Blue Velvet Preamplifier - on it's way!

[SwedishChef]

@Lavane, have you experienced problems with JJ 5AR4 in a preamp application also? In a lowish voltage, low current application like this I would expect any old (or new manufacture) 5AR4 would do fine, including JJ. Especially if you do the “yellow-page mod with two series SS diodes”.

I believe a 5V4 will be a good alternative in this preamp, and certainly less expensive than NOS 5AR4. 5V4 is slow-warm and has just a bit more voltage drop that 5AR4; specs close to provided Chinese rectifier.

Bit of an update. I completely agree with your comment here. In fact I have read all the data sheets on the rectifier tubes and I believe the 5AR4 seems like the most stable rectifier choice. It also seems like less voltage drop will prolong the life of the rest of my tubes. I also agree about the 5V4 tube.
So I ended up finding an Amazon gift card that I completely forgot about, and I used it to snag an extremely high priced Genalex u77 / 5AR4 new production on Amazon. Should be leaps and bounds better than what it comes with.

 

[SwedishChef]

I really couldn't help myself, after snagging the Genalex u77 / 5AR4 some kind of non-stop tube buy-a-thon addiction kicked in. Bork! Bork! Bork!

Picked up a matched pair of voltage regulator OC3 from Viva-Tubes for all of $8.69 for the pair that are GE.
Then just for the heck of it I bought some nice OC3 that were NOS JAN tubes on TubeDepot that have the shoulders and are more aesthetically pleasing for $8 each. Great prices on those voltage regulators from both those sites in my opinion.

You would think my tube buying would stop here, because I have the NOS Sylvania 6SN7 pair ready to go. But it didn't stop! Another sleepless night I found myself buying the 7N7 to 6SN7 adapters. Then I was 7N7 shopping! What the heck is wrong with me?

This mainly happened because I kept seeing more and more 6SN7 NOS pairs going for these insane prices. I looked at some on eBay and Reverb, then I said "I will never pay that kind of money for 6SN7 tubes" I don't care how amazing they look or how phenomenal they sound. Or even how great they test... These people are out of their freaking minds pricing these NOS 6SN7 this high. But maybe they're not out of their minds, maybe it's the people paying these prices for NOS 6SN7 that have a few screws loose? Anyhow, the 7N7 adapters seemed like a very logical purchase to make. I found a really nice pair of Tung-Sol 7N7 that tested like NOS should test. For those of us that don't mind using adapters, I truly believe that 7N7 is a great way to get high quality NOS tubes at prices that are still reasonable and not in the stratosphere. This is coming from a tube noob perspective and the hundreds of hours spent recently reading and shopping for tubes since this thread started. If you've shopped for NOS 6SN7 recently, you would likely agree with my me.

 

[nerdorama]

Well, I wouldn't say that folks that buy expensive 6SN7's have screws loose necessarily. If they have heard them and know what they are buying, the high priced spread may be not such a bad deal for the sound they get. I have so many SN7's that I will never buy any in my life span remaining. It appears that you don't have your line stage yet and haven't heard them but you are already buying tubes to "upgrade" it. I understand how this can get exciting and cause a lot of reading and shopping. I've been there. Just try to keep the horses before the wagon and take a step at a time. The 7N7's should be great too. Not sure if it would be easy to add a filament transformer into the BV but if so then the 12V versions of these tubes are much more reasonable in price.
John

 

[SwedishChef]

Well, I wouldn't say that folks that buy expensive 6SN7's have screws loose necessarily. If they have heard them and know what they are buying, the high priced spread may be not such a bad deal for the sound they get. I have so many SN7's that I will never buy any in my life span remaining. It appears that you don't have your line stage yet and haven't heard them but you are already buying tubes to "upgrade" it. I understand how this can get exciting and cause a lot of reading and shopping. I've been there. Just try to keep the horses before the wagon and take a step at a time. The 7N7's should be great too. Not sure if it would be easy to add a filament transformer into the BV but if so then the 12V versions of these tubes are much more reasonable in price.
John

Very exciting, so yes unfortunately was carried away for a moment. I'm back to reality and stopped the buying now. Think it was just the initial excitement of getting into tubes for the first time. Tiny amps with JAN GE5654 don't count as getting into tubes.

