Erlend is right: if you want more power and have 4 Ohm speakers, then A60+ is the right choice. Also, observe his massive additional capacitance. I also have extra power supplies. This makes sound even greater.
Otherwise, both versions are identical except for the on-board power supply. A60 can be fitted with just 2X20.000uF per channel whilst A60+ provides space for double: 4X20.000uF. A60+ uses fast Schotkey diodes, A60 has ordinary bridge.
However, to extract the maximum from the both amplifiers it is the best to have additional power supply. Simply, instead of connecting the boards directly to the transformer use additional larger power supplies. You have to connect (+) to the first AC terminal from the left, next connect ground to the second terminal and (-) to the third terminal.
Install 20.000uF/63V capacitors on-board. These capacitors are located very close to the output transistors and may provide extra decoupling and quickly provide sufficient power when needed. In this way you will provide extra dynamics to the music when sudden bursts occur in the AB mode. When supplied with extra capacitance, dynamics is outstanding: from ppp to fff.
Also, it is desirable to use dual mono scheme to attain really quiet operation. Preferably use transformers with two separate windings to have separation between channels and to prevent ground loops.
With the use of capacitance multipliers I was able to attain very low noise floor.
If you do intend to use this amplifier for domestic listening and have sensitive speakers, A60 is just large enough. But if you want to use it for parties select the larger beast.
Next week I will complete new chassis and make final measurements and present them here.
I hope this will be helpful but do not hesitate to ask additional questions.
Have a pleasant weekend.
PS: Erlend: I am glad to hearing from you again my dear friend.
Thanks Berlusconi 😄. Anybody wants to build a huge Class A amplifier?
Toroidal Transformer 230 V | 2 x 24 V | 3000 MP | - A1-Transformer Transformer | eBay
Toroidal Transformer 230 V | 2 x 24 V | 3000 MP | - A1-Transformer Transformer | eBay
Erlend is right: if you want more power and have 4 Ohm speakers, then A60+ is the right choice. Also, observe his massive additional capacitance. I also have extra power supplies. This makes sound even greater.
Otherwise, both versions are identical except for the on-board power supply. A60 can be fitted with just 2X20.000uF per channel whilst A60+ provides space for double: 4X20.000uF. A60+ uses fast Schotkey diodes, A60 has ordinary bridge.
However, to extract the maximum from the both amplifiers it is the best to have additional power supply. Simply, instead of connecting the boards directly to the transformer use additional larger power supplies. You have to connect (+) to the first AC terminal from the left, next connect ground to the second terminal and (-) to the third terminal.
Install 20.000uF/63V capacitors on-board. These capacitors are located very close to the output transistors and may provide extra decoupling and quickly provide sufficient power when needed. In this way you will provide extra dynamics to the music when sudden bursts occur in the AB mode. When supplied with extra capacitance, dynamics is outstanding: from ppp to fff.
Also, it is desirable to use dual mono scheme to attain really quiet operation. Preferably use transformers with two separate windings to have separation between channels and to prevent ground loops.
With the use of capacitance multipliers I was able to attain very low noise floor.
If you do intend to use this amplifier for domestic listening and have sensitive speakers, A60 is just large enough. But if you want to use it for parties select the larger beast.
Next week I will complete new chassis and make final measurements and present them here.
I hope this will be helpful but do not hesitate to ask additional questions.
Have a pleasant weekend.
PS: Erlend: I am glad to hearing from you again my dear friend.
Thanks for the highly enlightening response Berluscone.
I think I will opt for the A60 version of 3 pairs of transistors.
It will be enough for what I need.
I plan to use a power transformer for each board to build a dual mono amplifier.
I will probably use external capacitors in parallel with the ones on the onboard power supply or replace the onboard capacitors with 22,000uF capacitors.
Thank you very much.
Greetings from Brazil.
Me, Erlend, I am already building an adequate chassis. H=200 mm, W=420mm, L=460mm. Heat sinks 0,31 C/W.
For time being it is in raw state: not polished and without connectors, LEDs and switches. I named it "The DoubleDecker". It has enough room to place transformers in the basement and capacitance in the first flor. It has plenty of room for a real beast.
Otherwise, A60 delivers the first 20W of pure class A with quiescent current adjusted to 50-60 mV. After about 12Vrms it goes into AB mode.
Have a pleasant week end.
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Hi vmk2002
I am very glad to hear from you again. Now I know you will make a great amplifier and more importantly, you are learning. That's good. I do not have schematic and would appreciate if you publish one. In that case we would be able to make simulations.
