Bass DI zod / Reddi ?

[CJ]

ouch.

wait, wasn't there a forum member named ouch?

he kept getting shocked all the time,

like me , every damn day,

 

[Spencerleehorton]

Just needing a few more high wattage resistors to arrive then I can start some testing.
Had to split the turret boards into 3 so it can all fit into case.

 

[Spencerleehorton]

Had some 2.2k 1W resistors I found and had some other 1.2k 3w resistors.
So I wired it all up and getting these voltages so far.

At bridge on B+ getting 240v
After 3 x 2.2k getting 148v
Will replace 2.2k with 1.5k then measure again hopefully will get 67v drop and get to 170v

Heaters I’m getting
6.6v @ bridge
H+ then goes to 4.76v

Not quite sure what to try with the heaters but I have a 330R in there and on the schematic it says 390R and a ? Along with the 1500R also has ?

Not quite sure what to do with the heater resistors??

 

[Spencerleehorton]

My tube is marked 6H1N and it says it’s a E88CC.
B+ now with 1.5k resistors it’s at 164vdc so could try changing one 1.5k for a 1k which should get me there for B+

H+ now has the 1.5k and 390R and it’s @ 4.65v, so it would seem I’m going the wrong way as it did have 330R in there and I did get a 0.1v more!!
The LM317 calculator says to put in 390 and 1.5k to get 6.3v out?

 

[Spencerleehorton]

Putting a 1k sine through shows that the output pot goes from 1.8v up to 3.65v with putting in 0.775v.
Waveform looks a bit iffy?

 

[volker]

6.6v @ bridge

H+ now has the 1.5k and 390R and it’s @ 4.65v, so it would seem I’m going the wrong way as it did have 330R in there and I did get a 0.1v more!!
The LM317 calculator says to put in 390 and 1.5k to get 6.3v out?

Your input voltage is too low to regulate to the calculated value. The LM317 needs at least around 2V overhead to regulate depending on the current, and that's what you're effectively getting out.

Either remove the regulator and just filter with some RC, heat with AC, or make the diodes Schottkys and use a low dropout regulator.

 

[dmp]

Yup either use your current transformer and run AC heaters or get a 9V transformer for DC.
I did a post over in the preamp section where I compared different heater methods (AC, AC humdinger, AC elevated, DC) and with the wiring and ground layout good, AC can match DC performance for tubes that are made for low noise audio. I don't know if that tube needs DC or not.
I used a 6N1P with DC heaters in mine.

 

[Spencerleehorton]

I’ve taken out the regulator and left in the 10000uf and now have 6.6vdc for the heaters, need to lower it a fraction.

Have used 2 x 1k and 1 x 1.5k on B+ and get 166vdc then I put another 1.5k in parallel on the 1.5k and get 175vdc so I reckon 3 x 1k will get me there

 

[Spencerleehorton]

Now getting closer voltages waveform looks even more weird!!
Lots of other checks needed as I’m pretty sure I’m getting wrong voltages every where else!!

 

[Spencerleehorton]

By my calculations to drop 0.3v at 600mA I need to use a 5W 5R resistor?
IS that right?

Anyways just read that within 5% is fine so anywhere from 6v to 6.6v

 

[CJ]

I used AC heaters on mine and get no hum. Twist the wires with a lot of twists per inch.

You might want to check primary inductance of XFMR if you stuck fuse in ammeter.

B+ can be off 20 percent either way with no problems.

I got the same tube and used stock bias resistor with no problems. No need to split cathode, tie them together and run half the resistance for cathode.

I have a three way switch for different cathode bypass caps but the switch always stays at the setting with the highest value cap which is 470 uf.

 

[ruffrecords]

My tube is marked 6H1N and it says it’s a E88CC.

I am not sure where you got that information from but it is not true. A 6HN1 has the same mu as an ECC88 but that is where the similarities begin and end. The 6HN1 has a completely differen gm and plate resistance which means its bias setting is totally different. If you want a cheap Russian near equivalent to an ECC88 try an 6HN23.

Cheers

Ian

 

[Spencerleehorton]

So are we saying I need to bias this tube differently?
As in change the 220R and 470uf?
My voltage here was 1.2v rather than 1.8v as per schematic.

I’ve written 6H1N, Ian has put 6HN1? I assume this is a typo?

 

[Spencerleehorton]

I’ll try and tie the cathodes together and see what happens.
If it hums I’ve always got the option of a couple of 220R resistors to do a CT on the heaters or put a wirewound pot on there.

 

[Spencerleehorton]

I will do a voltage check and share my results on the schematic.

 

[Spencerleehorton]

Pins 3 and 8 on tube now sharing and get 3.1v
Pot goes from 1.7v to 4v output and waveform looks much better.
Dc on pins 2 and 3 of xlr keeps building? Starts at 5.4v then rising to 6.3v after a couple of minutes then I shut down?
Ac wise on pin 2 and 3 on xlr it’s 5.67vac to 12.82vac.

 

[Spencerleehorton]

Just recorded on my phone a test with the bass guitar and with pot at min, it sounds good, as soon as I add any gain with the pot it goes very distorted, I wasn’t aware that this was going to distort it quite so bad??
Need to change something to get a cleaner but higher gain signal without so much distortion?

 

[ruffrecords]

So are we saying I need to bias this tube differently?
As in change the 220R and 470uf?
My voltage here was 1.2v rather than 1.8v as per schematic.

Depends on the circuit configuration but with 1.2V across 220R you have nearly 5mA quiescent current which is right where I would expect it for an SRPP. If it is supposed to be 1.8V then that implies the quiescent is supposed to be nearer 9mA which is what I wold expect for a single ended stage with a transformer plate load.

Cheers

Ian

I’ve written 6H1N, Ian has put 6HN1? I assume this is a typo?

 

[Spencerleehorton]

 

[Spencerleehorton]

So are we saying that the distorted sound is normal?
Thinking about it, I used a bass amp for output so I’ll try into line in rather than hi-z input