Has anyone used the Hashimoto Transformer on a 300b? Looking to replace my OPT on a Willsenton 300b and i'm looking at the Hashimoto HC-203u and Heyboer. Still waiting on the reply from Heyboer, but i'm told they make top notch OPT. Curious to your opinions/experience with these OPT. Thanks
Hashimoto OPT
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Heyboer *can* make a good OPT, if they have a decent model to work from. The Peerless S-265-Q copies are very good. But I don't know how they'd do with an SE design from scratch, especially if you don't provide the specifics yourself. Not sure it would best a Hammond, but maybe it would. I'd be interested to hear they're response. I don't imagine it would beat the Hashimoto, either in quality or price. Hashimotos are pretty well-regarded. Two of my experienced DIY pals use them with very good results. Personally I don't think you could go wrong there.
I am currently listening to Hashimoto transformers on my push pull 300B amplifier and they are shockingly good. I was amazed. Comparing them to my Magnequest B18 nickel core, they are both are outstanding; I couldn't choose. For single ended I have Tamura, Tango and Magnequest. I couldn't really choose as all are excellent with slightly different sound. Again, my nickel core Tamura are slightly better focus than the Tamura amorphous core which are very smooth and easy to like. I don't think Heyboer makes many SE transformers. I have his Peerless S-265-Q copies, but am loving the Hashimoto and Magnequest at the moment so haven't used them yet.
I have used the 300B with 2.5k, 3k and 5k primary and prefer 5k which produces slightly less power and slightly less distortion.
I have used the 300B with 2.5k, 3k and 5k primary and prefer 5k which produces slightly less power and slightly less distortion.
I too prefer 5k for the 300B.
Over at FB group (300B Tube Lovers) there is a thread on R300. One owner has used Hashimoto H-20-3.5U and reported more extended highs and more air and separation. Not sure on upgrading the R300 any further but let's see what Stephe reviews for 2024.
The typical operating point of 350V with a 4K load (as in the WE data sheet) is prone to very high levels of 2nd harmonic distortion. What's really needed for hi-fi is 6K or higher. This is one reason I have never used the 300B in any of my amplifiers. It's not clear to me why these operating conditions are popular, other than a willingness to sacrifice distortion for output power. I would urge you to play with the load line to determine the power supply voltage and idle current that will produce the best sound with this transformer.
If you don't know how to use the calculator below or don't have time, post your intended operating conditions and I'll run it.
Load Line Calculator
Jack
You can get low THD and good power with 350V and 5k load, despite your simulations. I typically get < 0.5% THD @ 1 Watt/8 Ohm. The driver operating point also will determine final THD numbers.
And no... there is nothing wrong with my test equipment or set-up, it is accurate.
The WE data sheet indicates a limiting value of 5% THD will occur at 7W output if zero-signal plate current is 60mA (fixed bias) and the load is 4K. Operating the tube at 410V/80mA provides a marked improvement, but it's still not as linear at 3.5K as it would be with a higher-Z load. The load line for your operating conditions is below. The shaded area represents operation with a signal excursion that reaches 0V at the grid (the limit for an A1 amplifier). Distortion is a little above 4% and output power about 11W.
The image below shows the same no-signal conditions (410V/80mA) but with an 8K load. Note that the load line is now much closer to horizontal. The shaded area represents a lower maximum output power of about 5.7W, but THD is now 1.3% instead of 4%.
Finally, just to demonstrate that this isn't all due solely to output power differences, here is the same load line as the first one (3.5K load) but with output power at 5.7W. Despite the fact this represents an excursion that never touches zero grid volts, distortion has increased from 1.3% (8K load) to about 2.4%.
I don't understand the relevance of your post. The importance of the "first watt" is understood, but many tubes can provide good numbers at small excursions.
Jack
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I just installed some new production 3.5K 30W ISO Tango iron on my "Budget DIY 300B amp". Yeah it's no longer a budget model, but these transformers are awesome! I was using some Edcor 5K 25W units previously, trying to keep the price down, but this new iron elevated this amp to a whole new level of sonic goodness.
425V on the plate, 65V on the cathode with a 880 ohm cathode resistor using 300B-Z tubes. I know some people on this forum have made it very clear they think the 6SN7 cascode driver I used in my zero feedback circuit are all poor design choices. Not gonna argue with them because I've listened to this amp, as well as many other people who have built it and I know how good it sounds
The measurements start around the 8 minute mark. I'm never using more than about 3W maybe 4W and the THD vs frequency with this iron at this power level, leaving plenty of headroom for transients, just sounds insanely good to my ears.
425V on the plate, 65V on the cathode with a 880 ohm cathode resistor using 300B-Z tubes. I know some people on this forum have made it very clear they think the 6SN7 cascode driver I used in my zero feedback circuit are all poor design choices. Not gonna argue with them because I've listened to this amp, as well as many other people who have built it and I know how good it sounds
The measurements start around the 8 minute mark. I'm never using more than about 3W maybe 4W and the THD vs frequency with this iron at this power level, leaving plenty of headroom for transients, just sounds insanely good to my ears.
Yep, why I think money is better spent on good iron than trying to upgrade lesser iron with expensive parts.
I like seeing the third order line being much lower than the 2nd order, which in turn will make the third order much lower than the total THD. This is as much a factor of the tubes used as the transformer. Also I usually test this at about 1/2 the amps power. Even if you "only use 1W", transients are going to demand more than this.
Nearly all SETs produce more 2nd, due to the inherent asymmetry of tubes. What's more important to know - especially in a Chinese amplifier where the iron is always suspect - would be high frequency response and low frequency power bandwidth. The latter is the weak point of many SETs, even those with good quality iron.
Is this intended to be used with a high-pass filter and a subwoofer? Even so-called high-efficiency speakers will likely need more than this to cover low frequencies satisfactorily.
Jack
It's very difficult to read the numbers on most of those images. Can you perform screen captures instead?
In that case, you will be certainly be operating well over 1W. Cornwalls are no more efficient in the bass region than many other speakers. I know, I've owned them, and I sold them for that reason.
Jack
setup1
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FWIW, I've used the HC203U + H-203S for 2A3 amps, and more recently, the H30-3.5S in Komuro-inspired SE300B mono blocks.
IME using Japanese output transformers, as one goes up in price, the core size and quality is improved as well as extending bandwidth at both frequency extremes.
The 300B mono block amps in action.
Just curious, is this the same Wilsenton amplifier that StepheK tested? The relatively flat distortion all the way down to 30Hz seems optimistic to me, but I haven't read through all the posts.
He is testing it at 1W...
If that's real, there's no reason to replace the transformers. I'm highly suspicious of those numbers though.