ST 35 Options

I recently reconnected an ST35 I assembled a few years ago starting with old output transformers, a new power transformer and the Triode PCB. I am impressed with how good it sounds, and started thinking about assembling another using newer components. I don't really need another amplifier, but do enjoy putting planning and making a chassis and putting the amplifiers together.

If anyone has experience and or opinions regarding one or more of the various options for a new ST35, I'd appreciate hearing about that experience and opinions, suggestions as well. So far I've looked at:

tubes4hifi version, I like the single board and toroid transformers.
dynakitparts, I've used their transformers for a Mark lll and see some interesting layout possibilities with the separate PCBs.
Ebay offers a single board option that is based upon the older single board version, I assume that may be the PCB I bought from Triode.

Edcor offers power and output transfromers. I've used their transfromers in other projects, they seem like a good option using the dynakit parts PCBs or possibly the Ebay PCB.

Perhaps there are other options I've missed, if so, I'd appreciate knowing about them.

Thank you.

TN Allen wrote:I recently reconnected an ST35 I assembled a few years ago starting with old output transformers, a new power transformer and the Triode PCB. I am impressed with how good it sounds, and started thinking about assembling another using newer components. I don't really need another amplifier, but do enjoy putting planning and making a chassis and putting the amplifiers together.

If anyone has experience and or opinions regarding one or more of the various options for a new ST35, I'd appreciate hearing about that experience and opinions, suggestions as well. So far I've looked at:

tubes4hifi version, I like the single board and toroid transformers.
dynakitparts, I've used their transformers for a Mark lll and see some interesting layout possibilities with the separate PCBs.
Ebay offers a single board option that is based upon the older single board version, I assume that may be the PCB I bought from Triode.

Edcor offers power and output transfromers. I've used their transfromers in other projects, they seem like a good option using the dynakit parts PCBs  or possibly the Ebay PCB.

Perhaps there are other options I've missed, if so, I'd appreciate knowing about them.

Thank you.    

A clone of Dynaco ST35 is available from dynakitparts.com and this is the only available that
could be expected to have the same performance as a Dynaco ST35.

The unit from tubes4hifi differs, it is best describes as an EL84 stereo amp. It does not use
Dynaco st35 circuit, nor does not use Dynaco Z-565 transformers.

Edcor does not have ( to my knowledge) clone of the Z-565 transformer, thus some adjustment of
the NFB might be needed.

But if one needs a "generic" EL84 amp, all the above will fit the bill.

Thank you for the insightful response. I realize I should have been more critical of the association made by marketers between the ST35 designation and their products, which as you point out are not really Dynaco ST35 amplifiers, but EL84 amplifiers. If I assemble another amplifier, it probably will be using dynakit components.

How critical do you think the Z-565 transformers are to the particular sound of the ST35? Perhaps they are the reason I find the amplifier I assembled using original Z-565 transformers so pleasing.

It's my opinion, and that of many others, that the Z-565 transformers or exact clones are essential to the sound of the ST-35.
The same transformers were also used in the SCA-35.
Here's another option for boards:
http://tronola.com/html/daves_store.html
I rebuilt an ST-35 using these boards and the Enhanced Fixed Bias (EFB) system board add-on. That amp compares well to any I've heard, at least until it runs out of power!

I second Dave Gillespie’s work.  I’ve built a few versions.  The EFB circuit is a real measurable improvement over the stock circuit.  I also incorporated an adjustable feedback circuit.

Here’s my latest version.

TN Allen wrote:Thank you for the insightful response. I realize I should have been more critical of the association made by marketers between the ST35 designation and their products, which as you point out are not really Dynaco ST35 amplifiers, but EL84 amplifiers. If I assemble another amplifier, it probably will be using dynakit components.

How critical do you think the Z-565 transformers are to the particular sound of the ST35? Perhaps they are the reason I find the amplifier I assembled using original Z-565 transformers so pleasing.

The transformers and Dynaco designs are intertwined. Thus using original design AND
dynaco transformers will get a good result. Change either and you might have to
resort to instrumented tuning to get the NFB and stability correct. Not impossible but it
takes time and efforts to do, also needs some instruments and possibly an assortment
of tubes with parameters spread and some different speakers to verify stability.

I've built two of these using the original transformers. The output transformers are the most important component. Second in importance is using the EFB board mentioned above, which makes up for some cut corners in the original design.

Hey Folks, I am new here.  This is my first post. I have built  many amps repaired restored at lest twenty st70's, an sca35, and  a  couple pass2/3 preamps.

Anyway, I  found this  a few weeks ago and bout this so I thought I  would share.

None of this is mine,  I am not affiliated in  any way with the  seller or the items. This is all on evilbay.


I am  waiting  on the tube sockets and then  I can do final assembly. I'll post some pics and impressions then.

I tried to post the links, but oops, I am just too new.

The users name is Ifnickel search for him and you will see a very nice chassis and the associated card to build that version of the st35.

THis is a cut and paste from his listing

"Hello Tube Lovers,

Hello Tube lovers I just received a new lot of PCBS. I have here the bare board for sale of ST-35 Dynaco Replica New Design!!!!!
The board is similar as the old Shannon Parks Audio SCA-35 design Rev C, and D, that is obsolete.

The PCB was tested 100%, and we have amplifiers built with it sold. We've sold boards to NY, NJ, CA, MI, MN, FL, UK and we keep going! it's been a success!
We decided to start with bare PCB for sale, and we might put a kit together if we found interest.

It uses ½ 12AX7A and ½ a 12AU7 per channel. The 12AX7A is a low noise preamplifier that directly drives the cathodes phase splitter 12AU7. We also replaced a single cathode resistor and capacitor with four individual resistors and capacitors. The original cathode bias resistor has been replaced with individual feature that allows your ST-35 to perform to its full potential. The circuit incorporates 4 trim pots to set individual Bias per EL-84. Once adjusted with 0.35V, the amplifier is ready to operate. For best performance is recommended to have a well quad matched EL-84 tube on this project."