Dear RATs,

another DIY tube amp project is finished. You
can view the according web pages at:

http://www.ndh.net/home/schlangen/ro...t/el34set.html

but they are only in German language so far, sorry.

Scrolling down that page you get to a link table
for the schematics, breadboard circuits, datasheets
of used tubes, and so on.

This amp partly originated from the "2 1/2 weeks to go"
thread in this newsgroup and it took me only 2 1/2 *months*
to complete ;-)

On the first spot this amp looks like a generic EL34 SET
amp with 6SL7 drivers, GZ34 tube rectification and CLC
filtering, but it differs somewhat from more common designs
by utilizing a highish B+ of 430 volts and also a highish
reflected load of Ra = 10k (many usual designs use a B+
of around 300-340 volts and a Ra of 3k4 or even less instead).

Tnx2 to Patrick Turner for the tips on high B+ and Ra with
EL34, and Ronald Pit for giving me a hint where to get
some decent priced NOS JAN Sylvania 6SL7.

This amp was made as a present to the father of my GF, and
last sunday he brought over his favourite classics CDs,
mostly large orchestra and Italian operas (solo voices
and choirs) for a try of that amp.

What shall I say, he had tears in his eyes after listening
to his favourite stuff for some hours like he never had
heard before.

I wouldn't have expected that from an EL34 DIY
"low-fashion-factor" (and not-that-high budget)
design, even with quite some added tweaking.

Indeed, this EL34-thing is highly musical (Choky probably
would say it sings). On the other hand it ain't no "rocker",
but that wasn't he goal and can't be expected from ~5 watts
per channel.

Tnx again to all RATs giving tips and answering my questions!

Next project is on the bench already :-)

Tom

--
A gleekzorp without a tornpee is like
a quap without a fertsneet (sort of).

Hi RATs!

OK, it is a gift, so the pretty is excused

Now, make an ugly amp for you to listen to and modify at will

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

tears=sings

be well!
I'm glad for ya and old man.

--
Choky
Prodanovic Aleksandar
YU


"Tom Schlangen" wrote in message
...
Dear RATs,

another DIY tube amp project is finished. You
can view the according web pages at:

http://www.ndh.net/home/schlangen/ro...t/el34set.html

but they are only in German language so far, sorry.

Scrolling down that page you get to a link table
for the schematics, breadboard circuits, datasheets
of used tubes, and so on.

This amp partly originated from the "2 1/2 weeks to go"
thread in this newsgroup and it took me only 2 1/2 *months*
to complete ;-)

On the first spot this amp looks like a generic EL34 SET
amp with 6SL7 drivers, GZ34 tube rectification and CLC
filtering, but it differs somewhat from more common designs
by utilizing a highish B+ of 430 volts and also a highish
reflected load of Ra = 10k (many usual designs use a B+
of around 300-340 volts and a Ra of 3k4 or even less instead).

Tnx2 to Patrick Turner for the tips on high B+ and Ra with
EL34, and Ronald Pit for giving me a hint where to get
some decent priced NOS JAN Sylvania 6SL7.

This amp was made as a present to the father of my GF, and
last sunday he brought over his favourite classics CDs,
mostly large orchestra and Italian operas (solo voices
and choirs) for a try of that amp.

What shall I say, he had tears in his eyes after listening
to his favourite stuff for some hours like he never had
heard before.

I wouldn't have expected that from an EL34 DIY
"low-fashion-factor" (and not-that-high budget)
design, even with quite some added tweaking.

Indeed, this EL34-thing is highly musical (Choky probably
would say it sings). On the other hand it ain't no "rocker",
but that wasn't he goal and can't be expected from ~5 watts
per channel.

Tnx again to all RATs giving tips and answering my questions!

Next project is on the bench already :-)

Tom

--
A gleekzorp without a tornpee is like
a quap without a fertsneet (sort of).

