So I had always wanted to get into tube audio but had been waiting until I found a great deal on an amp.
I was at an auction house and noticed a ST-70 that was going up for sale. While I was looking it over a member of the auction team approached me and told me about the amp. The original board had been serviced and all caps replaced with a mix of Orange Drops and Dayton caps. The selenium rectifier had been replaced, a set of xf2 Mullards and a f32 Mullard gz34 were on board, driver tubes were RCA black plate 7199s. Also included in the auction were a Weber Copper Cap and 2 full quads of NOS Sylvania fat bottle 6CA7 outputs.
So the auction starts and one of the last items was the amp. I was worried as there was an obvious flipper in the crowd who was buying all the vintage audio up. Once the amp went on the auction block I put in the first bid at 100 dollars and was surprised when nobody else put in a bid. I later learned that the other audio guy had gone to the bathroom and missed bidding on the amp
After the auction the team member who I spoke with told me that I got an amazing deal as the 2 Quads of 6CA7 alone are worth 5-6 hundred dollars.
I took the amp home and biased it up and listened for a couple of hours. While I liked the amp I thought it was a little laid back and sounded veiled, so off to the internet I went to look at mods when I found the tubes4hifi page. I decided on the standard VTA board I was wary of changing out the cloth lead transformer for a newer one. After a shipping mixup which Roy corrected immediately I had the board built with russian PIOs and a new quad cap installed.
Right now I have 200 hours on the amp with the fat bottle Sylvania 6CA7s, RCA long black plate 12bh7s on the outside and a CBS-Hytron 5814 black plate in the center position. I have never heard an amp so detailed in my life and it just keeps getting better and better!!
Thanks Roy!!
Up next will be a preamp build
I was at an auction house and noticed a ST-70 that was going up for sale. While I was looking it over a member of the auction team approached me and told me about the amp. The original board had been serviced and all caps replaced with a mix of Orange Drops and Dayton caps. The selenium rectifier had been replaced, a set of xf2 Mullards and a f32 Mullard gz34 were on board, driver tubes were RCA black plate 7199s. Also included in the auction were a Weber Copper Cap and 2 full quads of NOS Sylvania fat bottle 6CA7 outputs.
So the auction starts and one of the last items was the amp. I was worried as there was an obvious flipper in the crowd who was buying all the vintage audio up. Once the amp went on the auction block I put in the first bid at 100 dollars and was surprised when nobody else put in a bid. I later learned that the other audio guy had gone to the bathroom and missed bidding on the amp
After the auction the team member who I spoke with told me that I got an amazing deal as the 2 Quads of 6CA7 alone are worth 5-6 hundred dollars.
I took the amp home and biased it up and listened for a couple of hours. While I liked the amp I thought it was a little laid back and sounded veiled, so off to the internet I went to look at mods when I found the tubes4hifi page. I decided on the standard VTA board I was wary of changing out the cloth lead transformer for a newer one. After a shipping mixup which Roy corrected immediately I had the board built with russian PIOs and a new quad cap installed.
Right now I have 200 hours on the amp with the fat bottle Sylvania 6CA7s, RCA long black plate 12bh7s on the outside and a CBS-Hytron 5814 black plate in the center position. I have never heard an amp so detailed in my life and it just keeps getting better and better!!
Thanks Roy!!
Up next will be a preamp build
