playloud
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I know there has been a dearth of companies making accurate transformer replicas in the last few years, so I was excited to see a new entrant pop up recently: Soursound, in Portland.
I now have some experience with Bryan Sours - who has rewound the blown Marstran/Heyboer 1202-84 from my JTM 45/100 clone - and can report that he is a joy to work with and the iron sounds fantastic!
The other good news is that he has copied the winding geometry from this one, so is now able to offer the 1202-84 to others. If you want a nice layer wound OT with attention to detail, I highly recommend it. He is also offering a Dagnall 100w set (C1998/T2562) and working on 18W and JTM45 sets.
Here's the blown Marstran iron I sent him. As you can see, it was wound on a bobbin (rather than being layer wound, like the originals):
Upon receipt, Bryan tore it down and made a few interesting observation:
- The varnish had not managed to fully impregnate the core. Apparently Heyboer submerge their transformers in a vat of varnish, in batches, and basically wait until it stops bubbling/achieves a steady state. Although much less laborious than using a vacuum pump to do it manually, this approach can lead to air pockets, as it clearly did here.
- The 4 ohm secondary wire was really thin. The originals only had 3 taps (100V and 8/16 ohms), and Marstran (like many other builders) had added the extra 4 ohm tap for convenience. However, it isn't possible to remove the 100V winding without significantly affecting the winding geometry apparently, so it was just buried within the transformer (i.e. without an exit wire). Having the additional tap increases the total volume of wire which has to be contained within the transformer, hence the lighter gauge of wire (and increased arc potential).
- The secondaries exited really close to each other, another location for arc potential.
- Apart from the aesthetic layer of paper on the outside, all internal insulation was tape - and this was used inconsistently (i.e. different thickness per layer).
I don't really hold any of this against Heyboer, as they are building to a particular price point (and are still in business!) but do think it's worth noting. Compared to, say, a Merren (layer wound, original spec wire etc.), it's really a different level of construction.
Bryan suggested that he rewind to the original design, without the 4 ohm tap. He also revised the secondary wire colors to make them historically accurate (as shown on the following schematic).
Here are some progress pics he sent me during the rewinding process. It also got some new zinc-plated endbells with a cool patina:
And here it is in the amp, back on the other side of the Pacific. It certainly looks the part!
As for the sound...
I actually had a good recording of the previous OT not long before it blew, together with an input recording that I played through my reamp box (when I was testing out the transparency of the Powerbrake). So I was able to do a pretty much head-to-head comparison of the two OTs (using the same IR, amp settings, input gain and TAE). The only thing that changed was 2 of the GECs and I upped the screen resistors from 470R to 1k (shouldn't make much difference at this level of overdrive).
Here are the results:
I know sound is subjective, but I was quite blown away by how different it sounds! Especially considering that the lamination and winding geometry/turns ratio are the same. Bryan explained the dielectric properties of varnish/wire/insulation all make a difference, primarily via coupling capacitance between the primary and secondary, but it's the kind of difference that most modern transformer winders would consider immaterial. I guess we can decide for ourselves!
I also slapped together a quick mean-spectrogram which confirms what I'm hearing. I'm starting to see why transformer-winding is such a rabbit hole!
Oh, and here's one more clip of me noodling aimlessly to give a better indication of overall tone:
Apologies for the long post, but hopefully this will be helpful to other members!
I now have some experience with Bryan Sours - who has rewound the blown Marstran/Heyboer 1202-84 from my JTM 45/100 clone - and can report that he is a joy to work with and the iron sounds fantastic!
The other good news is that he has copied the winding geometry from this one, so is now able to offer the 1202-84 to others. If you want a nice layer wound OT with attention to detail, I highly recommend it. He is also offering a Dagnall 100w set (C1998/T2562) and working on 18W and JTM45 sets.
Here's the blown Marstran iron I sent him. As you can see, it was wound on a bobbin (rather than being layer wound, like the originals):
Upon receipt, Bryan tore it down and made a few interesting observation:
- The varnish had not managed to fully impregnate the core. Apparently Heyboer submerge their transformers in a vat of varnish, in batches, and basically wait until it stops bubbling/achieves a steady state. Although much less laborious than using a vacuum pump to do it manually, this approach can lead to air pockets, as it clearly did here.
- The 4 ohm secondary wire was really thin. The originals only had 3 taps (100V and 8/16 ohms), and Marstran (like many other builders) had added the extra 4 ohm tap for convenience. However, it isn't possible to remove the 100V winding without significantly affecting the winding geometry apparently, so it was just buried within the transformer (i.e. without an exit wire). Having the additional tap increases the total volume of wire which has to be contained within the transformer, hence the lighter gauge of wire (and increased arc potential).
- The secondaries exited really close to each other, another location for arc potential.
- Apart from the aesthetic layer of paper on the outside, all internal insulation was tape - and this was used inconsistently (i.e. different thickness per layer).
I don't really hold any of this against Heyboer, as they are building to a particular price point (and are still in business!) but do think it's worth noting. Compared to, say, a Merren (layer wound, original spec wire etc.), it's really a different level of construction.
Bryan suggested that he rewind to the original design, without the 4 ohm tap. He also revised the secondary wire colors to make them historically accurate (as shown on the following schematic).
Here are some progress pics he sent me during the rewinding process. It also got some new zinc-plated endbells with a cool patina:
And here it is in the amp, back on the other side of the Pacific. It certainly looks the part!
As for the sound...
I actually had a good recording of the previous OT not long before it blew, together with an input recording that I played through my reamp box (when I was testing out the transparency of the Powerbrake). So I was able to do a pretty much head-to-head comparison of the two OTs (using the same IR, amp settings, input gain and TAE). The only thing that changed was 2 of the GECs and I upped the screen resistors from 470R to 1k (shouldn't make much difference at this level of overdrive).
Here are the results:
I know sound is subjective, but I was quite blown away by how different it sounds! Especially considering that the lamination and winding geometry/turns ratio are the same. Bryan explained the dielectric properties of varnish/wire/insulation all make a difference, primarily via coupling capacitance between the primary and secondary, but it's the kind of difference that most modern transformer winders would consider immaterial. I guess we can decide for ourselves!
I also slapped together a quick mean-spectrogram which confirms what I'm hearing. I'm starting to see why transformer-winding is such a rabbit hole!
Oh, and here's one more clip of me noodling aimlessly to give a better indication of overall tone:
Apologies for the long post, but hopefully this will be helpful to other members!
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