Three Amplifiers vs One Man. My DIY quest

Simon Says said:
These are the options I get if I go with Zilla: https://www.zillacabs.com/tolex. The new Fawn is different from the aged one. Coffee could be an option, but shellac works wonders with tweed. However, I don't know how well it would stick to plastic. Choosing a new colour may be a better approach. Take a look at Rough Blonde or Rough Brown as potential options.
Click to expand...
Ahhhhhhh, ZEBRA, HELLO!!!
 
Simon Says said:
I ate Zebra once, but won't have it on my amp
Click to expand...
One of the best burgers I ever had was Camel (seriously, but I think the camel toe jokes are bound to follow) when I was in Morocco! I get ya', but when I saw the options on that link, it seemed like the obvious choice!! I must have read the room wrong ;~)) Thanks for letting us follow this journey, I am thoroughly enjoying it!!!
 
Moondog Wily said:
One of the best burgers I ever had was Camel (seriously, but I think the camel toe jokes are bound to follow) when I was in Morocco! I get ya', but when I saw the options on that link, it seemed like the obvious choice!! I must have read the room wrong ;~)) Thanks for letting us follow this journey, I am thoroughly enjoying it!!!
Click to expand...
This AC30 will most likely be my living room amp. My wife would say no, I'm sure ;)
 
Simon Says said:
I could go with Blues. I won't use it without reactive load. But that still won't give me the same flavour. I will do some more reading and shootouts
Click to expand...
I actually prefer the sound of Golds or Emi Red Fangs over the Blue's. But the classic Vox tones were mostly blues and greenbacks. If you like the voice of the Gold better, then it will be great with the Vox amp.
 
Just an update on where I am with my build right now.

The issues I had with the tube sockets aren't resolved. The new hole locations in the preamp stage are fine, but I can't drill new ones in the PA stage as they will interfere with the retainers. My plan was to modify the layout, which I have already done, but it doesn't look quite right. However, I have found the correct 22mm bases in Germany, and I will order them when I get paid next since I have run out of funds for this month.

I should have done the search earlier instead of rushing to drill into the chassis. I realize now that I need to take my time and do things right.

Another issue I was pondering is the power tubes. I was planning to use EL83 (6CK6) tubes, but I was also considering linking pin 1 and 9 so that I could use the standard EL84M. Unfortunately, it's not that simple. After looking at the EL83 datasheet, I discovered that pin 9 is marked as NC (no connection), so it can't be linked with pin 1. The pin 1 (as well as pin 6 and 8) on the EL84 is marked as IC (internal connection) on the datasheet. As a result, some EL84 tubes like GE 6BQ5 have pin 1 linked to pin 2, which on the EL83 would link screen grid and the control grid. Additionally, pin 6 and 8 are not internally connected, but they pass through the glass envelope and the metal is exposed to the high vacuum. If I use the same wiring arrangement, I may run into issues. To avoid any problems, I would have to carefully go through the datasheet for every tube change and probe pins for shorts to ensure they will work properly.

In the end, I decided to stick solely to the EL83 arrangement and take advantage of some of its features. As mentioned earlier, the EL84 pin 8 is marked as an internal connection, which may or may not be connected to other elements of the tube. The EL83 uses pin 8 for internal shield, so by connecting the pin 8 to ground or cathode, I will electronically shield the tube from noise which is not possible with the EL84. Noise reduction was one of my main goals with this amp, so I am pleased with this.
 
Bogner said:
Good To Know. Thank You For The Update My Friend! Did You Make A Tolex Decision Or Did This You Wrote Of Above Have Your Mind Consumed? (It Sure Would Have Mine If I Still Had One) :)
Click to expand...
Thx man.

Kinda thinking rough blonde, but this may change.

I'm still plan to start populating the preamp boards after the weekend, so more pictures coming soon
 
Here's the quote on the nitty-gritty on EL84 "internal connections" I found on the Ampage forum via the wayback machine. For those interested to know more.

