WWW.DC300A.COM
I'm clearly out of my mind. I just purchased www.dc300a.com!
The madness is festering and multiplying.
Shawn.
No the link does not work yet. There is no site but I'm working on it!
I'm clearly out of my mind. I just purchased www.dc300a.com!
The madness is festering and multiplying.
Shawn.
No the link does not work yet. There is no site but I'm working on it!
Hi Shawn,
You are on your way to becoming a DC300A expert. I can think of much worse things to be.
-Chris
You are on your way to becoming a DC300A expert. I can think of much worse things to be.
-Chris
A way to protect the speakers and eliminate turn-on and turn-off thumps with a decent relay circuit. If you have room inside for a few relays and a small circuit board...
Shawn,
Yes by all means e mail me direct about this 🙂
I have some of TW's earlier albums such as "the heart of saturday night", "small change" and "closing time", on cd unfortunatley as my brother took his vinyl with him when he emigrated to Australia (as any one would) and it was he who first turned me on to Tom Waits. I'm not too keen on some of his later stuff, "swordfish trombones" and after....a bit to amusical and erm.."experimental" for my likeing.
P.S. what are "boots" in this context?
Yes by all means e mail me direct about this 🙂
I have some of TW's earlier albums such as "the heart of saturday night", "small change" and "closing time", on cd unfortunatley as my brother took his vinyl with him when he emigrated to Australia (as any one would) and it was he who first turned me on to Tom Waits. I'm not too keen on some of his later stuff, "swordfish trombones" and after....a bit to amusical and erm.."experimental" for my likeing.
P.S. what are "boots" in this context?
Relays
The length of the discharge time varries by location of the volume potentiometers. Fully CW: delay then slow quiet discharge perhaps 6 seconds. Fully CCW a burst of white noise followed by a rapid discharge, the whole thing 2 seconds.
The damn thing sounds great. Everything is very stable and from left to right it checks out well. There is room for some relays and a couple of small boards. I relocated the Bridge rectifier and now I have two potential locations for more "stuff".
I have not concluded the measurements Chris suggested, so more on that soon.
I may go down the realy road with relays for on and off and this way I can get the soft start too. We'll see.
Shawn.
EchoWars said:
The length of the discharge time varries by location of the volume potentiometers. Fully CW: delay then slow quiet discharge perhaps 6 seconds. Fully CCW a burst of white noise followed by a rapid discharge, the whole thing 2 seconds.
The damn thing sounds great. Everything is very stable and from left to right it checks out well. There is room for some relays and a couple of small boards. I relocated the Bridge rectifier and now I have two potential locations for more "stuff".
I have not concluded the measurements Chris suggested, so more on that soon.
I may go down the realy road with relays for on and off and this way I can get the soft start too. We'll see.
Shawn.
Boots
Boots are live recordings, short for bootleg recordings. I have hundreds of fantastic live shows of TW. Some have even been remastered like the last two shows performed here in Toronto!
Cheers,
Shawn.
jez said:
Boots are live recordings, short for bootleg recordings. I have hundreds of fantastic live shows of TW. Some have even been remastered like the last two shows performed here in Toronto!
Cheers,
Shawn.
Sounds interesting 😉
Do you have them in uncompressed digital format (WAV etc) and would you be willing to send as e mail attachment? Would be a hell of a big download so maybe just 'er.. "the best one" assuming you have broadband! If I am presuming far too much then just ignore 😀
Assuming that there is no music playing at the time, then the differing discharge time still suggest it's oscillating, (but see my final comments before getting worried) and that the amplitude and/or frequency varies with volume control position causing changes to discharge time. You need to get your oscilloscope out
😉
If it is unstable then you can expect it to sound better still when sorted! Putting it right may well be easier said than done 🙁
Changes may need to be made to the frequency compensation etc to account for different transistors etc (sorry, have not followed entire thread, just dipped in and out! Don't know PRECISELY what you have done). This is not an easy task as too much or too little can cause the big bang theory to become practice..
Lets hope it is not oscillating 😉
On a positive note, it's quite common and normal for an amplifier to be perfectly stable when in use but to oscillate whilst the smoothing caps are discharging and voltages are falling. This is more likely than the first scenario I described 😉
Do you have them in uncompressed digital format (WAV etc) and would you be willing to send as e mail attachment? Would be a hell of a big download so maybe just 'er.. "the best one" assuming you have broadband! If I am presuming far too much then just ignore 😀
Assuming that there is no music playing at the time, then the differing discharge time still suggest it's oscillating, (but see my final comments before getting worried) and that the amplitude and/or frequency varies with volume control position causing changes to discharge time. You need to get your oscilloscope out
😉
If it is unstable then you can expect it to sound better still when sorted! Putting it right may well be easier said than done 🙁
Changes may need to be made to the frequency compensation etc to account for different transistors etc (sorry, have not followed entire thread, just dipped in and out! Don't know PRECISELY what you have done). This is not an easy task as too much or too little can cause the big bang theory to become practice..
