Help me decide

for Dynaco Mark II/III/IV and DIY PP monoblocks

Help me decide

Postby rrd » Sun Apr 23, 2006 4:37 pm

Trying real hard to decide between the ST70 or the poseidon MKIV for my next project. I plan to build from scratch either way. Any opinions would be greatly appreciated. Thanks!
rrd
 
Posts: 11
Joined: Sun Aug 29, 2004 11:07 am

Postby TerrySmith » Sun Apr 23, 2006 4:50 pm

The ST-70 and the MK-4 is the exact same circuit except the power supply.

I prefer the MK-4 setup because you have a rectifier tube and choke for each channel. The ST-70 has one rectifier and one choke for BOTH channels. The rectifier (5AR4) is at it's limit in the ST-70, and is easily destroyed.

Just an idea, You could build a pair of MK-4's on the MK-3 chassis as seen on ebay, only you would have to drill holes for the smaller transformers.
T. Smith
User avatar
TerrySmith
KT88
 
Posts: 973
Joined: Sat Jan 31, 2004 12:51 pm
Location: Maryville TN

Postby WA4SWJ » Sun Apr 23, 2006 7:30 pm

Hi rrd,

I have an ST-70 clone using Shannon's board that sounds just awesome. I am continually amazed at how good it sounds. I have also just finished building 3 Mark III's with Poseidon boards too. Unfortunately due to one missing resistor value (on order) I haven't fired them up to their fullest yet. Should be able to do that later this week and can give you a direct comparison then. I also have 3 eiclones that use the same transfomers as the Mark III's (all of my amps have Dynaclone transformers) and they are awesome with EL-34's but don't have quite the detail as the ST-70. But they work amazingly well in home theater. The eiclones don't have the latest mods either. I'll do that when the Mark III's are running. I use the eiclones for home theater so I want to be able to run them until the Mark III's replace them.

FWIW, I'm running some "new" Mullards, 12BH7 phase inverters and a 5751 in the ST-70. I'm running SED EL-34's in the eiclones with JJ 6SN7's and 12AX7's. The Mark III's have Sovtek 5AR4's, EH 6550's, RCA 12BH7's and GE 5751's.

The comment Terry makes about the rectifier is true in the ST-70. I failed a JJ rectifier pretty quickly and replaced it with a solid state rectifier with a lot more filter capacitance on the circuit board. It just sounds superb. I think the added power supply capacitance gives it a lot more punch. Of course some folks don't like solid state rectification for some reason. Personally I can't tell any difference except as I mentioned about punch. I think it really comes from more capacitance in the power supply.

It is also a matter of cost to some extent. The ST-70 should cost a little bit less than 2 Mark III's. But if that's not an issue, ignore this comment.

Of course the Mark III's will have more power output if that's important too. How's your speaker efficiency?

After all this, I can say that any of these amps sound really, really good and are a great deal of fun to build. In terms of sound, it's all good. Shannon's measurements also help let you know that the amps work as planned. Of course measurements don't always tell the entire story.

One other questions I'd also ask myself is what would suit you - monoblocks or one stereo amp?

Hope this helps a little. I can comment more on the Mark III's sound later.

Hope this helps a little.

Regards,
Ed Long
User avatar
WA4SWJ
KT88
 
Posts: 650
Joined: Mon Dec 27, 2004 8:39 pm
Location: Belleview, FL

Postby rrd » Sun Apr 23, 2006 8:39 pm

Hello Ed and Tom,
Thanks for your comments. I do like the idea of a power supply and choke for each channel. I’ll be real interested in your comparison Ed. Is the solid state rectifier documented anywhere?
rrd
 
Posts: 11
Joined: Sun Aug 29, 2004 11:07 am

Postby WA4SWJ » Mon Apr 24, 2006 5:34 am

I bought a Curcio rectifier board for my ST-70 after the GZ-34 arced over. To be honest I think the board has a significant design flaw. The HV traces are right on the edge of the circuit board. The board is mounted vertically so the electrical clearance from those traces to the chassis bottom cover plate is too close. So I insulated it with electrical tape on the board and the chassis plate. I got this board mostly because I didn't want to design a board (which I can do) and I wanted something fast. Plus I didn't want to mount a bunch of loose parts in the bottom of the amp. So I did it that way. Works fine but the caveat above about electrical clearance is important. Otherwise, as I've stated, my ST-70 sounds extremely good with solid state rectification.