 

[FlaCharlie]

I have read all the data sheets on the rectifier tubes and I believe the 5AR4 seems like the most stable rectifier choice. It also seems like less voltage drop will prolong the life of the rest of my tubes. . . . I used it to snag an extremely high priced Genalex u77 / 5AR4 new production on Amazon.

A lower voltage drop rectifier will actually increase the voltages on the other tubes and run them harder. The voltage drop differences between rectifiers will be less in a preamp though and will probably not change the operating points significantly. Different operating points can change the sound, however.

That's usually what people hear when they try different rectifiers and say one sounds better. If the resulting voltages / operating points were adjusted to the same levels the changes in sound would likely be minimal and perhaps even inaudible.

Not sure what you mean by "stable". In a preamp, I don't think that any of the types you've mentioned would be any less stable than another because preamps don't run them hard.

The rectifier tubes that are most often mentioned as having problems in amplifiers are the new production 5AR4s although some brands are much worse than others. Most would say to avoid the JJs although, in a preamp, even they would probably do fine.

Spending a lot for a premium 5AR4 might make sense if it's being used in an amp that stresses the rectifier but any of them should be OK in a preamp.

Picked up a matched pair of voltage regulator OC3 from Viva-Tubes for all of $8.69 for the pair that are GE.

When it comes to voltage regulators, I'm not sure how they would be "matched". Probably just the same brand.

You would think my tube buying would stop here, because I have the NOS Sylvania 6SN7 pair ready to go. But it didn't stop! Another sleepless night I found myself buying the 7N7 to 6SN7 adapters. Then I was 7N7 shopping! . . . I found a really nice pair of Tung-Sol 7N7 that tested like NOS should test.

The 7N7 is a much cheaper way to go. But you might not want to go down that rabbit hole any further and start buying all sorts of 7N7s.

Except for one type (I forget the number) all loctal tubes were made by Sylvania, regardless of the brand printed on them. Perhaps Sylvania used slightly different internal structures in some of the 7N7s, just as they did with their 6SN7s, but they're all Sylvania.

 

[SwedishChef]

A lower voltage drop rectifier will actually increase the voltages on the other tubes and run them harder. The voltage drop differences between rectifiers will be less in a preamp though and will probably not change the operating points significantly. Different operating points can change the sound, however.

That's usually what people hear when they try different rectifiers and say one sounds better. If the resulting voltages / operating points were adjusted to the same levels the changes in sound would likely be minimal and perhaps even inaudible.

Not sure what you mean by "stable". In a preamp, I don't think that any of the types you've mentioned would be any less stable than another because preamps don't run them hard.

The rectifier tubes that are most often mentioned as having problems in amplifiers are the new production 5AR4s although some brands are much worse than others. Most would say to avoid the JJs although, in a preamp, even they would probably do fine.

When it comes to voltage regulators, I'm not sure how they would be "matched". Probably just the same brand.

The 7N7 is a much cheaper way to go. But you might not want to go down that rabbit hole any further and start buying all sorts of 7N7s.

Except for one type (I forget the number) all loctal tubes were made by Sylvania, regardless of the brand printed on them. Perhaps Sylvania used slightly different internal structures in some of the 7N7s, just as they did with their 6SN7s, but they're all Sylvania.

I was aware of the 7N7 Sylvania production thing. I've slowed way down and I am not currently buying anything now. But it's certainly nice to have the 7N7 option now.

As for those OC3 was likely a selling tactic by Viva-Tubes to get rid of a massive inventory of GE voltage regulator OC3 they are sitting on. I expect the JAN tubes that look nicer will be the OC3 that I go with.

 

[Ski]

I look forward to hearing this.



