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Blue Velvet Preamplifier - on it's way!

SwedishChef

SwedishChef

Member
Hello Tube Heads,

After going back and forth for about a month I decided to pull the trigger on a Blue Velvet Preamp from AliExpress. I've had phenomenal luck with all the clones and almost all my AliExpress audio purchases. It was between a Wada Shigeru preamplifier and the Blue Velvet. Yesterday I decided I wanted to jump on the 6SN7 wagon.

The BV that I went with has two inputs.
Will be switching between a fever TDA1541 DAC and my Darlington Labs MM-6.

The Rectifier is a 5Z4P, I know the P means China.
Supposedly these are the upgrades but I believe the Slow Warm Tube was used in this circuit for a reason. I'm reluctant to try anything that's not a slow warm!
Rectifier Tube Options:
5Z4P (comes with)
5Z3P
5AR4
5U4G
5U4C "told this was an average tube"
GZ34
5U3C "black plates"
WE274 "stupid expensive "

Voltage Regulator Tube:
WY3P (comes with two)
OC3

Audio:
6N8P (comes with two)
6SN7
CV181
6H8C

The plan is to immediately install two Sylvania 6SN7GTB with the yellow letters that people seem to enjoy in the 6SN7 discussions online.
I'm completely on the fence with replacing the OC3 and the 5Z4 rectifier, unless someone here tells me it makes a profound sound difference.


Information worth adding.
From what I've read, 6SN7 to 7N7 adapters can be used on the BV. One Blue Velvet DIYer commented that he enjoyed the sound of 7AF7 more than any of the 6SN7 tubes in his collection.

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SixCats!
 
SwedishChef said:
Hello Tube Heads,

After going back and forth for about a month I decided to pull the trigger on a Blue Velvet Preamp from AliExpress. I've had phenomenal luck with all the clones and almost all my AliExpress audio purchases. It was between a Wada Shigeru preamplifier and the Blue Velvet. Yesterday I decided I wanted to jump on the 6SN7 wagon.

The BV that I went with has two inputs.
Will be switching between a fever TDA1541 DAC and my Darlington Labs MM-6.

The Rectifier is a 5Z4P, I know the P means China.
Supposedly these are the upgrades but I believe the Slow Warm Tube was used in this circuit for a reason. I'm reluctant to try anything that's not a slow warm!
Rectifier Tube Options:
5Z4P (comes with)
5Z3P
5AR4
5U4G
5U4C "told this was an average tube"
GZ34
5U3C "black plates"
WE274 "stupid expensive "

Voltage Regulator Tube:
WY3P (comes with two)
OC3

Audio:
6N8P (comes with two)
6SN7
CV181
6H8C

The plan is to immediately install two Sylvania 6SN7GTB with the yellow letters that people seem to enjoy in the 6SN7 discussions online.
I'm completely on the fence with replacing the OC3 and the 5Z4 rectifier, unless someone here tells me it makes a profound sound difference.


Information worth adding.
From what I've read, 6SN7 to 7N7 adapters can be used on the BV. One Blue Velvet DIYer commented that he enjoyed the sound of 7AF7 more than any of the 6SN7 tubes in his collection.

View attachment 2770428
Click to expand...
Welcome. I assume you have read:
https://www.enjoythemusic.com/diy/1110/blue_velvet_line_preamplifier.htm Did your purchase follow the original circuit faithfully?

My suggestion would be to listen to the tube set supplied for a while to become familiar with the line amp and how it sounds, before starting to experiment with different tubes.

A few comments: I have not been able to hear a difference between 6SN7 and 7N7 (in other equipment), but perhaps you could.

Regarding the rectifier: https://www.tubeampdoctor.com/media/pdf/50/4f/7f/specifications_5z4p.pdf This is the only data sheet i could find. I don’t read Chinese but it looks like the first cap is limited to 4 uF. What is the first cap in your power supply? Some of the Chi Fi pieces seem to be oblivious to such limitations. Before changing the rectifier tube take measurements of what voltages you have and compare after replacement. I would prefer to go with a NOS 5 AR4, if you have one, but you may get a higher B+ (which may or may not be acceptable). 5U4/5R4 will likely drop the voltage too much. Check the specified current max on your 5 V supply before trying any 5U4 type due to their 3 amp filament requirement.

