Modern type axial foil caps have quite thin outer layers of tape; the one in pic was grazed with a soldering iron to the outer foil; and rendered useless due to moisture ingress. A cap with this must be rejected fom audio circuits.
The same applies to modern resistors; can become noisy if outer layer is scrapped.
Nomex tape is bit pricy, but burn resistant and saves alot of troubles so I wrap a couple of turns round delicate components.
Pic of the previous amp; this latest one built on exactly the same circuit lines except with slightly lower A-A imp enabling a maximum output power of 550W.
The work continues.
richy
Attachments
No, not useless because I'm using them. I have an amp in which both coupling Auricaps got badly burned. I sanded the rough edges off and leveled the crater with some wax, then a sticker. No problems after several years. I'm not saying this is a good thing to do, I'm just saying this is what I did. Very open sound. Haha.
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Had my Stealth-5 finished after a smaller mod - adding an extra line input, an iPod dock and a selector switch.
Tubes are glass 12A6 and metal 12SJ7 and 12SC7. Transformers are standard 8K PP OP trannies and a special ordered mains transformers. No bells or whistles but it plays good music without sounding bad. Goes well with my small 5" Sonido horn speakers.
(Don't tell me, I had accidently swapped a pair 12SC7/12SJ7).
Tubes are glass 12A6 and metal 12SJ7 and 12SC7. Transformers are standard 8K PP OP trannies and a special ordered mains transformers. No bells or whistles but it plays good music without sounding bad. Goes well with my small 5" Sonido horn speakers.
An externally hosted image should be here but it was not working when we last tested it.
(Don't tell me, I had accidently swapped a pair 12SC7/12SJ7).
The cables are from Jupiter, they sell the bulk cable here:
Cotton Insulated Cable
They are very good interconnects, I highly recommend. They are on the warm and bassy side, but not overly so...
@richwalters, so far so good, but I made a mistake with a resistor value in the heater power supply so heater voltage was too high. I shut it off after a couple hours to preserve my tubes and should have it fixed and running again in a couple days. From what I have heard so far I am sure I will be happy with it.
If changing interconnect cable made audible difference, then it's either it was a bad cable before switching or after switching. Or there is something wrong with the amp / preamp. Cables, Interconnects and Other Stuff - The Truth
New SE amp for the stable. Basically the JELabs EL34 which started from an abandoned 300b project. One of the 300b's hit the hard hard floor and that was that...it sounded OK but not sooo good that I felt compelled to get another tube or matched pair. Being that I had plenty of EL34 tubes kicking around and the amp was 90% there I figured what the heck.
Allied 6K7VG PT
James 6123 OPTs
Triad chokes
Auricap coupling caps
Broskie PS-1 heater supplies for the EL34's
JJ new issue E34L's
JJ new issue GZ34
Tung Sol new issue 6SL7's
Choke loaded grids for the power tubes
The only mod I really made to the circuit was replacing the resistor bias with red LED bias on the 6SL7's. I have preferred this mod on a few amps that I have built recently.
LED's running 1.72V which looks to be about 2.75mA for the 6SL7's
E34L's running at 76mA
B+ 405V
Speakers are Fonkens with CHR70's...
Allied 6K7VG PT
James 6123 OPTs
Triad chokes
Auricap coupling caps
Broskie PS-1 heater supplies for the EL34's
JJ new issue E34L's
JJ new issue GZ34
Tung Sol new issue 6SL7's
Choke loaded grids for the power tubes
The only mod I really made to the circuit was replacing the resistor bias with red LED bias on the 6SL7's. I have preferred this mod on a few amps that I have built recently.
LED's running 1.72V which looks to be about 2.75mA for the 6SL7's
E34L's running at 76mA
B+ 405V
Speakers are Fonkens with CHR70's...
Little old here but new life is always good.
what will do this speaker in a metronome?
I have four of them. in a H frame she do pretty good,
big bas, very clean two of them in one H frame.. the next step
is a damped U frame, but the metronome I want also test
Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories
the audio is faulty but you can here the bass, here I hade switch bandpass midd from low to high and not high to llow, coils and caps wrong connected.
http://www.youtube.com/watch?v=SvuHYLOzXFQ&feature=relmfu
what will do this speaker in a metronome?
I have four of them. in a H frame she do pretty good,
big bas, very clean two of them in one H frame.. the next step
is a damped U frame, but the metronome I want also test
Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories
the audio is faulty but you can here the bass, here I hade switch bandpass midd from low to high and not high to llow, coils and caps wrong connected.
http://www.youtube.com/watch?v=SvuHYLOzXFQ&feature=relmfu
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Don's 6C33C
It took the best part of a day but I got Don's 6C33C up and going. This "beast" has four DC power supplies under the bonnet, two large chokes and two power trannies one for the 6C33C heaters (6A each). It is a three stage amp using a 6SL7 driver tube. The two triodes are connected by a cap but the second triode is connected direct to the 6C33C grid. The top plate is thick ABS plastic and the base Australian Spotted Gum. Dom makes all my bases now. He had the wiring for the 6SL7 completely stuffed so I had to pull all this down and rewire correctly. The amp played first time after the re-build and sounds absolutely fantastic. It has a lot of gain. It must be the best of Don's amps so far. I think he said 12WRMS per side for an SE!!!
You bias the 6C33Cs up to 220mA but at 150mA the power tranni got real hot. Also the filament toroid gets very hot too. The specs for these trannies requires some checking. Don had one bad 6C33C which had one plate (to in the bottle) glow red. I think only one plate was connected at manufacture.Lucky I have a box full of these big tubes and was able to drop one in and enjoy the music!!
It took the best part of a day but I got Don's 6C33C up and going. This "beast" has four DC power supplies under the bonnet, two large chokes and two power trannies one for the 6C33C heaters (6A each). It is a three stage amp using a 6SL7 driver tube. The two triodes are connected by a cap but the second triode is connected direct to the 6C33C grid. The top plate is thick ABS plastic and the base Australian Spotted Gum. Dom makes all my bases now. He had the wiring for the 6SL7 completely stuffed so I had to pull all this down and rewire correctly. The amp played first time after the re-build and sounds absolutely fantastic. It has a lot of gain. It must be the best of Don's amps so far. I think he said 12WRMS per side for an SE!!!
You bias the 6C33Cs up to 220mA but at 150mA the power tranni got real hot. Also the filament toroid gets very hot too. The specs for these trannies requires some checking. Don had one bad 6C33C which had one plate (to in the bottle) glow red. I think only one plate was connected at manufacture.Lucky I have a box full of these big tubes and was able to drop one in and enjoy the music!!
Attachments
Looks great, I really like my EL34 SET. I also used the James OPTs. Recently, I did the "Hazen" Mod, strapping g3 to cathode using a .1 uF film cap in place of a jumper wire. It is worth trying IMO.
Here is my cheap headamp, it is 24V supplyed tube with mofsets on the ends.
I stucked it between the glass sheet, so now evrybody can see my gross soldering and first eagle pcb. It plays good, but I can't get totally rid of mechanical hum, which is spreading through the glass very eficiently. This glass was quite cheap too, because I cutted and drilled it mysel except lamp hole and corners which costed me about 2e...
I stucked it between the glass sheet, so now evrybody can see my gross soldering and first eagle pcb. It plays good, but I can't get totally rid of mechanical hum, which is spreading through the glass very eficiently. This glass was quite cheap too, because I cutted and drilled it mysel except lamp hole and corners which costed me about 2e...
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.