Mark

 

[SwedishChef]

Was spinning records today all afternoon.
Rectifier was upgraded to Genalex u77 / 5AR4.
Kept the WY3P voltage regulators in there just for the cool glowing eyes factor, I have several sets of 0D3 waiting to test. So far no audible difference whatsoever from using different voltage regulators...
Using the Sylvania 6SN7 yellow letters I bought and they sound great!
What's kind of funny is it had way more bass punch with the metal base 6N8P that it came with. I need to determine if that extra bass was coming from the 6N8P tubes or the 5Z4 rectifier I yanked. It will be an interesting preamp to play with, and so far I am seriously loving it! Sounds so smooth and great!

Switchy Switchy Tubes ver da bestie bestie sound.
Bork! Bork! Bork!

 

[SwedishChef]

Update!

Threw some Tung-Sol 0C3 voltage regulators in there, they glow purple!
While I couldn't tell a major sound difference with different voltage regulators, I will say that it would appear that Tung-Sol and GE 0C3 are way more stable... Meaning the China WY3P that put on one hell of a light show get wicked hot after a couple of hours of continuous use. I believe the hotter they get, the more unstable they become. This is just my observation, but it seemed like after a couple of hours of use the WY3P China Orange fire rings needed a break because the sound started getting some distortion at higher frequency. Another hour or so I think I could have roasted a marshmallow over the WY3P.

I couldn't help but try the GE 6SN7GTB grey plates that were given to me free. What's funny is I like the sound of the GE grey plates better than the Sylvania pair that I paid $35 for. Go figure! The GE 6SN7GTB are definitely a brighter tube than the Yellow Letter Sylvania, and on top of being brighter sounding there's more detail and clarity up top from the GE grey plates.

For now this is the configuration I will be keeping the Blue Velvet in. Any changes or further mods I will try to keep you updated.

 

[FlaCharlie]

Threw some Tung-Sol 0D3 voltage regulators in there, they glow purple!
While I couldn't tell a major sound difference with different voltage regulators, I will say that it would appear that Tung-Sol and GE 0D3 are way more stable... Meaning the China WY3P that put on one hell of a light show get wicked hot after a couple of hours of continuous use.

Although I couldn't find a data sheet for the WY3P (Chinese data sheets are often hard to find), online sources say it's the equivalent of the 0C3 / VR105. These would produce a regulated 105v so two of them would be 210v.

The 0D3 / VR150 is the American version of the Chinese WY4P. These would produce a regulated 150v so two of them would be 300v.

What alerted me to look them up was that you commented on the purple glow of the OD3s, so I assumed the ones you replaced were a different color. Orange, maybe?? The different types use different gasses in them and they all glow with different colors.

VR tubes need to be fed with voltages that are higher than their output voltage. Assuming the voltage being fed to them is high enough that both types function correctly, what you've done by using a pair of 0D3 in place of the stock WY3P is to increase the voltage substantially and totally change the operating point of the 6SN7s.

I'm not so sure that's a good idea, depending on the circuit and the original operating point. The 6SN7s may not mind the additional voltage but it's possible that other parts might be overstressed as a result. Chinese gear sometimes runs parts very close to their limits and increasing the voltage by almost 50% could push them beyond their limits.

Are you sure both of the stock tubes are WY3Ps? I ask because I saw a reference to an unidentified preamp that uses one WY3P and one WY4P. That combination would produce 255v.

I'm no expert on VR tubes but I used one for the first time (a 0D3) in an amp that I built last year. As I recall, some precautions / measures need to be taken when using two or more in combination. I'm sure others can offer more details about them.

Here's a data sheet that covers the American VR types.

 

[SwedishChef]

Although I couldn't find a data sheet for the WY3P (Chinese data sheets are often hard to find), online sources say it's the equivalent of the 0C3 / VR105. These would produce a regulated 105v so two of them would be 210v.

The 0D3 / VR150 is the American version of the Chinese WY4P. These would produce a regulated 150v so two of them would be 300v.

What alerted me to look them up was that you commented on the purple glow of the OD3s, so I assumed the ones you replaced were a different color. Orange, maybe?? The different types use different gasses in them and they all glow with different colors.

VR tubes need to be fed with voltages that are higher than their output voltage. Assuming the voltage being fed to them is high enough that both types function correctly, what you've done by using a pair of 0D3 in place of the stock WY3P is to increase the voltage substantially and totally change the operating point of the 6SN7s.

