Transformer templates

[merlin2049er]

Hi.

Finally some of the parts I've order are starting to roll in. I'm looking for transformer templates for the Dynaco Z565 and the PA774.

I'm trying to fit these transformers on the 12x8x3 chassis I got. Hopefully they'll fit.

Thanks,
JG
:morning:

[Shannon Parks]

I'm trying to fit these transformers on the 12x8x3 chassis I got. Hopefully they'll fit.

The Dyna trannies squeeze onto the top pretty easy. Those who have squeezed the Hammonds on top need to help me pack on my next trip! Yep, it's been done.

I voted 'other' - I've heard an Eico HF-85 can sound good. The Foreplay is a steal at $150 if you don't need phono.

Shannon

[dado5]

Howdy,

I voted for the GG, but I am also building a 12sn7 based unit based on a Maple Tree Audio unit. The GG has a rep for being neutral and accurate whereas the Maple Tree has more of a traditional tube signature according to the reviews. Both are low gain, simple and cheap to build so I figured why not go for two?

Rob

[JG]

Hi,

I've heard the same about the Grounded Grid Pre Amp, neutral , and fast.

It's $499 for the kit, still a little pricy compared to the foreplay @ $149.

Thanks for voting,
JG

[dado5]

JG,

I am scratch building both units. Using torroid transformers, pre-fab tube terminal boards and Auricaps for coupling, they are still under $120 each to put together. I am going to use the same size Hammond boxes for these as for the ST35.

The scat for the GG is in Bruce's book Audio Reality. $30.00 at his web site www.transcendentsound.com or from www.tubesandmore.com.

The scat for the Maple Tree Audio piece is at

http://hollowstate.netfirms.com/manuals.htm click on the Line 2 and PS1 manuals.[/url]

Thanks,
Rob

[Shannon Parks]

...The scat for the GG is in Bruce's book Audio Reality. $30.00 at his web site www.transcendentsound.com or from www.tubesandmore.com...

I gotta get this book.

Shannon

[dado5]

It is a very good book. Lots of basic info in the first section. The second part is gold however. It has the schematics (with design descriptions and parts lists!) for all of his designs.

Knowing that almost every piece of high end tube gear out there is derivative of either WE's or Halfler's concepts, it is very nice to see some well thought out, original designs. His OTL takes Futterman's framework and makes it more stable with some very simple and elegant solutions. Borderline genius IMO. His other amps (and the GG as well) follow along more conventional lines but still involve unique approaches. The book is very highly recommended if for no other reason than to view his work.

Thanks,
Rob

[SteveS]

OK, so I haven't actually got the ST-35 built yet... but all the parts are in. So when it is assembled it will be connected to a BH Foreplay. I'll report back then. In the meantime I have no problem voting for the Doc's products, honest pricing, fun to build, extremely well supported.

Ofcourse my problem is that my speakers situation is in a bit of a mess at the moment - so giving anything an honest evaluation is a little difficult.

That was one of the reasons I was drawn to this project as an amp however because the speaker options are much broader with a few more watts to drive them.

steveS

[dado5]

The three big reasons for me are: Cheap, easy to build and.....EL84!

I loved every EL84 amp I have heard. Old Scotts, the Jolida 102 and the Manley Stingray are all fantastic sounding amps.

I started Bruce's EL509 OTL in earnest as far as acquiring all the passive parts but it is a big bite to chew. The tubes are expensive and it uses a boatload of power xfmrs. This was a bit hard on my limited budget. The amp project has be on more or less indefinite hold. I discovered this site (I forgot how now) about a month ago and will buy the board early next month.

This ST35 is considerably cheaper than the OTL, much easier to put together and a safer sonic bet IMO. I have never heard an OTL but I have never heard an EL84 that I didn't like.

