Re: Testing
Sorry Ove, I didn't see this. My amps input sensitivity is 1.2Vrms so the sound card can drive it close to clipping.
I did half of the power supply to try one of these out. Why I have to make things so hard to do I don't know - all in the name of good looks. Very tricky to solder the wires inside my transformer shielding box.
In the end I got it done, one side at least.
Hooked up the completed amp board (other one is not done yet) and fired it up. SNAP!!!!
Just kidding. 🙂
Works well. Here's some photos:
Operating. It has an amazing-to-be-working Hitachi Hitray tube that I scrounged out of a table radio from the early first half of the last century.
Typical sine wave at some lower frequency. Clipping is nice, but starts on the bottom first. Not sure able how much idle current there should be. This was at ~900mA/device. Too high? Too low? Glen?
Pretty sweet squarewave at 20kHz.
Nice looking so far. A little incentive to finish.
😎
Radioman62 said:
Sorry Ove, I didn't see this. My amps input sensitivity is 1.2Vrms so the sound card can drive it close to clipping.
I did half of the power supply to try one of these out. Why I have to make things so hard to do I don't know - all in the name of good looks. Very tricky to solder the wires inside my transformer shielding box.
In the end I got it done, one side at least.
Hooked up the completed amp board (other one is not done yet) and fired it up. SNAP!!!!
Just kidding. 🙂
Works well. Here's some photos:
Operating. It has an amazing-to-be-working Hitachi Hitray tube that I scrounged out of a table radio from the early first half of the last century.
Typical sine wave at some lower frequency. Clipping is nice, but starts on the bottom first. Not sure able how much idle current there should be. This was at ~900mA/device. Too high? Too low? Glen?
Pretty sweet squarewave at 20kHz.
Nice looking so far. A little incentive to finish.
😎
A quick listen.
Low
gain
.
I'm used to much higher gain - nearly 30db in Patchwork...so I had to turn things up.
I re-adjusted the idle current to 800mA, having taken the time to read Glen's site.
Nice and quiet at idle, more so than I thought it would be. Very clear midrange and highs. Bass is not what I'm used to - seems attenuated. It's a 10 watt amp though and the speaker I'm using is not the most efficient.
I assume that Q5 is the VAS, and it's running really hot. I put a small sink on it and it's still cooking. This normal Glen?
It has a brutal turn on thump. I guess it's the tube lighting up?
Anyway, pleased so far. The will beget another speaker project - a high efficiency 2-way or maybe, just maybe a fullrange! Nah, I'm just Fonkin around. 🙂
Low
gain
.
I'm used to much higher gain - nearly 30db in Patchwork...so I had to turn things up.
I re-adjusted the idle current to 800mA, having taken the time to read Glen's site.
Nice and quiet at idle, more so than I thought it would be. Very clear midrange and highs. Bass is not what I'm used to - seems attenuated. It's a 10 watt amp though and the speaker I'm using is not the most efficient.
I assume that Q5 is the VAS, and it's running really hot. I put a small sink on it and it's still cooking. This normal Glen?
It has a brutal turn on thump. I guess it's the tube lighting up?
Anyway, pleased so far. The will beget another speaker project - a high efficiency 2-way or maybe, just maybe a fullrange! Nah, I'm just Fonkin around. 🙂
Re: Re: Testing
Nice!
🙂
Are you using those fancy 15MHz TO-3's you mentioned previously instead of the specified 2N3055/MJ2955?
If so be sure to fully test for high frequency local oscillation (i.e. connect the cro probe before the output inductor), especially if you haven't added base stoppers or an RC zobel before the output coupling cap.
Cheers,
Glen
MJL21193 said:
Sorry Ove, I didn't see this. My amps input sensitivity is 1.2Vrms so the sound card can drive it close to clipping.
I did half of the power supply to try one of these out. Why I have to make things so hard to do I don't know - all in the name of good looks. Very tricky to solder the wires inside my transformer shielding box.
In the end I got it done, one side at least.
Hooked up the completed amp board (other one is not done yet) and fired it up. SNAP!!!!
Just kidding. 🙂
Works well. Here's some photos:
Operating. It has an amazing-to-be-working Hitachi Hitray tube that I scrounged out of a table radio from the early first half of the last century.
Typical sine wave at some lower frequency. Clipping is nice, but starts on the bottom first. Not sure able how much idle current there should be. This was at ~900mA/device. Too high? Too low? Glen?
Pretty sweet squarewave at 20kHz.
Nice looking so far. A little incentive to finish.
😎
Nice!
