What's your ideal starting voltage?

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VaporDemon
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Just wanted to get an idea what people shoot for as an initial B+ voltage post rectification. Or even what you prefer on the high voltage winding at the transformer. Specifically in a modern high gain application. Even a range would be informative. This can be a new amp build or for modding. Working on replacing a PT in an amp and found a couple possibilities but not sure what might be too low for a modern high gain amp. original PT was around 700 volts on the high voltage winding and voltage after the main dropping resistor was around 460 volts and I'm considering bringing that up a bit but I would like to have some input from builders/modders that have some experience. Thanks in advance!
 
700vdc mains supply after being rectified? And 460vdc after the dropper? Or do you mean 700vdc at the high voltage secondaries (50 watt I assume) and 460vdc after rectification?

460 vdc B+ is plenty if that’s with tubes loaded. Start going higher and you run into tube screen reliability problems, especially if you’re using el34’s. You can go up to 480vdc or so but I wouldn’t go past that.

Depending on your circuit and desired result, you’ll probably want to run anywhere from 340-400vdc to the preamp section, measured at the dropping resistors after the screen supply. 460vdc mains supply will get you there no problem.
 
I got reading about how to spec a transformer Monday so I’m completely new at this but isn’t 700v insane?
Or are you talking a 350-0-350 winding?

If so I get 495v before the diodes. And 490v B+.

Again I’m new. So if I’m off I’d appreciate you explaining it to help me out.
 
700vdc mains supply after being rectified? And 460vdc after the dropper? Or do you mean 700vdc at the high voltage secondaries (50 watt I assume) and 460vdc after rectification?

460 vdc B+ is plenty if that’s with tubes loaded. Start going higher and you run into tube screen reliability problems, especially if you’re using el34’s. You can go up to 480vdc or so but I wouldn’t go past that.

Depending on your circuit and desired result, you’ll probably want to run anywhere from 340-400vdc to the preamp section, measured at the dropping resistors after the screen supply. 460vdc mains supply will get you there no problem.
700vdc mains supply after being rectified? And 460vdc after the dropper? Or do you mean 700vdc at the high voltage secondaries (50 watt I assume) and 460vdc after rectification?

460 vdc B+ is plenty if that’s with tubes loaded. Start going higher and you run into tube screen reliability problems, especially if you’re using el34’s. You can go up to 480vdc or so but I wouldn’t go past that.

Depending on your circuit and desired result, you’ll probably want to run anywhere from 340-400vdc to the preamp section, measured at the dropping resistors after the screen supply. 460vdc mains supply will get you there no problem.
Hey thanks for the reply! Yeah it was 350-0-350 on the high voltage secondaries pre rectification and then 460 was after the dropper. It’s a Jet City 50. I found an Edcor PT that’s 360-0-360 which is what the proper spec is for that jet city 50 but I’d have to do a work around to power the switching circuit. They also have one that is exactly what I need for all the secondaries except the high voltage secondary is 345-0-345 and I’m wondering if that might be a bit low as a starting point. As far as what I’m going for, my goal is to get it somewhere between modern modded Marshall and SLO. I already did the SLO mod but I’m hoping to tighten it up and get it a bit more modern.
 
I got reading about how to spec a transformer Monday so I’m completely new at this but isn’t 700v insane?
Or are you talking a 350-0-350 winding?

If so I get 495v before the diodes. And 490v B+.

Again I’m new. So if I’m off I’d appreciate you explaining it to help me out.
Thanks for the reply! Sorry I was referring to a 350-0-350 pt like you said. I was getting a reading around 700 on the secondary from one 350 to the other. And it was 460 after the main dropping resistor but that PT blew a week after those readings were taken.
700vdc mains supply after being rectified? And 460vdc after the dropper? Or do you mean 700vdc at the high voltage secondaries (50 watt I assume) and 460vdc after rectification?

460 vdc B+ is plenty if that’s with tubes loaded. Start going higher and you run into tube screen reliability problems, especially if you’re using el34’s. You can go up to 480vdc or so but I wouldn’t go past that.

Depending on your circuit and desired result, you’ll probably want to run anywhere from 340-400vdc to the preamp section, measured at the dropping resistors after the screen supply. 460vdc mains supply will get you there no problem.
I forgot to mention the 460 was with tubes in.
 