Thanks,
Rob

[dhuebert]

I plan to build (eventually, it took over a year to complete the st35) the preamp featured on Norman Koren's site www.normankoren.com . I have spoken about his site before on this forum. I like his design philosophy and his designs, though complex, look really good to me. I especially like his bias servos on the power amp. Maybe in two or three years I can report back on results.

[jg]

I've got my ST-35 Amp about 80% done. I'm waiting for my tubes and transformers from Ned. Then I'll drill my holes in the chassis and mount and test everything. I've also got to mount my input and output capacitors too.

Besides that, everything looks good, can't wait to hear what it sounds like. I've made only 3 substitutions in the project. I've replaced the power cord and strain relief and fuse holder with a IEC connector (with a built in fuse holder) and the caps. I've also upgraded the input jacks and binding posts. (I've also skipped the standby switch)

As for the preamp, I was thinking of a passive preamp, (ie selector switch, input jacks, output jacks and stepped attenuator).

Any drawbacks using something this simple?

Thanks,
JG

[EWBrown]

I've used the "passive preamp" approach and it works well. The first version was a cast aluminum box with one of the 100K stereo pots from radio shack, and four of the RCA jacks from the parts list. The 2nd version uses a 100K step attenuator I got from Taiwan on E-bay, and four "isolated" RCA jacks from AES. Both work equally well, I like the feel and function of the 2nd one better. SInce I have been building multiple amps (DIY35s, SEs, rebuilt and "Cloned" Dynack ST70s, etc, I figured the external "passive preamp" approach was best for my needs. The main audio source is an old, but still great, Rotel RCD-855 CD player.

I did build a linestage/cathode follower preamp using 4 6N1Ps (similar to 6DJ8s or 6922s) and 5Y3GT. THis gives about 18 dB gain, plus cathode follower in case I wanted to drive a low impedance device, this preamp is stil under development, I still have to optimize plate and cathode resistor values, but it is quite good as present.

I've also used different AC power entry components, as you have described, and one unit witn a 6A RF filter and IEC connector.

/ed brown in NH

[dado5]

Hi JG,

Although there are often cited technical problems with passive attenuation relating to high frequency roll-off, I have never personally encountered this. The music played through the passives I have used (Creek OBH-10 and a home brew unit) has always sounded clear with all the upper registers intact.

That said however, I have noted that the passives I used tended to sap the music of some drive and intimacy when compared to active pre-amplification. I lent my home brew passive to a friend and used my Grado headphone amp in it's place and I found that the sound was considerably more involving...it seemed closer and quicker. I borrowed two other pre amps (Rogue 99 & a Sonagraphe) and this impression was confirmed.

It is basically a trade off IMO. You will likely trade some additional coloration for better pace and feel with an active pre vs. a passive.

If cost is a concern, DIY tube pre amps are the way to go. They are usually very simple circuits. And since they use small tubes and transformers, they are usually very cheap to build. I am building two and each one costs less than a DACT stepped attenuator.

My .02

thanks,
Rob

[EWBrown]

One method I've also tried is a very simple linestage, consisting of the 100K pot or stepped attenuator and a cathode folloewr. What I used was a direwct copy of the ZSLA-1 located here: http://www.decware.com/new%20site/mainmenu.htm

THis has the schematic and parts list so it's easy to duplicate.

Very simple, no voltage gain stage, does nicely for line driving and impedance matching and gets around the potential high frequency losses.
My next step was to add a gain stage in front as in their ZSP-1 kit.
I was able to glean enough info off their website to DIY my own.
The additional gain is useful for using devices (like portable CD players, etc) that have relatively low line outout levels.

In the EL34 SE amp, I included a 100K step attenuator and that works well, as there are no extra plugs, jacks or cable to dampen the sound.

/ed b in NH

[JG]

Thanks Ed.

I looked at this unit from Decware, and found the schematic and notes. Again, decware doesn't mention the transformer they use. (and the unit they list @ $575, quite pricy for a few components.)

Can you let me know what you used for this linestage?

Thanks,
JG