FU-19 (FM30, 829B) Single-Ended Tube Amp!

opnly bafld · « **Reply #40 on:** 2 Jan 2025, 05:10 pm »

I have an amp with the same metal chassis and no safety ground so I put one in and the added hum was low enough I didn't bother with a cap. YMMV

viggen · « **Reply #41 on:** 2 Jan 2025, 09:31 pm »

Quote from: opnly bafld on 2 Jan 2025, 05:10 pm

I have an amp with the same metal chassis and no safety ground so I put one in and the added hum was low enough I didn't bother with a cap. YMMV

thanks i was worried about the hum after grounding.

Jon L · « **Reply #42 on:** 3 Jan 2025, 08:37 am »

Quote from: opnly bafld on 2 Jan 2025, 12:54 am

After the fire and when it takes other parts with it?
The large brown filter caps are junk and can take more expensive parts with them when they decide to go.

Are you talking about the 330uF cap and the 100uF(per schematic) brown caps?
One thing I may do is install a switch to turn the feedback on/off. I have seen reports of cutting that feedback loop made sound "clearer" and "more powerful," but I really don't need any more of either at the moment..

opnly bafld · « **Reply #43 on:** 3 Jan 2025, 01:42 pm »

Quote from: Jon L on 3 Jan 2025, 08:37 am

Are you talking about the 330uF cap and the 100uF(per schematic) brown caps?
One thing I may do is install a switch to turn the feedback on/off. I have seen reports of cutting that feedback loop made sound "clearer" and "more powerful," but I really don't need any more of either at the moment..

Yes

A beam power tube without feedback will definitely sound different, I certainly would not run one without it.
Have you seen more than the one comment on AK?
gadget73 posted: "2) it flattens out the frequency response and reduces distortion. It also reduces the output impedance of the amp so its less sensitive to speaker selection."

My beam tetrode* 6P14P single ended has the same feedback, it is getting disconnected today only because I'm strapping the tubes triode and it will no longer be beneficial.

* Most refer to beam tetrodes (KT kinkless tetrode) as pentodes because even though they operate a little differently the end result is similar.

SET Man · « **Reply #44 on:** 4 Jan 2025, 02:05 am »

Quote from: viggen on 2 Jan 2025, 04:30 pm

The link i bought from has a few other versions. the one JL and I got are the same with different enclosures.

https://www.aliexpress.us/item/3256805709492361.html?spm=a2g0o.order_list.order_list_main.5.21ef1802jLu98g&gatewayAdapt=glo2usa

Hey!

viggen, thank you for the link and info. Hmmm... why so many different enclosures? Look like the last one, more expensive one have choke?

I am so tempted to get one since I like the look of those tube. But I've talked myself out of it

I really don't need another tube amp and I do have another audio project to do and save money to get spare tubes for my amps

Anyway, it is fun to read about these amps here

viggen · « **Reply #45 on:** 4 Jan 2025, 05:44 pm »

Quote from: SET Man on 4 Jan 2025, 02:05 am

Hey!

viggen, thank you for the link and info. Hmmm... why so many different enclosures? Look like the last one, more expensive one have choke?

I am so tempted to get one since I like the look of those tube. But I've talked myself out of it I really don't need another tube amp and I do have another audio project to do and save money to get spare tubes for my amps

Anyway, it is fun to read about these amps here

i said the exact thing trying to convince myself not to get it haha.

viggen · « **Reply #46 on:** 12 Jan 2025, 04:55 am »

i need to retract what i said about the amp when using FU19 tubes. it's really good with a different powercord. not nearly as forward and rough with a huffman powercord vs the moon audio blue dragon.

i still prefer the 3E29 though.

that being said, this amp still proves to be supremely musical and enjoyable. i just like leaving the music playing at all times since acquiring this amp.

and, that being said again, i really should have a tech look at it since i use it so often. but... lazy.

