Feeler: Classic Solo

[Deepdark]

looks really interesting. Do you have any idea of a build cost (with edcor output and cinemag input) ?

 

[ding]

About $75 mouser cart + $chassis, $audio and power transformers, $cabling for 1 channel.

EDIT: You can probably get that cart cost down a bit but I like 1w resistors for tube stuff.

 

[ruffrecords]

I did a rough BOM a while back which included the PCBs, tubes, enclosure, transformers and engraved front and rear panels and it came to close to $500.

As usual,  most of the money (nearly 80%)  is in the transformers, panels, enclosure and tubes in that order.

Cheers

Ian

 

[Deepdark]

I did a rough BOM a while back which included the PCBs, tubes, enclosure, transformers and engraved front and rear panels and it came to close to $500.

As usual,  most of the money (nearly 80%)  is in the transformers, panels, enclosure and tubes in that order.

Cheers

Ian

Damn, i will officially need one board for sure.

 

[Deepdark]

Finally, I'll be in for 2 hahaha. Is it include the toggle switch boards? I'll make an mouser card for the stuff I like to use. I'll give a look at teh power transformer, too. Probably will go with an kind of Hammond or Edcor, mounted outside a la LA2A/Pultec. And will install a small transformer Inside the case for the phantom power. I saw on the schematic a transformer rated at 50VA, for phantom power. It must be a typo lol. 15VA should be fine to feed 2 mic pre, right?

 

[Deepdark]

These one could work, but we'll need another transformer for the phantom power:

Hammond 369JX
Hammond 270CAX
Hammond 269AX
Hammond 269JX
Hammond 270X

All to be installed outside the case, a la LA2A/Pultec. Since our dollar here in canada is really bad now (exchange rate vs Euro is 0.66$,  USD 0.71, and GBP is 0.48$). Stuff from Don audio will end up to be pretty expensive. Antek looks promising, though. This model should perfrom well I think, and is rated 50VA. With a proper strip, we coud feed 2 board easily. http://www.antekinc.com/as-05t240-50va-240v-transformer/

 

[ding]

These one could work, but we'll need another transformer for the phantom power:

Hammond 369JX
Hammond 270CAX
Hammond 269AX
Hammond 269JX
Hammond 270X

All to be installed outside the case, a la LA2A/Pultec. Since our dollar here in canada is really bad now (exchange rate vs Euro is 0.66$,  USD 0.71, and GBP is 0.48$). Stuff from Don audio will end up to be pretty expensive. Antek looks promising, though. This model should perfrom well I think, and is rated 50VA. With a proper strip, we coud feed 2 board easily. http://www.antekinc.com/as-05t240-50va-240v-transformer/

I've been looking at that antek one too. I was also looking at their 25-0-25 for phantom but it's kinda overkill at 25va.

http://www.antekinc.com/an-0225-25va-25v-transformer/

 

[ruffrecords]

Some of those Hammonds have a 50V tap on the HT secondary for output tube bias.  Rather than have a separate transformer for phantom power you could use this tap. It would have to be half wave rectified and it would automatically be commoned to the HT supply 0V which is not ideal but probably OK for a stand alone pre. Definitely worth a try.

As they are all EI type transformers I think it is definitely a wise move to mount them on the outside of the case. I am in the process of getting a quote for a suitable toroid transformer. If the price is good I will be happy to supply it to DIYers at cost.

The 4toggle PCB is not automatically included. A lot of people will be building DI boxes or may decide to do the input end in a different way. However, it is such a small board, and it contains two circuits I might just throw it it in.

Cheers

Ian

The schematic says 50VAC not 50VA for the phantom ac input

 

[Deepdark]

Some of those Hammonds have a 50V tap on the HT secondary for output tube bias.  Rather than have a separate transformer for phantom power you could use this tap. It would have to be half wave rectified and it would automatically be commoned to the HT supply 0V which is not ideal but probably OK for a stand alone pre. Definitely worth a try.

As they are all EI type transformers I think it is definitely a wise move to mount them on the outside of the case. I am in the process of getting a quote for a suitable toroid transformer. If the price is good I will be happy to supply it to DIYers at cost.

The 4toggle PCB is not automatically included. A lot of people will be building DI boxes or may decide to do the input end in a different way. However, it is such a small board, and it contains two circuits I might just throw it it in.

Cheers

Ian

The schematic says 50VAC not 50VA for the phantom ac input

The 50V tap is on lots of their 300 series (369jx and so on). They are also of better quality, more robust and they have both 120/240 taps on primary. They aren't cheap, though. I would recommand Those Hammond instead of the cheap Allied (Made by Hammond, by the way).

