diytube.com

Just recently finished my kit from Bob Latino of Tubes4HiFi.










I snuck in a few little upgrades too, including:

Teflon Tube Sockets and PCBs
Kimber TCSS wiring
Cardas RCAs / Binding Posts / Input wire
Kiwame / Takman Resistors
Mundorf Coupling Caps
Nichicon 100uF Electrolytics
Pilot light
Teflon solder strip for pentode / triode switch wiring
Heavy Duty On/Off Switch
Custom brass input and name labels
IEC Plug

Holes had to be drilled/cut for the new RCAs, larger switch, pilot light, solder strip and IEC. Since the chassis is 16 gauge stainless, it takes a bit of effort. The binding posts required a little bit of modification but fit in the existing slots. I used black lacquer coated phenolic boards and drilled them out to hold the posts in place. The tube compliment is Sylvania JAN input tubes, Winged C output tubes and Sovtek rectifier.

It was a fairly easy build and a nice recommendable kit. The sound is lush and engaging :)

Wow! Sweet!

Cheers!

Thanks Geek, I'm actually restoring a PAS at the moment and am using the same power supply that you used in your tutorial.

Here's a sneak peak:

I have Sal doing the final wiring and checkout this coming week and she'll be good to go :)

Hey Bryan,
Great job on the ST-70, looks awesome. I'll get to your preamp next week pending my wife getting out of the hospital this weekend... Its been a rough week for me. Thanks for understanding.

Regards,
Sal

Wow! That amp has just been Overhauled.

Good job! Nice build.

As one who has used that board in the past you will be surprised how much better it will sound if you install the power supply board that is available from several sources. When I built mine years ago it sounded so so even with the larger caps that you can put on the driver board and really woke up when the beefy PS board was installed.

6bg6ga wrote:As one who has used that board in the past you will be surprised how much better it will sound if you install the power supply board that is available from several sources. When I built mine years ago it sounded so so even with the larger caps that you can put on the driver board and really woke up when the beefy PS board was installed.

You've done a comparison? Do tell of your experience!

Cheers!

Very good to know. You're referring to the capboard like the one Triode Electronics sells right? (http://store.triodestore.com/capboards.html)

highflyin,

Any issues with hum due to the rear-mounted input jacks? I've recently done this with my ST-70 and I'm getting a small amount of hum (can't hear it with music playing but certainly more than there was with the inputs on the front). I see you used sheilded wire. I used a twisted pair on mine. I'm wondering if there may be some advantage to using actual sheilded wire vs. twisted pair.

Thanks,
Joe

Hi Joe,

I didn't notice any hum. I deliberately used thinnish 24 gauge wire with floating shield because I didn't want the transformers to bother the signal. I'd imagine it would help in your situation to swap the wire out. The shield should be connected at the RCA ground but not connected at the PCB.

To 6bg6ga,

The quad cap included with Highflyin9's kit is a 550 volt rated low ESR 80, 40, 30, 20 German made F&T Authenticap and works well with the Dynaco VTA ST-70 amp kit. It is also surge rated to 600 volts. Adding a under chassis cap board does not increase the sound quality on this amp kit at all. The ST-70 can only use just so much capacitance - and - adding a lot of capacitance (after the choke) slows down the power supply. The Sheldon Stokes designed under chassis board sold by Triode Electronics does have more capacitance but it is only rated at 500 VDC on the last three sections. Even the original Dynaco quad cap was rated at 525 volts. I have used the Triode board before and IMHO it does not make the amp sound any better, play any louder and again it is lower voltage rated.

To highflyin9 - One of the nicest custom VTA ST-70 amp kit builds I have seen - beautiful work ...

Bob Latino

You've done a comparison? Do tell of your experience!

As a matter of fact I have.

At one point in time I owned the same driver board as shown in the picture on one of my amps. A friend also purchased one and installed it in his amp. I ordered a power supply board and installed it in mine. There was a night and day difference between the sound of the two amps. The bass was more defined and tight on mine with the power supply board and to be blunt it was more musical. Since then I have purchased an additional 6 power supply boards and installed the power supply board on each one. I keep a dynaco around with a stock power supply just to prove the difference. I do have a favorite power supply board and board supplier. This manufacturer also supplies a number of different dynaco hop ups as well as an exceptional Dynaco driver board that uses a 6SL7 6SN7 combination. Now Bob lets face facts here....the 12AT7 is a nice upgrade from the stock board and I'm sure you try to sell the hell out of them because thats your living. Sorry but its not the best in the way of driver boards and neither is the basic Dynaco design.

Now I have the equipment ..two pair of identical speakers, two Aikido line stages to set up the ideal listening comparison and have done so. As Bob has put it.."IMHO" there is a difference and one that has been experienced by a number of audiophiles with trained ears. I would highly recommend the driver board, power supply and bias circuits available by Geek. I have used ALL the available driver doards out there as well as a few designed at home.

To highflyin9

Your build is excellent. I'm not putting it down by any means. I do feel that there is always room for improvement in anything and that is why I suggested the power supply board. When you are ready for an upgrade I would suggest visiting Geeks site and looking at the 6SL7/6SN7 driver board. It has a CCS for one thing. I was always happy with the Mapletree driver board but the 6SL7/6SN7 board is in a class all by its self. It is by far the most outstanding set up out there today.

Just my .02 and my humble opinions

I'm wondering if there may be some advantage to using actual sheilded wire vs. twisted pair.

I'm sure there are some that are more than willing to disagree with what I am going to say here but I highly recommend using shielded mic line for signal applications. I guess its the pro sound experience speaking out. I have built a number of line stages as well as amplifiers and at some point in time experienced hum issues. My experience is that mic line works good for me.

To 6bg6ga,

Re: > "The bass was more defined and tight on mine with the power supply board and to be blunt it was more musical."

My question to you is this > What quad cap were you comparing the under chassis cap board to ? I doubt that your comparison of the under chassis cap board was with the F&T low ESR 550 volt Authenticap because if it was you would have said so. You make a blanket statement suggesting that the under chassis cap board is superior to ANY and EVERY quad cap. Maybe it was superior to the quad cap you had in your amp ? Was the quad cap in your amp an original Dynaco quad cap ? These original quad caps, being 40 - 50 years old, are by now on most original amps, on their last legs anyhow.

Maybe we are comparing apples to oranges here. Your statement insinuates that ANY cap board is superior to ANY quad cap and I cannot agree with that. As I stated in a post above the section of that cap board that powers the two output transformers is only rated at 500 volts. An ST-70 runs at 440 - 445 VDC continuous on pins 3 and 4 and at turn on will probably surge near or slightly above 500 VDC. The caps in sections 2 and 3 of that cap board IMHO do not have enough of a margin of safety and as such, I won't use that board.

Bob Latino

Bob01605 wrote:What quad cap were you comparing the under chassis cap board to ?

I'm sure Bob has a valid point. Not all can caps are created equal. The previous owner of my Dynaco Mark III put in these CE Manufacturing caps. As you can see from the photo, they didn't hold up very well.