Haven´t noticed Peter,but i´ll be happy to look into it during the day.

The add on of a few small signal novals will usually be ok though. Most of them draw between 200mA and 300mA which at the voltages involved ain´t all that much power,in watts,all things considered.
I often add a tube or two to various amplifiers and have yet to run into issues from it.

Having said that it always helps to have referenced heater voltage before pulling any modifications,of the reason above,as that gives you a rather fair idea of the VA involved.
Need be you could always run the extra tubes off of the main heater circuit for the powertubes. Just add a balance pot of for instance 500 Ohms and go at it.

Feels like we left a few brands out. Echolette and Dynacord in their own rights,but there were others too.
One of these others is in my opinion the Hohner MH series. True enough Hohner made other tube amps too,but the MH series are in my opinion rather sturdy built amps that in stock form will give a Fender Twin a run for the money any day Hhem some MIGHTY fine clean amps. In fact,to this day i doubt that i´ve ever heard nicer tremolo and reverb then them onboard a Hohner MH.

Apart from that MH-25 up there i also have an MH-50 head. The latter being the more powerful,obviously,but already from MH-25 and upwards a Hohner will suffice in modified form for use even with the loudest rocknroll band. Handed overdriven signal them twin PL-84´s will deliver,take my word for it.

The one in the picture has been my weapon of choice for numerous gigs. Main reasons being that,of course,it sounds "da bomb" and that aside..it´s all i need in a rather portable package.

Since the advent of that MH-25 in modded form i´ve been on the lookout either for yet another MH.45/MH-50 or a MH-60. The latter being an amp that sports the EL-503´s,which i´m rather familiar and fond of.
True enough they´re expensive powertubes,but they´re also real sturdy and real powerful (this goes for the EL-504 too btw)

The MH amps does have its drawbacks though. They´re NOT built by "German" standards and to be honest they can strike you as downright sloppy put together.
They´ve even got a few point which i for one at least regard as poor engineering. Them being amps with a separate power and preamp stage the wiring loom between the two parts stem from a soldersupport atop the powertransformer. In my book that´s a no-go as less informed people can get to that solderstrip...and hurt themselves.
In turn there´s a highly loaded resistor that resides at that same solderstrip that is for the reverb and this is underestimated for load. Ergo it is real common that this resistor is blown,and hence the amp lacks its reverb function.

In fact,as you get into it the entire two sections need tidying up in my opinion. That doesn´t deprive from these wonderful amps sound though. Albeit the stock speakers often being of low dB efficiency..that can always be handled and..these amps DO sound absolutely lovely as is.
If clean sound is your thing....
In fact,were i to chose between a Fender Twin and a highpowered MH today my vote goes for the MH. It´s THAT good.



Here´s my solution to making the amp way more safe-to everyone. That there socket is rather cheap after all and makes for all the difference. Signal in turn is sent from the preamp the other side of the chassis and is hardwired in place stock. I replace that with a common RCA dito,making the whole thing detachable.

If rocknroll is more your game....which it is to me...these amps make for absolutely tremendous platforms to work from.

Zitat von: Racing am Sep 08, 2015, 12:03
Haven´t noticed Peter,but i´ll be happy to look into it during the day.
tance 500 Ohms and go at it.

Thank you! Normally I wouldn't hesitate either. But as the diameter is the same as the
one of the TH-winding, I doubt I can load it by almost 1A.

Peter

Well Peter....



I just picked up that GA-200 i bought and took that picture for you.
I want to bring your attention to that the first pair of wires to the left is for the bias circuit. Then the rather heavy duty wires for the heaters for the powertubes,that indeed has a fuse of 10A.
The FOLLOWING pair though is the heaters for the preamp and them wires,i measured the diameter of them,are at least 0,5mm in dia.
Now.
Most small signal pentodes and triodes has a heater draw of 200mA to 300mA. 3 of them IOW don´t even make for a full ampere...adding one tube brings the tally to 1200mA..and yet another one brings 1500mA (or 1,5A) and see...



That´s what even the stock fuse is set to for this GA. IOW..adding a couple of novals and increasing heater draw to 1500mA...it´d be a BIG surprise if that would load the circuit beyond what it´ll take.
However..
Most of these amps are run rather low as far as heater voltage. This amp hands you approx 6,1VAC for both windings in 220VAC mode. At that setting HT B+ dials in at 565VDC under load.
IOW..make sure you get ample heater voltage all said and done. They seem somewhat "underwound" from that aspect. In 240VAC mode (we get the same wall voltage up here in Sweden as do you guys) i saw 5,6VAC...

Wow,

thanks for the photo and the measurement! 0.5mm is the same diameter as in the BA200.
According to the "official" formula and a current density of about 2,8 (I assume), a winding
with that diameter should be capable of pushing about 0.5A.
(http://www.jogis-roehrenbude.de/Transformator.htm)
But as the GA200 uses 3 preamp valves, I guess I can do it when using the BA200 xformer.

The fuse values on the other hand are no reliable indication on current delivery capability.
A 1,5A fuse doesn't mean you can load the winding by that amount. So the 0.9A of three
preamp valves is the maximum I would stress the coil with.

Btw.: I leave for vacation tomorrow morning and won't be able to post the next two weeks.
:urlaub:
kind regards,
Peter

If it worries you you could always  hook them to the powertube heater circuit.?
All that would be needed from that respect is to replace the hardwire from the one tap to ground with a balance pot like in the pic above.
Would certainly work just as well.

No. Granted that fuse rating by no means is a surefire way of capacity. Voltage drop is though as it hands you and indication of VA capacity

Hope your vacation  brings what u wish! :topjob: