[Marco Prozzo]

I've only been able to find one mention of this on this thread (I think by BigFish), but no input on the results: Has anyone tried using 7N7 tubes with the appropriate L-Ocatal adapter (available on eBay or from Jim Cross)?  Way cheaper than 6SN7's and identical in construction as I understand it.  Dan gave them a thumbs up, but no input here....anyone try them? 

[Philistine]

I've only been able to find one mention of this on this thread (I think by BigFish), but no input on the results: Has anyone tried using 7SN7 tubes with the appropriate L-Ocatal adapter (available on eBay or from Jim Cross)?  Way cheaper than 6SN7's and identical in construction as I understand it.  Dan gave them a thumbs up, but no input here....anyone try them?

I've tried them Marco - 7N7's, and they are a good lower cost alternative to 6SN7's.  They are difficult to find in quantity and the cost of the adapter mitigates the lower tube cost benefits if you've already invested in 6SN7 adapters.
My fellow Brit - owenmd - has my adapters and has a few tubes he's playing with currently, I'll let Mark comment on his findings.

[Marco Prozzo]

I've only been able to find one mention of this on this thread (I think by BigFish), but no input on the results: Has anyone tried using 7SN7 tubes with the appropriate L-Ocatal adapter (available on eBay or from Jim Cross)?  Way cheaper than 6SN7's and identical in construction as I understand it.  Dan gave them a thumbs up, but no input here....anyone try them?

I've tried them Marco - 7N7's, and they are a good lower cost alternative to 6SN7's.  They are difficult to find in quantity and the cost of the adapter mitigates the lower tube cost benefits if you've already invested in 6SN7 adapters.
My fellow Brit - owenmd - has my adapters and has a few tubes he's playing with currently, I'll let Mark comment on his findings.

Thanks.  The adapters are $38+shipping (assuming you already have a 6SN7 adapter) on eBay.  Current eBay listing average around $10-20 per tube with the high priced ones being from the Greek connection (John - Lowbander80) at $79 a pair for NOS Sylvanias.  Compared to $300-400 for TS Rounds that would seem to make the $40 for the adapter a moot point.  But if they are simply an OK substitute and don't have the sonic chops then I guess I get your point.

[owenmd]

Hi Marco,

As Phil mentioned, I'm currently assessing some 7N7's using Phil's 7N7 to 6cg7 adapters from Taiwan.... they are currently out of stock of this adapter but more will be coming soon apparently.  The other type 7N7 adapters to 6sn7 would obviously necessitate  two adapters in place per tube.... not sure if I like that... I guess it would be fine...?

I have just a few hours on four different types of 7N7's including some tall bottles so its really too early to tell, but some of them appear to sound better than the average  ($120/pr) 6sn7's I've tried.  I don't have the Tung Sol 6sn7 round plates as a reference, so can only compare between the ones I have.  The 7n7's I'm trying average $60 to $70 a matched pair from Vintage tube services.

Once I get a handle on the results I will comment more.

Cheers for the weekend...!

Mark

[Marco Prozzo]

Thanks, Mark.  The 7N7 route sounds like it has some potential.  I doubt that piggybacking adapters would be of any detriment to signal quality, but it may make the resulting adapter a bit awkward. I'm pretty sure the lower portion of the Bolder adapters are an extension (to bring the adapter out of the box) that amounts to something similar to piggybacking two adapters. Correct me if I'm wrong, but it appears that way.  I have adapters from Jim Cross in FL, and that is how his are built.  He can also make L-Octal adapters for around $75/pair I think.  He took a week to make my octal adapters at the same cost. 

The Taiwan adapters appear to require, or may require, pulling off the cover to get them out, which is a PITA in my cabinet.  Am I wrong there - do they come out easily with the tube, or are they left down in the box when you pull the tube?

I look forward to hearing about your results, Mark.  My friend, Peter, has ordered a MW TP for his system after I brought mine over to his place and did a series of blind tests with him.  He's thinking of trying 7n7's as a reasonably priced alternative. 

[funkmonkey]

I can't speak for everyone with the Taiwan adapters but mine stay with the fat pins on the 6SN7s.  No problem removing them, cover stays closed.