If mounted outside the chassis, ideally we must use an aluminium chassis.

 

[Deepdark]

These one could work, but we'll need another transformer for the phantom power:

Hammond 369JX
Hammond 270CAX
Hammond 269AX
Hammond 269JX
Hammond 270X

All to be installed outside the case, a la LA2A/Pultec. Since our dollar here in canada is really bad now (exchange rate vs Euro is 0.66$,  USD 0.71, and GBP is 0.48$). Stuff from Don audio will end up to be pretty expensive. Antek looks promising, though. This model should perfrom well I think, and is rated 50VA. With a proper strip, we coud feed 2 board easily. http://www.antekinc.com/as-05t240-50va-240v-transformer/

I've been looking at that antek one too. I was also looking at their 25-0-25 for phantom but it's kinda overkill at 25va.

http://www.antekinc.com/an-0225-25va-25v-transformer/

You can easily get one from mouser or digikey woth the BOM. Triad has a wide range of power transformer and I never had trouble with them.

 

[ding]

Ian, how many mm apart are those switches on the addon board? I'm trying to get a front panel made.

 

[ruffrecords]

Ian, how many mm apart are those switches on the addon board? I'm trying to get a front panel made.

They are 12mm apart.

Cheers

Ian

 

[ruffrecords]

Here is a pic of the V2 guts in a Hammond case. This is my ribbon mic and DI box. I had some minor hum problems that have been fixed by altering the orientation of the toroid. I have added a dual 1K pot at the output to load the transformer to help get more distortion and to allow the output level to be adjusted when the DI is over driven. You get more distortion with a true 600 ohm load so a proper 600 ohm balanced pot would be best or you can just slug the transformer with a 620 ohm resistor.

The mains transformer is one by Carnhill. Cost me £25. Unfortunately it does not have a 50VAC winding so I have got a quote from a transformer manufacturer for a custom toroid. Looks like it will be in the region of 30 to 35 Euros/dollars plus shipping if we order enough. It is dual primary so it will work just about anywhere. If there is enough interest I am happy to arrange a group buy.

https://drive.google.com/file/d/0B_n67A1hN3qtaktyQUdtZGRrX28/view?usp=sharing

Cheers

ian

 

[Deepdark]

Here is a pic of the V2 guts in a Hammond case. This is my ribbon mic and DI box. I had some minor hum problems that have been fixed by altering the orientation of the toroid. I have added a dual 1K pot at the output to load the transformer to help get more distortion and to allow the output level to be adjusted when the DI is over driven. You get more distortion with a true 600 ohm load so a proper 600 ohm balanced pot would be best or you can just slug the transformer with a 620 ohm resistor.

The mains transformer is one by Carnhill. Cost me £25. Unfortunately it does not have a 50VAC winding so I have got a quote from a transformer manufacturer for a custom toroid. Looks like it will be in the region of 30 to 35 Euros/dollars plus shipping if we order enough. It is dual primary so it will work just about anywhere. If there is enough interest I am happy to arrange a group buy.

https://drive.google.com/file/d/0B_n67A1hN3qtaktyQUdtZGRrX28/view?usp=sharing

Cheers

ian

Looks good this will be my main dual pre hehe

 

[ding]

I've reached out to Edcor and asked them if they could wind me a slightly customized output transformer for this project. I wanted a 2.4k pri / 600-600 sec no center tap so I can use one of the 600 secondaries for a meter and one for the output. They said they would be happy to do it at $14 each with a minumum of 25 pc. If anyone is interested we could set up a group buy. Anyone up for it??? If we can get 13 people to buy 2 each that would cover it.

 

[Deepdark]

I'd be in for 2

 

[ding]

I'll start a feeler thread and see what happens.

 

[ruffrecords]

I have just uploaded the latest version (0.5) of the Classic Solo build instructions. I have added sections on avoiding hum, microphony and noise, information on modifying it to get more distortion for DI boxes, and a section on mains transformers.

https://drive.google.com/file/d/0B_n67A1hN3qtNUdYX1FjamMxUkE/view?usp=sharing

Enjoy

Cheers

ian

 

[Deepdark]

how did you managed the input transformer screen connection? Is it connected to the signal ground or connected to a mounting standoff pad?

 

[Deepdark]

here is a cheap option for the phantom transformer:

https://www.digikey.ca/product-detail/en/241-5-48/241-5-48-ND/1117982

If mounted at the far opposite side of the board, it should works great. I used somethig similar in a REDD47 and never had trouble. It's darn cheap too!