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How about 6SL7's - any thoughts on microphonics ? I am thinking about a 6SL7 directly coupled to grid of the 2A3 (as driver for the 845) since I would have plenty of B+ to play with. I do have a 12AX7LPS bought for this purpose but somehow, using that little pimple of a valve when there's an 845 on the chassis just doesn't feel right anymore.
The Sylvania 6SL7WGT, brown base with short black plates, is the least microphonic in my experience, also the best-sounding 6SL7 IMO.
If there's any DC coupling to be done, I'd recommend it to the grid of the 845. That way you can drive it into A2 so get more power for a lot less dissipation. Transformer coupling also opens up this possibility but is more expensive.
I remember when I first mooted - on this forum - that I was doing "grid current" there were shrieks of horror and predictions of early failures. Fortunately sanity has prevailed and nobody bats an eyelid about A2 now.
In an earlier post on this or another thread, I said I'd been running this set of 845s for about 10 years. Well I've since checked the dates and it's closer to 13 years. My spare set is still on the shelf.
I remember when I first mooted - on this forum - that I was doing "grid current" there were shrieks of horror and predictions of early failures. Fortunately sanity has prevailed and nobody bats an eyelid about A2 now.
In an earlier post on this or another thread, I said I'd been running this set of 845s for about 10 years. Well I've since checked the dates and it's closer to 13 years. My spare set is still on the shelf.
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I have a Hammond 126B interstage transformer in my "junk box" that will allow me to drive the grid of the 845 from the plate of the driver. I don't intend to push much for A2, there's a thread I started on that topic already and it is better served with a different operating point and topology than I am now considering. What i am now considering is more of an A1 dominated amp, Sakuma inspired if you will.
I also envisage direct coupling of the input tube to the grid of the 2A3 given that there is no shortage of B+ on-hand, or I can use another 126B interstage as I have a pair of them.
I also envisage direct coupling of the input tube to the grid of the 2A3 given that there is no shortage of B+ on-hand, or I can use another 126B interstage as I have a pair of them.
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I certainly have some ideas set out but they are not set in stone - this was supposed to be a quick and simple project to use up some SV811-10's from a friend who no longer wanted his amplifier - it sounded like a great opportunity to dismantle his amplifier, which was a complex A1+A2 amp built on two chassis and to use the parts to make something simple myself, to put 'my stamp' on it. This was distracting me from building my 2A3 Loftin-White but what the heck, free parts, how can I resist. But this SV811-10 isn't a simple tube to use as I have now since discovered. There aren't many designs out there for this tube and it is no longer in production. Initially looking to avoid high B+ and re-use a power trafo it only made sense if operated in A2 but there didn't seem a path forward to make a simple A2 amplifier. So I moved my goal to an A1 amplifier and I started to study Sakuma's designs, offering A1 operation with DHT driving DHT in simple cathode biassed designs. I thought why not an SV811 driving an SV811 - but they like to be run hot to keep the getter activated and that adds a complication when you need to run your driver as hot as your output combined with voltage limitations on interstage transformers etc. Short story - it got complicated again. So... I started to realized that I might prefer to switch to the 845 and go back and look at Sakuma's designs, cathode biassed, lots of iron, not always that conventional but sure look like fun. Does any of this make sense, am I the only weird guy here ?
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you don't need the ultimate 845, or 811 to be happy...
I can build you the sv811 amp very easy with all the things for A2, quite good... but I would not use an hammond, too mundane, sv811 deserve the best
Tonight I am listening to kt77 plugged into a el34 amp... just as good,
I only heard the kt77 in a mega setup, i was impressed not by the power but by the potential of the tube...
So, my kt34 are fully broken in, the kt77 are unused, I have a stock of it.
So..
EL34, high resolution in the upper midrange, it will resolve and expose any harshness in your setup, record etc.
KT77, more homogeneity, a lot less resolution, trading for a more analog sound in the upper range.
EL34, have this reducing ability and very cold, resolving each instruments, in my setup it doesn't sound tubby at all....
THE KT77, however, have a more analog sound, but a few things impressed me, maybe just too early but:
1. the bass has a little more resolution
2. they are more 'airy' with room echoes, lot of spaciousness, blended sound too.
3. VERY analog, the EL34 highs sound like SS amps,
4. for the kt77 the high voice shhhh are soft, analog
5. the impulse on the p, t , c can be clearly heard, on the EL34, it is kinda not as impulsive, weird,
so i prefer the kt77 despite their lack of impartiality in the resolution of the EL34, they still resolve with a very nice micro-resolution that the EL34 kinda lacks., Sounds contradictory.
I can build you the sv811 amp very easy with all the things for A2, quite good... but I would not use an hammond, too mundane, sv811 deserve the best
Tonight I am listening to kt77 plugged into a el34 amp... just as good,
I only heard the kt77 in a mega setup, i was impressed not by the power but by the potential of the tube...