🙂
Are you using those fancy 15MHz TO-3's you mentioned previously instead of the specified 2N3055/MJ2955?
If so be sure to fully test for high frequency local oscillation (i.e. connect the cro probe before the output inductor), especially if you haven't added base stoppers or an RC zobel before the output coupling cap.
Cheers,
Glen
MJL21193 said:
Gain is scaled for 10W with 1Vrms in. Yes, there is a brief fart towards the end of the tube warm up period as the DC operating point suddenly stabilizes – lets you know that the amp is OK and ready to use 😀
I had no bass issues with mine (>90dB or something @ 1W speakers).
Q5 is the VAS and it dissipates about one watt. With a reasonable heatsink tab (cut and bent from a bit of scrap aluminium) it will sit at about 70-80 deg C.
Cheers,
Glen
Re: Re: Testing
I have done some more testing and have nailed a kind of "standardization" so that I can compare with other projects of mine.
I use the amps volume (or the card) to have 1W over 8 ohm at the output. Then I attenuate the signal to have the same level at the input as the output from the soundcard.
Maybe a hard and unveiling test but at least I tell how I got the figures. This time a little better then the ones I presented above.
I will soon make a new link at my homepage about all projects, where I will present my strugglings testings and projects in a more uncluttered form 🙂 This year I really got into DIY audio, up the ankles and more lately
. I have to many unfinished projects right now. This one is the third near finished audio project this year 
There will maybe be one or two more I hope. As you can see in the background there is more stuff in my cellar 
I will present figures on my homepage, maybe next week. For the moment you can have some more pictures.
No coffee in the mug 🙄
My "standard" paralelled 16ohms 1/2W for each cannel)
Inside again
Klein10 clipping at 1kHz on my good old Tectronix 🙂
10kHz squarewave
20kHz squarewave
Oh, my card just gives about 765mV rms (0dB)MJL21193 said:
I have done some more testing and have nailed a kind of "standardization" so that I can compare with other projects of mine.
I use the amps volume (or the card) to have 1W over 8 ohm at the output. Then I attenuate the signal to have the same level at the input as the output from the soundcard.
Maybe a hard and unveiling test but at least I tell how I got the figures. This time a little better then the ones I presented above.
I will soon make a new link at my homepage about all projects, where I will present my strugglings testings and projects in a more uncluttered form 🙂 This year I really got into DIY audio, up the ankles and more lately
. I have to many unfinished projects right now. This one is the third near finished audio project this year There will maybe be one or two more I hope. As you can see in the background there is more stuff in my cellar I have also clipped on a heatzink on those VAS's. I can touch it for a second or two, so maybe 55 degrees?MJL21193 said:
With my Sovtek there is nearly no thump. But with my Philips and Telefunken a really brutal "knmphh" The Sovtek also measured best dynamic compared to all other tubes I tested. My NOS ECC803S was worst ...MJL21193 said:
I will present figures on my homepage, maybe next week. For the moment you can have some more pictures.
No coffee in the mug 🙄
My "standard" paralelled 16ohms 1/2W for each cannel)
Inside again
Klein10 clipping at 1kHz on my good old Tectronix 🙂
10kHz squarewave
20kHz squarewave
Resurrecting this thread with an update. Someone asked me via e-mail if a 12AY7 twin triode tube could be used in this amplifier instead of the 12AX7. Looking at the characteristic curves for the 12AY7 it appears to me that this tube may in fact be a better choice, and it will plug right in as a substitute.
Vg-k for the 12AY7 is significantly higher at the set LTP tail current with a plate voltage of ~110V. The tubes gm is also a little higher. This will yield higher open-loop gain but shouldn’t be a problem as far as stability is concerned as the K10A is compensated on the conservative side.
The 12AY7’s higher Vg-k may also permit a significantly higher LTP tail current, which means that the amplifiers slew rate and squarewave performance could be further improved.
I’m currently adding an insulated ceiling to by electronics workshop and won’t be in a position to plug in and test the amp with a 12AY7 for a while.
Cheers,
Glen
Vg-k for the 12AY7 is significantly higher at the set LTP tail current with a plate voltage of ~110V. The tubes gm is also a little higher. This will yield higher open-loop gain but shouldn’t be a problem as far as stability is concerned as the K10A is compensated on the conservative side.
The 12AY7’s higher Vg-k may also permit a significantly higher LTP tail current, which means that the amplifiers slew rate and squarewave performance could be further improved.
I’m currently adding an insulated ceiling to by electronics workshop and won’t be in a position to plug in and test the amp with a 12AY7 for a while.
