[bloodhawk]

I thought the Tung Sol 7236 was a ruggedized 5998. I also thought, based on reading about them on the Bottlehead forum a little, that they sound the same.

I'm currently using a Tung Sol 7236 and a Telefunken ECC82 (12AU7), and I'm not lacking for bass, but I don't listen to EDM or anything like that.

Partially true, but the transconductance on the 7236 (12000, iirc) is lower than that of the 5998 (15000)

 

[FunyunBreath]

There's a pretty significant difference to my ears between the two. Once upon a time I had 2 Speedballed Cracks and an A/B switch so that I could instantly switch between different sets of tubes in the same circuit

The bass difference between the tubes isn't so much "quanitity" but rather quality. 5998 has more texture/slam and goes deeper, 7236 is faster and clearer but overall much less interesting.

Clarity/detail between the 2 tubes is about identical though.

 

[Allanmarcus]

I wonder if the impedance is just so high on the crack that the 5998, or even the 421a, lower it enough that dampening factor comes into play, and the Crack can control the driver better with those tubes, even 600 ohm headphones.

Update: I got this info TubeWorld. I need to learn what these mean

5998=421A Dual Power Triode
(5998 is an uprated 6AS7G and has a 13 watt plate dissipation rating)
(the 5998 sounds very clear and has superb overall sonics,
the 421A Western Electric sounds even better; slightly more magical sound)
(5998 Mu = 5.4, Gm = 15500, Rplate = 350 ohms, Vplate max = 250 volts and Vplate max 5998A = 275V)
(7236 Mu = 4.8, Gm = 12500, Rplate = 350 ohms, Vplate max = 300 volts)
(7236 is a computer rated 5998A, 7236 and 5998A are uprated from 5998)
(6AS7G Mu = 2, Gm = 7000, Rplate = 280 ohms)
(6080 Mu = 2, Gm = 6500-7000, Rplate = 280-300 ohms)

5998 substitute = 7236
7236 is a computer rated 5998A


Update 2: interesting article here: http://www.tubeaudiostore.com/tubmatdem.html

 

[Paladin79]

It has been a while since I studied tube theory but Mu as I recall is voltage gain. Gm is transconductance. That amp starts out with a stock 6080 and I would think the bias voltage is based on that tube. The 6as7g is quite close so I found it to be a decent match. I probably should have done more testing when I had two stock cracks side by side just as Funyun did but my interest was in other areas

Ok I just tried various tubes I have laying around, please note I do have VU meters on my Crack amp, the Tung Sol 5998's had a higher volume level than Chatham 6080, GE 6080, RCA 6AS7G, 6H13C's etc. Quality of sound, that is a bit debatable.

test music... Otis Redding Dock of the Bay, Warren Zevon..Nighttime at the Switching Yard.

 

[attmci]

It has been a while since I studied tube theory but Mu as I recall is voltage gain. Gm is transconductance. That amp starts out with a stock 6080 and I would think the bias voltage is based on that tube. The 6as7g is quite close so I found it to be a decent match. I probably should have done more testing when I had two stock cracks side by side just as Funyun did but my interest was in other areas

Ok I just tried various tubes I have laying around, please note I do have VU meters on my Crack amp, the Tung Sol 5998's had a higher volume level than Chatham 6080, GE 6080, RCA 6AS7G, 6H13C's etc. Quality of sound, that is a bit debatable.

test music... Otis Redding Dock of the Bay, Warren Zevon..Nighttime at the Switching Yard.

In the Crack, the 6080 is setup as a cathode follower, which has a fixed plate voltage.

The driver stage is a common grounded cathode amplifier. It's cathode voltage is set by the 1.57V LED, and the plate is loaded with a 22.1K resistor.

 

[Paladin79]

That certainly makes sense Atmci, I get so involved with other projects that I do not think about the Crack setup very often. I could recall the LED setup.

 

[Kitchener]

Hello.
My account is quite fresh around here.
I've been lurking for about six months, trying to absorb as much as possible from this ever expanding thread, but only registered recently.
-to bother Ohcrapgorillas for details about his Crackhouse, incidentally.

Anyway, I'm hoping someone here might be able to lay some wisdom on me with regards to putting a choke in the Crack PSU.

I've purchased a Hammon 157M choke to replace a resistor in the PSU.
Specs: 8H, 100mA, 259Ohms, 400V.

