• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

SVP and FVP preamp builders

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#41
I still plan on trying more experimental ideas. Like more jfets or another device, maybe one than can do more current. Just looking at taking the “ if some is good, then more is better” approach

might even move away from Allen’s schematic and try Patrick Turners. The way I build now, all I have to do is build different modules. I just dial in the voltages I need.

also different tubes to try.
 
#42
rchamber said:
P.S. For other makers who are using Super Regs...are you using one for both channels, or two, one for each? What Op Amp to replace the LF351 that shows in TPCB. 2nd Ed?
Click to expand...

Robert,

Both my SVP and RTP3 have SuperRegs that I bought as kits from VSE. And I used one per channel, reflecting the dual mono PSU I use for each of the preamps.

I replaced the LF351 in all of mine with AD797, as suggested in the manual, and also carried out the "LM317 begone" mod Allen recommends in the manual, where the voltage regulator on the MOSFET in the current source is replaced with an appropriate resistor. I should add that I am impressed with the SuperRegs, as they have proved very stable and reliable over the five or six years since I installed them.

Alex
 
#43
I purchased one SuperReg about 20+- years ago, and at the same time purchased both of Allen's books...my copy of TTPCB is Second Edition, but long before the instructions recommended replacing the LF351 with AD797 and the "LM317 begone" mod. I have recently visited the Vacuum State website with the thought of purchasing a second SuperReg which would include the updated instructions...when I reach the website I am informed that it is not secure and when I try to purchase a SuperReg I get all kinds of red flags about compromised security. I have tried to contact Vacuum State about this via info@vacuumstate.com and the three USA listings of World Wide Agents, maybe more, and have received no replies.

I am unable, at least for the moment, to find the instructions included with the SuperReg kit I purchased long ago, so only have what is in TTPCB V2.

I am pretty sure I could build a second SuperReg on perf board if I could obtain a copy of the instructions included in the later kits. Could anyone help me with this? If so, please send me a PM.

Thanks and Best Regards, Robert
 
#44
rchamber said:
I purchased one SuperReg about 20+- years ago, and at the same time purchased both of Allen's books...my copy of TTPCB is Second Edition, but long before the instructions recommended replacing the LF351 with AD797 and the "LM317 begone" mod. I have recently visited the Vacuum State website with the thought of purchasing a second SuperReg which would include the updated instructions...when I reach the website I am informed that it is not secure and when I try to purchase a SuperReg I get all kinds of red flags about compromised security. I have tried to contact Vacuum State about this via info@vacuumstate.com and the three USA listings of World Wide Agents, maybe more, and have received no replies.
Click to expand...
Robert,

I just went onto the VSE site from my MacBook Air (MacOS Catalina) and went as far as adding a SuperReg kit to my basket, and had no security warnings. The problem may lie with your security and privacy settings.

Alex
 
#45
rchamber said:
when I reach the website I am informed that it is not secure
Click to expand...
FireFox on Win7, adding https:// to vacuumstate.com, I get "Firefox does not trust this site because it uses a certificate that is not valid for vacuumstate.com. The certificate is only valid for heaven.mac-web.ch."
In Chrome, I get "Your connection is not private
Attackers might be trying to steal your information from vacuumstate.com (for example, passwords, messages, or credit cards). Learn more
NET::ERR_CERT_COMMON_NAME_INVALID
This server could not prove that it is vacuumstate.com; its security certificate is from heaven.mac-web.ch. This may be caused by a misconfiguration or an attacker intercepting your connection."

https://heaven.mac-web.ch/ seems to be/was the website creator/maintainer for vacuumstate.com, but they should not be on the same certificate. That's a significant lapse for a web-seller.

I don't think it is a hack. I think nobody is minding the store.
 
#46
I just accessed the Vacuum State website on a MacBook Air and found the same indication that it is insecure. When I add https://, Firefox says, "Firefox detected a potential security threat and did not continue to vacuumstate.com. If you visit this site, attackers could try to steal information like your passwords, emails, or credit card details." Exactly the same as on my usual Dell XPS 13.

I just sent an inquiry to Joe Rasmussen.
 
#48
rchamber said:
Hi handwound et al,

The gain of the phono stage can be varied to suit the phono cartridge, MM or MC, to produce a line level output voltage comparable to the voltage levels of other sources in-systeme. In other words, the gain of the output stage is not key to achieving adequate output for a MC cartridge.