Tom Schlangen wrote:

: Dear RATs,
:
: another DIY tube amp project is finished. You
: can view the according web pages at:
:
: http://www.ndh.net/home/schlangen/ro...t/el34set.html
:
: but they are only in German language so far, sorry.
:
Very nice!
You can probably improve greatly on the Google translation at
http://tinyurl.com/kjt6
but it already gives a rough idea (:-))

Hey, nice animated gif of the EM80, too! ;-)

Hi kyser,

So you went with the basic Angela circuit
and the 125ESE's despite your initial
reservations, Tom? 8^)

Basically, yes. Please remember the "Error in schematic?"
thread. After all these discussions there I simply
breadboarded it (only difference being GZ34 rect instead
of GZ37) measured it and listened to it and moved on from
there.

The original circuit parts values for the power stage
gives around 20% 2H-distortion at full allowable G1 swing
(~35V) giving ~5 watts when using a reflected load of
Ra=2,5k like suggested in the original schematic.

Which would make a nice geetah amp but sounds awfull
for hifi-usage. Probably that's why they wrote "it rocks"
or something like that on the Angela page.

The tweaked power stage circuit as you can see on my
homepage (without any NFB) gives a very little bit less
power at full allowable G1 grid drive, but produces only
1/4 of 2H-distortion of the original circuit. The mild
NFB I introduced reduces it further. 3H-distortion is at
~1/3 of the original circuit.

So, my initial reservations were proved by actually
building it, measuring it and going on from there :-)

The circuit shown at Angela would give a much better
starting point if they simply would change the "white" lead
secondary (Ra 2,5k) to green (Ra 10k) or yellow (Ra 5k)
and correct the 28 volts bias value, which is definitely
wrong even with the original circuit (probably copy & paste
error from the 2A3 circuit also shown there).

BTW, with the original cathode resistor value of 880 ohms
and B+ at ~380 volts, the EL34 runs at a plate current
of less than 40mA.

Tom

--
The first rule of magick is simple: Don't waste your time
waving your hands and hoping, when a rock or club will do.

Hi Ross,

Hey, nice animated gif of the EM80, too! ;-)

this was fetched with permission of the author
from www.jogis-roehrenbude.de, which has a
very extensive and complete chapter on magic
eyes/bands tubes with lots of pictures, data
and info on them.

These pages are a must, if you are interested
in such tubes.

Tom

--
Do not meddle in the affairs of wizards,
for you are crunchy and good with ketchup.

Hi Tom

yes, I noticed your recent cryptic comments on the flaws in the Angela
design. I'm still in the process of building one, and will certainly take
all your comments and modifications on board.

BTW, someone commented on the Angela site (no specific URL, look under the
125ESE section in "Hammond Transformers") on the possibility of using
cathode feedback to lower output impedance by running the EL34's cathode
current through the secondary of the OPT to ground, based on an SE EL34
design by Claus Byrith on the Lundahl Transformers site (
http://www.lundahl.se/pdfs/claus_byrith/cb_seamp.jpg).

This might be of interest to you, if you haven't seen it.

Cheers

David
"Tom Schlangen" wrote in message
...
Hi kyser,

So you went with the basic Angela circuit
and the 125ESE's despite your initial
reservations, Tom? 8^)

Basically, yes. Please remember the "Error in schematic?"
thread. After all these discussions there I simply
breadboarded it (only difference being GZ34 rect instead
of GZ37) measured it and listened to it and moved on from
there.

The original circuit parts values for the power stage
gives around 20% 2H-distortion at full allowable G1 swing
(~35V) giving ~5 watts when using a reflected load of
Ra=2,5k like suggested in the original schematic.

Which would make a nice geetah amp but sounds awfull
for hifi-usage. Probably that's why they wrote "it rocks"
or something like that on the Angela page.

The tweaked power stage circuit as you can see on my
homepage (without any NFB) gives a very little bit less
power at full allowable G1 grid drive, but produces only
1/4 of 2H-distortion of the original circuit. The mild
NFB I introduced reduces it further. 3H-distortion is at
~1/3 of the original circuit.

So, my initial reservations were proved by actually
building it, measuring it and going on from there :-)

The circuit shown at Angela would give a much better
starting point if they simply would change the "white" lead
secondary (Ra 2,5k) to green (Ra 10k) or yellow (Ra 5k)
and correct the 28 volts bias value, which is definitely
wrong even with the original circuit (probably copy & paste
error from the 2A3 circuit also shown there).

