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The BIG Dyna ST70 driver board thread

I have most recently augmented my setup by building the active crossover kit offered by audio-kits.com. It is an affordable, fixed frequency, op amp based design that can be ordered as a bare PC board or with parts included. It runs extremely quiet, partly out of good design that makes provisions for bypass caps on the ICs, and partly due to a minimum number of stages. I am very pleased with it.

For my needs, everything below 700Hz is being fed to a solid state Scott 325R I was given and everything above 700Hz is going to my ST70 w/ the medium gain VTA driver board.

The sound is phenomenal. The horns in my Klipsch Fortes bring out the detail of whatever tubes I'm rolling through my '70 (currently Winged =C= EL34s outputs and Amperex 12au7s in the driver), and I have observed that sparing the ST70 serious bass duties really focuses it's energies on resolution. Also now that I have the solid-state bass control I grew up on, I don't need to disqualify tubes for being too bass shy for my tastes. It really is a best-of-both-worlds situation.

I am seriously having a hard time believing my setup can sound this good. Thankfully I have enough vinyl to spin to keep me from thinking about it too hard.
:music:
 
Thanks Kegger!

As always, it's a pleasure to see you and your helpful input in this thread.

The perpetual soldering-iron-on-the-kitchen-table phenomenon is testing my wife's patience, so it may be a while before I get to audition all three of the extra ST-70 driver boards I've acquired. The driver due in next is a rather low-output topology, so I am focused on other projects that will upgrade existing components and add needed gain into my signal chain to help offset this.

In the meanwhile, I'm anxious to hear more about the new Triode Electronics and Mapletree drivers as there's not much feedback out there in regard to them.

Some guts need to be spilled...
 
Brinkman said:
...
The perpetual soldering-iron-on-the-kitchen-table phenomenon is testing my wife's patience, ...
Click to expand...

WAF is always an issue:yes:. I was banned to my patio last year (spring) and don't have a hope in .... of coming back in anytime soon:sigh:.

Good Luck and know that your reports are read and appreciated.

Thanks
 
A man needs a shop I have decided. I don;t have one myself. If there was a reason to make me move to a different house that would be it as I don't have anywhere to put one here. My friend has a shop made out of a storage shed in his backyard. I live in one of those neighborhoods where you gotta get approval for one but it might be worth it. But then I would have to get electric service run out there too.
 
The Curcio upgrades have kept me interested but I've never gone through with a trial. I think the fact that the SoB driver requires the SoB power supply makes it a slightly more involved purchase, and added to that is the fact that the power supply upgrade is catered to it's "complementary" driver, as opposed to the ST70 by itself.

The Curcio upgrades seem comparable to the K&K audio upgrade, and though I've never heard either, I've completed the assembly of the K&K kit just the other day but am waiting to install it until I've got my new phono stage (Hagtech Ripper) up and running. It would be sensible to listen for any improvements with my current reference driver still in place.:music:
 
shelly_d said:
WAF is always an issue:yes:. I was banned to my patio last year (spring) and don't have a hope in .... of coming back in anytime soon:sigh:.

Good Luck and know that your reports are read and appreciated.

Thanks
Click to expand...

Thank god for my basement, its a mess down there, but its my mess... :banana:

My son laughs as I have 4 areas (benches) where I build and fix things..

Truthfully, I have to clean it up one day... its amazing how much crap you can fit in a 1000 sq foot basement...

Sal
 
salb203 said:
... its amazing how much crap you can fit in a 1000 sq foot basement...

Sal
Click to expand...

That's almost the size of my entire 2 bedroom Condo. Since we are a family of 3 living in about 1200 sq feet and its cluttered - I can well believe it. I was banned for reasons of solder fumes in the house.
 
As an update:

I finally installed the K&K audio board and it sounds outstanding.

First thing I did was disconnect my active crossover to hear how well my revamped (solo) ST70 would handle bass paired with my modified Klipsch Fortes. I gotta say, it sounds nice. Not distractingly deep, nor overly present, but not yet "perfect" by audiophile standards. But certainly apt. Honestly, the presentation sounds much more natural than the bi-amping scheme, though the bass DID sounded more accurate with some SS reinforcement.