Lets hope it is not oscillating 😉
On a positive note, it's quite common and normal for an amplifier to be perfectly stable when in use but to oscillate whilst the smoothing caps are discharging and voltages are falling. This is more likely than the first scenario I described 😉
HP331A & Radford LDMS2-2
I have a line on a HP331A. It seems a bit high on the accuracy, rated at being able to measure 0.1% but heck for checking for problems I guess it would do? Any more thoughts?
I also looked at a Radford LDMS2-2 Low Distortion Measuring Set but I can not find a single thing about it on the net.
Cheers,
Shawn.
anatech said:
I have a line on a HP331A. It seems a bit high on the accuracy, rated at being able to measure 0.1% but heck for checking for problems I guess it would do? Any more thoughts?
I also looked at a Radford LDMS2-2 Low Distortion Measuring Set but I can not find a single thing about it on the net.
Cheers,
Shawn.
The Radford set is probably worth looking at if in good condition. They made some good audio test gear in their day. I would guess it would measure down to at least 0.01% or less. It's the same Radford that is famous for Hifi amplifiers, and they were at one time claiming zero distortion for their transistor amplifiers
I believe this was later amended to 0.005% or there abouts (from memory). I would guess they must have made decent test gear to be able to measure this!? I certainly remember seing several technical reviews of amps in the hifi press (back in the day!) that mentioned using Radford test gear 😉
I believe this was later amended to 0.005% or there abouts (from memory). I would guess they must have made decent test gear to be able to measure this!? I certainly remember seing several technical reviews of amps in the hifi press (back in the day!) that mentioned using Radford test gear 😉
Hi Shawn,
I'd grab the HP 331A. The darn things almost never die. It will also cover some fairly high frequencies.
I'm sure a little modding may drop the measurement floor down some too.
The Radford sounds interesting, but if you can'tfind any info on it it may just end up being a white elephant. Later you may get a computer test set based on a sound card.
-Chris
I'd grab the HP 331A. The darn things almost never die. It will also cover some fairly high frequencies.
I'm sure a little modding may drop the measurement floor down some too.
The Radford sounds interesting, but if you can'tfind any info on it it may just end up being a white elephant. Later you may get a computer test set based on a sound card.
-Chris
Re: DC offset - discharging cap(s)
RE : cap discharge how about fitting 3.3k 3 or 5 watt res across one of the main psu caps, as crown did to discharge after turn off?
standard measures surely?
p.s.
what about using multiturn ceramic 1watt top adjust presets for bias adjust? i have used these a few times now and they make life easier, i usually go for 500R values centre leg tied to one end obviously......
TomWaits said:
RE : cap discharge how about fitting 3.3k 3 or 5 watt res across one of the main psu caps, as crown did to discharge after turn off?
standard measures surely?
p.s.
what about using multiturn ceramic 1watt top adjust presets for bias adjust? i have used these a few times now and they make life easier, i usually go for 500R values centre leg tied to one end obviously......
Re: Re: DC offset - discharging cap(s)
I've been humping dirt and cement for 10 straight days now but that gig is nearing completion.
I have not yet finished checking out all of the suggestions you guys posted but if I can squeeze out some time in the up coming days I should be back with more scoop. Apex Jr. shipped out some caps to me and I should see those next week. 😉 Also, I ordered a couple of decent alps 100K pots from Parts Connection. I will have to add the supplementary resistors (R104, 204 - 10k) when I connect the new 100k pots. This will require another set of offset adjustments so I may hold back a little longer.
I just watched my Canon digital camera roll of the desk onto the floor. I'm so spent I didn't even try to reach out and stop it.
It's all good,
Shawn.
krmaudio said:
I've been humping dirt and cement for 10 straight days now but that gig is nearing completion.
I have not yet finished checking out all of the suggestions you guys posted but if I can squeeze out some time in the up coming days I should be back with more scoop. Apex Jr. shipped out some caps to me and I should see those next week. 😉 Also, I ordered a couple of decent alps 100K pots from Parts Connection. I will have to add the supplementary resistors (R104, 204 - 10k) when I connect the new 100k pots. This will require another set of offset adjustments so I may hold back a little longer.
I just watched my Canon digital camera roll of the desk onto the floor. I'm so spent I didn't even try to reach out and stop it.
It's all good,
Shawn.
anatech said:
The alps pots are ok but these are junk compared to the other products they make. Still they were almost $50 including delivery! I think I was ripped-off. The Canadian dollar needs some more weight. 😉
The opamp is marked:
UA739DC
FB127 Korea
Any takers on who made it and when?
Cheers,
Shawn.
That would be Fairchild and probably about August 1981....could be '91 but less likely 😉
There are MUCH better modern alternatives available but you would need to make up an 8 to 14 pin adapter.
There are MUCH better modern alternatives available but you would need to make up an 8 to 14 pin adapter.