I think the way you worded it made it a little confusing.

The first dropper in the B+ circuit is the resistor from screen supply to preamp supply. And that should be somewhere in the mid 300’s to 400vdc or so. I think what you’re referring to as “dropper” is the rectifier circuit.

In a 50w, the voltage does “drop” from 700vac or so to high 400’s vdc. But it’s the rectification that changes the voltage, not a dropper. A 100w will be opposite, rectifying mid 300’s vac to high 400’s vdc. Full vs half wave rectification.
 
Just wanted to get an idea what people shoot for as an initial B+ voltage post rectification. Or even what you prefer on the high voltage winding at the transformer. Specifically in a modern high gain application. Even a range would be informative. This can be a new amp build or for modding. Working on replacing a PT in an amp and found a couple possibilities but not sure what might be too low for a modern high gain amp. original PT was around 700 volts on the high voltage winding and voltage after the main dropping resistor was around 460 volts and I'm considering bringing that up a bit but I would like to have some input from builders/modders that have some experience. Thanks in advance!
You’ve already got probably the most well informed response you’ll get here via @RedPlated. I’ll just add that like many things there is a law of diminishing returns. Don’t push it. IMO with current production tubes it doesn’t make a lot of sense. Don’t exceed 480vdc at idle unless you intend to always variac the AC voltage. Not worth it.
 
I think the way you worded it made it a little confusing.

The first dropper in the B+ circuit is the resistor from screen supply to preamp supply. And that should be somewhere in the mid 300’s to 400vdc or so. I think what you’re referring to as “dropper” is the rectifier circuit.

In a 50w, the voltage does “drop” from 700vac or so to high 400’s vdc. But it’s the rectification that changes the voltage, not a dropper. A 100w will be opposite, rectifying mid 300’s vac to high 400’s vdc. Full vs half wave rectification.
Yeah sorry about the wording man sorry about that. I was definitely rushed when I posted. I also got my numbers wrong, So the 700V was AC from one 350 lead to the other I was just checking the transformer to see what it would measure to see if that was close to spec. In the attached schematic I got 462 vdc right at the output of the rectifier. Just after the choke it was 456 vdc. The dropper I was referring to was the main dropper which is R12 in the schematic and the actual reading was 392 vdc just after the resistor. Sorry for the mix up, I was having a rough day. The PT went a week later so at this point I'm going to just replace it but my thinking was get some input before I buy one just in case someone might suggest I bring the voltage up a bit. Thanks for your help man, I appreciate your time.
JCA50HPS.jpg
 
You’ve already got probably the most well informed response you’ll get here via @RedPlated. I’ll just add that like many things there is a law of diminishing returns. Don’t push it. IMO with current production tubes it doesn’t make a lot of sense. Don’t exceed 480vdc at idle unless you intend to always variac the AC voltage. Not worth it.
Thanks for your reply! Yeah I'm definitely fine keeping it at factory spec. If you check my last reply to RedPlated it explains my situation a tad more. I messed the whole original post up and got all my numbers wrong too. Just have to be more careful before I post next time.
 
You’ve already got probably the most well informed response you’ll get here via @RedPlated. I’ll just add that like many things there is a law of diminishing returns. Don’t push it. IMO with current production tubes it doesn’t make a lot of sense. Don’t exceed 480vdc at idle unless you intend to always variac the AC voltage. Not worth it.
+1
 
So i just wanted to throw this out there if anyone would like to give me their opinion. In my search for a replacement PT, I found a couple options and its basically one that's a direct drop in "upgrade" and a couple others that would require some small modifications to use.

#1 - Mercury Magnetics, Direct drop in for both mounting/dimensions and wiring, the heater winding is an upgrade at 7A, the high voltage winding is 370-0-370 at 160mA but not sure how that current rating compares since i'm still learning how to calculate power supply requirements, very pricey at $333 plus shipping. I know a lot of people say to avoid them due being overpriced?

#2 - Edcor - Definitely reasonable price wise, fairly close for mounting and size, also 7A for the heaters, 360-0-360 at 220mA, 70v winding for bias which would work for my application, but I would need to either use an external 12v supply for the channel switching circuit or change my relays to 3 or 5 volt relays and use the extra 5v winding for channel switching. Cost is $154 plus shipping.

