine now.
I 'd still recomend the sch from my post above (with the red corrections) and if not just add a 470ohm to 1k res. in ser. of +in (the DC offset will be under control at near 0 volume level). Tell me if you don't know what I mean exactly.
Happy listening!
Greg |
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| uvodee |
I orderd some extra parts (like the 100K pot and some R's with other values=1K)
and a whole bunch of values from a guy from ebay as well.
now it's time to go and look for some more expensive caps to switch and see what happens...
what do you think of nichicon computer grade?
Jean-Pierre |
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| uvodee |
I have an offset that lingers between -0 and 0.05 right now and i kept the meter connected for about an hour and it did not get any higher than that
J-P. |
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| GregGC |
| quote: | Originally posted by uvodee
I have an offset that lingers between -0 and 0.05 right now and i kept the meter connected for about an hour and it did not get any higher than that
J-P. |
That's not bad.
Is the 0V offset at min volume setting? |
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| uvodee |
it lingers between 0 and 5 mv
when there is no sound it goes to 0
mind you, it seems to differ when using different LM's
I had one (my first work) that went to about 600 mv...
may have been because of my abilities or inablities i should say ;)
J-P. |
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| GregGC |
| quote: | Originally posted by uvodee
it lingers between 0 and 5 mv
when there is no sound it goes to 0
mind you, it seems to differ when using different LM's
I had one (my first work) that went to about 600 mv...
may have been because of my abilities or inablities i should say ;)
J-P. |
It could be the missing ser. res. that I suggest you use. Some of the IC's are not as balanced as others. That why I suggested it. My amp for example, one channel is between -5mV@0 vol. and +8mV@max vol. The other one 0-15 mV (with the 1k res ser to +in). Also when you measure the DC offset don't connect any source to the input of the amp, so that the output AC signal doesn't affect the DC offset reading. |
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| giambi77 |
| I really love the finish on those; nice and professional-looking! The colors are....festive to say the least ;) |
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| uvodee |
"Also when you measure the DC offset don't connect any source to the input of the amp, so that the output AC signal doesn't affect the DC offset reading."
In that case, Greg, the reading is 000 mv
when the rca jack coming from the cd player is not connected, the reading is O!
J-P |
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| uvodee |
set of LM 3875's and as you could expect, I have a new question!
Beside the Basler transformers I have (quite a few I may say), I also have a toroid that has:
- input 120 vac
- output 88 vct (44vas/0/44vac dual secondary)
- Av= 400
- I = 5.2 A
- weighs about 5 lbs, diameter is 5"
The wiring =
A) 2wires (1 is purple and 1 is transparent) they serve as input wires
B) 1 grey wire and 1 blue wire (when measuring both = 88volts
C) 2 naked copper wires,twisted around each other and protected with a loose black sleeve. When measuring the grey or blue wire with the copper wire(s) I get 44 vac
Can I use this one toroid for 2 LM3875's ??????? And if so, how do I use this toroid?
Jean-Pierre |
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| uvodee |
this is the drawing
Jean-Pierre |
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| GregGC |
| quote: | Originally posted by giambi77
I really love the finish on those; nice and professional-looking! The colors are....festive to say the least ;) |
Thanks.
I got bored from black and silver. |
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| Peter Daniel |
| quote: | Originally posted by uvodee
Can I use this one toroid for 2 LM3875's ??????? And if so, how do I use this toroid?
Jean-Pierre |
If you have one transformer like this, I don't see a way to use it. If you have two, you can connect primaries in series and effectively reduce secondaries by half. |
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| GregGC |
| quote: | Originally posted by Peter Daniel
If you have one transformer like this, I don't see a way to use it. If you have two, you can connect primaries in series and effectively reduce secondaries by half. |
Unfortunately, I think Peter is right. |
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| uvodee |
I keep working with the Baslers then, have enough of them and also some Abbotts...
non toroids though and I was hoping to make something with a see through round enclosure...
J-P |
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| gpapag |
I was in need of a small (20WRMS max) stereo amp with input selector, volume control and headphone outlet that would communicate music for the "computer hours" i.e. 3-4 hours daily. I had a steel enclosure from an abandoned project, so no metal work was needed, a well made 2x14,5V/2A E-I x-former, two LM 1875 and a rainy weekend in front of me. Two bridges with discrete BYV28-100 diodes followed by 100uF, (one PSU common for both channels), inverted topology LM1875, Rin=10K, Rfb=330K, Vin+ tied to grnd., 1000uF//0.1uF per polarity, 1uF across pins 3 & 5, shunt volume control 22k series, 100k carbon Log shunt potentiometer. No “audiophile grade” parts.
