Options for replacing EF86? E180F?

[rotation]

Hi,

I'm working on a tube microphone preamplifier where input tube is EF86/6267. I find this tubes quite noisy, some of them are ok from beginning but later become noisy. I could simply change the tube, but prices are quite high and many new tubes are noisy from beginning.

Since i love the sound of EF86 input stages i would really like to change this tube with another sharp cutoff pentode tube. I can get SQ, gold pin E180F or normal version of EF184. Both are about 5 times cheaper than EF86 and stock is almost unlimited.

Schematic of preamplifier i'm working on is here:
http://img56.photobucket.com/albums/...raf/REDD47.gif
Input stage looks exactly like example for AF amp in Philips datasheet for EF86, but i can't find nothing similar for E180F.

So, what should i do to replace EF86 with E180F? I compared some values and E180F have higher Ia, Gm, Mu and lower Ri.
I guess i have to change Ra, Rk, Rg2.
If you look at schematic of mic pre there is 330k resistor which loads EF86. Does it remain the same for E180F?

Yeah, many questions. I would be very happy if anyone tells me how to start so i can experiment.
Btw, anyone have experiences in replacing this two tubes?

Regards from Miha

[kevinkr]

Originally posted by rotation
Hi,

I'm working on a tube microphone preamplifier where input tube is EF86/6267. I find this tubes quite noisy, some of them are ok from beginning but later become noisy. I could simply change the tube, but prices are quite high and many new tubes are noisy from beginning.

Since i love the sound of EF86 input stages i would really like to change this tube with another sharp cutoff pentode tube. I can get SQ, gold pin E180F or normal version of EF184. Both are about 5 times cheaper than EF86 and stock is almost unlimited.

Schematic of preamplifier i'm working on is here:
http://img56.photobucket.com/albums/...raf/REDD47.gif
Input stage looks exactly like example for AF amp in Philips datasheet for EF86, but i can't find nothing similar for E180F.

So, what should i do to replace EF86 with E180F? I compared some values and E180F have higher Ia, Gm, Mu and lower Ri.
I guess i have to change Ra, Rk, Rg2.
If you look at schematic of mic pre there is 330k resistor which loads EF86. Does it remain the same for E180F?

Yeah, many questions. I would be very happy if anyone tells me how to start so i can experiment.
Btw, anyone have experiences in replacing this two tubes?

Regards from Miha

How about D3A, the German Post Office Pentode? You can get these on eBay for about $11 each last time I checked. (U.S. types like 7788 and 6688 might be worth a look as well.) Yes you will need to figure out the optimum operating points for any tube you substitute.. These high transconductance types all run at very high currents compared to EF86, but are much quieter. New plate, screen, cathode resistor values will be required..

[rotation]

Originally posted by kevinkr



How about D3A, the German Post Office Pentode? You can get these on eBay for about $11 each last time I checked. (U.S. types like 7788 and 6688 might be worth a look as well.) Yes you will need to figure out the optimum operating points for any tube you substitute.. These high transconductance types all run at very high currents compared to EF86, but are much quieter. New plate, screen, cathode resistor values will be required..

Hey,
6688 is E180F and D3A is EF184.. I can get this tubes for 2,5 euros or even cheaper. I would like to focus on E180F/6688 because i can get SQ version for same price.

Miha

[Wavebourn]

6J32P, 6J52P, 6J53P

[kevinkr]

Originally posted by rotation


Hey,
6688 is E180F and D3A is EF184.. I can get this tubes for 2,5 euros or even cheaper. I would like to focus on E180F/6688 because i can get SQ version for same price.

Miha

Doubt there is a much better made tube than the Siemens & Halske D3A, SQ or not.. The German Post Office was very particular about what they used in their equipment. Note that Philips made an SQ version of the D3A, and I don't see any reference in the vade mecum or elsewhere that cites the EF184 as an equivalent to the D3A and comparing data sheets indicate they are different tubes. Pin outs and transconductance are different. IMO SQ tubes are nice, but not necessarily a reason not to consider other types which might be comparable in quality. Your choice obviously..

[rotation]

Originally posted by Wavebourn
6J32P, 6J52P, 6J53P

Guy have them all Have you maybe tried to replace EF86 with E180F or any other similar tube? What do you suggest?

Miha

[panos29]

D3A is no way an EF184! D3A is a supertube by all means with no substitute! Only some Russian tubes are close but very inconsistent in performance.

e180f can also be substituted by 6J9p(which is excellent sounding and avalable).

P.S I love e180f sound! too bad I only have 2

Is there any spare one I can get from you as I am using these in my favorite SE pre?

[rotation]

Thanks for informing me about D3A. About the E180F; i can get you some if you want, send me PM.

Miha

[Klimon]

E80F should work in most circuits as drop-in for ef86; this might be exactly what you're looking for.

Simon

[Wavebourn]

Originally posted by rotation


Guy have them all Have you maybe tried to replace EF86 with E180F or any other similar tube? What do you suggest?

The first one (6J32P) may be used with no modifications; the last 2 need more current. 6J52P is similar to D3A. 6J53P has anode made of titanium so can keep up with powers needed for best linearity.

The "guy" knows them all well.


Enjoy!