I think that is a non issue. This amp sounds lovely and the cap acts as a speaker protect at the same time.
I don't have a way to measure ripple. It sounds the same to my ear. I would probably just use the normal PSU that I had. I just built these because I it was there and recommended for this amp. You know me. This amp will likely end up in the cupboard with the other hundred or so amps I've built. It was a fun project and hopefully some help to others.
Blessings, Terry
Unless iit goes short.
I have a amplifier test rig with power connections, input and output all on flying leads with croc clips. On the output I have a DC speaker protect module.
Must have saved a fortune in speakers over the years.
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But, if you were building your best amp, wouldn’t you default to no-cap?
I'm pushing you on this because you’ve built and heard more amps than most, so your opinion carries some weight. Say I’m going to build myself a nice Class A amp, do I go single or dual rail ? Simplicity says single rail, but audiophile says the most expensive and inconvenient approach is always preferred.
Note, this is rarely a question for tube amps...
You'll lose all the bass before the speaker cap shorts. All the volume peaks too if the rail cap is the same age & condition. Amps with dried up rail caps go to 1/5 or 1/10th the power out. Change output caps and the rail cap every 15 years or 100000 hours, they cost a whole $3 each. 1 $3 rail cap, 2 channels, 70 w/ch for 5 sec.
The relays I see on all the ebay/amazon/ali speaker protection listings look competent to break a 10 amp DC short. MAX. All AC rated contacts when you can read the lettering.
Bigun, if your class A amp toasts a headphone with DC, you've lost what, $70? I've got a great sounding $40 headphone, which I hate wearing when not producing recordings. Whereas my 50 w/ch amp can blow $400 in drivers in my speaker with DC, each channel (which are still available, most speakers drivers are not available). I'm retired, and not from the CEO position, either. I'd have to go back to 200 hz bass & a 6 1/2" speaker for months to save up after that disaster. Cost is 0.2% HD of an AX6? Maybe <.1% according to some reports. I've got a .03% HD CS800s that can drive the same speakers as the AX6, sounds exactly the same to me except slightly less hum.
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I think I would not go single rail if I was aiming to build my "best" amp. However, I'm always intrigued by a design I haven't built. Mile is great at keeping ideas flowing. The Slewmaster thread was another as well as Valery's designs. Now that we're shut in I've had a taste to build some more circuits. I still have a stock pile of parts. I need to use up some of them.
Blessings, Terry
Terry , you must have your own lab to make the boards so fast, assemble and listen to this amp while I was still debating if I should buy the nichicon kg Ist or IInd type. Congrats !
Is it ok to use a regular Non regulated DC power supply with the single ended 50w retro ?
I believe that regulated power supply is a must is this case.
Thanks! Where, please? I didn't find it. In my thread that I mentioned I tried to discuss a specific issue I had with that amp, not the amp in general.
Best regards!
You can put zener diode regulator parallel the 100 uf cap if you wish. I used 30 v, see schematic on page 22 Retro Amp 50W Single Supply - Page 22 - diyAudio
I have external regulator 74 v to 69 v since my transformer is so hot at 125 vac (designed for 117 vac). Stack of zener diodes to 70 v, 5 TIP142 with .33 ohm emitter resistors for current sharing, on a Pentium 2 heat sink where the PV14 regulator used to go in the ST120 chassis. Can't attest to performance without the regulator, it might work.
If you watched the video I posted you will see the PSU I used for the initial testing I did. It is just a simple dual voltage power supply. I ignored the ground and just used the V+ and V- outputs and . No regulation and it worked and sounded fine. My sine wave generator broke so I don't have a good way to look at the scope so I can't say if the amp measures better with the regulated supply.
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In an attempt to leave no stone unturned I built the PSU15R. Again I started with Prasi's design and added a bridge and a larger filter cap.
Also, I though I'd mention that a 10k pot is way more than needed. A 5k or even a 3k is plenty. You don't really see any drop in voltage until you hit about 2.5K
Blessings, Terry
Also, I though I'd mention that a 10k pot is way more than needed. A 5k or even a 3k is plenty. You don't really see any drop in voltage until you hit about 2.5K
Blessings, Terry
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With 10k pot output voltage can be set from 45v to 110v, with 2.5k pot only from 45v to 60v.
I only tested with 77VDC. I have a 5K in it. My cap is only 100V so 110v is out of the question.
I used a IRFP9240. The schematic calls for IRFP9150.
Corect, with 10k pot output voltage can be set from 45v to near input voltage in regulator.
Goodday all,
I want to use a 50 Vdc rail for this amp, can I use BD139/140 iso 2SC4793/2SA1837. I will use 2n3773/ 2n3055 or BD xx output transistors ?
Thanks🙂
I want to use a 50 Vdc rail for this amp, can I use BD139/140 iso 2SC4793/2SA1837. I will use 2n3773/ 2n3055 or BD xx output transistors ?
Thanks🙂
Gain change for Cellphone input
Good evening all,
I have build this amp, just a question or two if anybody can help.
1. I want to use this amp with a cellphone as a source, and cannot get a decent output , the sound seems lacking a bit. The feedback resistor is 6k8, must it be increased or decreased. It works great if I use a active preamp to boost the signal a bit.
2. This is a square wave output at 1kHz, the slope on the front side seems to be sloping up and down on the positive and negative wave. Is this acceptable ? Looks the same at 10kHz.Biased at about 15mV using BD243/244C as drivers and 2N3773 as outputs.
Help will be appreciated. Sorry , using 50Vdc as supply, have not yet connected a zobel to the output or an output inductor with a resistor. Negative rails clips a little before positive, will adjusting DC offset to midpoint make the square wave look better ? 🙂
Regards
Good evening all,
I have build this amp, just a question or two if anybody can help.
1. I want to use this amp with a cellphone as a source, and cannot get a decent output , the sound seems lacking a bit. The feedback resistor is 6k8, must it be increased or decreased. It works great if I use a active preamp to boost the signal a bit.
2. This is a square wave output at 1kHz, the slope on the front side seems to be sloping up and down on the positive and negative wave. Is this acceptable ? Looks the same at 10kHz.Biased at about 15mV using BD243/244C as drivers and 2N3773 as outputs.
Help will be appreciated. Sorry , using 50Vdc as supply, have not yet connected a zobel to the output or an output inductor with a resistor. Negative rails clips a little before positive, will adjusting DC offset to midpoint make the square wave look better ? 🙂
Regards