[owenmd]

The Taiwan adapters appear to require, or may require, pulling off the cover to get them out, which is a PITA in my cabinet.  Am I wrong there - do they come out easily with the tube, or are they left down in the box when you pull the tube?

No problem with either the 6SN7 Taiwanese adapters or the 7N7's.... they stay firmly attached to the tubes.


A quick note about 7N7's.... although they can be found quite cheaply on places like Ebay, apparently they are notorious for microphonics and other issues.  It may be worth paying the extra to get a guaranteed pair if you have an interest... Andy at tube services reckons he will be lucky to get a 50% usable yield from his stock of 7N7's...!

[Peter_S]

If I've got this right, the Taiwanese adaptors site on top of the 6sn7 adaptors, and therefore shouldn't raise the issue of having to remove the top of the TP to get at them.  I wonder about adding an extra set of contacts to the chain - my sense is that it's better not too.  But as Marco points out, the 6sn7 adaptors already sit on small 9-pin risers to gain clearance over a capacitor that sits close to the stock tube sockets, so that already puts us one step farther out.  Anybody know if those risers are necessary?  There are other direct 7n7-9pin adaptors available, but they don't have the "riser" off the 9 pin, and I don't know if they would fit on the stock TP socket: http://cgi.ebay.com/Adapters-7N7-TO-12au7-tubes-amplifier-SUB_W0QQitemZ250428140305QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item3a4eae2b11&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

[Philistine]

If I've got this right, the Taiwanese adaptors site on top of the 6sn7 adaptors, and therefore shouldn't raise the issue of having to remove the top of the TP to get at them.  I wonder about adding an extra set of contacts to the chain - my sense is that it's better not too.  But as Marco points out, the 6sn7 adaptors already sit on small 9-pin risers to gain clearance over a capacitor that sits close to the stock tube sockets, so that already puts us one step farther out.  Anybody know if those risers are necessary?  There are other direct 7n7-9pin adaptors available, but they don't have the "riser" off the 9 pin, and I don't know if they would fit on the stock TP socket: http://cgi.ebay.com/Adapters-7N7-TO-12au7-tubes-amplifier-SUB_W0QQitemZ250428140305QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item3a4eae2b11&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

Peter, I believe these adapters may not work.  I bought the 7N7 to 6CG7 adapters from this seller (he always quotes the adapters the wrong way for me as I would expect them to be called 6CG7 to 7N7), and currently the seller has told owenmd he's waiting for new stock of these.  I was going to piggy back a 7N7 adapter on top of a 6SN7 adapter but was advised not to do it by JG2, even though they would work it avoids another contact as you mention.  I had no problem getting the 7N7 adapters to fit around the caps.
Phil

[Peter_S]

I had no problem getting the 7N7 adapters to fit around the caps.

Phil - do you mean that you had no problem getting the 9pin to 7N7 adaptors to fit around the caps?  The ones associated with my link? If they do fit in, why would they not work?  I agree that the 6SN7 to 7N7 adaptors are not optimal since they add another connection.

Thanks, Peter

[Peter_S]

Oh, and the second part of my question, I guess, is whether the 9pin "risers" on JC's 9pin to 6sn7 adaptors are necessary, regarding clearance of that capacitor, and whether they can be removed.  Thanks in advance to anyone who knows about that.

[Marco Prozzo]

Oh, and the second part of my question, I guess, is whether the 9pin "risers" on JC's 9pin to 6sn7 adaptors are necessary, regarding clearance of that capacitor, and whether they can be removed.  Thanks in advance to anyone who knows about that.

Hey Peter - I think Dan has been mounting those caps on the back of the board since folks have been using the adapters more and more.  Since you are getting a current one, they should be on the back and not interfere.  You can shoot Dan an email to confirm that, or perhaps he'll chime in here, but that's how mine came back after the Hypermod.  I was under the impression that the low adapters might stay in the socket when the tube is pulled, which is the question I was asking - and it seems that it comes out with the tube.  Therefore the Taiwan adapters could be another option for you (available on eBay and usually take a week).  The 7N7 adapters I saw on eBay are from an NC seller - they these ones which would piggyback on another adapter.  You may also want to ask Roger, the guy who works on tube gear locally, to see if he might make an adapter for you.  I bet he would. 

