St-35 build pic.

[RobertWStephens]

Hello! Here is the pic of my st-35 project. I had a lot of fun building this. The voltages check out and there is no hum. I just need to crank some tunes to break everything in. Thanks for all the help from the forum!!! Peace. Robert

[TomMcNally]

Looks great - let us know how it sounds with the tube rectifier.

... tom

[RobertWStephens]

Hello! Does anyone have any experience on how long the ST-35 takes to break in and for the sound to open up? I was just curious what others had experienced. Tom was right about the 6v lamp being too bright. I will be at the auto parts store tomorrow looking for a 12v bulb. Peace. Robert

[WA4SWJ]

Hi Robert,

Maybe it really happens but I don't happen to believe in break-in when it comes to amplifiers. It might happen with speakers because they are mechanical devices mostly, but amps? I don't believe in that. I doubt anyone has measured any difference between a new amp and one that is "broken in". I'd like to read a paper on that subject if it has measured data to support improvement after a "break in" period. I might be convinced then. This is just my opinion. What I think breaks in are your ears when listening to something new. You forget what you heard before and your brain begins to like the new sound. Sort of like your nose getting adjusted to a new smell - after a while you don't notice it.

What I found in my ST-35 was that even after a year or so of use it still did not sound as open as my ST-70 amp. It was somehow muddy - on the same speakers with the same CD player driving it. It was definitely inferior to my ST-70. I finally gave up on it and put it aside. Sometime later I got it out and listened again. Still muddy. But by that time I had built up some more tube inventory. I installed a NOS GE 5751 in place of the JJ 12AX7 and an RCA NOS 12BH7 in place of the JJ 12AU7 phase inverter. Immediately the amp sounded much, much better. I like the way it sounds now.

I am not slamming JJ, they make some great tubes (ask Eric about their KT-88's) and I have a lot of JJ tubes. It's just that replacing the two front end tubes in my ST-35 made an immediate, significantly noticeable difference in sound. I kept the JJ output tubes in place. I might try something else for them later but for now they are just fine. The amp finally sounds good.

Hope this helps some.

Regards,

[erichayes]

Hi All,

For music reproduction, I prefer Sovteks over JJs in current production 6BQ5s (JJs are better in guitar amps) for a variety of reasons, one of which is a relative lack of break-in time. They're listenable after about an hour and change very slightly over the year's time I put on them--and that's a 24/7/52 year except for power outages.

JJs, on the other hand, are like fingernails on a blackboard for the first 5 hours, becoming listenable after about 25 to 30 hours. When I used to set one of my amps up with JJs, I'd set the bias and balance--they're pretty stable in that respect--and go into town for the afternoon after applying signal and speakers. Now that I have a dedicated burn-in bench, the amp doesn't see a set of speakers until 30 hours have passed.

For some reason, the JJ 6BQ5s are the only output tubes they make that are like that, with the possible exception of the KT77s, which I haven't auditioned yet. Their 6L6s and EL34s improve with time, but they don't have to be quarantined when first put in, and the KT88s are impressive right out of the chute.

While there is some psychoacoustics involved with listening to a "new" amp, there are real physical things happening, too. This is particularly true with a tube power amp built on a (worst case) metal plate and mounted on a wooden base, due to heat dissapation--or lack thereof. Metal film resistors typically have a temperature coefficient of ±50 ppm/°C, but if they get too hot their value will change permanently. Carbon film resistors aren't even spec'd--hell, you could use a carbon film as a thermistor, they're so squirrelly. Same thing applies to caps--heat 'em up and they're gonna change

My favorite story of an amp breaking in was actually a review of a SET amp in Glass Audio about 10 years ago. The reviewer was Irish, and he remarked to the effect that listening to a SET amp for the first time was similar to drinking a single malt whisky for the first time . . . they both take getting used to.

So does listening to 78s and 8 track tapes.

