Sure, give me a few days to grab the piece of paper with all the hand written details on it and convert that into an Express Sch file.
-PB
-PB
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I guess I'm a little late for the party as usual....
I agree on the need to build a SET, as it is the only way I will ever answer the questions about SET sound quality for myself. I settled on the 6A3/6B4G/6C4C due to the broader offering of the 6V filament versions. I've collected a pair of 6A3s and a pair of 6B4Gs and have begun playing with them.
I've got a pair of Edcor GXSE10-8-2.5K transformers but feel something better is in line. The CXSE25-8-3.2K looks nice, but I think a 25W transformer is overkill and not optimal. I just can't see it for a 3.5W amp.
With that in mind, a couple of days ago I sent a request to Edcor for two transformer quotes for my amp.
I'm looking at a 10W 3.5K to 8 Ohm transformer with possibly a cathode feedback winding (also 8 Ohm), and UL tap (40%). I figure I might as well get all the bells and whistles in it. If the CF winding does not work out, the next time I'll get the ones without it.
I figure a 10W transformer ought to cover a lot of ground. It is slightly small for a 300B, but not much, and would work well for the 6P41S amp I built as well.
I also requested a quote for a 5K primary version.
I agree on the need to build a SET, as it is the only way I will ever answer the questions about SET sound quality for myself. I settled on the 6A3/6B4G/6C4C due to the broader offering of the 6V filament versions. I've collected a pair of 6A3s and a pair of 6B4Gs and have begun playing with them.
I've got a pair of Edcor GXSE10-8-2.5K transformers but feel something better is in line. The CXSE25-8-3.2K looks nice, but I think a 25W transformer is overkill and not optimal. I just can't see it for a 3.5W amp.
With that in mind, a couple of days ago I sent a request to Edcor for two transformer quotes for my amp.
I'm looking at a 10W 3.5K to 8 Ohm transformer with possibly a cathode feedback winding (also 8 Ohm), and UL tap (40%). I figure I might as well get all the bells and whistles in it. If the CF winding does not work out, the next time I'll get the ones without it.
I figure a 10W transformer ought to cover a lot of ground. It is slightly small for a 300B, but not much, and would work well for the 6P41S amp I built as well.
I also requested a quote for a 5K primary version.
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Sounds good to me - a bigger output transformer may provide lower bass response with less phase shift than a smaller one, so even if you think the power rating is higher than you need it's not necessarily a bad thing.
I have a few of the 6C4C tubes too, but I just had to hear the 2A3 for this amp - but maybe after this project I'll look for a plan to use those Russian tubes as they look really nice.
I don't know if the price is right for you, but I had been strongly recommended to use Magnequest DS-025 and I trust the source of this recommendation. It's also used by Don Garber. I didn't use it because they won't sell single units, only pairs and this project is mono.
I have a few of the 6C4C tubes too, but I just had to hear the 2A3 for this amp - but maybe after this project I'll look for a plan to use those Russian tubes as they look really nice.
I don't know if the price is right for you, but I had been strongly recommended to use Magnequest DS-025 and I trust the source of this recommendation. It's also used by Don Garber. I didn't use it because they won't sell single units, only pairs and this project is mono.
I can understand a difference between the mono-plate and dual-plate tubes, but I'm wondering how much difference there is between the 2A3 and 6A3, if any.
The voltage along the filament will vary, so Gm will vary along it's length. This is the only effect I can think of. I wonder if it makes enough difference compared to the normal 20% spread in tube values.
With transformer size it seems to me that there has to be a tradeoff between increased inductance and hence better bass vs greater secondary inductance and possible loss of micro-detail as the signal level drops relative to the magnetic domain structure of the larger transformer.
The voltage along the filament will vary, so Gm will vary along it's length. This is the only effect I can think of. I wonder if it makes enough difference compared to the normal 20% spread in tube values.
With transformer size it seems to me that there has to be a tradeoff between increased inductance and hence better bass vs greater secondary inductance and possible loss of micro-detail as the signal level drops relative to the magnetic domain structure of the larger transformer.
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No problems at all. Helps a lot to drive triodes. The bad reputation comes from Fender/Marshall using 12AX7's in this position, not appropriate. Here is mine.
