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My first DIY amplifier 20 years a go
My first DIY amplifier 20 years a go
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Old 9th September 2013, 06:27 AM   #481
Acca is offline Acca  Serbia
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My first DIY amplifier 20 years a go
Heh,I tried it with only 470u caps on PSU,and very small buzz comes out
You must try
p.s. If you wish you can add filter to input stage,but it's filtered well (see 15k + 1000uF)
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Old 9th September 2013, 07:45 AM   #482
Acca is offline Acca  Serbia
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My first DIY amplifier 20 years a go
I put this small module in my active speakers
When I finish it I'll post pic's
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Old 9th October 2013, 06:46 AM   #483
ashok is offline ashok
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My first DIY amplifier 20 years a go
Any updates from anyone ?

My efforts have been stalled temporarily.
Cheers.
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Old 9th October 2013, 04:38 PM   #484
gaborbela is offline gaborbela  Canada
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Hello
I was busy with a similar project like these, just finished the PC boards layout.
The main reason I stopped work on these project I need to order some exotic parts to the final amp at the same time I place the order for other project.
Also I did return some old parts to PartsConnexion for exchange so I must place the order I ASAP.
I have to mention by the help of Wahab the circuit was a bit modded (I think you built your amp based on that, you know that) but by me that was never tested (yet).
So really I do not know sound wise it was a upgrade or not or the same how it was.
I'll test it soon.
Also want to compare the sound of the amp with the LC type since that became so popular.
By the way Marc built the discrete darlington amp modded by Borys from LC LatFet version and he wrote he get the best balanced sound around 50mA bias.
Knowing that I really have to re test these amplifier to.
Do we really need that high bias? The amp stable with low bias with a adequate heatsink.
I do not think other people work on the orig project now.
Greetings Gabor
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Old 9th October 2013, 05:37 PM   #485
ashok is offline ashok
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My first DIY amplifier 20 years a go
I keep checking on progress on the LC type circuit. I recently read something about shorting out some resistors and that it resulted in better bass. But they said earlier that it has superb deep bass and bass control. So it got noticeably better by removal of some components ?
All this is so confusing as we really don't know what the reference system is.

I can say that your 20 year old circuit sounds great and can be improved with some refinements. I can't say now if the refinements only made an improvement in measured performance and nothing audibly. I can't even say if the simplest configuration sounds better ! This is possible. Remember that the typical resistor load with bootstrap on the VAS sounds nicer than a CCS load on the VAS in some circuits. Poorer measurement but better sound !

I'm trying out the ex-plendit version of your circuit. The input transistors are turned around. The rest appears to be similar.

Cheers.
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Old 14th October 2013, 12:17 PM   #486
ashok is offline ashok
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My first DIY amplifier 20 years a go
Approaching completion. Board is ready. Needs to be fixed to the heat sink. Same board size and heat sink as used for the '20 year old amp' !
I plan to try it at 50 to 80 mA bias. I just flipped the input transistors and reconnected the input stage. It's a new board. Trust there are no errors.
Supply will be +/- 36 to 40 V depending on our mains supply !
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Old 14th October 2013, 09:13 PM   #487
gaborbela is offline gaborbela  Canada
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Ashok
can you post the circuit please, easier to follow or understand any mode you made. Also we can refer to the circuit any time.
I will test soon these version.
Let see if that make these little amp more stable and sound wise how much it will change.
I have the layout for these, was designed so I can test the Toshiba 2SJ201/2SK1530 MosFet to.

Only reason I do further test to see if I can get the amp a bit more stable with Class A/B bias
Honestly I'm more than satisfied of the sound of the amp using the latest semiconductor set.

Greetings Gabor
Attached Images
File Type: png BG1-Daelington.PNG (139.4 KB, 321 views)
File Type: png BG1-HexFet_Toshiba_Sch.png (141.1 KB, 316 views)
File Type: png BG1-HexFet_Toshiba_Brd1.png (79.8 KB, 304 views)
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Old 15th October 2013, 05:42 AM   #488
ashok is offline ashok
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Hi G,
There is a small error in the first circuit with the 22 ohm compensating resistor. The Q12 base must go to the collector of the BD139 bias transistor Q50. Otherwise the resistor will not have any effect.
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Last edited by ashok; 15th October 2013 at 05:44 AM.
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Old 15th October 2013, 05:51 AM   #489
ashok is offline ashok
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My first DIY amplifier 20 years a go
Here is the circuit. It's been copy pasted from the Beige Bag Spice program.
I've attached the power supply rejection ratio of the circuit with RC filtering for the input stage and the same stage with a capacitance multiplier attached to the input stage . My current board is with the capacitance multiplier. I can disable it later to see how it sound.
From the graph you can see a huge improvement in the PSRR at LF with the cap multiplier.
Curves: Red -- + ve rail PSRR with plain RC filter
Grey -- - ve rail PSRR with plain RC filter
Blue -- + ve rail PSRR with cap multiplier
Green -- - ve rail PSRR with cap multiplier
Attached Images
File Type: gif Explendit.gif (13.3 KB, 292 views)
Attached Files
File Type: doc Explendit PSRR.doc (48.5 KB, 43 views)
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Last edited by ashok; 15th October 2013 at 05:59 AM.
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Old 15th October 2013, 01:22 PM   #490
gaborbela is offline gaborbela  Canada
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Quote:
Originally Posted by ashok View Post
Hi G,
There is a small error in the first circuit with the 22 ohm compensating resistor. The Q12 base must go to the collector of the BD139 bias transistor Q50. Otherwise the resistor will not have any effect.
Thank you
I just left out that compensation resistor, probably not even need to be used in these circuit.
I remember when you wrote about (U used it at the basic circuit) so I put it in to the circuit to remember about that 22R and I forget there.

I will take a look at your new circuit , didn't had time yet.....

Greetings Gabor
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File Type: png BG1-Darlington.PNG (139.0 KB, 264 views)
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