Allen covered this in his notes on the FVP5A/SVP1 schematic: "R2 sets the phono stage gain and can range from 15R to 150R. Typically 47R for most MC's ." He also noted on this schematic: "For MM usage set R1 at 100R and change the 392R in the second cathode to 1K6." I think he meant to say ...set R2 to 100R... as evidenced by his note for the FVP5: "R2 can range from 150R down to 15R, which adjusts the phono gain from 40dB up to 60 dB - with no side effects. MM or MC, your choice." Also, R1 shows as the cartridge load in both schematics. In his notes for the FVP5 he did not, however, mention the change of the second phono valve cathode resistor to 1K6. So he left us with some questions; has anyone built for MM phono?

RC
Click to expand...
Has anyone built the FVP5A and the phono stage section load it with a 0.5 mv mc cartridge?
Is the 2SK170 in stable mode with resistor R2=15R for 60db gain?
How is the sound quality of the phono stage?
 
#50
demetrios said:
Has anyone built the FVP5A and the phono stage section load it with a 0.5 mv mc cartridge?
Is the 2SK170 in stable mode with resistor R2=15R for 60db gain?
How is the sound quality of the phono stage?
Click to expand...
I have used mine with 0.5mV Lyra cartridges, but with 47R in the input stage. The phono stage sounds excellent - similar to my RTP3, but slightly more "beefy" and less spacious, though I would claim that that is exclusively a result of the phono stage topology.

Alex
 
#52
rchamber said:
...
I haven't seen that...could you amplify with some explanation or...even a schematic?
Click to expand...
Over the years of building different pre amps , but all mostly Allen’s design. I realised a couple of things. The power supply means more than what I thought it would. Allen’s design of the FVP was for four valves was a design constraint. What if we used different topology’s, but maintained the giant power supply. Patrick believes his was better than Allen’s, I have healthy reservations on that. I would need to compare. I met Patrick, but not Allen. Though I have met Joe. Patrick is very matter of fact. So much so that someone complained about his services that he has no “wu” I prefer not to get caught up in mysticism.

there is a link to Patrick site somewhere here. I will see if I can find it
 
#55
handwound et al,

Well, that link should solve the mystery of Patrick Turner's Rocket phono stage and more,,,that certainly covers my inquiry...thank you! Even so, I would opt to build Allen's FVP5A/SVP1 , as presented in the TPCB Vol. 2, first. The big black hole in Allen's presentations is the lack of anything significant about the power supply except for his admonition for choke input...otherwise O.K.. I would opt for LCLC, and perhaps an AZ1. As for how to load for which phono cartridge, that will have to come later...I have a new EMT TSD SFL which has output of 1.05mV to try.

Robert
 
#56
rchamber said:
handwound et al,

Well, that link should solve the mystery of Patrick Turner's Rocket phono stage and more,,,that certainly covers my inquiry...thank you! Even so, I would opt to build Allen's FVP5A/SVP1 , as presented in the TPCB Vol. 2, first. The big black hole in Allen's presentations is the lack of anything significant about the power supply except for his admonition for choke input...otherwise O.K.. I would opt for LCLC, and perhaps an AZ1. As for how to load for which phono cartridge, that will have to come later...I have a new EMT TSD SFL which has output of 1.05mV to try.

Robert
Click to expand...
I think the FVP in TPCB is a much older version than is on the vacuum state website.
 
#57
handwound said:
I think the FVP in TPCB is a much older version than is on the vacuum state website.
Click to expand...
The one I built is this one, which I retrieved from the VSE website a while back. I don't have my TPCB to hand to compare it to.

Alex

FVP5a.gif
 
#58
Just something to also consider. On the schematic there is no cap across the input jfet like in older FVP drawings. I recommend putting one in. It stops if from picking up AM radio. I am also considering a THINGY instead of the voltage divider floats. I have 3 different float voltages in mine. I taken them all off one divider. It’s the one in the phono stage that I think the THINGY would be required.
 
#59
handwound said:
Just something to also consider. On the schematic there is no cap across the input jfet like in older FVP drawings. I recommend putting one in. It stops if from picking up AM radio. I am also considering a THINGY instead of the voltage divider floats. I have 3 different float voltages in mine. I taken them all off one divider. It’s the one in the phono stage that I think the THINGY would be required.
Click to expand...
"THINGY"?
 
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