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Rectifier rolling


michaelwjones
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On 11/4/2022 at 9:25 AM, captainbeefheart said:

Here is the Delon full wave doubler circuit, I'm sure you have seen it before.

 

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The Lafayette Stereo 250A uses this very circuit, except the cap values are 250uF.

It runs a quad of EL86, which (I think) draw a bit more current than EL84.

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IF your end goal is performance nothing beats regulation. Here, it even uses a tube pass device. Since it's regulated go ahead and use a tube rectifier it won't change performance.

 

<100mOhm output impedance and <300uV noise. 

 

See we can use tube rectifiers and even tube pass devices AND get excellent performance.

 

 

https://audioxpress.com/article/t-reg-a-high-voltage-regulator-for-tube-amps

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18 hours ago, 82 Cornwalls said:

???


 

I deleted more info on my previous post after you made your post with ??? being I do not believe you really want more info on this subject from me. What I posted with the video is not something that concerns an audiophile because the effect mentioned in the video is not something you will hear or should be concerned about. I think your question mark post was just something personal for some reason against me. Sorry, it is just the way I feel. 

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16 hours ago, michaelwjones said:

 

Actually I started this thread on rectifier rolling and as I acknowledged in a subsequent post plug-in SS rectifiers had been considered. After reading the posts, it affirmed my lay conclusion that due to the nearly instantaneous availability of higher voltages. a SS rectifier is best in a circuit designed for SS rectification.

Going to plug-in SS rectifier when you amplifier was designed for tube rectification is not something I would recommend without checking, changing the bias of your amplifier either yourself or using some electronic geek or shop. Chances are, if your amplifier is biased conservatively you will be OK but the only way to be sure is by doing some testing. Using a plug in SS rectifier is going to increase the voltage on your rails a considerable amount, 30 to 40v's. 

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5 hours ago, henry4841 said:

Using a plug in SS rectifier is going to increase the voltage on your rails a considerable amount, 30 to 40v's. 

 

Or more.

 

If your amp has a 5Y3 rectifier the impedance is nearly 500 ohms compared to 5AR4 of maybe ~80 ohms.

 

Typically in 6V6 or 6BQ5 type amps with a DC load of ~100mA, that's 50v lost right off the bat. Those amps are typically cathode biased and running near max plate dissipation already. With 48mA and 250v on the plate, if you add another 50v bias is going to shoot those power tubes well past their max plate dissipation. Now your looking at 300v and 60mA, 18 watts plate dissipation with a 12 watt tube will red plate and not last very long.

 

I 100% agree with Henry in that unless you  know what you are doing or have checked with the  manufacturer of your amplifier do not swap around rectifiers. I was sort of under the impression this was an engineering discussion about when designing an amp why choose tube or SS. But there is also the conversation of having an existing amplifier most likely with a tube rectifier and you want to try a SS plug in. I never new they were that popular but it appears a lot of people are buying these things.

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On 11/8/2022 at 6:27 AM, henry4841 said:

You are to be commended for doing real world test and not just simulations on some software which is what one mostly sees on forums these days. 

Well thanks!

 

I have some experience with this topic and found the topic worth the effort.

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On 11/8/2022 at 1:19 PM, captainbeefheart said:

First is these people doing these changes aren't going to step the voltage down on the primary. I see what you are trying to do which is create the same operating point for the circuit in order to compare just the rectifier and not the changes made to the operating conditions around the tube. E.g. higher plate voltage and current if bias isn't adjusted.

 

This leads to a completely new problem created by reducing the primary voltage so low. The tube heaters are now running low, for 117v to 6.3v secondary at 111v the heater will be now ~5.8v. This is most likely lowering emissions and subsequent transconductance of the devices.

I had considered this.  I've been noodling selling a revised embodiment of this amplifier and, to know how it behaves over a range of operating conditions becomes an issue.  The performance with a tube rectifier from 110 to 125VAC on the primary is largely unaffected based on what I've measured.  

 

So, what's unaffected mean?  Power v. %THD at 20, 500, 1,000, 5000, 10000Hz similar, FFT of components similar, sound same.

 

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  • 2 weeks later...
On 11/8/2022 at 6:27 AM, henry4841 said:

You are to be commended for doing real world test and not just simulations on some software which is what one mostly sees on forums these days. 

Ok, here's a forum dedicated to this sort of thing. 

 

I've put it on my site.  I'll perform various amplifier, network or loudspeaker test if they provide value and are interesting (to me!).   I have a well-equipped test bench/lab and can perform measurements in electrical and acoustical domains.  Always looking to add capacity to the lab as well and, should a test require a special instrument or setup, will get it. 

 

The link is below, no ads and guests can view attachments.  If it becomes a bot magnet or just becomes a drag it'll go away.

 

https://www.northreadingeng.com/forum

 

 

 

 

 

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3 hours ago, Bubo said:

My EE Chip Designer Friend RIP who was way into Tubes at one point.

 

On his amps, he said the first hing he did was pull the rectifier tube, and stick two diodes into the sockets,

FWIW

A few of the McIntosh service shops were doing the same thing with tube amps that came in for work.  The rectifier was pulled and replaced with a plug in.  The rectifier tube was returned in a white box.   

 

I know because I was a technician working on them back then (late 70s). 

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2 hours ago, John Warren said:

A few of the McIntosh service shops were doing the same thing with tube amps that came in for work.  The rectifier was pulled and replaced with a plug in.  The rectifier tube was returned in a white box.   

 

I know because I was a technician working on them back then (late 70s). 

When did McIntosh go with SS rectification in their tube amplifiers ? 

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It could be, more likely, you like the amplification design in the MC30 and not the type of rectification.  I probably love the sound of one amplifier that others would not like at all. Reason for so many different types of amplifiers on the market. This hobby is entertainment and not all science. 

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