Good luck and enjoy you new line amp.
 
The 5AR4/GZ34 would probably be a better choice over the Chinese rectifier.
Just don't use a JJ brand 5AR4, they won't last. Tungsol is supposed to make a good one. They also make a decent 6SN7 that won't break the bank. I use a quad of them in my preamp.
 
@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.
 
The two JJ's were in amplifiers I ne er ran very hard at all. They may be ok in a preamp, ut I personally wouldn't trust them. I've had good luck with Sovtek and old stock 5V4's though. <edit> one JJ shifted our in my
ST-70 that has the yellow sheet mod.
 
Last edited:
Lavane said:
The 5AR4/GZ34 would probably be a better choice over the Chinese rectifier.
Just don't use a JJ brand 5AR4, they won't last. Tungsol is supposed to make a good one. They also make a decent 6SN7 that won't break the bank. I use a quad of them in my preamp.
Click to expand...

their 6SL7 are good, too. use em in my
tavish phono.
 
I have a blue velvet using DC on the filaments. It supports 6.3 and 12.6 volt filaments SN7s. I can use it with 12SN7s and 12SX7s.

The 12 volts tubes are typically less expensive than the 6 volt tubes. And the 12SX7s have a reputation for being among the best of the SN7 tube types.

I have used it with all three types of tubes. I cannot tell the difference with any of them. The Blue Velvet circuit is not a low distortion SN7 implementation. Mine has a minimum of 0.1% distortion. That may be related to why I don't notice a difference in tubes.

Instead of glow tube regulators I used an LR8N with a mosfet.

Steve
 
I have used the Blue Velvet almost every day for 15 years. In the same chassis I built an SN7 based 18db per octave active crossover. So I use 4 SN7 tubes.

I planned to build a few more (office, home and family) so I stocked up on SN7 and SX7 tubes whenever I could get them for a good price.

I have only had to 2 tube failures. And they were the cathode followers in the active crossover. I didn't elevate the heaters.

I estimate that the current preamp tubes have been used for maybe 10,000 hours. At this rate I have enough SN7s for 100+ years.

Steve
 
steve... said:
I have a blue velvet using DC on the filaments. It supports 6.3 and 12.6 volt filaments SN7s. I can use it with 12SN7s and 12SX7s.
Click to expand...
I almost built the BV several years ago. In the end, I decided to roll my own with a design that connects the output stage cathodes directly to the output jacks. Like you, I collected sleeves of many 12V versions of the popular octals back then, including 'SN7, 'SL7 and 'SF5. Sadly, I haven't found a good use for them yet.

Jack
 
TriodeLuvr said:
I almost built the BV several years ago. In the end, I decided to roll my own with a design that connects the output stage cathodes directly to the output jacks. Like you, I collected sleeves of many 12V versions of the popular octals back then, including 'SN7, 'SL7 and 'SF5. Sadly, I haven't found a good use for them yet.

Jack
Click to expand...

howd the build go? hows the preamp?
 
It's about 90% done, but I put it on the back burner while I work on my SETs. I just discovered the PC that I use for distortion measurements isn't working properly, so I need to slide that into the bench schedule now. Always something. I'll report back on the SETs and the preamp soon as there's progress.

Jack
 
Great information on the BV! Thank you everyone for posting on my Blue Velvet thread. I ended up ordering the Sylvania 6SN7 with yellow letters and the eBay seller was awesome. He is actually sending me other 6SN7 tubes to try free since I am a tube noob.

He mentioned that he would not use the China WY3P at all and said to find some RCA OC3 or another vintage new old stock OC3 to use.

The eBay seller also mentioned upgrading the rectifier tube to a 5U4G. He said that it would likely be more stable and sound better. I can't verify this, I am just listening to someone way more knowledgeable than I am in the tube department. Since he mentioned this rectifier tube, I ended up watching some rectifier tube shootout videos on YouTube. The Westinghouse 5U4G seems like a very popular rectifier choice.

So it looks like I will be replacing everything from the start. I will test all the China tubes and see how it sounds provided they all arrive undamaged.

It really makes me happy that I made the purchase when I read that people have been continuing to use their BV preamplifier for so many years! I'm really excited to get this Preamplifier and to start experimenting with different tubes.
 
steve... said:
I have used the Blue Velvet almost every day for 15 years. In the same chassis I built an SN7 based 18db per octave active crossover. So I use 4 SN7 tubes.

I planned to build a few more (office, home and family) so I stocked up on SN7 and SX7 tubes whenever I could get them for a good price.

I have only had to 2 tube failures. And they were the cathode followers in the active crossover. I didn't elevate the heaters.

I estimate that the current preamp tubes have been used for maybe 10,000 hours. At this rate I have enough SN7s for 100+ years.

Steve
Click to expand...
Would love to see pictures of your BV build!
 
It would have been better if the chassis was larger.

Solid state rectification through out. 10000+ uf of capacitance for the filaments. No hum or hiss. Ripple was very low (if I remember correctly a couple of millivolts).

The board at the bottom of the wiring diagram has 2 LR8N regulaters with mosfet pass devices. One for the crossover's cathode followers and the other for the Blue Velvet Pre.

The proto boards house Steve Bench's 18db per octave active crossover. The crossover point is approximately 1khz. There are outputs for high frequency, low frequency and bandpass. I have ESS AMT1As that I modified to do biamp or single amp inputs. I also have another system with Klipsch bookshelf speakers for the lows and ESS AMTs for the highs. The selection of the crossover point was based on the original ESS design.

The crossover was adapted from Steve's 6DJ8 design. The higher gm 6DJ8 was probably a better choice than the SN7s but I wanted an all SN7 design.

I have a BEZ 6SN7 pre with a tube rectifier and glow tube regulators. I have a Mingda pre with a tube rectifier, 5751 gain stages and 12au7 cathode follower outputs.

The Mingda has 1/10 the distortion of the Blue Velvet. I like the Mingda but I prefer the warmer presentation I get from the Blue Velvet.

The BEZ has more distortion than the Mingda and less than the Blue Velvet. I used it for many years before I got the Blue Velvet. I don't notice a difference between the tube rectification and the solid state rectification.

Steve
 
steve... said:
It would have been better if the chassis was larger.

Solid state rectification through out. 10000+ uf of capacitance for the filaments. No hum or hiss. Ripple was very low (if I remember correctly a couple of millivolts).

The board at the bottom of the wiring diagram has 2 LR8N regulaters with mosfet pass devices. One for the crossover's cathode followers and the other for the Blue Velvet Pre.

The proto boards house Steve Bench's 18db per octave active crossover. The crossover point is approximately 1khz. There are outputs for high frequency, low frequency and bandpass. I have ESS AMT1As that I modified to do biamp or single amp inputs. I also have another system with Klipsch bookshelf speakers for the lows and ESS AMTs for the highs. The selection of the crossover point was based on the original ESS design.

The crossover was adapted from Steve's 6DJ8 design. The higher gm 6DJ8 was probably a better choice than the SN7s but I wanted an all SN7 design.

I have a BEZ 6SN7 pre with a tube rectifier and glow tube regulators. I have a Mingda pre with a tube rectifier, 5751 gain stages and 12au7 cathode follower outputs.

The Mingda has 1/10 the distortion of the Blue Velvet. I like the Mingda but I prefer the warmer presentation I get from the Blue Velvet.

The BEZ has more distortion than the Mingda and less than the Blue Velvet. I used it for many years before I got the Blue Velvet. I don't notice a difference between the tube rectification and the solid state rectification.

Steve
Click to expand...
I bet that sounds amazing!
 
SwedishChef said:
The eBay seller also mentioned upgrading the rectifier tube to a 5U4G. He said that it would likely be more stable and sound better. I can't verify this, I am just listening to someone way more knowledgeable than I am in the tube department. Since he mentioned this rectifier tube, I ended up watching some rectifier tube shootout videos on YouTube. The Westinghouse 5U4G seems like a very popular rectifier choice.
<snip>
.
Click to expand...
The 5Z4P has 2 amp heater draw; the 5U4 is 3 amp. Please verify your BV power transformer can support a 5U4 before plugging it in.
 
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