How good is the Tamura TamRadio iron?

I have a set of Akia M8 transformers and waiting for an old Sony TC-500 to turn up.
Will compare the two, as they seem to be the same size measurement wise .
The M8 are not Nickel, sanded off the surface corrosion and they are GOSS .
Will do the same to the Sony Tamradio
 
Will measure both with the Akai M8 and Sony TC500 Tamdario transformers for freq responce with the Tektronix .
Will also measure inductance ,but by the sheer size they are unlikely to produce any serious bass below 40Hz .
The Tamradio has a 600 ohm winding so maybe quite useful for a headphone amp
 
Will measure both with the Akai M8 and Sony TC500 Tamdario transformers for freq responce with the Tektronix .
Will also measure inductance ,but by the sheer size they are unlikely to produce any serious bass below 40Hz .
The Tamradio has a 600 ohm winding so maybe quite useful for a headphone amp


Thread '5K Tape Machine OTs Tested'
5K Tape Machine OTs Tested
 
Great , saves some work .
Sony 15H- 0mA DC
Akai 24H-0mA DC
quite a big difference for same size iron
 

paulbottlehead

Active Member
Great , saves some work .
Sony 15H- 0mA DC
Akai 24H-0mA DC
quite a big difference for same size iron
The Akai doesn't have the 600 ohm winding, so there's more room for more copper on the primary. It also seemed to saturate more easily, so it may have an air gap that isn't quite as large, which will certainly help with primary inductance.
 
Will measure the Sony Tamradio with a SE 6BL7 plates strapped together.
The metal is silver/ white and looks very much like Nickel - Permalloy probably accounts for the drop in inductance to 16H rather than the copper difference between the Akai and Sony Tamradio .
With some CFB should be able to push them out to 18kHz
 

paulbottlehead

Active Member
Based on the size of the TC-500 iron and the application, it's not nickel. The transformer would need to be quite a bit larger to function properly with a nickel stack, and size matters a lot in something like a TC-500.
 
Generally Nickel is part layered with M6,the later Tamura permalloy were %38 Nickel.
Those small 5K Tamradio's aren't up for more than 3 watts anyway.
 
Generally Nickel is part layered with M6,the later Tamura permalloy were %38 Nickel.
Those small 5K Tamradio's aren't up for more than 3 watts anyway.
Based on Pauls’s tests, 2.8W at 1kHz, 10% distortion. Well suited to an inexpensive and nice sounding 45 amplifier.
 
I think you would get better results with a triode strapped 4P1L driven close to A2 2- 2.5 watts 1.2K Plate R in triode , far less distortion near full power than a 45.
A PSE 6BL7 can be driven much harder than the manual dictates at 12 watt max both plates max dissipation , which would be jammed in an old TV cabinet , but in free air ,15-16 watts both plates strapped , 2.5-3 watts output 1.1K Plate R , lower than a 45 !
 

paulbottlehead

Active Member
The 6BL7 is not so linear compared to the DHTs. I would not recommend using it as an output tube if you can afford something like a 2A3 instead.
 
I compared the Sony Tamradio to an Akai M8 set of transformers and the Akai cores were corroded as expected but the same size Sony Tamradio cores are pretty much as the came out of the factory clean and Nickel in appearance as Nickel does not corrode .
Then I have a stack of %60 Nickel PB EI96 lamination NEW and again clean and whitish in appearance for comparison.
The EI cores are destined for a custom wind to match the Tamura 7000 series at %38 Nickel and M6 stripped for the remainder.
May go to %50 and see if their is any sonic difference in sound ,
Sony manual quotes 30Hz-18kHz which was hifi back in the 60's
 

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paulbottlehead

Active Member
You'd really need to pull them apart to know. What you may be looking at is a keeper or something compressible in there for squeezing down on the channel frame.
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These both look like nickel from the front, but the lower transformer is GOS. Inspecting both the Akai and Sony transformers, I see keeper E lams turned around with no matching I lam at each end of the stack. The Akai transformer I have here is not well saturated in varnish, and that will change the appearance of the lams.
 
One of the Sony Tamradio's I have is cooked so will pull it apart and have a look .
I did pop the bottom cover off and all the laminations appeared clean and the same colour .
 
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