Another version of the amplifier

Hi,

The idea of building a tube amplifier did not stop at my first completed project, which allowed me to understand concepts of amplifier work and design. At the same time, I wanted to build an amplifier that I would like to own. When searching for schematics on the Internet and viewing images of amplifiers, the choice fell on the Dynaco ST-70, about which there is extensive information on the web. Given its popularity and availability, I decided to reproduce this amplifier in its entirety.
The first step in making an amplifier was to get parts. As this amplifier is still popular on eBay, I decided to first look there and see if I can buy a damaged ST 70 and then restore it. However, due to the popularity of this amplifier, I could not win it at auctions because the prices are very high. I decided it would be easier to buy all the parts separately and put them all together.
I was able to buy brand new transformers (two output transformers, one power transformer). The choice of output transformers fell on the Polish manufacturer INDEL, which offers transformers at an affordable price. I purchased the power transformer from AliExpress, agreeing that the seller will make the transformer with the required winding configuration.
On eBay, I found a seller in Serbia who sold me a board designed for the 6U8A preamp tubes (7199 replacement). As for the choice of chassis, it had to be designed in the Fusion 360 software itself, followed by laser cutting and folding of polished stainless steel 1.5 mm thick (gauge 16) by a local company. The choice of choke fell on Hammond's products.
Minor modifications have been made to the circuit; the amplifier could already be equipped with a volume control by inserting a 500k ALPS potentiometer in the circuit. It was also decided to do without the voltage takeoff sockets.
In addition, the amplifier is equipped with 6E1P "magic eye" tubes that visualize the signal level, although originally there were PCB boards for the tone regulator circuit, which did not fit due to their complexity and location. A separate preamplifier with a tone control and a cathode follower is currently being built, but that's a different story.
In the end, I am very happy with my project. Thanks to all the forum members, maintainers and a special thank you to Bob Latino.
Any reasonable criticism is recommended

I will try to post a picture of the project in the forum

Nice looking !
Are you planning to make a cover in a non-magnetic material ? If so i would like one.
Also, do you have contact information for the power transformer maker ? Getting them
from US is very expensive, a eastern source might be much more attractive. There is also
some transformers that seems unavailable ( PA085 , the 230Volt for MkIV comes to my mind).

I don't plan to make a cover yet. The manufacturer of transformers is the Polish company Indel. http://indel.pl. In my case a transformer TGL 40/001 was used. It is for these reasons that I am using a transformer from this manufacturer, and looking at transformer prices today, they have risen. I bought these transformers at the end of 2020 from a local electronics retailer, which cost me 110 EUR (125 USD) for both.

Juris wrote:I don't plan to make a cover yet. The manufacturer of transformers is the Polish company Indel. http://indel.pl. In my case a transformer TGL 40/001 was used. It is for these reasons that I am using a transformer from this manufacturer, and looking at transformer prices today, they have risen. I bought these transformers at the end of 2020 from a local electronics retailer, which cost me 110 EUR (125 USD) for both.

It was the mains transformer that interested me ...

The power supply was made in China according to my requirements. The cost of production was 56 USD, cheaper than shipping. I can't complain about the quality of the performance

Juris wrote:The power supply was made in China according to my requirements. The cost of production was 56 USD, cheaper than shipping. I can't complain about the quality of the performance

Do you have a link or email adress ?

Whatever i find at aliexpress there is shipping cost 85-95 USD, more then the transformer cost. This
makes these transformers less attractive then finding a local maker.

I'd love to know more about the magic eye tube circuit. Not sure I'd do it myself, but I'd like to know how you tied it in.

For this purpose I make two 60x60 mm PCB boards with soldered tube sockets

This is very sharp. Love to see a pic of the underside, wired up.

Also interested in the Magic Eye tubes.......And how they are being implemented.

I posted an image that was created somewhere at the design stage. As for 6E1P, simple circuit diagrams can be found on the Internet. I will write a reference to an example of the schematics below.

http://www.soundgaragetales.com/wp-content/uploads/2009/04/em80_schematic.gif