Tell me please 6DJ8 tube is the same as ECC88 ?
I am not in tube world and do not know well the EU/US markings.
I have few ecc88 in stoc and I am going to try them, but as far I know they need to biased a bit higher. The heater connection is bit differed, I will cutt one track tomorrow and try ecc88 or e88cc I do not remember which one I have.
I am not in tube world and do not know well the EU/US markings.
I have few ecc88 in stoc and I am going to try them, but as far I know they need to biased a bit higher. The heater connection is bit differed, I will cutt one track tomorrow and try ecc88 or e88cc I do not remember which one I have.
Hi Borys,
due the reverse (negativ and positiv rail and signal connection) and different (GND and NFB) connections i had to rework the whole layout => see attached picture.
There is a lot of space lefting but that is because this size match other slewmaster IPS. Price is the same for board what ever the size under 100x100mm 2 layers=> 10u up to 100x100mm 2 layer = 38$ shipping to france included
due the reverse (negativ and positiv rail and signal connection) and different (GND and NFB) connections i had to rework the whole layout => see attached picture.
There is a lot of space lefting but that is because this size match other slewmaster IPS. Price is the same for board what ever the size under 100x100mm 2 layers=> 10u up to 100x100mm 2 layer = 38$ shipping to france included
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I would leave off the excess board area. The smaller the better AFAIAC. We are always fighting for space in a chassis.
the goal is the possibility to swap fron a IPS to a another in the same case without the need of drill/tapper new hole each time=> just screw the board on the same spacer for each IPS. My UniSlewmaster with a IPS fit on a 300 length heatsink. On the VSHA IPS you can see intermediate hole that allow the board to reduce to 80mm length instead 100mm
Marc
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Marc
Nice work !!
After I will thry to play with ecc88 tube I will try to implement an universal board with jumper to switch over the heater connections between ecc82 and ecc88.
I am only not sure how high ecc88 must be biassed, I will start with 4,7kR load resistors and approx 10mA of bias.
Terry
I have another IPS that U must build 😀
The A9 is really simple and very nice sounding. I think you have build apex A9 amplifier, if not the heart of it can be connected to slewmaster OPS.
Regards
Peter
Nice work !!
After I will thry to play with ecc88 tube I will try to implement an universal board with jumper to switch over the heater connections between ecc82 and ecc88.
I am only not sure how high ecc88 must be biassed, I will start with 4,7kR load resistors and approx 10mA of bias.
Terry
I have another IPS that U must build 😀
The A9 is really simple and very nice sounding. I think you have build apex A9 amplifier, if not the heart of it can be connected to slewmaster OPS.
Regards
Peter
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Hi Peter,
Yes I saw that you were doing a layout for an A9 IPS. I will of course, build it once you have finished. I did build the A9 and the AX9. Both sound great. I have already built an AX11 IPS and attached it to a Slewmaster with great results so I look forward to the A9.
Blessings, Terry
Yes I saw that you were doing a layout for an A9 IPS. I will of course, build it once you have finished. I did build the A9 and the AX9. Both sound great. I have already built an AX11 IPS and attached it to a Slewmaster with great results so I look forward to the A9.
Blessings, Terry
Valery,
Thanks for the post! I'm with you, the 12AU7 is a ruggedized 6SN7/6CG7, and works well down to very low Ik and Vak. The Ongaku used a 6SN7 input stage SRPP at 105V! I suggest 6DJ8/ECC88 because it's even lower and it's rp is less than half of the 12AU7, so necessary with very low plate loading. You'd probably want to reduce the 3k3 loads down to around 1k, but I'd suggest a larger Ik, say around 5mA? However, Terry and Peter have the proto and I leave it to them. I have less energy to undertake wonderful designs these days, but I have built a tube into a GNFB network some years back and it was extremely successful sonically. Wonderful tube sonics, and incredible bass and depth of image.
Hugh
Thanks for the post! I'm with you, the 12AU7 is a ruggedized 6SN7/6CG7, and works well down to very low Ik and Vak. The Ongaku used a 6SN7 input stage SRPP at 105V! I suggest 6DJ8/ECC88 because it's even lower and it's rp is less than half of the 12AU7, so necessary with very low plate loading. You'd probably want to reduce the 3k3 loads down to around 1k, but I'd suggest a larger Ik, say around 5mA? However, Terry and Peter have the proto and I leave it to them. I have less energy to undertake wonderful designs these days, but I have built a tube into a GNFB network some years back and it was extremely successful sonically. Wonderful tube sonics, and incredible bass and depth of image.
