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VRD Mono Blocks


muel

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Craig:

No doubt the streets of those old forum days were often bumpy and still mostly unpaved. But listen, so you don't have to guess the reason or 'motive' behind the question I asked, let me explain: For one, I am not in the least bit interested in pointing out the limitations of anything (well, that's not entirely true in a certain respect, but I'll get to that...). Every design involves a balancing out of compromises and choices, and my intention was not to describe, reveal, or point out the limitations of cap input ripple filters. They can be just as good as power supplies with a choke after the rectifier.

I was going to share that there were a couple of occasions many years ago when I had experienced the same thing with that particular rectifier (GZ37, Mullard). Depending on the amount of input capacitance in use, it can be sensitive to possible failure, just as can any valve rectifier that's working into capacitance well beyond that for which it's rated. And that you already know this was not in contention, either. I knew it at the time,too, and just forgot to double check. I'm human; I made a mistake. What you explained above reminded me of my situation.

I made the mistake of sort of 'poo-pooing' the specs on that valve, which I think specifies a max cap input value of only 4uf (I think....I'm going from memory but it's been a long time). I used it in an amp I had made some changes in, which previously used both a 5AR4 and subsequently significantly higher capacitance. The GZ37 failed fairly quickly, and I had just bought it -- you know those Mullards can be expensive.

Most of what I have learned about tube audio electronics has come from my own research; from what others who know (and still know...) considerably more about it than do I; and to a great extent from my own mistakes and failures. This was one such failure, and I was disappointed. The GZ37 is not only a really fine rectifier, it's also a very elegant-looking one!

Edited by erik2A3
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Erik,

Well I put little faith in man written specs so I always field test. The testing I did with all these rectifiers was to confirm which would work without issue or changes in my amplifiers so I could better advise my customers. I'd rather fry an expensive tube myself then have a customer do it carelessly rolling different rectifier types with wreckless abandon

The information on the internet is very merky to say the least on this subject. For instance Upscale audio talks up the Phillips 5R4GYS as a perfect 5AR4/GZ34 plug in replacement which is total BS.....The examples this type of misinformation are endless....

Edited by NOSValves
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  • 2 weeks later...

After a few months of driving Craig nuts I placed my order today for a pair of VRD's :) I heard nothing but good about these mono blocks and cant wait to pair them with my NBS

Prepare to be amazed!

Which coupling caps did you decide on?

Edited by jorjen
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After a few months of driving Craig nuts I placed my order today for a pair of VRD's :) I heard nothing but good about these mono blocks and cant wait to pair them with my NBS

Prepare to be amazed!

Which coupling caps did you decide on?

Jupiter Copper

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" we should have ordered them together " okay now your creeping me out :tongue: I'm hoping to see them by the end of August cant wait

economies of scale my friend!

I can not wait to hear the review. keep us posted.

Edited by Schu
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" we should have ordered them together " okay now your creeping me out :tongue: I'm hoping to see them by the end of August cant wait

economies of scale my friend!

I can not wait to hear the review. keep us posted.

economies of scale that was not going to happen trust me :)

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