. Twisted solid core telephone wires for everything, careful routing and earthing. The result was an amp with stunning speed and clarity, guts, very good sound balance and despite the necessary long internal cabling (40cm signal in, 50cm signal out, 40cm PSU power, 50cm 230VAC ), no hum, buzz or other noise. For the record, here are some measurements (Both channels driven, 50 Ohm 0 Hz-100KHz signal generator, 8 Ohm dummy load, 20 Mhz dual analog Scope, digital multimeter. Ambient temp 18 d C., rel. hum. 60%, heatsinks 45 +/- 5 d C, case vibration +/- 2 nm, 0.00001g vertical, +/- 3pm, 0.000001g horizontal) :
1. PSU
DC: +/- 20Vdc.
Ripple (100Hz) measured at the pins (#3,5)of the LMs:
Both LMs Undriven : 450mVp/p.
Both LMs at Full Output (14 WRMS): 4Vp/p
Note: -DC had approx 10% higher ripple than +DC
PSU DC modulation by audio signal (Both Channels driven to Full Output):
Signal freq. (Hz) Modulation amplitude (Vp/p)
50 8
100 8
500 1.5
1000 0.5
2. LMs Output:
AC:
0V input signal : Output (noise modulated by 100Hz signal) 2mVp/p
2Vp/p input signal: Output 30Vp/p just before (1mV) clipping, i.e. 14W RMS/8Ohm
Freq. Response:
Flat +/- 1 db 5Hz-100KHz.(the limit of my signal generator).
The amp goes much higher actually. One day I observed a high freq. signal at the amp. output, something btn. 50 and 60 MHz. I thought that it started oscillating. After some *&$@# I was lucky enough to find out that what was oscillating was actually the signal source and this high freq. signal was faithfully amplified by the LM1875. So, band limiting the input is not a bad idea.
Input/Output Phase Shift:
8 Hz: 10 d.
70KHz: 15 d.
15Hz-30Khz: 4 d. max.
DC offset (mV RMS):
No input signal applied. Input jack was loaded with various dummy resistances, representing the driving source output resistance. For each such dummy source, three measurements were taken. One with volume control 100% (full travel), one at 50% of the travel, and one at 0%.:
Dummy Source: 0 Ohms
Volume position LH Amp RH Amp
100% travel -50 -60
50% travel -54 -64
0% travel -100 -133
Dummy Source: 1 KOhm
Volume position LH Amp RH Amp
100% travel -54 -58
50% travel -54 -64
0% travel -107 -134
Dummy Source: 10 KOhm
Volume position LH Amp RH Amp
100% travel -40 -45
50% travel -45 -52
0% travel -109 -135
Dummy Source: 100 KOhm
Volume position LH Amp RH Amp
100% travel -29 -35
50% travel -35 -44
0% travel -107 -134
Dummy Source: 1 MOhm
Volume position LH Amp RH Amp
100% travel -26 -31
50% travel -32 -41
0% travel -108 -134
Dummy Source: Open
Volume position LH Amp RH Amp
100% travel -28 -29
50% travel -35 -38
0% travel -107 -133
The maximum DC offset of 134mV equals 2.3mW RMS into 8 Ohms and occurs at 0% volume setting. Normally the volume will be between 25% and 50%, where the DC offset induced output is 0.2-0.4 mW . Not a big deal. The variation of the DC offset due to the input loading though indicates, that in principle, a buffer is needed. If it will have detrimental effects on the sound, is a question.
Regards
George |
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| GregGC |
George,
Thanks for the excellent description. It sounds like a great amp.
If you are in a tweaking mode, can I propose a resistor of 10k from +in to GND. I think you'll get much better DC at 0% travel (if that is 0 volume, 10k res. connected to gnd).
Or 22k-47k between -In and GND and +in 10k-100k to gnd.
Greg |
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| gpapag |
Greg thanks for the comments.
In fact i tried all these you propose, one by one and combined. Variations of +/- 10mV was the result. So i ended with the simplest schematic, the one that i reported. I think that the offset is caused to large extent to the long signal route from input jacks to volume control to LMs. This i can not change as i have to settle to this chassis. As i wrote before, it is not much of a problem. On three past projects (LM1875 non inverted, TDA7294 inverted, LM3886 inverted) all of which had much smaller signal routing, the DC offset was less than about 60mV worst case.
Regards
George |
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| GregGC |
| Happy listening George! |
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| tolka |
I have a pair of Yamaha NS200's and love them muchly, however I need some advice re: the amplifier to do them justice. Please help...
Thanks |
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| GregGC |
| quote: | Originally posted by tolka
I have a pair of Yamaha NS200's and love them muchly, however I need some advice re: the amplifier to do them justice. Please help...
Thanks |
I really like the way they sound with the amp that I build. Much more resolution and freedom of the sound, compare to the Yamaha amp that I have. Highs and mids are great and base is plenty also. I'd say, put together one and see how it sounds to you.
