[Rob Martin]

Without going into design specifics, can anyone tell me where to fault
find a single ended guitar amp that is "motorboating" at higher
volumes.

The wiring and components check out OK. It was ordered as a kit from
Weber.

Thank you,

Rob Martin

[Eeyore]

Rob Martin wrote:

Without going into design specifics, can anyone tell me where to fault
find a single ended guitar amp that is "motorboating" at higher
volumes.

The wiring and components check out OK. It was ordered as a kit from
Weber.

It's normally caused by inadequate supply decoupling ( too low value or 'tired'
power supply electrolytic caps ).

Graham

[Phil Allison]

** Generally - it is due to a lack of wind .....





....... Phil

[Ian Iveson]

Without going into design specifics, can anyone tell me where to
fault
find a single ended guitar amp that is "motorboating" at higher
volumes.

Assuming you are correct in saying the wiring and components are OK,
then the design must be at fault. Hence "design specifics" are
inescapable.

Motorboating is a low frequency oscillation. Oscillations arise from
the relations between different parts of the amp, and so have no
single cause. In your case the relations include the power supply
transformer and filter, the filters at the anodes of gain stages, the
couplings between stages, and the gain in whatever loop is getting
excited.

I guess the measure least likely to upset the character of the amp
would be to use a larger cap at the anode of one of the gain stages or
splitter...whichever is presently inadequate.

But there are any number of options, probably. The behaviour of these
filters depends on resistance as well as capacitance.

A circuit diagram would be useful. Can you post a link, or a circuit
to ABSE (alt.binaries.schematics.electronic)? If not, perhaps you
could describe its circuit. In particular, where is the volume
control? Presumably when you say "higher volumes" you mean as a result
of turning the amp up, rather than playing louder?

cheers, Ian

[Ned Carlson]

Rob Martin wrote:
Without going into design specifics, can anyone tell me where to fault
find a single ended guitar amp that is "motorboating" at higher
volumes.

The wiring and components check out OK. It was ordered as a kit from
Weber.

Which one, Gerald or Ted? ;-)

Try a smaller value of coupling capacitor ahead of the output tube,
or a smaller value of cathode resistor bypass cap on the output tube.
Often people use larger values that what's needed
for a guitar amp, you can run into farting distortion and
motorboating doing that..


--
Ned Carlson
SW side of Chicago, USA
www.tubezone.net

[west]

"Phil Allison" wrote in message
...


** Generally - it is due to a lack of wind .....

...... Phil

Phil ... I live in Florida but I'm going to visit a dear friend in
Gooramadda. I'll be traveling all over South - East Australia and wonder if
you and I can have an eyeball, as they say. I think it will be interesting
and fun to meet you. What do you say?

Cordially,
west

[Eeyore]

west wrote:

"Phil Allison" wrote in message

** Generally - it is due to a lack of wind .....
...... Phil

Phil ... I live in Florida but I'm going to visit a dear friend in
Gooramadda. I'll be traveling all over South - East Australia and wonder if
you and I can have an eyeball, as they say. I think it will be interesting
and fun to meet you. What do you say?

An 'eyeball' ?

Were you considering removing one ?

Graham