Shannon uses solid state rectifiers in his amp circuit board designs. Of course they can be converted to tube rectification if one wants to. The eiclone is a good representation of how solid state is done. Take a look at the eiclone manual. That approach can be taken with the ST-70 too with some minor modifications.

I'll let you know how the Mark III's sound this week. I can't wait to get those darn resistors. Only one little part missing that I didn't have! But they'll be here in a couple of days.


Regards,
Ed Long
User avatar
WA4SWJ
KT88
 
Posts: 650
Joined: Mon Dec 27, 2004 8:39 pm
Location: Belleview, FL

Postby WA4SWJ » Mon Apr 24, 2006 5:36 am

One other thing - when I installed the rectifier board in the ST-70 I also installed a CL-90 inrush protector to help with inrush. Works fine also.
Ed Long
User avatar
WA4SWJ
KT88
 
Posts: 650
Joined: Mon Dec 27, 2004 8:39 pm
Location: Belleview, FL

Postby WA4SWJ » Wed Apr 26, 2006 6:06 pm

OK Guys and Gals,

Here are my three new Mark III clones with Poseidon drivers:

http://community.webshots.com/photo/354 ... 8377awVjmG

There are three pictures. If you click on the "album" link just below the picture you can go back a page to the other two pictures plus others if you like. Or, you can click the "previous" photo at the upper right.

I just finished them this evening. I was waiting for the plate load resistors for the phase inverters. I didn't have the new 68K ohm value in the junk box. Soldered them in this evening when I got home and fired two of the amps up. I had previously fired up the one on the left. Yes, those are geeky blue LED's in the octal socket centers. Only the right two amps are on in these pictures driving those kinda grunchy speakers in the background.

Well, they are brand new and have not even stabilized yet but they sound great even without the best speakers I have and without my best CD player. So, I am estatic! These will replace my eiclones as L-C-R amps for my tube-based home theater. The eiclones will be moved to drive the rear speakers now after I make Shannon's previously posted mods to them. I'll send a picture of the whole thing when I get it all modified.

What fun! I don't know yet but these sound as good as my ST-70 when it was driving those speakers. I'll hook them up to my A-25's after they settle down a little. But they have lots of punch and what sounds like a great top end. The speakers in the picture are very "bright". The tweeter output is overpowering the woofers. I'll someday have to adjust the crossovers. I built those a while back from a bunch of sale parts from Parts Express. Even so, they don't sound too bad.

Anyway, another fantastic set of amps. Thanks Shannon for the driver boards and the inspiration! Now I have a set of Eric's HF-89 clone transformers to do something with. Those should be really impressive sounding. (I mentioned before that I'm addicted and I really am.)

Regards,
Ed Long
User avatar
WA4SWJ
KT88
 
Posts: 650
Joined: Mon Dec 27, 2004 8:39 pm
Location: Belleview, FL

Postby TomMcNally » Wed Apr 26, 2006 8:21 pm

Nice job Ed ! Your neighbors will love you !

My Poseidons knock dishes to the floor 2 rooms away with the monster Cerwin Vegas!

... and I thought I was outta control with the blue LEDs !


Image
User avatar
TomMcNally
Darling du Jour
 
Posts: 2729
Joined: Sat Nov 19, 2005 2:19 pm
Location: Northfield, NJ

Postby WA4SWJ » Thu Apr 27, 2006 4:53 am

Thanks Tom,

I have a couple of clocks like that but they're binary. You have to add up the numbers 1-2-4-8 - powers of 2. I get lots of questions about them and once explained I get two reactions - either they leave with heads shaking or "That's cool!" and they try to learn how to read the clock. A couple of guys come in occasionally and try to remember how to read it.

Mine have red LED's though.

Unfortunately they don't have tubes although I've seen some nixie tube clocks on the Web.
Ed Long
User avatar
WA4SWJ
KT88
 
Posts: 650
Joined: Mon Dec 27, 2004 8:39 pm
Location: Belleview, FL

Postby TomMcNally » Thu Apr 27, 2006 5:43 am

The blue led clock is pretty worthless when it comes to being a timepiece ...
almost as much math involved as the binary variety,
and the blue spots stay in your eyes for hours.

Nixie and Numitron clocks are another one of my hobbies ...