Greg |
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| Raka |
| quote: | Originally posted by Peter Daniel
If you have one transformer like this, I don't see a way to use it. If you have two, you can connect primaries in series and effectively reduce secondaries by half. |
And the flux will reduce too. That is a good thing. |
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| uvodee |
schematic please
and also, i have 4 transformers 110 volts in, 3 wire out 12.5V-0-12.5V , 8 A
how should I go around using them at their best for the GC....
J-P.
(beware you guys I have a lot of transformers here!) |
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| uvodee |
how can I use these transformers for a gainclone?
I have 4 of them.
do I only need 2 of them or all 4 for a left and right channel?
can I use 2 of them and make leads to the left and right amps out of the bridge?
How do I make them suitable for a gc?
Thanks
Jean-Pierre |
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| GregGC |
| quote: | Originally posted by uvodee
how can I use these transformers for a gainclone?
I have 4 of them.
do I only need 2 of them or all 4 for a left and right channel?
can I use 2 of them and make leads to the left and right amps out of the bridge?
How do I make them suitable for a gc?
Thanks
Jean-Pierre |
You need one transformer and one Bridge per rail. So two transformers and two bridges will give you single power supply for the two channels (L and R). So one traf for +V and one for –V. With the voltages you measured you are very close to the max. allowable voltage for LM 3578 (it’s 84v/2=42V per rail absolute max.) You’ll have 27v*1.41=38V and with 10% fluctuation you’ll get to 42V. Too close in my opinion but it should work.
If you don't need more that 30W (my case) you can yuse 1 traf per chanel +/- 13*1.41=18Vdc. I suggest do that first and if you need more pwer than just reconnect the pwer supply. |
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| uvodee |
Gregc, I was thinking more in this direction.
these transformers (abbottt technologies. inc. ) are pretty hefty puppies (mil. grade) and quite the works!
as they are 8 A, so 200 VA, I was thinking of using only one (1) for both channels, it is to say using 2 wires to one bridge and parallel another 2 wires to the others bridge and these bridges would then lead to their L or right channel.
Don't you think the transformer would be powerfull enough for this. I think I could live with around 20 to 25 watts, I mainly ilsten to classical anyway.
Jean-Pierre.
ps I don't need to economise on these transformers, I have 4 anyway and can get many more for $15 each. |
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| GregGC |
| quote: | Originally posted by uvodee
Gregc, I was thinking more in this direction.
these transformers (abbottt technologies. inc. ) are pretty hefty puppies (mil. grade) and quite the works!
as they are 8 A, so 200 VA, I was thinking of using only one (1) for both channels, it is to say using 2 wires to one bridge and parallel another 2 wires to the others bridge and these bridges would then lead to their L or right channel.
Don't you think the transformer would be powerfull enough for this. I think I could live with around 20 to 25 watts, I mainly ilsten to classical anyway.
Jean-Pierre.
ps I don't need to economise on these transformers, I have 4 anyway and can get many more for $15 each. |
Jean-Pierre,
In my setup I use 1 220VA traf per chanel of about 40-50W. Mind you I use no more than 5-10 W when listening to music.
In your case you can use only one transforme for the two chanels (as you mentioned). Use two bridges and create a star GND in the PS section. Run separate set of 3 wires (+,- and GND) to each Amp to minimize interference through the PS wires. I think it'll sound great.
My only concirn was the voltage. 13VAC is fine for 20W/8Ohms. per chanel. If you have 4Ohm speackers the power goes up to 40W. On the other hand the 27VAC would be really too close to the max. voltage. So I'd do what you suggested. |
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| uvodee |
I am going to inspect some damaged property (water flooding) and when I come back this evening, I am going to get this new project going.
That will be my 3rd gc!
Thanks
J-P. |
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| uvodee |
My guess is that with this construction I am not going to set the Puget Sound area without electricity when I connect it to the GC's, am I right?
Jean-Pierre
worried but extra carefull! |
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| GregGC |
| quote: | Originally posted by uvodee
My guess is that with this construction I am not going to set the Puget Sound area without electricity when I connect it to the GC's, am I right?
Jean-Pierre
worried but extra carefull! |
Looks good to me. |
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| fedde |
I'd include a primary fuse!!!
Fedde |
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| carlosfm |
| quote: | Originally posted by fedde
I'd include a primary fuse!!!
Fedde |
And it will blow.:eek:
Two bridges with a CT trafo?:confused:
Jean-Pierre, I'm sure that you can easily mod that trafo for independent secondaries (4 wires).
Just separate the two wires that are joined together in the centre.;) |
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| GregGC |
| quote: | Originally posted by carlosfm
And it will blow.:eek:
Two bridges with a CT trafo?:confused:
Jean-Pierre, I'm sure that you can easily mod that trafo for independent secondaries (4 wires).
Just separate the two wires that are joined together in the centre.;) |
Carlos, excuse the lack of understanding of your statement. Why would the fuse blow and what's wrong with the way it is right now?
Greg |
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