In the GE book, 6BQ5 & 7189 share the same basing pinout: 9CV;

2 is grid
3 is internally jumped to both cathode & suppressor
4 & 5 are heaters (6.3Volts)
7 is plate
9 is screen
1, 6, & 8 show *IC* which is taken to stand for *Internally Connected*, which I understand means that the pin at least goes through the glass envelope and its metal is exposed to the high vacuum inside. Whether or not an *IC* pin actually connects to an internal electrode, and which one, does not seem to be universally required unless the basing diagram shows a connection to a particular electrode, 9CV does not, and 1, 6, & 8 show no guaranteed connection whatsoever.

On my GE 6BQ5 tubes which would be assumed to correspond to their own handbook, everything is as I listed above, and also pins 1 & 2 are jumped internally. Pins 6 & 8 are there going through the glass, but have no electrical connection to each other or anything else inside. These GE tubes have 6BQ5 USA etched on the glass with the typical dot pattern below, in white writing there was added GE 6BQ5/EL84. The box also says 6BQ5/EL84.

My RCA 6BQ5's are the same way, also RCA 7189, as well as recent Ei 6BQ5 from Yugoslavia. The Sovtek EL84 & EL84M do not have any connection to pin 1, so they actually follow the basing diagram more closely than the others. I do not have any true NOS European EL84's to compare, but it is considered the exact substitute for the traditional US 6BQ5. On my RCA's the 6BQ5 is applied within their typical octagon with USA above it, additionally painted on the glass is 6BQ5/EL84, the box has 6BQ5/EL84 as well. My 7189 tube is identified within the octagon with USA above it, indicating RCA manufacture, but this NOS one was relabeled and marketed by Raytheon with an apparently original box, except the box shows 7189A, this tube does not have pins 6 & 9 internally jumped though, see information below about actual 7189A. The Ei is only marked Yugoslavia 6BQ5 on the tube, the box has EL84/6BQ5. The Sovteks are visibly different from each other, supposedly made in different plants, the standard tube has EL84/6BQ5 on the glass, the box only EL84. The Sovtek EL84M is painted only that way on the glass with Made in Russia shown in English, there are additional Russian designations including what is likely their tube number, 6Pi14Pi-EP, with Pi representing the single cyrillic character equivalent to the greek letter *Pi*. This tube appears to have a date code of 9108, from 1991. Both Sovteks have the thin shiny pins these are known for.

In the GE book, the 7189A has a different basing all its own: 9LE;

Same as above for the most part:

2 is grid
3 is internally jumped to both cathode & suppressor
4 & 5 are heaters (6.3Volts)
7 is plate
9 is screen

On this one the difference is it clearly shows an internal jumper between pins 1 & 2, but also it has pins 6 & 9 shown jumped internally as well.

My only 7189A appears to be falsely labeled, it was marketed by Westinghouse in their notorious later violet box, on the tube is printed 7189A Westinghouse Made in Germany. It appear identical with the Sovtek EL84 except the pins are not the thin shiny ones like Sovteks have currently, but look more like traditional US NOS pins. It is electrically identical to the Sovtek EL84, and there is no implementation of the 7189A pinout specification.

What this means is that if you use only pins 2, 3, 4, 5, 7, & 9 in an amp design, it will be pin-compatible with all of the above tubes. Of course it's up to each operator how hot you want to stress yours and with how high a voltage
;-)


part2

If an amp calls for 7189A and doesn't work with 7189, 6BQ5, or EL84, I would expect that the designers were using pin 6 instead of pin 9 for their screen connection, this would be easy to correct, but maybe it was a stressful circuit and not intended to use commercial tubes. If 7189A doesn't work in a 6BQ5 or 7189 circuit, there could be the possibility that unused pins (1), 6, & 8 were utilized during assembly merely as utility soldering terminals (pin 1 would be really dumb apparently) for connections not intended to be made to the tube to begin with. This can easily be modified for broader substitution possibilities. There is also some possibility at one time that US 6BQ5's did not have an internal jumper between pins 1 & 2 either, but my specimens all are jumped.

