"Shortest Way" SW51 Amp Impressions (Simple SET Amp)

Power on time 7 hrs
Ambient temperature 23 °C

Some change observed.
Left is EF184, Right is EF805S viewed on laptops
Top is EF184, Bottom is EF805S viewed on phones

Top of SW51+ transformer housing


Front of SW51+ transformer housing


temperature difference has narrowed to approximately 5~6 °C.

Select BH Crack temps for comparison

Transformer, 6080 tube


E80CC tube, BH Crack overview

 

I'm feeling ok with this. Should I be ok with this? I think it's ok. Yup. Or no?

 

Koray is very good to deal with. All 4 of mine are from the same batch as your R channel (U9005608J).

My ambient w/o AC is in the low 30s °C, AC on is in the high 20s (we don't like to crank it too much, the reduction in humidity is enough and we just hang out in underwear at home). In summer I don't leave anything w/ tubes on overnight when the AC is off in the living room.

Thanks for confirming. This is consistent with what I've been getting using the "dB" markings on the Nanopatch+.

The consensus was/is that these tubes are specced for use in the SW51. Zamp was in the discussion before and didn't raise any alarms. I guess they just run hotter. I'm putting them back in.

 

Thank you for that. Also, thanks atomicbob for the flir work. Truly appreciate the effort fellas

 

@atomicbob What's your sonic impression so far, Bob's?

 

Insufficient time AB comparing to say anything meaningful. Got waylaid by outdoor grilling, wine and quality time with my best friend, my wife. Also distracted by old friends .., Khadas Tone Board DAC -> BH Crack -> HD650 and listening to 1970s rock. Billy Joel 52nd Street in particular is very entertaining though this setup. Needs a little EQ but very satisfying after. Trumpet solos by Freddie Hubbard are especially captivating.

 

I recommend using the EF805 tube as an additional one, not the main one.
This tube is lower-voltage than the 6Z51P/EF184, so its operating mode in the amplifier is not optimal.
In the amplifier, it has a high anode current (which is probably why the transformer warms up more)
The pipe manufacturer allows the operation of tubes with an excess of one parameter. But we are humane people, not wild animals, so it's better to spare the tube.
If the EF805 tube is very good in sound, and you want to keep it as the main one, then I will think about how you can upgrade the amplifier to use only this tube.

Addendum: For those who want to compare these tubes, I attach links to the datasheet

EF805S

EF184

 

How suitable is the Mazda 6F24 tube? (Not to be confused with a Tesla loctal tube with the same designation):
http://www.r-type.org/exhib/acn0029.htm

 

I didn't find a detailed dataset on 6F24. Therefore, I am focusing on the dataset of a very similar 6F23 tube.
I can say for sure that the amplifier will work, no explosions or fires are expected.

I don't have enough information for the rest of the conclusions. If anyone has a link to a detailed datasheet for the 6F24 tube, I will be grateful.

According to the brief characteristics, we can say that the 6F24 is very close to the 6Z51P/EF184 tube

 

Found this not sure whether that helps

 

Thank you so much for your help.
Unfortunately, the namesake tube is in the table. 6F24 in this table has a loctal socket. Tube manufacturers gave a funny riddle with the name 6F24

 

I admit I am a tube noob but I will not give up:

https://frank.pocnet.net/other/Mazda/Mazda-DataBooklet1970Valve&PictureTubes.pdf

 

Thank you very much. Very good link, I didn't know it.
According to this description, 6F24 is very similar to 6Z51P

It would be ideal to find the graphs of this tube, but probably they are simply not available on the Internet. It is easier to buy this tube and remove the charts yourself. For example, such a universal device



The photo of the device is not mine, but I also have two such wonderful devices.

 

A L3-3 is a handy thing to have if you tubophile. In Germany there is a guy who developed his own tube tester:

http://roehrentest.de/

He has put the BOM and how to build it online.
Of course if you have two L3-3 no need to build your own tube tester.

 

So is damage more likely to happen to the tube over time, or to the amplifier itself?

If the tube wears out prematurely, I'm not too bothered. I think most people's concern is that running the EF805S will harm the amp in the long run.

 

Thanks for the information. I have another tube amp where the designer/builder said not to exceed 80C in operation. Usually it runs at 45C or cooler, depending on tubes .The temperature is hottest at the top of the transformer.
Would you have a maximum temperature value for running the SW51+ safely? I use an inexpensive infrared thermometer to measure.

 

Thank you, a wonderful site. I have two L3-3s not out of greed, I have had one device for 20 years, the second device, along with collectible radios of the 30s-50s, was given to me by my client, who had to part with his collection because of the playful hands of his grandchildren.
L3-3 is good for checking 1-3 tubes or for removing characteristics. When you need to check a lot of tubes, it is better to use other devices, for example uTracer

https://www.dos4ever.com/uTracer3/uTracer3_pag0.html




The results of uTracer measurements can be obtained much faster and more clearly.

If the transformer temperature does not exceed +80C, the amplifier will work for a long time. But this must be observed.

The upper temperature limit is usually determined by the upper temperature limit of electrolytic capacitors and the upper temperature limit of transformers. For capacitors, this is +85C or +105C.For transformers wound with a standard wire (with insulation not polyurethane varnish), the actual temperature is allowed +80C.

 

Thanks. If I take temperature readings from the hottest spots by the transformer cover, is that reliable enough?

 

@Zampotech what is the thermal resistance of the power transformer cover?
How much higher is the temperature of the top of the power transformer than what is easily measured at the top of the transformer cover?

 

If the temperature is stationary, the temperature difference will be 15-20 degrees at the top of the lid and 10-15 degrees at the bottom of the lid.
But of course a lot depends on many factors.

A simple rule of thumb is that if the hand is noticeably hot and uncomfortable on the hood, then the amplifier is working in the limit mode.