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I picked up this tube amplifier

Thinking it a knock off of a maggy 8600
Perhaps some tweaking.
Glad you're enjoying it.
Also liking the idea of putting tube in freezer to try and ID.
I think its a good idea to let warm to room temp before trying to use afterwards.
I'm thinking rapid heating of glass might cause it to crack.
I have no way of knowing. Maybe it wouldn't but why risk it.
 
If you have a buddy with a tube tester, have him test it as a 12AU7 and a 12AX7. Whichever tests in the proper range will ID it. Both tubes look very similar, so there really aren't any structural features to help out.
It does look have top seams which is generally an Amperex mark. Can you find any small black acid etchings on the lower part of the tube? They can help ID the tube type as well as time and place of manufacture.
 
nj pheonix said:
Thinking it a knock off of a maggy 8600
Perhaps some tweaking.
Glad you're enjoying it.
Also liking the idea of putting tube in freezer to try and ID.
I think its a good idea to let warm to room temp before trying to use afterwards.
I'm thinking rapid heating of glass might cause it to crack.
I have no way of knowing. Maybe it wouldn't but why risk it.
Click to expand...
Entry level integrated kit, standard pattern, everybody offered a version.
Very basic two stage single ended stereo arrangement.
 
I might give consideration to converting it to Dave's 8600 circuit. Mostly would depend on how it sounds and measures. You'd lose the tone controls but that probably isn't the end of the world.

I'm assuming 6bq5/12ax7 at least. If its 6bm8 the tone controls might not be so bad. Those have a triode internally so you would have enough gain for a proper output stage with feedback, and a 12ax7 for enough gain to have tone controls that work. Otherwise it would likely be all passive, or maybe built into the feedback circuit on the power amp.
 
I am on the hunt for a pair of small speakers that could work well with this tube amplifier i have. Currently it is driving my altec lansing high fidelity 95. I felt like it is little too much for the amplifier.

How many watts do you think this amp is giving out...? I mean by looking at it i think somewhere close to 10 watts per channel...?

My guess maybe absolutely wrong. I checked few amps that looks similar to mine on aliexpress. They say it does around 3 watts per channel. However the aliexpress stuff has much smaller components.
 
properly biased a single ended EL84 is good for around 3 watts at typical voltages. Improperly biased will be less, excessive voltage will be more.
 
tonyg88 said:
I wonder if you buy 7189/A tubes instead of EL84 if you could run the bias hotter.
Click to expand...

Probably... on the presumption the PS could support it. But, not sure that higher bias in itself is paramount to increasing output.

As well, if the amp is intended for EL84/6BQ5 the tube sockets could be wired such that it's not directly compatible with 7189A tubes. 7189A has pinout differences from 6BQ5 and 7189.
 
whoaru99 said:
Probably... on the presumption the PS could support it. But, not sure that higher bias in itself is paramount to increasing output.

As well, if the amp is intended for EL84/6BQ5 the tube sockets could be wired such that it's not directly compatible with 7189A tubes. There are differences in pinout between 6BQ5 and 7189 vs 7189A.
Click to expand...
Right I think it’s the only the A version with the weird pin lay out. Far from an expert but I did have it in my mind that bias is related to output power but maybe it isn't.
 
Should be possible to get a little more power, but I doubt it would break 5 watts. Mostly it would allow more power because it allows higher plate voltage. Getting the bias set right allows for max output, above and below the proper level and it will make less output power.
 
probably true, if you want real SE power it needs a more stout tube than anything in the 6bq5 family. If you really wanted to stick with that family, parallel 6bq5's would get further than what a single 7189 could.
 
Right. Real progression on headroom would be like Dyna ST-35 to Dyna ST-70 to twin Dyna Mk-3 for example.
 
I was thinking just in terms of single ended amps. AB push-pull will give more power for the same tubes as parallel SE would.
 
gadget73 said:
I was thinking just in terms of single ended amps. AB push-pull will give more power for the same tubes as parallel SE would.
Click to expand...
My point was that you need to substantially increase power capability to make a meaningful difference. A couple of watts more or less fiddling with tube rolling won't cut it.
Basically, look for a different amp with at least 50% increase in power capability, double would be better. This gets expensive fast with SE.
 
century tek said:
Look up the tube data for the EL84 / 6BQ5.
Click to expand...

I am not expert but i looked up at the data Sheets. It says somewhere around 17 watts per channel. So according to what i thought... i think this will be producing something in between 10 to 15 watts per channel.
 
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