I am sorry but I had to gloat a little bit.
Seriously, this was a much anticipated project by me. I started planning on this build from the first day Nelson made mention of it. I have read everything Nelson has wrote about the project and watched all the youtube videos many times. I was afraid it was not going to meet my anticipated expectations but it has surpassed them. I build for a hobby and have around a dozen amps laying around my house and others elsewhere and this amp is one of the two best I have found with my horns. I now await the SE design to see how it does against the other amp I like as well. There are two amps now on top of my hill. This amp and a tube SE.
Last edited:
Hello wdecho.I experimented with a buffer between my tube pre and the V-fet last night. It worked and made the tube pre usable but the amp lost it's magic with the tube pre. With this amplifier I much prefer a SS pre, more precisely my BA3 front end as a pre, than my tube pre I like better with my other FW clone amps. Obvious to me is this amp does not need the tube pre to take the SS edge off with users of horns. The SS sound that is talked about in the debate of SS vs Tube gear is not there with this amp.
If you need a pre with this amp as I do you definately want to use a quality SS pre and not your tube pre.
I never thought I would be the first to post on this build. I am eagerly looking forward to others opinions on build and sound. I do take pleasure of being one of the few in the world to be able to hear as Nelson designed PP SIT amplifier.
Your observations regarding the choice of a preamp are interesting; especially for the vac tube. Pls allow me to suggest one more experiment. Maybe there is no use for a preamp at all; granted that the source of music which you are using already has a volume controlled headphone or a line level outputs.
Wdecho; What horn speakers do you have? thx.I am sorry but I had to gloat a little bit.
Seriously, this was a much anticipated project by me. I started planning on this build from the first day Nelson made mention of it. I have read everything Nelson has wrote about the project and watched all the youtube videos many times. I was afraid it was not going to meet my anticipated expectations but it has surpassed them. I build for a hobby and have around a dozen amps laying around my house and others elsewhere and this amp is one of the two best I have found with my horns. I now await the SE design to see how it does against the other amp I like as well. There are two amps now on top of my hill. This amp and a tube SE.
Use a proper tube preampI experimented with a buffer between my tube pre and the V-fet last night. It worked and made the tube pre usable but the amp lost it's magic with the tube pre. With this amplifier I much prefer a SS pre, more precisely my BA3 front end as a pre, than my tube pre I like better with my other FW clone amps. Obvious to me is this amp does not need the tube pre to take the SS edge off with users of horns. The SS sound that is talked about in the debate of SS vs Tube gear is not there with this amp.
If you need a pre with this amp as I do you definately want to use a quality SS pre and not your tube pre.
I never thought I would be the first to post on this build. I am eagerly looking forward to others opinions on build and sound. I do take pleasure of being one of the few in the world to be able to hear as Nelson designed PP SIT amplifier.
All of the last post have merit. The tube pre I have been using is the Oddwatt Forewatt.
http://diyaudioprojects.com/Tubes/E...S-12AU7-ECC82-Tube-Preamplifier-Schematic.png
I do need a pre with my sources. If one uses say a dedicated CD player it would only require a passive pre, or B1 because a player has about 2V out whereas a computer or phono is 1V or less.
My speakers are modified Klipsch LaScala's I bought in '86 new. I have my own designed Xover with an Altec 511B horn and a selenium tweeter. I do have a very high quality sub I built but I do not even turn it on most of the time. With my Xover and attenuation of the mids and highs I have plenty enough bass without the sub.
To answer the last question I do have a number of different tube pre's but for the present I have only tried the one I have found best before this amp. This amp does not need a tube pre to smooth out the sound as I have found I like best with other SS amps. I am planning to build the LSK pre outlined at the BAF now that I have found that a SS pre sounds best with this amp. It will be fun to compare the difference between the LSK pre and the BA3 pre.
http://diyaudioprojects.com/Tubes/E...S-12AU7-ECC82-Tube-Preamplifier-Schematic.png
I do need a pre with my sources. If one uses say a dedicated CD player it would only require a passive pre, or B1 because a player has about 2V out whereas a computer or phono is 1V or less.
My speakers are modified Klipsch LaScala's I bought in '86 new. I have my own designed Xover with an Altec 511B horn and a selenium tweeter. I do have a very high quality sub I built but I do not even turn it on most of the time. With my Xover and attenuation of the mids and highs I have plenty enough bass without the sub.
To answer the last question I do have a number of different tube pre's but for the present I have only tried the one I have found best before this amp. This amp does not need a tube pre to smooth out the sound as I have found I like best with other SS amps. I am planning to build the LSK pre outlined at the BAF now that I have found that a SS pre sounds best with this amp. It will be fun to compare the difference between the LSK pre and the BA3 pre.
There are many ways to skin a cat.
Could be fun to hear what you think of your other tube preamps and the LSK pre.
Another interesting ss pre is the Iron Pre by Mighty ZenMod.
I experimented with a buffer between my tube pre and the V-fet last night. It worked and made the tube pre usable but the amp lost it's magic with the tube pre. With this amplifier I much prefer a SS pre, more precisely my BA3 front end as a pre, than my tube pre I like better with my other FW clone amps. Obvious to me is this amp does not need the tube pre to take the SS edge off with users of horns. The SS sound that is talked about in the debate of SS vs Tube gear is not there with this amp.
If you need a pre with this amp as I do you definately want to use a quality SS pre and not your tube pre.
I never thought I would be the first to post on this build. I am eagerly looking forward to others opinions on build and sound. I do take pleasure of being one of the few in the world to be able to hear as Nelson designed PP SIT amplifier.
Did you increase the input to 100K?
I did this on my VFET Part 2 and it works fine with the various preamps I have use.
The Amp is stunningly dynamic with amazing resolution. I'm looking forward to comparing it to the DIY version.
Did you increase the input to 100K?
No, I did not. I built it just as outlined. I doubt I will play with anymore tube preamps with this amp the SS BA3 working so well. I do plan on building the LSK version. I bought 8 jefts of each flavor last year in C grade but I have not got around to using them yet. I also bought some extra V-fets from circuitdiy before they dried up. I have a pair of each and also 2 extra 2SJ28's. I figured it couldn't hurt to have some extras.
I confess to being a 67 year old Nelson Pass groupie. Even though I did stray from the flock and built a number of tube amps in the last year. This V-fet has all the good qualities of a tube amp in a SS package along with the admirable traits SS brings to the table. So dynamic and quick are the two traits that stand out the most for me along with smooth vocals and great soundstage. Some of my other amps that were my favorites before this build now sound dull in comparison and they are well respected and very good amps.
Last edited:
Hi,
I thought someone might find this useful. Here is my Digikey BOM for the DIY kit.
Digikey BOM
-Not included in the BOM: Most of the transistors.
-Extras/surplus in the BOM: Panasonic 3W resistors (0.47 and 2K2 Ohm) and CL-60 for the power supply section.
-Caveat: Resistors chosen are CMF55 0.5Watt, L: 0,090" x 0,240" (2,29 mm x 6,10 mm) - I haven't checked if thats the right size for the PCB - and they are a bit on the expensive side. I would assume there are parts of equivalent quality at a more modest price.
I thought someone might find this useful. Here is my Digikey BOM for the DIY kit.
Digikey BOM
-Not included in the BOM: Most of the transistors.
-Extras/surplus in the BOM: Panasonic 3W resistors (0.47 and 2K2 Ohm) and CL-60 for the power supply section.
-Caveat: Resistors chosen are CMF55 0.5Watt, L: 0,090" x 0,240" (2,29 mm x 6,10 mm) - I haven't checked if thats the right size for the PCB - and they are a bit on the expensive side. I would assume there are parts of equivalent quality at a more modest price.
2015 VFET PART2 with to pair of VFET per channel
Hi,
I have received this VFET with the my 2 KIT :
2SJ28 : 89 / 84 or 89 (it's dificult to read)
2SK82 : 81 / 81
2SJ28 : 118 / 118
2SK82 : 86 / 86
Can you tell me if I could try to make the amp with the original 2015 VFET PART2 with to pair of VFET per channel ?
Can we make your kit with others VFET, not matched ?
Thank you very much for the kit.
Pierre.
Hi,
I have received this VFET with the my 2 KIT :
2SJ28 : 89 / 84 or 89 (it's dificult to read)
2SK82 : 81 / 81
2SJ28 : 118 / 118
2SK82 : 86 / 86
Can you tell me if I could try to make the amp with the original 2015 VFET PART2 with to pair of VFET per channel ?
Can we make your kit with others VFET, not matched ?
Thank you very much for the kit.
Pierre.
Last edited:
Pass DIY Addict
Joined 2000
Paid Member
Unless you are addressing a very specific problem with ground loop hum, I would recommend removing the thermistor you have between the 0v point in your PSU and the AC mains ground. I had this same arrangement in my Aleph-X amps and it worked very well until one of my PSU caps developed a short, driving voltage into my 0v reference point for the PSU. As the voltage climbed higher, the transformer drew more current from the wall outlet in an attempt to maintain the power supply. The thermistors ended up glowing like a light bulb before finally blowing the fuse and all of my thermistors. Luckily, the amp circuit and speaker survived this little spectacle of fireworks. I have since rebuilt my amps with a direct heavy gauge line from the PSU 0v to the AC mains ground. Safety first.
You certainly have a point. The Cl-60 is just a 10 ohm resistor when cold to isolate the the amp from any unwanted stray noise generated from the IEC ground. If you have clean power and ground from the outlet a wire is probably better. I was actually referring to not have my metal heatsinks ground at the IEC to prevent shock in case of failure of amp. When you build with a wooden case you should tie all metal to ground for safety. I have since done this and tidied up my wires and put the lid on. I am still amazed with the sound.
I am very much looking forward to others comments on this amp. Come on guys get busy.
you can expect Burning VFet Amp Festival
I was curious if you have built this amp Zen but did not ask. I saw you showing off the Pass SIT's many months ago and figured you have used them for a SIT build. I believe you are going to be impressed as I was when you hear a PP SIT amp.