So, my kt34 are fully broken in, the kt77 are unused, I have a stock of it.
So..
EL34, high resolution in the upper midrange, it will resolve and expose any harshness in your setup, record etc.
KT77, more homogeneity, a lot less resolution, trading for a more analog sound in the upper range.
EL34, have this reducing ability and very cold, resolving each instruments, in my setup it doesn't sound tubby at all....
THE KT77, however, have a more analog sound, but a few things impressed me, maybe just too early but:
1. the bass has a little more resolution
2. they are more 'airy' with room echoes, lot of spaciousness, blended sound too.
3. VERY analog, the EL34 highs sound like SS amps,
4. for the kt77 the high voice shhhh are soft, analog
5. the impulse on the p, t , c can be clearly heard, on the EL34, it is kinda not as impulsive, weird,
so i prefer the kt77 despite their lack of impartiality in the resolution of the EL34, they still resolve with a very nice micro-resolution that the EL34 kinda lacks., Sounds contradictory.
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I’m committed to using the Hammond transformers partly because I already have them, partly because I think the performance is plenty up to the task (and sometimes underestimated) and also because I've had good results from using them before.
Actually, I had the opportunity to visit their Waterloo based factory this week to see where the transformers are made and to have a chat with the gentleman who designs them. It was fascinating to see the machines used to make the interleaved EI cores, the finishing ovens etc.
Of course I’m not at liberty to publish anything about the details of my visit but I think we will be seeing more of interest from this company and I’m looking forward to building more amps using these transformers.
Attached - a couple of photos of some of their heritage
Actually, I had the opportunity to visit their Waterloo based factory this week to see where the transformers are made and to have a chat with the gentleman who designs them. It was fascinating to see the machines used to make the interleaved EI cores, the finishing ovens etc.
Of course I’m not at liberty to publish anything about the details of my visit but I think we will be seeing more of interest from this company and I’m looking forward to building more amps using these transformers.
Attached - a couple of photos of some of their heritage
Attachments
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I am just saying that James are better, and there is better than James... I paid 1K for my new amp 80watt PP transformers, directly from the builder in Japan, they are very special, a real steal, my basement has a lot of hammond and edcor :0
I have no fear the hammond sound awesome in PP with ultralinear and decent feedback, without feedback or little feedback I doubt it. It is a different game with little feedback or 0 feedback... my hammond failed me miserably without feedback.
I have no fear the hammond sound awesome in PP with ultralinear and decent feedback, without feedback or little feedback I doubt it. It is a different game with little feedback or 0 feedback... my hammond failed me miserably without feedback.
I'm happy with my 1650N. I have them connected to triode strapped 6P36S. I use a 6R speaker on the 16R tap to reflect ~2k instead of 4k3.
I've just sent an inquiry to Toroidy. I want to know what a 200W 1k:6R PP transformer costs shipped to Canada
At this point, I'm temped to buy a toroid wrapping machine, cores and wire, and see if I can wind my own for less money. I've seen machines that sit on a tabletop for under a grand...
I've just sent an inquiry to Toroidy. I want to know what a 200W 1k:6R PP transformer costs shipped to Canada
At this point, I'm temped to buy a toroid wrapping machine, cores and wire, and see if I can wind my own for less money. I've seen machines that sit on a tabletop for under a grand...
I have a batch of 6SN7's in matched pairs for tube rolling purposes on my 845's.
These valves can show micro phonics, possibly associated with them being from a usage where large production quantities were on demand, and audio applications were not on the agenda, so trialing brands and deselection can be seen as a prudent method to give the 845's their best chance to deliver.
These valves can show micro phonics, possibly associated with them being from a usage where large production quantities were on demand, and audio applications were not on the agenda, so trialing brands and deselection can be seen as a prudent method to give the 845's their best chance to deliver.
Hello,
I have dozens of 6sn7 and 6sl7 from world war 2 .
All my chassis so far have used circular holes which were closed by a circle on the inside of the chassis that could be mounted with some kind of grommet in between to isolate the tube.
BUT the main reason i used these circles was to be able to easily change it into one with a different socket hole without having to use a drilling machine.
In the attachment you can see i used these technique for other parts too like connectors.
Greetings, Eduard
I have dozens of 6sn7 and 6sl7 from world war 2 .
All my chassis so far have used circular holes which were closed by a circle on the inside of the chassis that could be mounted with some kind of grommet in between to isolate the tube.
BUT the main reason i used these circles was to be able to easily change it into one with a different socket hole without having to use a drilling machine.
In the attachment you can see i used these technique for other parts too like connectors.