#3 - Edcor - Also close for mounting and size, 7.5A heater winding, 12v 500mA relay winding, a 60v bias tap, except the high voltage winding is 345-0-345 at 400mA so higher current but lower voltage. $160 plus shipping.
 
Before I’d pay $350 for MM I’d buy the set of 3,50watt o’netics for the same price. Already specked for a soldano 50w slo.
 
700v secondaries is what I use for a 50w build. I shoot for a B+ of around 480v. What you drop this down to for the rest of the B+ nodes is personal preference. I make sure to keep V1a plate voltage higher than 160v.
 
Before I’d pay $350 for MM I’d buy the set of 3,50watt o’netics for the same price. Already specked for a soldano 50w slo.
Yeah! Those are a great price for SLO spec and it’s a complete set. Putting that on my list of possibilities for sure.
 
700v secondaries is what I use for a 50w build. I shoot for a B+ of around 480v. What you drop this down to for the rest of the B+ nodes is personal preference. I make sure to keep V1a plate voltage higher than 160v.
Great info thanks! In stock configuration V1a is at 187 at pin 6. When taking voltage readings on the plate should I be grounding the other test lead or measuring between cathode and plate?
 
Amp makers that:
- Demanded wire transfer payment on the balance due to their Step-Daughter's German bank account in order to evade the financial authorities and then sabotaged that very same product with circuit destroying epoxy resin.
- Sold tubes worth 440 EUR to a loyal customer but refused to ship them, which resulted in a 5 YEAR odyssey to get his money back.
- Sold a fully rebuilt custom amp to another loyal customer that had design flaws and parts that made the amp break down 10 days after receivership, which resulted in the customer paying almost half a grand USD out of pocket to fix it.

All of the above are the actions of @novosibir aka Helmut "Larry" Grohmann of Larry amplification. Do you really want someone only 7 years younger than Joe Biden and with a self admitted malignant narcissism disorder (like D*n*ld Tr*mp) building your amp? Buyer beware!
If you read the signature of this frustrated, bitter pensioner who is filled with hatred and envy of my life without thinking, then some people might initially get the impression that I am a despicable person from whom it is better to keep a distance...

... in any case, that would correspond to the longing wish of this obviously psychopathic person and the real events only become clear once you have heard the response from the other side, my side, in addition to his subjective, falsified and drastically dramatized presentation.

In any case, I doubt the mental health of this senior citizen if events that happened 13 years ago and through which he suffered no disadvantage or damage are still burning in his soul so much today that he sends them out into the world through his signature, fanatically like a sex offender, with the sole aim of doing me the greatest possible harm and dragging my reputation through the mud.

Below I will examine the details and then ask you to use common sense to judge how mentally ill someone appears to be who, like a defiant preschool child, cries and denounces 13-year-old events that a normal-thinking person would only laugh at:

"Demanded wire transfer payment on the balance due to their Step-Daughter's German bank account in order to evade the financial authorities"

We used to have frequent financial transactions in the past, but here I had asked him once to transfer the money to another account this time and it was for another reason than he claimed.

This didn't put him at any disadvantage and it didn't cost him a single cent more.

Why is he crying about it now 13 years later and wanting the rest of the world to know about it?

Does he really think others will find this information interesting? How mentally ill is he really?

"and then sabotaged that very same product with circuit destroying epoxy resin"

The partially epoxy covering did not damage the circuit, but actually had a protective function for the components and is comparable to how H. A. Dumble completely covered his circuits with goop.
The reason for this at that time was so that his then best friend Mike Fortin, near whom this grandpa lives, would not again drill his curious eyes into my then very current circuit of my preamp and not copy another Larry circuit and then use it as his own development presented, just as Mike Fortin had done several times before.

I only had the 'top secret' area of my preamp cast with resin. See for yourself and judge how 'destructive' this was:

200_3264.jpg


By the way, I recently heard from someone that Mike Fortin had promised him a certain amount of money and other benefits if he brought his Larry preamp to him for re-engineering after receiving it. This was no longer possible after my copy protection. Did that upset him?