I've seen it posted that stuffing a choke in lets you replace the last electrolytic capactor in the PSU with a film capacitor with weaker specs and, more importantly, smaller dimensions than a 220uF 250V+ film cap.
-this Reddit post had some details but the comment appears to have vanished.

Sooo, given my choice of choke, would it be advisable for me to replace the lytic cap with a 100uF 250V film cap?
-Or should I just put in a choke and bypass the last lytic with a 2.2uF film cap?

Thanks for reading.
Disclosure: I have a similar thread over at Bottlehead where I initially just asked for alternatives to the Triad C-7X.

 

[attmci]

Hello.
My account is quite fresh around here.
I've been lurking for about six months, trying to absorb as much as possible from this ever expanding thread, but only registered recently.
-to bother Ohcrapgorillas for details about his Crackhouse, incidentally.

Anyway, I'm hoping someone here might be able to lay some wisdom on me with regards to putting a choke in the Crack PSU.

I've purchased a Hammon 157M choke to replace a resistor in the PSU.
Specs: 8H, 100mA, 259Ohms, 400V.

I've seen it posted that stuffing a choke in lets you replace the last electrolytic capactor in the PSU with a film capacitor with weaker specs and, more importantly, smaller dimensions than a 220uF 250V+ film cap.
-this Reddit post had some details but the comment appears to have vanished.

Sooo, given my choice of choke, would it be advisable for me to replace the lytic cap with a 100uF 250V film cap?
-Or should I just put in a choke and bypass the last lytic with a 2.2uF film cap?

Thanks for reading.
Disclosure: I have a similar thread over at Bottlehead where I initially just asked for alternatives to the Triad C-7X.

I knew you from the Bottlehead. Did Doc. B. ignore you there? Unbelievable.

I saw a lot of your questions had been answered: https://bottlehead.com/smf/index.php?topic=10729.0

BTW, if you wanna to replace the last caps, you need a pair. And yes, the quality film caps are expensive.

 

[Kitchener]

I knew you from the Bottlehead. Did Doc. B. ignore you there? Unbelievable.

I saw a lot of your questions had been answered: https://bottlehead.com/smf/index.php?topic=10729.0

BTW, if you wanna to replace the last caps, you need a pair. And yes, the quality film caps are expensive.

Oh no no, I find they’re very helpful over at Bottlehead. They generally put up with my rambling

I’m just “throwing a wide net” trying to gather as much info as possible.

A pair?
Are you referring to the pair of output capacitors?

I’m already replacing those with a pair of Mundorf 100uF 250V film caps.

The PSU has three electrolytic capacitors, each rated at 220uF 250V.

I could be mistaken, but I mean to recall reading that fitting a choke will let you replace the last of the three PSU caps with a single film cap; not a pair.

 

[buldogge]

Hello.
My account is quite fresh around here.
I've been lurking for about six months, trying to absorb as much as possible from this ever expanding thread, but only registered recently.
-to bother Ohcrapgorillas for details about his Crackhouse, incidentally.

Anyway, I'm hoping someone here might be able to lay some wisdom on me with regards to putting a choke in the Crack PSU.

I've purchased a Hammon 157M choke to replace a resistor in the PSU.
Specs: 8H, 100mA, 259Ohms, 400V.

I've seen it posted that stuffing a choke in lets you replace the last electrolytic capactor in the PSU with a film capacitor with weaker specs and, more importantly, smaller dimensions than a 220uF 250V+ film cap.
-this Reddit post had some details but the comment appears to have vanished.

Sooo, given my choice of choke, would it be advisable for me to replace the lytic cap with a 100uF 250V film cap?
-Or should I just put in a choke and bypass the last lytic with a 2.2uF film cap?

Thanks for reading.
Disclosure: I have a similar thread over at Bottlehead where I initially just asked for alternatives to the Triad C-7X.

You can proceed exactly as you have written...either way works. I used the Triad but th Hammond 157M would be fine, as well.

Also, you can replace either resistor with the choke. I chose to replace the 1st one (across along the back)....thus C-L-C-R-C...C-R-C-L-C is also fine.

I opted for a 2.2uf bypass, as I also did the schottky diode bridge...but...a 100uf 250v film works very well, here.

-Mark in St. Louis

 

[Kitchener]

You can proceed exactly as you have written...either way works. I used the Triad but th Hammond 157M would be fine, as well.