Hugh
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Joined 2009
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I don't think the 6N1P is an equivalent, despite what you read from sellers on eBay; there are closer Russian equivalents to the ECC88 but no matter when folk have the ECC88 already in their hands 🙂
Hi Peter,
I didn't notice the zip file until this morning. I built the A9 IPS this afternoon and it is playing as I type. I'm using TL072P for the IC. I have some OPAs on order. I tried NE5532 and they worked but for some reason I had 42mV offset with those and 0.0 offset using the TL072P. I also didn't have any small 3u3 caps for the input so it has a 10u electo in there right now.
Sounds very nice as one would expect. Using it with my little Slew Mini LFET OPS. I did some quick scope shots for your pleasure.
Blessings, Terry
EDIT: I forgot to mention, I didn't have any 15V zeners so I used 13V. Not sure how that affects things.
I just hooked the amp up to my A/B setup. I compared it to a VSSA. The VSSA has slightly more definition in the highs. Cymbals and high at are clearer on the VSSA. Mids and bass are basically the same. This amp may be less fatiguing, especially with female voices. I'll try to find time to hook up the original Apex A9 and compare them.
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Terry
You are so quick,awesome job. Use some more hi-spec op-amp OPA series or new LME series. The difference should be noticeable.
I am moving my lab now and in next few days I am back on track.
Regards Peter
You are so quick,awesome job. Use some more hi-spec op-amp OPA series or new LME series. The difference should be noticeable.
I am moving my lab now and in next few days I am back on track.
Regards Peter
The TL072 is JFET input, the NE5532 has bipolar input. The bipolar input needs more bias current, which is the reason of the higher offset.
Try good quality JFET input type, such as OPA2134.
Sajti
I see your point. I suppose someone could just saw off the excess if they needed the smaller footprint.
Hi Peter,
I have one OPA2134. I'll try that and see if I can hear a difference. I substituted those in the Eyesee IPS and couldn't see or hear any difference but maybe it will be different in this one. As I said I have more of them on order so will have them in a few days.
Blessings, Terry
Here's an update. I had a pair of LM4562NA op amps so I tried those. Beautiful! I was pleasantly surprised how much difference that made. Virtually indistinguishable audibly from the VSSA now. Square waves look slightly better now. One thing of note, at least for me was the output current actually went down slightly from the TL072. When I tried to make this change in the Eyesee, the bias on the OPS when sky high. With this IPS the bias actually went down slightly with the 4562. All that to say that with this op amp this IPS is beautiful. Well worth the effort.
Blessings, Terry
Blessings, Terry
Thanks Terry. I have tried so far only OPA2134 and LME9720, there is audible difference in between op-amps. Now I have only left to check what VAS load resistors are the best, at the moment they are 220kR on board.
I have made small heat-sink for VAS transistors - piece of metal with two holes for tie-raps, it helps to keep the bias more steady.
The schematic from post 128 is for +/-60V rails supply, just in case the the zener load resistors can be recalculated for lower supply rails. For +/-45V the 3.3kR resistors (pack of 4 on each rails) can be replaced with 2.2kR.
Regards Peter
I have made small heat-sink for VAS transistors - piece of metal with two holes for tie-raps, it helps to keep the bias more steady.
The schematic from post 128 is for +/-60V rails supply, just in case the the zener load resistors can be recalculated for lower supply rails. For +/-45V the 3.3kR resistors (pack of 4 on each rails) can be replaced with 2.2kR.
Regards Peter
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Hi Peter,
I didn't have a big variety of op-amps. Most of the uses I've had for them has been servos and the TL072/1 have worked just fine. I bought the others to try in the A9 and Eyesee. This LM4562 sounds really good. Any amp that can match the VSSA in detail is a great amp.
I am running +-50v right now because the Slewmaster mini only has one pair of outputs. I plan to try it at 60v once I get your OPS working.
That's a good idea for the VAS heatsink. I meant to feel those transistors to see how hot they were running. I notice that you used yellow LEDs. Those are a little different voltage than the red ones I used. Do you think there will be a problem?
Blessings, Terry
I didn't have a big variety of op-amps. Most of the uses I've had for them has been servos and the TL072/1 have worked just fine. I bought the others to try in the A9 and Eyesee. This LM4562 sounds really good. Any amp that can match the VSSA in detail is a great amp.
I am running +-50v right now because the Slewmaster mini only has one pair of outputs. I plan to try it at 60v once I get your OPS working.
That's a good idea for the VAS heatsink. I meant to feel those transistors to see how hot they were running. I notice that you used yellow LEDs. Those are a little different voltage than the red ones I used. Do you think there will be a problem?
Blessings, Terry