Greetings, Eduard
Attachments
There is the Potthoff winder, suitable for DIY toroids:
http://www.pat2pdf.org/patents/pat4127238.pdf
https://www.diyaudio.com/forums/tubes-valves/132378-holy-smoking-toroid-winder.html
the big difference between transformers: one is specially engineered to work without GNF.
my $$ transformers have 1hz to 70khz without any feedback, they are in fact 150 watts each if you use hammond specification. They also have less winding losses, which gives them another great advantage.
The SET from hammond, I highly doubt will sound good without a decent amount of GNF
my $$ transformers have 1hz to 70khz without any feedback, they are in fact 150 watts each if you use hammond specification. They also have less winding losses, which gives them another great advantage.
The SET from hammond, I highly doubt will sound good without a decent amount of GNF
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I can confirm that feedback is not necessary to get great performance out of the Hammond transformers I’ve used in the past but I do hope your expensive transformers are a lot better, otherwise why would you spend the money ?
I had good results using Feedback with solid-state amps and believe feedback is a great tool to use to improve performance in the solid-state amplifiers where the active parts are clearly nonlinear, however I haven’t found it to be necessary with the transformer based amplifiers that I have made but maybe a feedback topology is something to try in the future as I have been able to completely reverse engineer at least one Shindo amplifier which I quite like the look of and it uses Feedback although I have to say the feedback is before the output transformer
I had good results using Feedback with solid-state amps and believe feedback is a great tool to use to improve performance in the solid-state amplifiers where the active parts are clearly nonlinear, however I haven’t found it to be necessary with the transformer based amplifiers that I have made but maybe a feedback topology is something to try in the future as I have been able to completely reverse engineer at least one Shindo amplifier which I quite like the look of and it uses Feedback although I have to say the feedback is before the output transformer
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I had shuguan basic ones, they are nice. Had them at 1100 volts, driven by 6sn7, with some feedback, they only drive such speakers as you have, big alnico cones. I upgraded input stages and removed cathode caps, the sound was blooming, auricaps everywhere, just intoxicating sounding.
I don't understand why the feedback is not from the output transformer, it makes 0 sense.
I have a few hammond push pull, they cannot play without feedback.
Shindo 'designs' makes 0 sense to me, it is backward every concept of getting the distortion low.
Unless there is a specific tone that he can obtain this way, I have no clue. I guess I should just snip out parts at random and mix up some tube stages in my amplifiers, they might sound more romantic...
its like the el84, kt77, el34, they are awfully colored, there is such a great margin and truth, stable sound with kt88 and 120, it is just impossible to get back to the other tubes, including the big power tubes 845.
Maybe the PX-300B is worth touching, its a decent 40 watts triode, (or the telefunken 34B?) , just the price kept them out or my reach... but you never know...
I don't understand why the feedback is not from the output transformer, it makes 0 sense.
I have a few hammond push pull, they cannot play without feedback.
Shindo 'designs' makes 0 sense to me, it is backward every concept of getting the distortion low.
Unless there is a specific tone that he can obtain this way, I have no clue. I guess I should just snip out parts at random and mix up some tube stages in my amplifiers, they might sound more romantic...
its like the el84, kt77, el34, they are awfully colored, there is such a great margin and truth, stable sound with kt88 and 120, it is just impossible to get back to the other tubes, including the big power tubes 845.
Maybe the PX-300B is worth touching, its a decent 40 watts triode, (or the telefunken 34B?) , just the price kept them out or my reach... but you never know...
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I will look at the shuguan and I think it might be slightly cheaper I read that psvane was started by some engineers that left the other company because they were disgruntled and several key engineers moved with them to create the new company
As far as I know, Shindo stuff is quite highly regarded but the main purpose for the feedback in the amplifier I reverse engineered, is to linearize the amplifier. And when you think about it, this avoids putting a transformer with all of the parasitics inside the feedback loop. I think it’s a sensible way to use Feedback and there are many valve amplifiers which use Feedback before the output transformer. feedback also has the benefit in stereo applications of ensuring much better channel matching and you don’t need to include the transformer for most of the benefit from that
talking of feedback and getting back on topic I have read that a few people use Feedback with an 845 output stage and I’m not sure why as I thought this valve is linear enough without.
As far as I know, Shindo stuff is quite highly regarded but the main purpose for the feedback in the amplifier I reverse engineered, is to linearize the amplifier. And when you think about it, this avoids putting a transformer with all of the parasitics inside the feedback loop. I think it’s a sensible way to use Feedback and there are many valve amplifiers which use Feedback before the output transformer. feedback also has the benefit in stereo applications of ensuring much better channel matching and you don’t need to include the transformer for most of the benefit from that
talking of feedback and getting back on topic I have read that a few people use Feedback with an 845 output stage and I’m not sure why as I thought this valve is linear enough without.
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