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Amp Camp Amp - ACA
Amp Camp Amp - ACA
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Old 13th February 2018, 12:25 PM   #3701
Dennis Hui is offline Dennis Hui  Canada
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Amp Camp Amp - ACA
Another data point. The JLH amplifier has a comparable size
output cap and has significantly higher damping factor.
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Old 13th February 2018, 01:50 PM   #3702
6L6 is online now 6L6  United States
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Exactly!

The JLH is push-pull. The topology is dictating damping factor, not the output cap.
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Old 13th February 2018, 02:00 PM   #3703
Dennis Hui is offline Dennis Hui  Canada
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Quote:
Originally Posted by 6L6 View Post
Exactly!

The JLH is push-pull. The topology is dictating damping factor, not the output cap.
Definitely. I also like your suggestion of the Aleph.

Meper, here's a quote from Papa (from the Son of Zen article):

"A lot of people are really concerned about capacitors, almost as many as worry about wire. Capacitor distortion is small compared to the sins committed by output transformers and the gain devices (tubes or semiconductor), but occupies a disproportionate share of audiophile angst."
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Old 13th February 2018, 02:12 PM   #3704
MEPER is offline MEPER  Denmark
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Think it would be a good learning experience to build the AmpCamp. Then I could try different coupling caps to test if there is a difference. I guess the value of 3300 uF is not critical. An e.g. 4700 uF would probably also work. A 3300 uF foil capacitor is difficult to get. 10 x 330 uF will be physical large......and expensive. It also seems that high value and low voltage in foil capacitors is not that common.......?
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Old 13th February 2018, 02:54 PM   #3705
Eslheadphone is offline Eslheadphone  United States
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The ACA is a wonderful sounding amp. The electrolytic capacitors in the signal path are not a big deal. The electrolytics in the power supply of any amp are indirectly in the signal path. I remember Nelson saying that the active parts ( tubes , transistors ECT) have a bigger influence on the sound than the passive parts. I used Nichicon`s from Digikey part number 493-11043ND. I encourage to build the amp. I am enjoying mine.
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Old 13th February 2018, 07:12 PM   #3706
MEPER is offline MEPER  Denmark
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To demonstrate why I worrie about using electrolytic caps as coupling caps I found a good quality 6.8 mF / 16V cap. I made measurements using a professional LCR bridge. Parameters measured was Rs, Cs, D and Phase angle. On an ideal cap phase angle should be -90 degree, Rs = 0 and D = 0 at every frequency. I measued at 10, 100, 1k, 10k, 20k and 100k. Pictures attached of screen showing the values. At 10 and 100 Hz everything look Ok but already at 1 kHz things starts to get not so good and at 10k and 20k it gets very bad. Pure film caps measure much better. That said I have not measued a 6.8 mF film cap. But looking at the results I think you would worrie a bit also?


The real world seems to be a bit better as the measurement on the real amp shows good transfer function from 10 to 20 kHz.


The manual for the measurement equipment are 200 pages so there might something I have missed or need to learn when performing measurements like this. I am not an expert in measurement techniques.......yet :-)
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Old 14th February 2018, 08:59 AM   #3707
Loudthud is offline Loudthud  United States
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C1 and C3 are inside the feedback loop. This might reduce any distortion they cause, but does this cause a lump in the low frequency response?
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Old 16th February 2018, 02:38 PM   #3708
Murdoc is offline Murdoc  Germany
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If you are concerned, you could bypass the big 3300uF cap with a 1-2,2uF film cap. As you possess nice measurement equipment, you could measure the frequency dependent changed outcome of this new 3300||1,5uF cap, and later on, just hear the 3300uF a couple of days and then add the bypass film cap.
Bypassing caps is a highly controversial topic, so you can find many different opinions. Some prefer here caps with MKC (obsolete), just good metalized film, or PPS caps.
Linear audio has some articles about capacitors, which I enjoyed a lot. They are worth their price.

The same for the cap in the signal input. Here you can just use a film cap, or trust Papa'a decision, or, and he for sure will like it, play around it.

Kind regards,
Matthias
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Old 16th February 2018, 04:12 PM   #3709
MEPER is offline MEPER  Denmark
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I have read about bypassing a big cap with a smaller cap that has better high frequency performance and all the for and against (also a YouTube video that shows that there are no difference if the input is a sinus signal). What I did yesterday was to contact the Jensen Capacitor factory and ask if they have something "good". I got a positive reply and I have just ordered some 3300 uF / 63 V Jensen audio grade capacitors. I will pick them up next week from the factory. I live close to the factory ("Jensen" is a very old capacitor factory in Denmark). The size is 35 mm X 80 mm ......so a large one and also a "bit" more expensive than a normal 3300 / 63 cap. I assume the large size is to get low ESR etc. Will be interesting to make some measurement on it.....and hear how it sounds. When building the Amp I will need to mount the cap close to the PCB and then use short wires to the cap. It should be possible I think. Think I will get the kit when it is available and start from there. Then later build a new external PSUs for the monoblocks. I could also just get the PCB and the Mosfets.....and then get large cabinet(s) where there is space for PSUs etc. Don't know what will be the best solution.


I found a little bit of info at Jensen Cap homepage about Audio Grade Capacitors:
White Paper - A/S Tobias Jensen Production
.....but there are no real deep technical information on how such a cap is made....
The caps I have ordered it not to be found at the homepage yet.......
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Old 17th February 2018, 12:27 PM   #3710
zekeblue is offline zekeblue
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Anyone know what the current draw is from the wall for each of these amps? Particularly when using them at 24 volts DC. Thanks!
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