Direct wiring instead of a driver board?

[parabellum]

Do I even need a preamp with a ST70? I saw some mod that puts a volume control on it, is that possible?

[Slartibartfast]

Did you run across any problems with the schematic? What transformer did you use?

I did not run into any problems with the schematic, though after I finished it, I saw where I could have done a better job on component layout and hookup. Iused the Hammond 272JX. It is rated at 250mA @ 600V center tapped.

[parabellum]

Thanks. I'll probably build one myself then too. It looks pretty straightforward so hopefully it will work well together with the ST70

[kheper]

parabellum:

If you are still looking for NOS 12au7 tubes,
the RCA clear-tops are a relatively good
bargin.

[erichayes]

Do I even need a preamp with a ST70? I saw some mod that puts a volume control on it, is that possible?

No.

If you're working with "line level" devices, which are usually putting out a nominal 1 volt signal, all you need is a 100K gain control between the source and the input of the amp. Just so happens that Radio Shack carries an Alps dual 100K audio taper pot for around $4.00 that is excellent. Ignore the 40% loudness taps and wire it in: wiper to the amp input, high side to the source output, and low side to ground. Dont forget to ground the body of the pot, or you'll have hum problems.

If you want to get fancy, you can get a rotary switch from RS or Mouser, along with a handful of RCA jacks and a small chassis, and make a passive line switcher that will handle more than one source.

You have to determine what your goal is. If it's building stuff for its own sake, that's fine. If it's a desire to get as close to the original musical source as possible, then you have to take a minimalist approach, electronically. The more componentry you put between the source and the speaker, the less accurate the reproduction will be.

[parabellum]

parabellum:

If you are still looking for NOS 12au7 tubes,
the RCA clear-tops are a relatively good
bargin.

Thanks. I now have three options for those ... the Tung Sol 12au7, JAN5814A and the RCA's. That should ease the search I guess.

[parabellum]

Do I even need a preamp with a ST70? I saw some mod that puts a volume control on it, is that possible?

No.

If you're working with "line level" devices, which are usually putting out a nominal 1 volt signal, all you need is a 100K gain control between the source and the input of the amp. Just so happens that Radio Shack carries an Alps dual 100K audio taper pot for around $4.00 that is excellent. Ignore the 40% loudness taps and wire it in: wiper to the amp input, high side to the source output, and low side to ground. Dont forget to ground the body of the pot, or you'll have hum problems.

If you want to get fancy, you can get a rotary switch from RS or Mouser, along with a handful of RCA jacks and a small chassis, and make a passive line switcher that will handle more than one source.

You have to determine what your goal is. If it's building stuff for its own sake, that's fine. If it's a desire to get as close to the original musical source as possible, then you have to take a minimalist approach, electronically. The more componentry you put between the source and the speaker, the less accurate the reproduction will be.

I haven't even begun thinking about the sources yet other then that eventually I want to have a decent CD player, record player and a computer. I though most of those were at 2v and that shannons st70 had a 1.3v input. I am inclined to follow the minimalistic approach because it makes most sense to me. Thats why I looked into the Decware ZSP-1. It looks like a straightforward powersupply with volume control. Just like you said I was gonna modify it with a rotary switch to accept 3 sources at least.

[kheper]

Thanks. I now have three options for
those ... the Tung Sol 12au7, JAN5814A and
the RCA's. That should ease the search I
guess.

I just got 2 NOS Tung-Sol 12au7s and a
NOS RCA black plate off of an auction for
$17, including shipping. The date codes
are from 1956.

[parabellum]

Thanks. I now have three options for
those ... the Tung Sol 12au7, JAN5814A and
the RCA's. That should ease the search I
guess.

I just got 2 NOS Tung-Sol 12au7s and a
NOS RCA black plate off of an auction for
$17, including shipping. The date codes
are from 1956.

+


wow i couldnt find anything not even close to that price :(:(

I got 2 JAN5814A a few days ago for about 7 bucks each. The JJ KT77s came in the mail yesterday, I'm still waiting for the rest of them to come in.

Now i'm sniffing out transformers and Mike is really helping me out :)





PS You guys are gonna have to teach me some secrets in tube acquiring cause if I'm gonna keep on doing this i don't wanna keep getting ripped off hehe :)

[parabellum]

Just ordered Hammonds from Angela. Why in the world don't they put some kind of checkout software on their site. I have no idea what I ended up paying for shipping, or if the price from the site is still valid, if they have it in stock, no confirmation ... nothing.

[TomMcNally]

Angela does things the old fashioned way - I order almost every week,
and toward the end of the day you get a shipping notice from FedEx.
If it's on the site - that's the price, they clearly state they don't have
time to confirm, etc. Yeah, it's a bit different, but they get stuff to
you fast, in my case, ground is next day. A backorder might come
in another three days. I think the good prices and stocking on
Hammond is worth it.

[parabellum]

Angela does things the old fashioned way - I order almost every week,
and toward the end of the day you get a shipping notice from FedEx.
If it's on the site - that's the price, they clearly state they don't have
time to confirm, etc. Yeah, it's a bit different, but they get stuff to
you fast, in my case, ground is next day. A backorder might come
in another three days. I think the good prices and stocking on
Hammond is worth it.

I have no doubts about their honesty or trustworthiness. They were recomended by 4-5 of non related people.

All i am saying is that they could take their business onto the next level and automatize a whole lot of their work that they do by hand now with a simple 100 dollar shopping cart software. It would probably benefit them more then me.

[TomMcNally]

Angela does have lots of things in en eBay store ....

http://stores.ebay.com/Angela-Instruments

I think you make out better dealing direct though.

[sorenj07]

I'm also going to chime in in support of Angela. They don't mess around with fancy online checkout interfaces and stuff. What they are is a pretty serious, no-fuss online seller. The staff is also very responsive and helpful if something shows up DOA. Tube socket shows up broken? They reply to this news by saying that a replacement has been shipped out already. Quality.

[TomMcNally]

Yep - very serious - they didn't laugh when I asked them if they wanted this
Stanley knife back that I found in the bottom of a box of transformers.



Well I thought it was funny ! Yellow_Light_Colorz_PDT_04