[PromitheusAudio]

I started this thread to make easier for people to read comments about the Apollo preamp

What is the apollo preamp

The apollo preamp is the TVC and the Tube Active Preamp put together in a single chassis
the apollo has
1) XLR input, 2 pairs of RCA input
2) XLR output, 2 pairs of RCA output

The volume control is a dual mono version

One of the nice feature the apollo has the the ability to toggle between
1) TVC usage
2) TVC and tube output stage
So it could be used as a standalone unit or a full fledge preamp with gain with the TVC as the voltage gain

The gain for the unit is 6dB. 12dB gain can be made custom

It features a separate tube power supply which uses the 5y3 rectifer
The main unit uses 2 pieces of 6N1P for voltage amplication
The unit uses output transformers which allows true balanced outputs

The tubes that can be tube rolled are
1) 6922
2) 6dj8
3) 6h23
4) 7308
5) 6cg7 (lower gain)
6) 6fq7 (lower gain)
7) 6bq7 (higher gain)

[tanchiro58]

Hi Nick,

I have rolled the 6N1P tubes in my Apollo preamp with the Amperex 7308s. The sound does not buzzing like the RCA 6922s but it is very weak even though I turned up the volume. You told me to increase the value of the resistors to more than the existing 1K at the B+ voltage at 47mF and 200mF. Would you please let me know the exact value of those resistors? Thanks in advance.

Regards,
Tan

[PromitheusAudio]

Tan
Here is what you can do

Add 100R resistors to the grid. With the 6N1P is not needed but some tubes require them. Hence we started putting them just in case people start to tube rolled. You would need 2 pcs, 1 for each tube

On the resistors at the 47uf and 200uF, you would need to change all the resistors to 2K, you would need 3 pcs

And change the cathode resistor to 100ohm too, works out well, this is pin 3. You would need 2 pcs

I use Carbon Composition by Allen Bradley for all the resistors here. I like the tonal quality of this resistor

If you need the resistors let me know thru here, email during this season is pretty bad lots of spam

[SoundQuest]

Check out the new deck on my Apollo. Some black coarse material that I'm unable to identify.

[tanchiro58]

Tan
Here is what you can do

Add 100R resistors to the grid. With the 6N1P is not needed but some tubes require them. Hence we started putting them just in case people start to tube rolled. You would need 2 pcs, 1 for each tube

On the resistors at the 47uf and 200uF, you would need to change all the resistors to 2K, you would need 3 pcs

And change the cathode resistor to 100ohm too, works out well, this is pin 3. You would need 2 pcs

I use Carbon Composition by Allen Bradley for all the resistors here. I like the tonal quality of this resistor

If you need the resistors let me know thru here, email during this season is pretty bad lots of spam

Nick,

Are the resistors at the grids (2x100R) and cathode resistors at pin3 (2x100R) the same? How many watts on resistors (1 watt or 2 watt?) do I need to have? The more watts the better? I heard that Allen Bradley resistors have too much noise because of the high percentage (5-10%) whereas Riken and/or Tantalum have less noise and more musical even though they are more expensive, is that true? How many resistors do I need in total to be able to roll 6922s and 7308s? Thanks in advance.

[tanchiro58]

Nick,

I got confused with the replacement of the grids and cathodes of the tubes if I want to roll 6922s. Which pin do I need to solder the extra 100R for 6922? You said pin 3 resistor should be replaced with 100R which is already there. From pin 2 there is a 2 Ohm resistor. So where do I need to ADD a resistor 100R for grid? Thanks in advance.

Riken 2K 1W at B+ voltage



Tantalums 100R at pin2 and pin3/ I am not sure where the grid is belong to which pin?



Stock Allen Bradley replaced

[tanchiro58]

After replacing all the resistors to compensate with 6922s I hear some buzzing sound or microphonics (more on right speaker than left one). So what should I do to avoid that?

[PromitheusAudio]

Nick,

I got confused with the replacement of the grids and cathodes of the tubes if I want to roll 6922s. Which pin do I need to solder the extra 100R for 6922? You said pin 3 resistor should be replaced with 100R which is already there. From pin 2 there is a 2 Ohm resistor. So where do I need to ADD a resistor 100R for grid? Thanks in advance.

Riken 2K 1W at B+ voltage

Tan in the pictures, you can see a white copper wire coming from the volume pot. that is the 7n wire and the other channel is red wire
What you do is insert a 100R resistor in series with this wire going into the grid which is pin 2 and pin7. Note we join them together.
This is done to prevent oscillation in the 6922 series which is not apparent in the 6n1p i am using
On the high noise this is preference. The high noise results due to the construction and not the percentage. Also the noise value depends on whom makes the resistors
I would stick to tantalum or rikens for our products as it would sound good together

Again to prevent the buzzing or microphonics just insert the 100R resistor as above to avoid this problem

Cheers
Nicholas

[Gaara]

Check out the new deck on my Apollo. Some black coarse material that I'm unable to identify.

Thats not black hold pad is it?  Now you've got me thinking...

[tanchiro58]

What you do is insert a 100R resistor in series with this wire going into the grid which is pin 2 and pin7. Note we join them together.
This is done to prevent oscillation in the 6922 series which is not apparent in the 6n1p i am using

Nick,

In another words, I just take out the connection from pin2 to pin7 and replace with the Tantalum 100R resistor then solder the white wire to pin2. Is this what you tell me to do? Thanks again for a quick response and help.

Regards,
Tan

[tanchiro58]

Again to prevent the buzzing or microphonics just insert the 100R resistor as above to avoid this problem

Hi Nick,

I did insert 100Rs (one for each channel) to the white and red wires in series to pin2 and still have buzzing or microphonics which is very annoying when I volume up all the way on my amp. Note I am using RCA 6922s gold pin made in Germany. Do you have another way to prevent this problem? Thanks in advance.

Tan

[tanchiro58]

Nick,

Have you ever tried the PCC189 tubes to replace 6922s? I know that heater voltage of PCC189 is 7.6V whereas 6.3V of 6922. The cathode just won't heat enough so what would you do? Thanks in advance.

Tan

[highdfever]

Hi Nick,

Found some Hi-End manufacturers has changed the tube from 6922 (6H23) to 6H30 now and performance is even better.   

Will you try it out and is it possible to change the tube to 6H30 by some modification that could be done by the user?

[tanchiro58]

Hi Nick,

Found some Hi-End manufacturers has changed the tube from 6922 (6H23) to 6H30 now and performance is even better.   

Will you try it out and is it possible to change the tube to 6H30 by some modification that could be done by the user?

Andis,

I personally do not like the sound of 6H30 since I got BAT preamp before. IMO 6H30 is only for more juice. I have a pair of 6922 with no mark sounds very very musical. I will try pcc189 which is claimed to be superb over 6922 and no microphonics.

Tan