[Philistine]

I had no problem getting the 7N7 adapters to fit around the caps.

Phil - do you mean that you had no problem getting the 9pin to 7N7 adaptors to fit around the caps?  The ones associated with my link? If they do fit in, why would they not work?  I agree that the 6SN7 to 7N7 adaptors are not optimal since they add another connection.

Thanks, Peter

Hi Peter, the ebay seller has a specific 7N7/6CG7 adapter and also a 7N7/12au7 adapter I would play safe on assuming the 7N7/12au7 would work.  Also, as the seller has advised Mark that he does not currently have a 7N7/6CG7 adapter in stock, then I would believe he would have offered the 7N7/12au7 adapter as an alternative?  On this basis my asumption is that the pin layouts may be different, even though both are 9 pin.  Before buying the 7N7/12au7 adapter I would clarify its suitability with Dan.
Following on from Marco's reply on the capacitor/adapter fit - even if you have an older TP with the caps on the top it is still possible to shave off part of the adapter if you need to in order to create additional clearance. 
Phil

[owenmd]

What he said....!   

[Marco Prozzo]

 On this basis my asumption is that the pin layouts may be different, even though both are 9 pin.  Before buying the 7N7/12au7 adapter I would clarify its suitability with Dan.

On my BK707 tube tester the 9-pin socket to test 6cg7 and 12au7 tubes is the same socket.  So certainly the pin layout is identical. 

[JG2]

Marco is correct.  All the new TP mods and any that are in for Hyper upgrades have the caps moved to the underside of the board to allow proper clearance for the adapters.

If the 12AU7 / 6CG7 pinout is identical, as indicated on my B&K tester as well, the 12AU7 to 7N7 adapters should work.

[Wayne1]

There is a minor difference between the pin outs of the 6CG7 (EIA Base 9AJ) and the 12AU7 (EIA Base 9A).

That has to do with how pin 9 is used. In the 6CG7 series pin 9 is not used at all. In the 12AU7 series, pin 9 is the filament center tap. This can be used so the heater can be run from either 12.6 v or 6.3 V.

The adapters I build do not use extenders. They are hard wired, using my Nitro wire, from the pins of the 9 pin male to the sockets of the octal base.

[JG2]

Here is a tube pinout reference page that opens in a PDF :

http://www.google.com/url?sa=t&source=web&ct=res&cd=8&url=http%3A%2F%2Fwww.bustedgear.com%2Fres_Tube_pinouts.pdf&ei=foEhSsemOKWKtAPuq6j5Aw&usg=AFQjCNFT6ANlaeG06ZYqsAh1438WQWytzA&sig2=r1DMmURlSI0zIX6xpzdS_g

As Wayne mentioned, The only difference between the pinout of the 12AU7 and 6CG7 is pin 9. The 6CG7 has NC and the 12AU7 is heater common.

Thanks, Wayne!

[Marco Prozzo]

The adapters I build do not use extenders. They are hard wired, using my Nitro wire, from the pins of the 9 pin male to the sockets of the octal base.

Thanks for that correction, Wayne. 

[modwright]

Pin 9 of the transporter is tied to shield ground, not signal ground, although all grounds are utlimately star-grounded together.  This is because the 6H30 and 6N1P use this pin connected to an internal shield between the triodes.

This might lead one to believe then that a 12xx series tube could be used, because this pin is grounded, but because the circuit is designed for 6V tubes and series heaters with a 12.6V supply, it would not work.  The 12.6V heater voltage is divided between the two 6.3V filaments in the two tubes.  A 12xx series tube wired for 6.3V with pin 9 grounded would also require parallel filament wiring and a 6.3V supply.

'Cliff Notes' version: Don't use 12AX7, 12AU7, 12AT7, OR 12SN7 as well as other tubes with 12V filaments.  If you do so, you WILL damage the unit or tubes and this will not be covered by warranty.

Thanks,

Dan