I'm not so sure that's a good idea, depending on the circuit and the original operating point. The 6SN7s may not mind the additional voltage but it's possible that other parts might be overstressed as a result. Chinese gear sometimes runs parts very close to their limits and increasing the voltage by almost 50% could push them beyond their limits.

Are you sure both of the stock tubes are WY3Ps? I ask because I saw a reference to an unidentified preamp that uses one WY3P and one WY4P. That combination would produce 255v.

I'm no expert on VR tubes but I used one for the first time (a 0D3) in an amp that I built last year. As I recall, some precautions / measures need to be taken when using two or more in combination. I'm sure others can offer more details about them.

Here's a data sheet that covers the American VR types.

The 0C3 starts at 115V and operates at 105V. It's pretty much the standard upgrade for the WY3P since the WY3P is the Chinese version of 0C3. The 0C3 are more stable and don't get as hot as the China WY3P so it's kind of a no brainier upgrade. Not to mention other Blue Velvet owners are successfully running the 0C3 Voltage Regulators, so I assure you that I didn't just stick them in there without doing some prior research.

 

[SwedishChef]

Was spinning records today all afternoon.
Rectifier was upgraded to Genalex u77 / 5AR4.
Kept the WY3P voltage regulators in there just for the cool glowing eyes factor, I have several sets of 0D3 waiting to test. So far no audible difference whatsoever from using different voltage regulators...
Using the Sylvania 6SN7 yellow letters I bought and they sound great!
What's kind of funny is it had way more bass punch with the metal base 6N8P that it came with. I need to determine if that extra bass was coming from the 6N8P tubes or the 5Z4 rectifier I yanked. It will be an interesting preamp to play with, and so far I am seriously loving it! Sounds so smooth and great!

Switchy Switchy Tubes ver da bestie bestie sound.
Bork! Bork! Bork!

View attachment 2797842 View attachment 2797844

0C3* not 0D3 this was a typo from Android keyboard.
Do not own or will ever try 0D3 as it's not WY3P equivalent. My apologies for the keyboard fub up

 

[FlaCharlie]

0C3* not 0D3 this was a typo from Android keyboard.
Do not own or will ever try 0D3 as it's not WY3P equivalent. My apologies for the keyboard fub up

No problem, glad to hear that you're running the correct tube. I'm not sure why the Chinese version would run so hot.

 

[SwedishChef]

After using the Blue Velvet all of last year, and more than half of this year I'm finally ready to dive into some light modifications on it.
I've had it in front of a somewhat stock B&K ST-140 this entire time, and I freaking love this Preamplifier. It might me a stretch to say but if it's not the best $200 that I've ever spent in the Audio Hobby, it has certainly been the most fun $200 ever spent.
There has been a few different fever DACs hooked to it, and my Darlington Labs MM-6 has been on the second input.

I will say the 5AR4 rectifier is very stable and I believe my rectifier choice did possibly help extend my tube life.
I've tried several kinds of 6SN7 and even 7N7 & 7AF7 with the adapters. My favorite tubes by far have been GE 6SN7 grey plates (given to me free) for all the extra high frequency details and the sparkle they have. All the 7N7 seem to be identical to the Sylvania tubes, which makes sense because I remember reading all the 7N7 were made by Sylvania in the 50s. I haven't tried 7N7 tall boys or anything with the asinine prices, I've just been using what I initially purchased after I bought the preamp. The GE grey plates lasted me all of last year and I was really bummed out when they were finished.

Anyhow, I have ordered some Russian PIO caps and I plan on adding to the coupling capacitors! I also plan on adding an ALPS 100K volume potentiometer while I'm at it.

I wasn't expecting to get such an enjoyable experience. I'm sorry I haven't been back online to share more about it until now. I will take pictures when I do the upgrades this summer.

 

[ceylon]

I wasn't expecting to get such an enjoyable experience. I'm sorry I haven't been back online to share more about it until now. I will take pictures when I do the upgrades this summer.

enjoyed your postings about the BV. this was an especcialy good read. please keep us posted, and happy listening!