Cheers,
Glen
Radioman62 said:
Inside again
Hi Ove.
Having just come back to this thread and looking closely at your pictures and measurements, I think that you have grounding issues.
I cannot see your speaker earth return wires, but I can see that they do not connect to the single “star” earth on the PCB. I’m assuming that you have connected them to what appears to be an improvised star ground at those big filter capacitors.
I drilled the GND hole on the PCB out nice and large, so that the power supply ground and the speaker ground wires can be twisted and soldered in together.
It is important that the speaker earth return is connect here, otherwise the voltage drop induced in the ground wire to the PCB by the heavy filter capacitor currents (full wave rectified mains + harmonics) will become part of the output signal.
Cheers,
Glen
Thank you Glen
Hi Glen
Yes, you are right. I have another starground then the one on the PCB. Probably the hum I mentioned will dissapear if I rewire.
Thank you 🙂 This will be a nice christmas weekend fiddle, when all the Santa stuff is over.
Have you fixed some more with your unit or is it the larger amps of yours that is in the pipeline now ?
Hi Glen
Yes, you are right. I have another starground then the one on the PCB. Probably the hum I mentioned will dissapear if I rewire.
Thank you 🙂 This will be a nice christmas weekend fiddle, when all the Santa stuff is over.
Have you fixed some more with your unit or is it the larger amps of yours that is in the pipeline now ?
Re: Thank you Glen
No worries Ove.
I've been too busy building up my mechanical and electronics workshops and doing home renovations to do anything on the K10A since I blew one channel up. I'm almost there though. Just received my final batch of high-speed trannies the other day, will get back to work on finally finishing the monster amps maybe late Jan if I’m lucky.
Cheers,
Glen
Radioman62 said:
No worries Ove.
I've been too busy building up my mechanical and electronics workshops and doing home renovations to do anything on the K10A since I blew one channel up. I'm almost there though. Just received my final batch of high-speed trannies the other day, will get back to work on finally finishing the monster amps maybe late Jan if I’m lucky.
Cheers,
Glen
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Hmmm
A lot of money in that picture I guess
Now about your new Avatar. You have been changing fast lately.
Is this your local priest or is it you at some masquerade? he he
I guess another actor I don't recognice? He looks as he enjoy life though 😀
He looks like a Priest from Sweden after a better funeral in the 19'th century, when there was a feast in three days with alot of distilled refreshments at hand. Long... before we decided to be somekind of Police for the sober drinking (Swedish liquor and wine monopol) and sober life and sober this ... and sober that. I think the swedes are trying to be the most sober (sufficiently, moderately, exactly right) people in the world. Not just alcohol but in every other aspect as well 🙄
Anyway, I like my country but we are a bit conceited in our well-behaved manners :😉
So. therefore I will try to be a big shot and write all this pompous stuff about life/dead and how mankind develop trough times....
Hrmm. OK amplifiers it was. I promise I will not put up any picture of me in undies, even though I'm very happy just now
Cheers all and have a happy christmas and new year.
A lot of money in that picture I guess
Now about your new Avatar. You have been changing fast lately.
Is this your local priest or is it you at some masquerade? he he
I guess another actor I don't recognice? He looks as he enjoy life though 😀
He looks like a Priest from Sweden after a better funeral in the 19'th century, when there was a feast in three days with alot of distilled refreshments at hand. Long... before we decided to be somekind of Police for the sober drinking (Swedish liquor and wine monopol) and sober life and sober this ... and sober that. I think the swedes are trying to be the most sober (sufficiently, moderately, exactly right) people in the world. Not just alcohol but in every other aspect as well 🙄
Anyway, I like my country but we are a bit conceited in our well-behaved manners :😉
So. therefore I will try to be a big shot and write all this pompous stuff about life/dead and how mankind develop trough times....
Hrmm. OK amplifiers it was. I promise I will not put up any picture of me in undies, even though I'm very happy just now
Cheers all and have a happy christmas and new year.
LOL! Well in some ways I’m ascetic by nature and I really don’t know what it is like to have a hang over, but I certainly would not qualify as a priest. The guy in the avatar is Father Jack Hacket from the TV show ‘Father Ted’, which I think is a good laugh.
Cheers,
Glen
Cheers,
Glen
Ancient-thread resurrection. Have been cleaning up and sorting through my stuff - still have 6 pairs of boards left that are of no use to me.
This wasn't a for-profit adventure so I guess I'd be silly no to try to sell the rest of them.......
This is the best sounding hybrid amplifier on Earth, and now the entire universe as well as I've degaussed the remaining PCB's and cryogenically treated them in my freezer.
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