FullRangeMan · « **Reply #47 on:** 12 Jan 2025, 05:22 am »

Its in original condition?
Or you have made any mods?

viggen · « **Reply #48 on:** 12 Jan 2025, 06:17 am »

still original

FullRangeMan · « **Reply #49 on:** 12 Jan 2025, 06:24 am »

This amp have a interesting potential with hi sensitivity speakers.

Jon L · « **Reply #50 on:** 13 Jan 2025, 01:02 am »

Quote from: FullRangeMan on 12 Jan 2025, 06:24 am

This amp have a interesting potential with hi sensitivity speakers.

Yep, 829B on my 110+dB sensitive horns makes me wonder why I would need/want another amp..

FullRangeMan · « **Reply #51 on:** 13 Jan 2025, 02:41 am »

With a hi efficiency speaker as this one can have various small tube amps as they are inexpensive.
What is your speaker?

Jon L · « **Reply #52 on:** 13 Jan 2025, 06:24 am »

Running Altec 511B horns with Radian compression driver on top of 12" Alnico Philips woofer, actively biamped.

1214240914a_HDR by drjlo2, on Flickr

FullRangeMan · « **Reply #53 on:** 13 Jan 2025, 10:14 am »

Wow great speaker, how do like the Alnico Philips? Any shortcomics?

Jon L · « **Reply #54 on:** 13 Jan 2025, 05:03 pm »

My Philips AD4200M is a paper cone, alnico "full range" driver but sounds much better to my ears when actually crossed over to horns.
Modern woofers probably can extend lower with more excursion, but the lower-midrange/upper-bass is magical with these Philips

PhilipsAD4200M3a by drjlo2, on Flickr

SET Man · « **Reply #55 on:** 13 Jan 2025, 08:48 pm »

Quote from: viggen on 12 Jan 2025, 04:55 am

.....

that being said, this amp still proves to be supremely musical and enjoyable. i just like leaving the music playing at all times since acquiring this amp.

.....

Hey!

viggen, you are not making this easy on me. Now I want one! Must have self control

viggen · « **Reply #56 on:** 13 Jan 2025, 09:29 pm »

Quote from: SET Man on 13 Jan 2025, 08:48 pm

Hey!

viggen, you are not making this easy on me. Now I want one! Must have self control

if you got the right speakers, you're doing yourself a disservice for not getting this!

viggen · « **Reply #57 on:** 13 Jan 2025, 09:32 pm »

Quote from: Jon L on 13 Jan 2025, 06:24 am

Running Altec 511B horns with Radian compression driver on top of 12" Alnico Philips woofer, actively biamped.

i like your cabinet. have you also dabbled with altec compression drivers? curious how that would compare against radian. i've read the altec doesn't go as high. my speakers use 804a which is a lower end but seems to provide enough highs for me.

Jon L · « **Reply #58 on:** 14 Jan 2025, 12:07 am »

Quote from: viggen on 13 Jan 2025, 09:32 pm

i like your cabinet. have you also dabbled with altec compression drivers? curious how that would compare against radian. i've read the altec doesn't go as high. my speakers use 804a which is a lower end but seems to provide enough highs for me.

Even with the Radian with better high frequency extension than vintage Altec compression drivers, the 511B combo didn't quite have that sparkle and air I'm used to with using triple-stacked Great Heil AMT's. Situation was corrected by adding the NOS pyramid bullet via a cap at around 10kHz. Now that I have the bullets, I am always on the lookout for good-condition Altec compression drivers, but these measurements of Altec 806A compression drivers by Joseph Crowe isn't encouraging..

https://croweaudio.blogspot.com/2020/05/altec-806-8a-compression-driver.html

viggen · « **Reply #59 on:** 14 Jan 2025, 10:07 pm »

yah that's what i've been reading about altec compression horns but my ears like'm. and, the one i got has the smallest magnets hence lowest spl per watt. still around 100db. jeff day did a comparo between 802 and 804 and he said he can't hear the diff so i never bothered to upgrade (though it is tempting)... also read the jbl equivalent is the way to go.. but not sure i trust the guys from those vintage audio sites. their hearing and mine is probably not the same. tried a few jbls and preferrred altecs.

mine has the 811 horns.