cowanrg said:
If you've got that 50k resistor connected in series with the ground between your source component and the GainKone as it seems to me you've described it below, then that will result in some buzzing.
If you're going to use that 50k resistor, it needs to be connected between the hot pin on the RCA and ground.
That's typical. From a full charge, you'll get a bit of a drop in the first few minutes and then it'll level out before it starts dropping off again.
With a pair of 8 Ah batteries, you should get quite a lot of listening in before you need to recharge. To prevent deep cycling and reducing battery life, I wouldn't let 'em get much below about 10 volts (or 20 volts if you're measuring across both batteries).
You'd need some sort of soft start circuit to get rid of it.
At the low voltages you're using, it's not going to be a problem other than perhaps an annoyance.
se
nice.
i measured my DC offset, and it was 0.004, i think that is pretty low.
so i have that resistor hooked up wrong then, good. that buzz was BAD. ill swap it around and fix it. i'll also get some caps to put in there as well.
this thing is extremely efficient. i had it cranked, and it barely got the heatsink warm.
i measured my DC offset, and it was 0.004, i think that is pretty low.
so i have that resistor hooked up wrong then, good. that buzz was BAD. ill swap it around and fix it. i'll also get some caps to put in there as well.
this thing is extremely efficient. i had it cranked, and it barely got the heatsink warm.
cowanrg said:
That's pretty low alright. Lower than expected. With the typical 0.2 uA of input bias current for that chip, and a 220k feedback resistor, you'd expect something more like 0.04 volts than 0.004 volts.
Check the offset of your source component. If it's quite low or if it has a capacitor coupled output, then you don't really need that cap there in the first place. As they say, the best capacitor is no capacitor. 🙂
Yeah. Which is why you should be able to get quite a bit of time off those 8 Ah batteries.
se
About the buzz when resistor is in place from input to ground: I noticed that the amps is susceptible to oscillations at max volume when not shielded.
Another X-former possability
Cowanrg,
I was thinking about using the PE 129-030 transformer. It seemed that Peter was more satisfied with the bass using lower voltage. This is a 20-0-20 5A model and its less than $10. I figured if the alltronics model would work, so would that one.
Good luck finishing it up.
S.
Cowanrg,
I was thinking about using the PE 129-030 transformer. It seemed that Peter was more satisfied with the bass using lower voltage. This is a 20-0-20 5A model and its less than $10. I figured if the alltronics model would work, so would that one.
Good luck finishing it up.
S.
A great transformer for this app is sold by Steve at ApexJr. I've bought a few of these toroidals and have no complaints. They are 18-0-18 120VA and $15.00 a piece. I use one/chan and they have no problem driving most speakers. http://www.apexjr.com/miscellaneous.html#Toroids
Peter Daniel said:
If his description of how he had that resistor wired in was the way I read it, he didn't actually have it going to ground from the input, but rather in series with with the amplifier ground and the source ground.
You know how you can get that horrible buzz when you just have the hot pin of the RCA hooked up and the ground's aren't connected? Same thing here only not quite as bad as if you had a truly open circuit.
se
When I put mine together, I got some buzzing until I got the grounding correct. I still probably don't have it right, but I used the information from this site to tie the grounds properly, and it sounded quiet from that point on.
http://www.geocities.com/rjm003.geo/rjmaudio/diy_gc.html
http://www.geocities.com/rjm003.geo/rjmaudio/diy_gc.html
will a 120VA transformer be enough for a mono channel? i guess for $15 for a toroidal just to test it out, its worth it...
im in the process of moving...
in april, i will be living in a 3 bedroom, 2600 sqare foot house, (not uncluding finished basement), with just one other guy. it will be great.
in april, i will be living in a 3 bedroom, 2600 sqare foot house, (not uncluding finished basement), with just one other guy. it will be great.
When Dave(planet10) first showed them to me I was doubtful as well, but after using them for awhile in a prototype, I became convinced they work well. I have tested them against several different types of speakers, abeit nothing difficult, and the amp performed very well. They actually end up putting out 28VDC after rectification with the amp playing at a moderate level. I would say they are closer to 22VAC with the light load the chips put on them. When hooked to my father's AMTs and Klipsches they can really crank(of course, the Klipsches are very sensitive), but the amps never got very warm.
I am using 120 VA per channel and I expect it to work just fine. The original amp, AFAIK, uses 170 VA for stereo amp and twice that when adding another "Power Humpty". You will be somewhere in the middle.
It is fine, although as I remeber Stereophile review they noted that 170VA supply was a limiting factor to the amp. But I think it all depends how much you want to push it.😉
ok, so between the 24-0-24 5A from all electronics, and the one from apex, the apex one would probably be better?
this is just my first attempt at this, its the budget revision 🙂
i got everything surplus, and spend $20 for 2 amps. Panasonic 50V caps, allen bradley 1% resistors.
this is just my first attempt at this, its the budget revision 🙂
i got everything surplus, and spend $20 for 2 amps. Panasonic 50V caps, allen bradley 1% resistors.
Well, I just talked to Steve as I wanted to order some more of the transformers and he is out of them. Bummer 
hum, yeah... ill probably not push this, being as its just a prototype.
ill go with both, and just test them out. i already put the order through with all electronics. and i need a few things from apex anyway.
you know, i can honestly say, these old aiwa speakers arent that bad. granted, they are probably being thrown more power than ever expected, but when REALLY driven, they start to sound reasonable! its incredible. nowhere near my other speakers, but i'm not about to reach back there and unhook them to try them out. too many damn wires.
i think if it was original with a single 170VA for 2 channels, i should be good with 120VA on each channel. thats almost what the power humpty is.
am i correct that the VA rating of the all electronics one is around 240VA?
ill go with both, and just test them out. i already put the order through with all electronics. and i need a few things from apex anyway.
you know, i can honestly say, these old aiwa speakers arent that bad. granted, they are probably being thrown more power than ever expected, but when REALLY driven, they start to sound reasonable! its incredible. nowhere near my other speakers, but i'm not about to reach back there and unhook them to try them out. too many damn wires.
i think if it was original with a single 170VA for 2 channels, i should be good with 120VA on each channel. thats almost what the power humpty is.
am i correct that the VA rating of the all electronics one is around 240VA?
looks like it makes that decision easy!
eh, i already ordered the others, so ill just use them for now.
any idea why im getting a little bit of popping and clicking every so often? its most noticable when the speaker is louder. its not BAD, but if you really really listen for it, it just gets a little bothersome after awhile.
eh, i already ordered the others, so ill just use them for now.
any idea why im getting a little bit of popping and clicking every so often? its most noticable when the speaker is louder. its not BAD, but if you really really listen for it, it just gets a little bothersome after awhile.
- Status
- Not open for further replies.