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I also suspect the differences will be tiny, I only know that from reading the experiences of others that there can be some differences. But the main thing is that I don't expect to be satisfied with a.c. heater on 6C4C but with 2A3 I am expecting it to be OK. I may later try d.c. heating, but I don't want to need it from the get-go.
That's a really nice looking build. Yes I would agree that 12AX7 is terrible as CF, you need a tube with high transconductance. Maybe I will try something out on a plank of wood.
OH WOW, So pretty.
When I get a tube amp I might take it outside for a walk too.
Just makes you wonder when efficient artificial lightning that simulates sunlight will ever be invented.
When I get a tube amp I might take it outside for a walk too.
Just makes you wonder when efficient artificial lightning that simulates sunlight will ever be invented.
No, I actually consider it ugly, the Hammond box was for another project and it's a little too small. Thanks anyway!
About the light, from what I have seen in studio HMI's I think never. Especially the Attica skylight.
Did I mention how good it sounds?
Im probably going to be building a kt88 amp and i hope the paint finish comes out like yours has because that is what i am going for, this has nice lighting that makes everything sparkle but it also has beautiful contrast levels that let you see the black paint finish but also let you see the tubes shine, not too bright, not like what you would get here in australia.
this picture would be impossible to do here unless you use a filter and a reflector.
that sort of metallic black colour of the primary trafo bellhousings looks even better, whats the trafo and finish model number/colour?
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I did not paint the box by myself, it is a satin black, steel box, made by Hammond.
Hammond Mfg. - Steel Chassis & Bottom Plates (1441 & 1431 Series)
Paint on the trafo (actually the whole trafo, not just the bell) is Motip spray paint, anthracite hammerfinish. Nice to work with. Then you bake it in the oven to harden it.
Which design have you concluded?
Hammond Mfg. - Steel Chassis & Bottom Plates (1441 & 1431 Series)
Paint on the trafo (actually the whole trafo, not just the bell) is Motip spray paint, anthracite hammerfinish. Nice to work with. Then you bake it in the oven to harden it.
Which design have you concluded?
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No joy on the 10W SE transformers.
The response from Edcor is that they are not set up to make a CXSE transformer smaller than 25W at this time.
The response from Edcor is that they are not set up to make a CXSE transformer smaller than 25W at this time.
I don't know. Using 9.75# transformers for a 3W amp just seems wrong.
The UBT-3 looks nice at 5.6#, and the Transcendars are only 4#.
The UBT-3 has a multitap secondary and could be used for cathode feedback.
Any of them would be fine, and I'd like to compare with the GXSE15-8-3.5K.
The UBT-3 looks nice at 5.6#, and the Transcendars are only 4#.
The UBT-3 has a multitap secondary and could be used for cathode feedback.
Any of them would be fine, and I'd like to compare with the GXSE15-8-3.5K.
doesn't it take that size to have the increased bandwidth
they do make smaller 5-10watt trafos in the cheaper series
but with less bandwidth
so whats the difference other than 'more material' ?
they do make smaller 5-10watt trafos in the cheaper series
but with less bandwidth
so whats the difference other than 'more material' ?
More inductance, lower coupling capacitance and leakage inductance due to different construction technique.
My hunch is that there is more interleave in the larger better transformers. In addition there are more turns in the primary due to more winding window as a result of the larger core. This gives the inductance. The interleave gives the lower capacitance and leakage inductance.
My hunch is that there is more interleave in the larger better transformers. In addition there are more turns in the primary due to more winding window as a result of the larger core. This gives the inductance. The interleave gives the lower capacitance and leakage inductance.
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Ha !!! The 2A3 is VERY EASY to drive in a direct couple. You are very wrong !! .0006 A. at 150 to 195 VDC Ea through half a 12AX7 will kick a** over any other tube choice you use there !! As for dynamics, that is a function of how smart and well you implement the power supply, which is where most people get a F- grade.
The most dynamic 2A3 amp I have ever heard , by far, uses a driver AND a power supply similar to what I suggest, so I have HEARD it, many many times !!
Cheers.
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