BTW, with the original cathode resistor value of 880 ohms
and B+ at ~380 volts, the EL34 runs at a plate current
of less than 40mA.

Tom

--
The first rule of magick is simple: Don't waste your time
waving your hands and hoping, when a rock or club will do.

Hello Tom,
Nice job.
Trafo Baule seems to be an excellent source of reasonably priced custom made
irons.
I had some phone calls with him already and will try it for my next project.
A good idea is to give some photos of you on the workbench on your website.
So I can call you by name when me meet at the Bodensee tube fest in November
;-)

Thomas Schick

"Tom Schlangen" schrieb im Newsbeitrag
...
Dear RATs,

another DIY tube amp project is finished. You
can view the according web pages at:

http://www.ndh.net/home/schlangen/ro...t/el34set.html

but they are only in German language so far, sorry.

Scrolling down that page you get to a link table
for the schematics, breadboard circuits, datasheets
of used tubes, and so on.

This amp partly originated from the "2 1/2 weeks to go"
thread in this newsgroup and it took me only 2 1/2 *months*
to complete ;-)

On the first spot this amp looks like a generic EL34 SET
amp with 6SL7 drivers, GZ34 tube rectification and CLC
filtering, but it differs somewhat from more common designs
by utilizing a highish B+ of 430 volts and also a highish
reflected load of Ra = 10k (many usual designs use a B+
of around 300-340 volts and a Ra of 3k4 or even less instead).

Tnx2 to Patrick Turner for the tips on high B+ and Ra with
EL34, and Ronald Pit for giving me a hint where to get
some decent priced NOS JAN Sylvania 6SL7.

This amp was made as a present to the father of my GF, and
last sunday he brought over his favourite classics CDs,
mostly large orchestra and Italian operas (solo voices
and choirs) for a try of that amp.

What shall I say, he had tears in his eyes after listening
to his favourite stuff for some hours like he never had
heard before.

I wouldn't have expected that from an EL34 DIY
"low-fashion-factor" (and not-that-high budget)
design, even with quite some added tweaking.

Indeed, this EL34-thing is highly musical (Choky probably
would say it sings). On the other hand it ain't no "rocker",
but that wasn't he goal and can't be expected from ~5 watts
per channel.

Tnx again to all RATs giving tips and answering my questions!

Next project is on the bench already :-)

Tom

--
A gleekzorp without a tornpee is like
a quap without a fertsneet (sort of).

Hi Thomas,

Trafo Baule seems to be an excellent source of
reasonably priced custom made irons.

Can't talk about OPTs since I ordered only PTs
from him so far, but those surely have a great
price/value ratio, especially the bigger they
get and the more windings they have.

For that project I ordered 2 different rating
6,3V heater windings, 2A and 4A. The heater
windings weren't marked at the PT which
arrived and I couldn't tell from wire gauge,
so I asked about which is the 2A one and which
is the 4A one.

The answer was, that they are just the same,
4A at least, since there was enough room
on the bobbin, so no need to change the
wire on the winding lathe and the customer
gets more reserves than ordered.

That surely is good work with the customer
in mind.

He is very helpful, too, since for the ECL82PSET
project I needed a PT with certain exact core
and screw pattern and max. bobbin width dimensions
which are _not_ that usual, to have a drop-in
replacement for the restricted area on the chassis.
He promised to search for a suitable core, noticed me
on the next day that he found one, and as usual,
packed it full with copper up to 1 milimeter below
the max dimensions I gave him which resulted in
even higher current abilities than what I need.
No additional fee for that excellent service ...

So I can call you by name when me meet at
the Bodensee tube fest in November ;-)

The proposed Berlin triode fest didn't happen?

Tom

--
The large print giveth, the small print taketh away.
- Tom Waits

No,
just on private basis.
However, if you are in the area....

Thomas

"Tom Schlangen" schrieb im Newsbeitrag
...
Hi Thomas,
......
The proposed Berlin triode fest didn't happen?

Tom

--
The large print giveth, the small print taketh away.
- Tom Waits