Next, I purchased some KT88s and rolled a new tube into my phono preamp... I'm still assessing what I'm hearing, but right now, I'm very pleased. I'm looking forward to a more thorough post after the tubes break in.

Best.
 
That is a very interesting circuit. Do you happen to have the instruction manual with schematic you could scan and share?

Craig
 
NOSValves said:
That is a very interesting circuit. Do you happen to have the instruction manual with schematic you could scan and share?

Craig
Click to expand...

Unfortunately I lack a scanner (or printer... I use the printers in my electronics lab at school. Shhhh.....:nono:). I have seen a very similar driver schematic topology for the ST70 at the website of the poster "SY" at the DIYaudio forum. Just find a post by him there and there's a link to his website. He calls it the SYclotron. Alternately, you could try asking Kevin at K&K to email you the schematic. He has plenty of schematics he shares if you search the K&K forum.

As for the K&K driver, I'm very fond of it's dovetailing of 30's tube amp design (interstage transformers) with "sacrilegious" modern twists like CCSs and switch-mode power supplies. It does strip the ST70 of it's "Williamson" ethos, though there is no shortage of Williamson-style design if that is what one is after. I just find the result of blending high-bandwidth interstage transformers and CCS-coupled phase inversion and cathode supplies to yield superb results.

Best.
 
Well I had to get a power tranny for mine, I got it wired in and was bringing it up tonight and was wondering about the bias, I had line voltage at 85 volts and it seems I had no bias voltage yet, Is the ok or do i need to bring it up closer to line voltage to get the bias to come up.
Thanks Steven A.
 
Well it is not ok Kegger, I was playing it tonight and a few min after start up I herd a click sound and the left channel lost sound, I had the meters on the bias taps and they were fine even after the click sound and not red plateing on any tubes. I will dig into it in the morning and look around and see if i see anything.
This is the second time it has done this. Other wise it sounds great.
Steven A.
 
So I've been digging around lately, all the while considering eventually throwing down for another set of ST70 transformers and maybe a chassis. I feel pretty committed to my current K&K driver setup but would still like a way to audition different drivers. So that has me thinking of installing a few of those push-button barrier strips onto the underside of the chassis for easy wiring/unwiring of drivers. Any suggestions of where I can find barrier strips like this?

Since installing the K&K driver, I've also found myself becoming more curious about the more expensive "regulated" class of drivers. These would be the K&K audio, Curcio Electronics and Van Alstine models. I think it would be fun to hear these modifications in an A/B setup, just to hear if regulated power supplies have a very subtle influence or a more homogenizing influence over the front-end. Kind of like listening for similarities amongst amps without global feedback or DHTSE amps. If anyone who's compared any of the three drivers above against any of the other should feel compelled to comment it would be appreciated.

Also, I thought it would be useful to link to a possible ST70 driver schematic I came across. This here is a driver design by the poster "SY" who moderates at diyaudio.com. It is a link to a design on his homepage, so I hope he doesn't mind me linking to it here. At any rate, I found it interesting because he's offered it as a design for the DIY community and it has some resemblance to the K&K driver. Mind you, the K&K driver doesn't use Jensen input transformers (it uses arguably superior Lundahls), doesn't use NFB and has provisions for a regulated power supply (among other differences). Nonetheless, it's comparable.

Looking forward to tweaking my current driver. Next I am going to adjust my input transformers from a high gain to high input impedance configuration. Soon after, I may try wiring it from triode to ultralinear. Will post what I hear.

Best.
 
Very Similar... I think it runs 4 12AT7 tubes.... If I remember, the sockets were evenly spaced on the driver... Ill have to search through some pics to find.

I run SHannon's board with Wima caps and love... The setting of the bias is a bit complex for me... (I like my DIY MKIII for that reason :-) ).

I have a built version of Uncle Nerds board too... I will be selling my St35 to fund the parts for that setup. That way I can run either intercangibly.
 
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