Also, you can replace either resistor with the choke. I chose to replace the 1st one (across along the back)....thus C-L-C-R-C...C-R-C-L-C is also fine.

I opted for a 2.2uf bypass, as I also did the schottky diode bridge...but...a 100uf 250v film works very well, here.

-Mark in St. Louis

Thanks a lot, Mark!
This was great, exactly what I was looking for.

I’m probably going to try a bypass at first.
-I’ve already ordered one, along with some bypasses for the output caps, so I’ll sit on my wallet for now.

I think there’s been some discussion about what resistor to replace, but as I recall in the end it didn’t really matter?

It doesn’t matter how I hook up the choke, correct?
-polarity is irrelevant here?

 

[buldogge]

Thanks a lot, Mark!
This was great, exactly what I was looking for.

I’m probably going to try a bypass at first.
-I’ve already ordered one, along with some bypasses for the output caps, so I’ll sit on my wallet for now.

I think there’s been some discussion about what resistor to replace, but as I recall in the end it didn’t really matter?

It doesn’t matter how I hook up the choke, correct?
-polarity is irrelevant here?

Wiring connection choice shouldn't matter much...This what Paul Joppa wrote over on the Bottlehead Forum, some time ago, regarding the wiring/ dot marking on the C-7X choke:

"Yes there is some sense to twisting the wires (minimizing the current-loop area.

The choke works by reducing the current fluctuations of the power supply, but it does not of course completely eliminate them. The twisted wires reduce the magnetic hum field generated by the remaining fluctuations.

The most important twisting is the heater power wires, where the fluctuating current is very high - 2.5 amps for the 6080 heater.

The dot usually signifies the start of the winding, standard practice it to use that with the highest AC voltage, i.e. the input of a filter choke. In this application the difference will be very tiny, so don't stress."

-Mark

 

[Kitchener]

Wiring connection choice shouldn't matter much...This what Paul Joppa wrote over on the Bottlehead Forum, some time ago, regarding the wiring/ dot marking on the C-7X choke:

"Yes there is some sense to twisting the wires (minimizing the current-loop area.

The choke works by reducing the current fluctuations of the power supply, but it does not of course completely eliminate them. The twisted wires reduce the magnetic hum field generated by the remaining fluctuations.

The most important twisting is the heater power wires, where the fluctuating current is very high - 2.5 amps for the 6080 heater.

The dot usually signifies the start of the winding, standard practice it to use that with the highest AC voltage, i.e. the input of a filter choke. In this application the difference will be very tiny, so don't stress."

-Mark

Aha, I remember reading that!
-I suck at finding stuff I know I’ve read somewhere.
Thanks for the quote.

 

[Allanmarcus]

Another thing to so to help with power is to upgrade the included rectifiers with Schottky diodes. This was discussed on the Bottlehead board too. Not a hard mod, but it does require removing the 4 rectifiers. I desoldered them, but in hindsight, I should have just clipped them off (easier).

Here's how I did it. I got some help from a super friend with the wiring diagram

Note, I decided to just let the diode board hang since the green wires are pretty stiff. Other options include a 1" nylon spacer and some drilling, or super glue.

Does it sound better? The parts where like $10. It sounds $9.95 better I already have the choke as well. I supposed I could upgrade the caps, but meh.

BOM:

• 4 cree "Schottky" diodes (Parts Connexion # DIODES-68247) $1.50/ea
• 1 small board (Parts Connexion # PCB-77727) $1.95

My crack story: https://sites.google.com/marcusfamily.info/diynotes/my-stuff/bottlehead-crack

 

[bloodhawk]

Another thing to so to help with power is to replace the rectifier with diodes. This was discusses on the Bottlehead board too. Not a hard mod, but it does require removing the 4 rectifiers. I desoldered them, but in hind site, I just have just clipped them off (easier).

Here's how I did it. I got some help from a super friend with the wiring diagram

Note, I decided to just let the diode board hang since the green wires are pretty stiff. Other option include a 1" nylon spacer and some drilling, or super glue.

Does it sound better? The parts where like $10. It sounds $9.95 better

BOM:

• 4 cree "Schottky" diodes (Parts Connexion # DIODES-68247) $1.50/ea
• 1 small board (Parts Connexion # PCB-77727) $1.95

Nice! That should help a lot of new comers ...

This is what my crack looks like ...im in the process of moving this over to a 10x10 panel and a larger frame - https://imgur.com/a/EYi11 (Album)