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Friday, April 21, 2006

DAVE HUNTER RESPONDS! *READ THIS POST IF YOU ARE BUILDING THE 2 STROKE FROM SCRATCH*...

A couple of posts back, I cried out to Dave Hunter in cyberspace hoping he would hear my plea about a PT question I had...he has answered The Call. Mr. Hunter has graciously answered this question and provided critical information about changes to his original design since "The Guitar Amp Handbook" was published. You will want to read his comments before soldering your amp if you are building this amp using the book as your guide.

I have included email excerpts from Dave below. Some of his comments are information you would have if you purchase The Two-Stroke Amp Kit offered through Backbeat Books at this link: http://www.backbeatuk.com/ampkit/ampkit.htm. You can find the latest information about the amp design at this link and should seriously consider this option if you don't have at least 2 out of 3 of the following conditions met: 1) amp building experience; 2) a friend you can bug all the time about his previous amp projects; 3) a brother-in-law/friend/co-worker/self with access to tools for drilling.

That being said, Dave was kind enough to offer some very important Supplementary Build Notes to the amp and gave his permission for me to link this document you can only typically get when you purchase the kit. Thanks Dave!! Here is the link
Two-Stroke Amp Desgin: Supplementary Notes

Download this to get some very important and specific information about PT hook-up and other need-to-know details BEFORE YOU SOLDER.

Comments from Dave Hunter emails below-

April 19, 2006

I had a look at your amp kit blog: lovely work. I'm
impressed that you're building it from scratch from
parts you are sourcing yourself, but that is
definitely the best way to learn. I'm going to send
you an attachment of the Supplementary Instructions
document that I wrote up for the amp kit sales. There
are a few updates in that and a few minor corrections.
The 70ma PT should be fine (they change the specs on
these things without letting us know!), and the
instructions will also cover the extra wires that you
find on their newer PT compare with the one I
prototyped the kit with (again, these just started
turning up - nobody told me they'd changed them!).
People are having great success with this, though, so
you shouldn't have any problems.

Some people are finding a 20uF filter cap in place of
the first 40uF works best, makes the amp a little less
squasy because it reacts better with the 5Y3, but you
can always change that after if you feel you want to,
as long as you understand the safety practices
involved.

April 19, 2006

> Dave-
>
> Thanks for the response and the instructions!
>
> Quick question. I'm really only going use this amp
> with an 8 ohm speaker whether it's 10", 12" or 15".
> I only have one speaker out jack. Which OT wire
> should I use? I have plenty of room to add another
> jack if needed.
> -Ken in Seattle

Hi Ken,
WIth a single 8 ohm speaker and either 2x6V6 tubes or
a single 6L6 you want to use the white wire from the
OT secondary. If you sometimes want to use a single
6V6 change to the yellow wire, or put in a switch to
do so. Keeping it simple is always a good idea!

I forgot to say (but maybe it's in those notes) that
there was a mistake in the diagram such that the cap
on the Tone pot reads .047uF but it should actually be
the .0047uF that is correctly listed in the parts
list [p. 180 in the book].
Also, hopefully you understood this point but
one builder just emailed me who didn't, so... you DO
NOT connect pin 2 of V1 to ground - that's just to
indicate the connection for the shield of that
shielded wire to the ring terminal on the preamp tube
socket bolt.

All the best,
Dave

April 20,2006

> Dave-
>
> Many thanks for the OT advice. I noticed from the
> instructions you sent me, that you preferred the
> single 6L6 set up. I'm going to go with the two tube
> setup. And I did get the heads up about the .047uF
> cap…
> I wanted to tell you that I just finished reading
> your classic guitar rigs book and really thought it
> was fantastic. Before your book came out, a buddy of
> mine and I were complaining that there were no good
> reference recordings with all the amp and guitar
> settings explained. Thanks for making that CD. Also,
> your guitar amp book is the clearest, most
> articulate book of it's kind. I've been mining the
> internet for information like this. Your book
> brought it all together with common sense, a good
> dose of electronic theory, and engaging writing.
>
> thanks
>
> -Ken in Seattle

Hi Ken,
Thanks for your kind words about the books. I'm glad
you have found them informative. Re the 1x6L6 vs
2x6V6, since you've already punched a chassis for two
output tubes you might as well try the latter, and the
beauty is you can always swap the configurations
without changing anything because they are
individually biased, and the impedance match is the
same between on 6L6 and two 6V6s. When I say the 6L6
"sounded better" to me (albeit only slightly) that's a
subjective comment, and there are many cool things
about two 6V6s also. And even without an impedance
switch (which you could add easily) you can pull one
of the 6V6s for a half-power mode, and the OT won't be
all that bothered about the mismatch, even if it's not
an optimum situation in the purist's sense.

Good luck, and enjoy,
Dave

4 comments:

Anonymous said...

Dave is a really great guy. I met him personally when I picked up the kit at his home, and he was very helpful during the build process. My Two Stroke has performed flawlessly from day one, and is now over one year old.

AlexT

I have some pics of the project, how can I post them?

Ken Pendergrass said...

AlexT-
Thanks for check out my forum. Can you email me some pics at pendergaurd-forum AT yahoo-
I'll put them up to the blog.
thanks
-Ken

Geoff said...

wow, I wish I new this website existed before I sourced all my parts and finished my amp last week -
and have been troubleshooting it since (I'm a total newbie so I grounded the Pin 2 of the preamp tube!).

Thanks for writing a great book, and hell if it worked right the first time I wouldn't be learning all this extra stuff... which, is why I built it to begin with!
Wish me luck getting it going!

Keiff T said...

One thing I would have done differently is to use a solid state rectifier since a class A amp isn't going to give you any sag and it is easier to build that way. You will want to use a different PT with a lower primary voltage, although you could use a dropping resistor too.