Willsenton R300: Output Transformer Replacement, Hashimoto

[@gregj.gotham4402]

You really do great explaining of testing results which goes to the ear. Much is above my knowledge yet you are helping me understand so much. Thank you for the very fine information.

[@SkunkieDesignsElectronics]

Glad to help!

[@67bluefish]

Thanks for the video. I will be starting my Hashimoto OPT install next weekend.

[@pauljanda5262]

Incredible upgrade and great value on those Hashimotos. I'd be really curious to see how an also affordable Silk would do.

[@dtg474]

Incredibly cool Stephe!!!

[@jerryparsley2289]

Love these "Audio Autopsies"......Helps everyone understand what the quality of design work is, for these products. Wondering if your Analog Discovery pkg, includes "power response"( power to a given THD, over a frequency sweep)?( seems generally OPT-limited at lowest frequencies) Might reveal another limitation of OPTs. Thanks again.

[@SkunkieDesignsElectronics]

It will do a thd vs frequency at whatever power level you choose.

[@cobar5342]

Great deep dive Stephe. Really enjoyable By the way, the Hashimotos would cost about $1,000 per pair here in Australia.

[@SkunkieDesignsElectronics]

I'm getting a pair of Thermionic Labs OT soon. And if the ISO Tango are cheaper where you live, use them! If ANY replacement OT is gonna be 2/3 of the price of this amp, I would just sell it and move on.

[@CraigHollabaugh]

I look forward to your attempts at improving the HF ringing (mentioned 10pF cap). Thanks from Colorado.

[@SkunkieDesignsElectronics]

Coming soon! That just just an off the cuff guess on the cap needed :)

[@CraigHollabaugh]

@@SkunkieDesignsElectronics understand and won't hold you to it. 😎

[@Gullsz]

Be cool to see new opt on the Reisong A10

[@CollectingRetro]

Sounds like you got to the bottom of the WE 300B issue! That makes sense, not all remakes are actually following the original spec.

[@frankgeeraerts6243]

Indeed current remakes often ( but not allways ) are not up to the original specifications..........in this case the driver is rather the main problem than the output tubes. This amp was not designed by skilled people....neither is the commercial implemtation limiting the performance and the use of low quality transformers and other issues.

[@jackstanley3529]

Thanks Stephe for another enjoyable video. I'm wondering how the amp would perform if you removed the GNFB entirely. I built a triode connnected, cathode biased EL34 PP amp using good output transformers and zero GNFB. It is one of my favourite sounding amps and the 10kHz square wave has only a slight rounding of the corner.

[@SkunkieDesignsElectronics]

I tried this when I was wondering if the GNFB was causing the nasty frequency response dip: No, it wasn't causing the nasty frequency response dip and it added about 3-4% THD across the complete power spectrum!

[@deansayers7435]

Wow that waveform in the pic looks just like what you get from a marshall at the PI with a jose mod

[@Michlag]

Great, simply great.

[@terrydemol5354]

Awesome work! Very impressive dive into measured OP transformer performance within the context of whole amps design. I do a lot of guitar amp work and can't recall any guitar amp designers putting forth even close to what you have shown here. If I may add, it's worth checking LF distortion and waveform - for every 0.5 x freq = core mag level x 2 . Core will always be heading towards saturation at the lowest freq. Have you thought about trying a Toroidal OPT? They have very high performance at modest cost. The best - Vanderveen (Netherlands) also Toroidy (Poland).

[@SkunkieDesignsElectronics]

yeah, the problem is this circuit has other issues so I wouldn't use it to judge a transformer LF response.

[@terrydemol5354]

@@SkunkieDesignsElectronics Work in progress! :)

[@terrydemol5354]

@@SkunkieDesignsElectronics Work in progress! :)

[@jasontimothywells9895]

Wow , that frequency responce graph with the distortion is as deep as a well diggers arse . A friend of mine had one of those wileston amps and i did not think to much about it , now i wonder why the newness wore off to him after 3 days and trying a couole dozen deferent speakers . I cant wait to get the funds put together to buy some of your products when you get them available. 🥂

[@el_arte]

Hashimoto scores and wins!

[@SkunkieDesignsElectronics]

Hugely!

[@roberthurley4424]

great video! where do you get your Hashimoto transformers?

[@67bluefish]

Bought mine brand new on Ebay.

[@SkunkieDesignsElectronics]

ebay is a good source for them.

[@quysweat]

I also got a pair from ebay. Shipping takes about 10 days to Texas, usa

[@Luckiestmanalive-bb1mi]

The ringing and overshoot on the square wave tests suggests the power supply could use some tuning.

[@SkunkieDesignsElectronics]

If the Global Negative Feedback is removed, it disappears but the THD goes through the roof. A DHT amp shouldn't need global negative feedback to start with. The whole design is trash IMHO

[@jasontimothywells9895]

Awsome video my friend

[@georgeswanson9483]

Too bad you can't try a tube with more oomph but less mu than the 6SN7, the first tube that comes to my mind is the 6BL7, same pinout as the 6SN7 but less gain and much lower plate resistance (although with greater dissipation). It's not like you need all the gain this amp produces anyway and it'd do a much better job driving the 300B. Just a thought.

[@kubockferre5532]

hi i think that 5u4 gb rectifier sound better than 5ar4

[@primepreowned1]

You just can’t go wrong with any of the Japanese opt. They’ve just got it down

[@jimmysjunkyard]

This is expected result. The stock OPT is no way compared to Japanese or any other good made OPT...

[@SkunkieDesignsElectronics]

It's worse than any I have ever tested, the Boyurange A50 iron wasn't close to this bad.

[@jimmysjunkyard]

@@SkunkieDesignsElectronics i will not go with China made OPT unless from reputable source. There are some good to very good manufacturer in China, but they wont come cheap...

[@SkunkieDesignsElectronics]

My point wasn't that these other China transformers are great, but that the OT used in this "premium" amp are super poor quality, even compared to made in China amps that sell for 20% of what this one does.

[@jimmysjunkyard]

@@SkunkieDesignsElectronics well luckily that "premium" amp still "affordable".... how about that WE 300B? Vs Shuguang Treasure... 😅

[@jimmysjunkyard]

@@SkunkieDesignsElectronics btw which amp at 20% price you are referring to? Also maybe good to get another sample of those amp to make sure. Maybe your Willsenton has quality issue?