"Sold tubes worth 440 EUR to a loyal customer but refused to ship them, which resulted in a 5 YEAR odyssey to get his money back"

This has NOT HIM affected, but someone else. I didn't send the tubes he ordered because the other person bad-mouthed me on another forum and so I transferred his money back to him.

A few years later, the other person complained that he hadn't gotten his money back.

I could no longer prove the repayment because I had Wirecard Bank at the time, which has since been liquidated and I no longer had access to past transactions online.

Just for the sake of peace, I transferred this 440 EUR to the other person again.

But if that was the only thing Grandpa found to criticize from my transactions over the past 13 years, then I'm really good and it would be a mark of quality for me.

Other manufacturers sometimes have 100 cases of discrepancies in payment transactions within 13 years - and if there was another case, Grandpa would know about it, because he has been spending a lot of his time for several years researching my life in CIA style and probably knows about it even my shoe size.

Again, how mentally ill does a person have to be to waste so much energy trying to portray mosquitoes as elephants on the Internet?

"Sold a fully rebuilt custom amp to another loyal customer that had design flaws and parts that made the amp break down 10 days after receivership, which resulted in the customer paying almost half a grand USD out of pocket to fix it"

Ouch, how to make a long story short? Ok I'll try my very best.

Grandpa had bought a Marshall amp in Hamburg on eBay Germany, which I rebuilt to a 3-channel amp already in 1994 and initially just wanted the amp to be checked and serviced by me, so the seller sent it to me.

When the amp was with me, grandpa had new modding ideas almost every day, which he discussed extensively with me and it ended with me rebuilding the amp from scratch based on Dino 939 and he even wanted the original Marshall/Dagnall trannys replaced with my Dino trannys.

That was a pilot project for me to build a unique piece, for which I had to design a lot of new things just for this single amp, since the conditions in a Marshall chassis are completely different than in a Dino chassis.

Preamp tubes are at the back and not at the front like on the Dino, input is on the right and not on the left like on the Dino, trannys are both on the right and not right/left like on the Dino, etc. etc.

When the amp was in his hands after the complete rebuild, one of the filter caps failed 10 days later - but for cost reasons it was previously agreed not to change the old electrolytics after they showed me good readings, but that doesn't mean a guarantee. Why is he still crying about it still today?

A little later, Grandpa complained that when the gain was fully turned up in the British or Scream channel, a slight cross-talk could be heard in the Clean channel. A phenomenon that didn't appear here for me, otherwise I wouldn't have sent the amp. It wasn't my ears either, because before sending it, other guitarists with good ears had also played the amp and found it perfect.

But no matter, I simply believed him and in order to save him the high costs of shipping the amp back to Germany and back to Canada, I made a special board with a relay and sent it to him with very detailed instructions for installation.

Anyone with even a little bit of mechanical skill could have installed the board himselv within an hour and only 4 cables had to be soldered on.

Grandpa however was apparently too fine for it and had it installed by a technician who probably saw on his face that he was being ripped off regarding the costs?

As a thank you for everything and for more than 200 emails back and forth I now can read his signature dripping with hatred and bitterness under each of his posts? But it's not just me - he's so malicious that he wants everyone in the world to read his subjective, falsified and distorted version of history.

But he forgot that I had deducted about 20% of the actual costs to be calculated with the costs for the new rebuild - just so that the costs for the rebuild together with the costs for the amp he has payed wouldn't be too close to the price of a real Dino.

How can you help such a frustrated, bitter and mentally lost person to see things clearly and realistically again? Unfortunately, he is already too old for psychotherapy to be promising - this is over by the age of 40 at the latest, after which you are resistant to therapy. Yes, I know that, because I also used to study psychology in the past.

He's just a pathetic and pitiable person, this thegame, and now I feel more sorry for him than I can be angry with him. He doesn't have a good life, otherwise he wouldn't be like that.

Finally, I would like to apologize to all of you in advance for the future.

I don't want to bother you with my posts, but I don't know in advance who will read a post from thegame for the first time and therefore read his signature for the first time, so unfortunately I have to quote his posts every time the game publishes a post with this signature in the future and explain it with this text – until perhaps enlightenment comes to his brain and he changes his signature.

I'm really sorry guys, but there's no other way.

Please understand and just scroll over this post if you already know it.

Thanks!

Larry
 
 
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