You had problems with noise and I guess I know now why. One of main problems is that you must have either two small transformers for speaker protection or one transformer with two separated secondaries (four secondary wires). The problem is that connecting speaker protection creates additional ground loop which results in hum. This is very important to avoid. Another problem is that you have one power supply transformer. If you really want great sound you should use two separate transformers. Dual mono configuration.
Could you please provide a link to the version you have?
Tell us whether you have some other problems. I'd like to help, if I can.
Best regards
Hi Berlusconi. I have 2 transformers. Each has secondary windings 36-0-36 and 0-12 VAC. Moreover, 0V of the 2x36V winding on the board is connected to 0 of the 12V winding. In the discussion thread, they laid out the circuit, but with different denominations and other transistors. But there is a 10μF electrolyte at the input, but I don't have it. I now have an additional transformer 36-0-36 + 12-0, a board and an aluminum radiator 170x300x35mm. I try with MJL 4281/4302 transistors, while I rest against the heating of the radiator. It is stronger than 5200/1943. Could it be related to the value of the emitter resistors of the output transistors?
PS; The circuit from post 2 from analog_sa is similar to mine. The difference, as I said, is the value of the resistors and other transistors. I sketched the diagram on paper, and now I want to do it electronically. What format (or program) will be better?
PS; The circuit from post 2 from analog_sa is similar to mine. The difference, as I said, is the value of the resistors and other transistors. I sketched the diagram on paper, and now I want to do it electronically. What format (or program) will be better?
Ah, I see now,
The both diagrams are wrong, both intentionally wrong, but for different reasons. Correct is what you have. Once I will take time and make schematics from the bare boards.
I have tried NJW, MJL and 2SC/SA transistors at the output. Do not change what you have (1943/5200) they are good. All these debates which pairs are "better" or "more musical" are just different reactions to placebo effect. And, ON-Semi is not what some think it is.
Regards my dear friend
PS: Have you solved the problem with hum/noise?
The both diagrams are wrong, both intentionally wrong, but for different reasons. Correct is what you have. Once I will take time and make schematics from the bare boards.
I have tried NJW, MJL and 2SC/SA transistors at the output. Do not change what you have (1943/5200) they are good. All these debates which pairs are "better" or "more musical" are just different reactions to placebo effect. And, ON-Semi is not what some think it is.
Regards my dear friend
PS: Have you solved the problem with hum/noise?
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Hello everyone, has anyone ever dealt with this? can I use with this amplifier? https://aliexpress.ru/item/32860839512.html?spm=a2g2w.productlist.0.0.42c737deMwRdkN
Hi Paroxod4,
This amplifier may work without the soft start but I am using it for another reason: to prevent over-heating with high bias current.
The amplifier has relatively low initial power consumption. Also there is no need for slow start if you decide to have normal power supply with the total of 8X10.000uF capacitance (for both channels). Interesting, even with "just" 8x10.000uF the amplifier is really silent if you use separate transformers. Properly wired, this amplifier has very low noise. Even with 97dB speakers I have no problems with noise.
As previously stated, I use soft start with temperature switches on the both channels to protect the amplifier from possible temperature run-away at high bias.
I use THIS soft start, a bit more expensive but iseful. The amplifier has speaker protection, servo and power supply. With additional tempere control switch you can use the amplifier with more confidence.
I wish you a pleasant week end.
Berlusconi Hi. The one you have I know, I'm interested in this miracle, how it works without power.I ordered the A60 for a start without capacitors and transistors (I'm waiting for the original Toshiba) a 300W transformer with separate windings for each channel, plus 2x12v, I think I will have a problem with the chassis, everything is expensive.
Welcome to the club my dear friend,Berlusconi Hi. The one you have I know, I'm interested in this miracle, how it works without power.
You've made good decisions regarding the component selection. I have also, among others, used ISC output transistors and they are very fine. I have measured them carefully with curve tracer and I must say that I do not see the difference between ISC and "Toshiba" transistors. Both are Chinese: Toshiba China and ISC China too. Correct me if I'm wrong but there was Chinese spaceship on Mars so I don't question their capability to produce quality transistors too.
Meanwhile, I've made quite a few experimental work on this amplifier. Just let me know what you need.
And, you're right, this may prove to be an expensive adventure, especially heat sinks, capacitors and chasis if you want to do everything right. This costs.
I wish you a pleasant week end.