Additionally, there is available a Svetlana SV83 not claimed to be usable in an EL84 circuit, but according to their literature *EL84 can be used in an SV83 CIRCUIT without modification.* Only a jumper on the socket. I don't have one of these tubes, but from their technical literature I would suggest the above (2, 3, 4, 5, 7, & 9) wiring to the circuit, with an external jumper from the cathode pin 3 to their suppressor pin 6 would make it socket compatible with all tubes mentioned except a true 7189A. Their suppressor appears to be internally jumped to pin 1, another good reason to always avoid connecting pin 1 to anything when using any of these semi-compatible small power tubes. Lifting the connection from pin 6 would allow 7189A use when desired. The screen of SV83 has a lower voltage and wattage rating however, so that must be taken into consideration, otherwise the tube is similar and is reported to sound quite good.
Click to expand...
And the EL83 vs EL84 pinout for full illustration:

EL83 Pins:
1. Screen grid. Normally connected to external positive voltage.
2. Control grid. Nearest grid to cathode. Normally held negative of cathode.
3. Cathode. Source of electrons. Normally at ground potential.
4. Heater connection.
5. Heater connection.
6. Suppressor grid. Normally connected to cathode.
7. Anode. Normally connected to a high positive voltage
8. Internal screen (shield) to shield the electrodes.
9. No Connection

EL84 Pins:
1. Internal connection. Nothing must be connected to this pin of the valveholder
2. Control grid. Nearest grid to cathode. Normally held negative of cathode.
3. Cathode. Source of electrons. Normally at ground potential.
Suppressor grid. Normally connected to cathode.
4. Heater connection.
5. Heater connection.
6. Internal connection. Nothing must be connected to this pin of the valveholder
7. Anode. Normally connected to a high positive voltage.
8. Internal connection. Nothing must be connected to this pin of the valveholder
9. Screen grid. Normally connected to external positive voltage.
 
Last edited:
Just a really quick one, as I'm knackered;

Preamp boards mostly done. There's only one resistor off axis, but all the other components are clean. Unfortunately, I'm missing a few components, and I'm not sure if I misplaced them or if Mouser made a mistake with my order. I plan on ordering more parts from them soon, so I'll rectify this. I'll take better shots with close-ups in better light tomorrow.

More updates in a couple of weeks when I spend the coin on parts

BTW, I decided to go EL84 in the end with screens and grid resistors bumped to 1k and 3k. I explain why when I get my brains back

 
Simon Says said:
Just a really quick one, as I'm knackered;

Preamp boards mostly done. There's only one resistor off axis, but all the other components are clean. Unfortunately, I'm missing a few components, and I'm not sure if I misplaced them or if Mouser made a mistake with my order. I plan on ordering more parts from them soon, so I'll rectify this. I'll take better shots with close-ups in better light tomorrow.

More updates in a couple of weeks when I spend the coin on parts

BTW, I decided to go EL84 in the end with screens and grid resistors bumped to 1k and 3k. I explain why when I get my brains back

Click to expand...
I am in awe.
 
You must log in or register to reply here.

Similar threads

László
Your Favorite Amp's Tone Signature?
3 4 5
Replies
99
Views
3K
László
László
László
The National Department Of Amps That Sit In Mixes Well Doing...Things.
2 3
Replies
47
Views
823
László
László
László
The Amp/Pedal Match/Mismatch Thing.
Replies
13
Views
195
László
László
Monahan
Borrowed Rig vs. My Current Rig
Replies
6
Views
240
Bogner
Bogner
andy474x
I'm not crazy, and I can prove it - there's something real to my problem with V30's
Replies
10
Views
345
László
László
Back
Top