Image

Many more here: http://mcnally.cc/clock.htm
User avatar
TomMcNally
Darling du Jour
 
Posts: 2729
Joined: Sat Nov 19, 2005 2:19 pm
Location: Northfield, NJ

Postby WA4SWJ » Thu Apr 27, 2006 5:55 am

Tom,

Like I said - You are truly awesome!! I think that clock using analog meters is especially cool.

I built a digital clock years and years ago using a bunch of NAND gates and such. I still have it and it works, but the cabinet I built out of Plexiglass is poor so I don't use it any more. It's time base used the 60 Hz power line. Works well. I should drag it out and fire it up again.
Ed Long
User avatar
WA4SWJ
KT88
 
Posts: 650
Joined: Mon Dec 27, 2004 8:39 pm
Location: Belleview, FL

Postby EWBrown » Thu Apr 27, 2006 7:18 am

I still have an old nixie clock that I built back in 1972, as a kit from B&F Enterprises (a long gone electronic surplus and goodies store). The nixies are a tad dim and flakey after all these years, but it still works.

Interesting thing about neon bulbs and nixies: as they get weaker, they will get "flickery", and this is most noticeable in the dark, but they will work better in the presence light. Well, it turns out that neon tubes are somewhat light-sensitive, and can be optically "biased" with a small light source (like LEDs) and this will give them a longer useable lifespan, before they become hopelessly dead. I found that blue and UV leds seem to work best in this application.

I had built numerous LED and 7400 series IC-based clocks, and moved on to frequency counters, of my own designs.

BTW, Gary Kaufman has Nixie clock boards available on his site, look under "Links".

Or just go here: http://www.the-planet.org/nixie.html

/ed B in NH
Real Radios Glow in the Dark
User avatar
EWBrown
Insulator & Iron Magnate
 
Posts: 6389
Joined: Wed Mar 19, 2003 6:03 am
Location: Now located in Clay County, NC !

Postby TomMcNally » Thu Apr 27, 2006 7:44 am

I've built some TTL clocks, but never all discrete, I always used
counters like 7490s and 7492s. Lotsa fun. I've still got a
counter I built from a 73 Magazine article, was supposed to
use Numitrons, but I wired it up to LEDs (same drivers of course)

The clock in the picture above is one of Gary's boards. I just got
six more from him the other day. I build them as gifts and
sometimes sell kits or completed boards on eBay.
User avatar
TomMcNally
Darling du Jour
 
Posts: 2729
Joined: Sat Nov 19, 2005 2:19 pm
Location: Northfield, NJ

More nixie clocks

Postby dhuebert » Mon May 01, 2006 1:00 pm

I was watching "All That Jazz" on the weekend and noticed a nixie clock in one scene in Joe Gideon's house.

I'm sorry, what was the question again?

Don
User avatar
dhuebert
KT88
 
Posts: 820
Joined: Thu May 01, 2003 9:26 am
Location: Winnipeg Manitoba Canada

Postby WA4SWJ » Mon May 01, 2006 3:11 pm

You're right - the question was "Which one to build?".

I guess I would say that as nearly as I can tell so far, the Mark III's I built with the Poseidon driver boards sound just as good as the ST-70 I built with Shannon's driver. Obviously they have more power and that may make a difference as I listen more and more. At this point though, without much critical listening (as if I'm an audiophile), both the ST-70 and the Mark III's sound very open with extended high end and very good bass. Mid-range is also very even with lots of definition. I can hear cymbal touches very easily that I can't hear well on my transistor amps through the same speakers. My transistor amps truly sound muddy in comparison with these and they're pretty decent Yamaha amps from years ago - A-2070 and A-3070. So I am quite pleased with all these Dynaco copies I've been able to build using Shannon's boards.

I guess the build choice will be based on other factors besides how they sound. Like do you want a stereo amp or monoblocks? At least that's how I view it. I feel fortunate to have both types of amps to listen to. I guess that's what being finally single with no kids allows one to do. I do have to say that the eiclones I have do not sound quite as good as these amps. But I have not made the additional tuning mods Shannon has proposed yet. But I also have to say that the eiclone's ain't no slouches either. I'm sure they will open up some when I have time to make those modifications to the component values.

Regards and have fun everyone,
Ed Long
User avatar
WA4SWJ
KT88
 
Posts: 650
Joined: Mon Dec 27, 2004 8:39 pm
Location: Belleview, FL


Return to poseidon

Who is online

Users browsing this forum: No registered users and 10 guests

cron