[graematter]

I have some minor NFB buzzing that reduces significantly when I touch the NFB pot. The pot casing is grounded very well. I have shielded wires for the NFB wiring. 880dt Beyers. I can reduce the buzzing to nothing with the NFB knob at 50%. Any ideas? Or is the only possibility that my ground is not satisfactory?

 

[fishski13]

Quote:

I have some minor NFB buzzing that reduces significantly when I touch the NFB pot. The pot casing is grounded very well. I have shielded wires for the NFB wiring. 880dt Beyers. I can reduce the buzzing to nothing with the NFB knob at 50%. Any ideas? Or is the only possibility that my ground is not satisfactory?

is the shield tied to ground?

 

[nikongod]

 
Quote:

Or is the only possibility that my ground is not satisfactory?

This would be my bet.

 

[audionut]

Can anyone suggest some good sources for the 6n6pi? I'd like to try some in place of my JJ ECC99's to see how they sound in comparison. My searches haven't turned up many places to get these from. Thanks, Tommy.

 

[balderon]

http://shop.ebay.com/?_from=R40&_trksid=p3907.m570.l1311&_nkw=6n6p&_sacat=See-All-Categories
 
http://www.tubes-store.com/product_info.php?products_id=15 $10 min order

 

[funch]

 
Quote:

Can anyone suggest some good sources for the 6n6pi? I'd like to try some in place of my JJ ECC99's to see how they sound in comparison. My searches haven't turned up many places to get these from. Thanks, Tommy.

     I have the two that came with my Glassjar kit, and four more that I got thru ebay from the Ukraine that I'm not using.
 
     I also have an EZ80. PM me if you're interested.

 

[audionut]

Gentlemen, Thanks for the offers and links for the 6n6pi's, but I just realized via the Bijou website that you're not supposed to use the 6n6pi's if you've done the Regal Mods, which I have. Can anyone recommend any other tubes to roll, either in the input or output stage, that I can try in place of the JJ 6922's and ECC99's that I have in there now? Just looking to experiment a little to see how different tubes (NOS versions maybe, instead of new production JJ's?) might give me a different sound. Thanks.

 

[balderon]

There are many posts, some recent, discussing this very subject.

 

[kominak]

So I've read through the first 70 pages of this thread and I think I'm really going to build this amp.
Still want to be sure I understood everything right - please correct me if I'm wrong:
 
1. If I only plan to use the amp with 600Ohm headphones, I suppose I can:
    1a. remove the NFB
    1b. decrease the value of C5 to around 30uF so that I could use quality film caps (the rolloff point would be under 10Hz)?
2. I always used toroid power transformers in my guitar tube amps, I thought they're better for audio because of their smaller EMI field,
   but now I've read that EI core transformers are better for this amp because of their lower bandwidth
  (thus acting as a filter against radio interference?). Is it really so?
3. I plan to use NOS Tesla E88CC in V1 position. As it is basically same tube as 6922 is it possible to make regal's mod
   without any other changes?
4. I plan to use nos 6n6p in V2 position. Can I use either 6n6p or 6n6p-I? Which type is supposed to be better?
5. How important (in this design ) is it for the V1 tubes to be matched and for V2 tubes to be both matched and balanced?
(left V1a = right V1a;
 left V1b = right V1b;
 lV2a=lV2b=rV2a=rV2b)
6. Suggestions for quality coupling/output caps? I know it's a personal thing but I'd still like to get some tips. I prefer detail over smoothness.
 
Thanks a lot!
 

 

[regal]

I would recommend at least 50uf with the 600 ohm phones.  Definately remove the NFB,  yes use a EI core for tube amps, NOS Tesla 6922 work well with my mod but I preferred 6DJ8 Amperex tubes because the current is so low (6922 is for higher current applications but they still sound fine.)  I'm no expert on russian tubes but I think all 6n6p's are the same.  Obbligos may be a cap for you to look at but recommending caps is like recommending a flavor of icecream, but avoid electrolytics in all positions of the the amp board (not just the coupling caps).  Oh,  except the cathode bypass:  use a Slimic II 1000uF there.  Also dont forget to use an EZ81.
 
 
 
Quote:

So I've read through the first 70 pages of this thread and I think I'm really going to build this amp.
Still want to be sure I understood everything right - please correct me if I'm wrong:
 
1. If I only plan to use the amp with 600Ohm headphones, I suppose I can:
    1a. remove the NFB
    1b. decrease the value of C5 to around 30uF so that I could use quality film caps (the rolloff point would be under 10Hz)?
2. I always used toroid power transformers in my guitar tube amps, I thought they're better for audio because of their smaller EMI field,
   but now I've read that EI core transformers are better for this amp because of their lower bandwidth
  (thus acting as a filter against radio interference?). Is it really so?
3. I plan to use NOS Tesla E88CC in V1 position. As it is basically same tube as 6922 is it possible to make regal's mod
   without any other changes?
4. I plan to use nos 6n6p in V2 position. Can I use either 6n6p or 6n6p-I? Which type is supposed to be better?
5. How important (in this design ) is it for the V1 tubes to be matched and for V2 tubes to be both matched and balanced?
(left V1a = right V1a;
 left V1b = right V1b;
 lV2a=lV2b=rV2a=rV2b)
6. Suggestions for quality coupling/output caps? I know it's a personal thing but I'd still like to get some tips. I prefer detail over smoothness.
 
Thanks a lot!
 

 

[kominak]

Thanks a lot, regal. Do you know if it's important that the tubes are matched/balanced? Haven't found any info about this.

 

[graematter]

I'm now planning to remove my NFB. I will only be using 250ohm Beyer 880dts and think I should be alright. Are my assumptions correct? I bought the kit from Jeff at Glass Jar. As described on the Bijou site, I have to change R1 from 10k to 300. I don't have any more vishay resistors and was wondering if I could place a 300ohm resistor from radioshack. Would this greatly reduce my sound? I have no problem ordering a new resistor and doing this right; however, I'm leaving for college in 5 days and would like to do this now.
 
Please advise.
 
Graematter

 

[regal]

Quote:

Thanks a lot, regal. Do you know if it's important that the tubes are matched/balanced? Haven't found any info about this.

I really don't think so unless you get a pair that are way off,  the 6N6P you buy are true NOS so that I wouldn't worry about at all.  For the 6DJ8's I suppose it would be possible to have a pair way off but I didn't have in trouble with several different used ebay pairs.


 
Quote:

I'm now planning to remove my NFB. I will only be using 250ohm Beyer 880dts and think I should be alright. Are my assumptions correct? I bought the kit from Jeff at Glass Jar. As described on the Bijou site, I have to change R1 from 10k to 300. I don't have any more vishay resistors and was wondering if I could place a 300ohm resistor from radioshack. Would this greatly reduce my sound? I have no problem ordering a new resistor and doing this right; however, I'm leaving for college in 5 days and would like to do this now.
 
Please advise.
 
Graematter

I used a ratshack resistor for R1,  no problems,  some think they sound better than metel films in those positions.

 

[graematter]

Thanks for the response. I ended up using a carbon resistor. It sounds great. 

 

[kominak]

thanks, regal. So I guess I'll try bijou with some spare tubes I have around first.