I got my 200 wonderful transistors yesterday from the post office, sat down today and started to match them... They must be from some very different batches or something since most of the S2A/S2C were consistently off by 40Hfe. Provided I was using my multimeters built in Hfe measurement tool. I only got 9 matches out of the whole thing...
I believe the 2SC1815 averaged out to be 220Hfe and the 2SA1015 averaged out to be 180Hfe... Strange little things aren't they? I'll be doing better matches with a couple transistors I pulled from my stash and this latest batch, but the question begs; anyone need any transistors?
I believe the 2SC1815 averaged out to be 220Hfe and the 2SA1015 averaged out to be 180Hfe... Strange little things aren't they? I'll be doing better matches with a couple transistors I pulled from my stash and this latest batch, but the question begs; anyone need any transistors?
The only built the dynalo, headbanger, and Mini3. I currently don't own the last two. My ASKA is on a bread board and I don't have the the supply needed to listen to it, and I wouldn't. It's to easy to bridge connections and accidentally cause a massive offset of some kind.
I won't comment on the sound, apart from it sounds much better then my standard headphone out on my computer.
And now I feel the need to sell this amp to finance some other project... I can't get away from DIY!
I won't comment on the sound, apart from it sounds much better then my standard headphone out on my computer.
And now I feel the need to sell this amp to finance some other project... I can't get away from DIY!
Dynalo RCA Out
Hi lads. Sorry for digging out an old thread. I'm building a dynalo at the moment and I want to use it as a headphone amp and a preamp. How can I get a RCA output from it that I can feed my amp with without hurting it. There will be a DAC installed with it in one case and I want to be able to feed my amp with a signal from DAC going through dynalo amp. Is that possible? please advise me on what to do to achieve both Headphone out and RCA out. Thanks in advance
Hi lads. Sorry for digging out an old thread. I'm building a dynalo at the moment and I want to use it as a headphone amp and a preamp. How can I get a RCA output from it that I can feed my amp with without hurting it. There will be a DAC installed with it in one case and I want to be able to feed my amp with a signal from DAC going through dynalo amp. Is that possible? please advise me on what to do to achieve both Headphone out and RCA out. Thanks in advance
Hi All, I'm having problems with a Dynalo build, rev c pcb.
I had one channel working now its not, the oterh channel never worked.
I have gone through the schematic and checked component values and types and there are no problems with the build. All parts were very well matched and everything was checked several times before power up.
Power supply is Salas Shunt with about 350mA current +/- 16V
No op amps are fitted yet, but I intend to when its stable.
I use diodes on output stage for thermal stability, but they are not bonded to outputs.
All voltages are as per the DGardner site on voltage and current schematics except the following on channel 2:
Base of Q3 has 0.32V instead of 10.0
Emitter of Q3 has 1.14V instead 10.0V
Base of Q4 has -0.73V instead of -10.6 V
Emitter of Q4 has -1.5V instead of -10.6V
R19 is 200 Ohms and has about 6mA flowing (1.2V drop)
R11 and R15 (470 Ohm in parallel with 100K pot) 1.139V and 1.144V respectively These were matched quad with the other working channel that measure 1.518V and 1.512V
There are no oscillations on the power supply or the outputs.
the bad channel actually sets up ok, the DC offset though drifts several hundred mV in 15 minutes. Bias also drifts. I use 24ohm resistors and get around 400mV from memory. If I try and adjust the offset with R10 and R14 sometimes one of the LEDs goes out.
All parts are as per the Rev C schematic, including gain of 10. Input pot is omitted at this stage and setup is done via shorted inputs.
I have tested Q1,Q2,Q3,Q4 and they are ok. It seems that the jfets are not biassing and thats why there is no voltage across R1 and R2 or R8 and R9. I have tried replacing the jfets with a new set, maybe they are fakes? I tested for Idss and they matched well.
Confused especially as channel one was working and now its not.
I had one channel working now its not, the oterh channel never worked.
I have gone through the schematic and checked component values and types and there are no problems with the build. All parts were very well matched and everything was checked several times before power up.
Power supply is Salas Shunt with about 350mA current +/- 16V
No op amps are fitted yet, but I intend to when its stable.
I use diodes on output stage for thermal stability, but they are not bonded to outputs.
All voltages are as per the DGardner site on voltage and current schematics except the following on channel 2:
Base of Q3 has 0.32V instead of 10.0
Emitter of Q3 has 1.14V instead 10.0V
Base of Q4 has -0.73V instead of -10.6 V
Emitter of Q4 has -1.5V instead of -10.6V
R19 is 200 Ohms and has about 6mA flowing (1.2V drop)
R11 and R15 (470 Ohm in parallel with 100K pot) 1.139V and 1.144V respectively These were matched quad with the other working channel that measure 1.518V and 1.512V
There are no oscillations on the power supply or the outputs.
the bad channel actually sets up ok, the DC offset though drifts several hundred mV in 15 minutes. Bias also drifts. I use 24ohm resistors and get around 400mV from memory. If I try and adjust the offset with R10 and R14 sometimes one of the LEDs goes out.
All parts are as per the Rev C schematic, including gain of 10. Input pot is omitted at this stage and setup is done via shorted inputs.
I have tested Q1,Q2,Q3,Q4 and they are ok. It seems that the jfets are not biassing and thats why there is no voltage across R1 and R2 or R8 and R9. I have tried replacing the jfets with a new set, maybe they are fakes? I tested for Idss and they matched well.
Confused especially as channel one was working and now its not.
Attachments
Ajutzam, you can just take a feed from the output to head phone to a pair of RCA plugs. Your amp will be able to feed the headphones and RCA jacks at the same time. You could also use a switch to switch the ouptput to RCA from headphone socket.
its a bit odd and I dont understand how the output bias is set. I used the dc offset trimpots to adjust the output stage bias. I set the trim pots to max (100K) and accepted that the bias of N and P was slightly uneven. This gave me the bias I needed for the front end. DC offset without the servo drifts around 5 - 10 mV, not sure if I want to use the servo as its reasonably stable. Dynalo is a very nice hp amp
Hi. I'm trying to Idss match jfets. I got 50 of each type. I have no problems measuring k170s. All show within spec. When i change to j74 i get no readings or they heat up and show values way above spec for a second or explode. I'm using these schematics for mesurements.
https://www.cavalliaudio.com/diy/exstata/images/JFETMatching.gif
Everything is connected according to schematics and tripple checked for polarity. I also have a fet matcher from stompville http://www.stompville.co.uk/shop/23-jfet-matcher-kit.html
Again no problem with N channel k170.
Already destroyed 3 j74s trying to measure them. No broken ones in k170. All measured perfect with no problem. What am i doing wrong? Please help!
https://www.cavalliaudio.com/diy/exstata/images/JFETMatching.gif
Everything is connected according to schematics and tripple checked for polarity. I also have a fet matcher from stompville http://www.stompville.co.uk/shop/23-jfet-matcher-kit.html
Again no problem with N channel k170.
Already destroyed 3 j74s trying to measure them. No broken ones in k170. All measured perfect with no problem. What am i doing wrong? Please help!
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