[RobertWStephens]

Hello! Thanks for taking the time to reply. Half the fun of DIY is tweaking things to your taste. I think there are aspects of audio that fall into "unmeasurables". Ed, I will take your advice and order up some tubes to swap around in the 12AU7 and 12AX7 position to the ones you suggested. Peace. Robert

[maal]

Hello!
Does anybody know where to get a complete building-manual for Dynaco ST35? With layouts for the PCB´s included. THANKS!

[Brik]

Does anybody know where to get a complete building-manual for Dynaco ST35? With layouts for the PCB´s included. THANKS!

Here is a pretty good copy of the manual, although it does not have the traces/vias information for the PCB:

http://home.att.net/~brik/ST-35/Dynaco_ST35_Manual.pdf

[maal]

Does anybody know where to get a complete building-manual for Dynaco ST35? With layouts for the PCB´s included. THANKS!

Here is a pretty good copy of the manual, although it does not have the traces/vias information for the PCB:

http://web.tiscali.it/stereoslurp/Downl ... -%2035.pdf

/BriK

Thanks a lot! It isn´t to hard to make the PCB`s, but the best is of curse to by them somewhere. Maby on eBay?

[Brik]

I have had good results with blank PC-13 boards from two different suppliers on eBay. They are also available from:
http://www.triodeelectronics.com/pc13o.html

They are available pre-assembled from:
http://www.dynakitparts.com/store/catalog.aspx?cid=11

I prefer to see ceramic tube sockets for 6BQ5s to avoid heat damages.

One note of caution. Many ceramic tube sockets have pin-to-mounting-hole
alignment that is different from the one that is shown in the Dynaco manual.
You will have to adjust board-to-socket-pin wiring accordingly.

Good luck.

/BriK

[Brik]

Here is a budget, point-to-point build with a pair of $23 output transformers on a Hammond
10x6x1 aluminum chassis painted white.
Due to the limited chassis real estate, the Triode TF-110-48/UL 6600CTs are oriented “in phase”
with the Triode PA774 power transformer.





Some afterthoughts:

1) I should have used the Z565 clone output trannies since they take less space allowing a
proper orientation although that would have increased the cost by ~$70.
2) In a cramped, point-to-point build like this, chocolate-covered caps like the WIMAs
should be soldered last. It’s too easy to melt the covering otherwise. I want an "M&M" version!
3) WIMA caps with their short leads are not ideal for a point-to-point build.
4) The 1” height does not leave much room for the power filter caps in the chassis.
5) The budget TF-110s sounded just as good as the Z565s.
6) Gold paint on trannies definitely does not look good.
7) Yes. It has that vintage "rats nest" look to it under the hood..

/B

[SDS-PAGE]

Cool looking amp! I like how thin the chassis is. It makes the tubes relatively large. So, how much did you end up spending all together? Cheap is the way to go if you can make it sound nice. I like the color scheme too. The gold doesn't look too bad. I used cashmere beige on mine and looked pretty good with the wood. I had to prime with white several times though. BTW, do you have pics under the hood?

[EWBrown]

IIRC, the PA774's core axis is (front to back) horizontal, and that of the OPTs is vertically oriented.

So the windings are still 90 degrees "out of phase" which is what you want. Nice construction, that beats my 9X10X1.5 inch "micro" ST-35 build. With that one, I used a rev D board, mounted on top, with the AC power primary wiring, and the volume control, and I/Os under the chassis. Y there is somewhat exposed DC HV, :o but it wuld take at least a minor effort to get "bitten", and I have no resident toddlers or kittens. Yellow_Light_Colorz_PDT_06 so the chances of an accidental "gefingerpoken" incident are slim. On that build, the OPTS are teh TF-110-48-ULs and the power trannie is a Hammond 270 series (275-0-275VAC) so it runs a tad lower power iut, perhaps 14 or 15WPC vs 17-18.

/ed B in NH

[K-MAN]

I noticed when I put new JJ/6BQ5 tubes in my amp it took awhile to get a more mellow, warm sounding amp. I think the nature of vacuum tubes means they will change sound with age, especially the first little while and whether it sounds better or worse is personal I believe.

[Shannon Parks]

This latest ST35 is so tiny and cute, I almost want to hug it. Yellow_Light_Colorz_PDT_09

Nice work.