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1972 V4B!

baddarryl

baddarryl

Oct 26, 2008
1,738
1,537
Cape Fear!
#1
OMG! I heard this very amp at a friend's show a couple of years ago and nearly creamed myself. Long story short some time later he told me it was at a local shop. I ran over there to pluck it. It wasn't perfect and there was a reason it was there as I talked to the original owner. As I recalled its tone I determined no matter what it took would be worth it. My tech ended up re tubing the 7027A's, replacing the electro catalytic capacitors, and quite a few other things inside at a very reasonable cost. He advised against upgrading it to 6550's for reasons that were beyond me.

At any rate I unplugged my SVT VR and put this into my Heritage 810 at practice Friday and holy smokes! Tube saturation from Heaven!! I have to push the VR with a VT Bass Pedal for that effect, but it's just not the same. Both other guys in the band said that was the best mix we ever had. I was concerned it may not be loud enough and no it won't get there clean, but we like that tube over drive in this band and with that cab I only had to put on about 7. Absolute tonal bliss when pushed with my 2 bands Stingray. What a Rock and Roll combination!!
90BC3BA5-41CA-4080-86A8-8B5DEC166BC8.jpeg
 
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#3
coreyfyfe said:
Looks great.

The 6550s really tax the power transformers in these amps for no gain of output power. They were an option when 7027A weren’t readily available but now that JJ and new sensor are making good replacements it’s not really worth going with the 6550s.
Click to expand...

I was under the impression the JJ 7027A does not have a good reputation for reliability in this amp.

I see Tung Sol 7027A and Tung Sol 7581A recommended frequently. However be aware there are older (New Sensor made) Tung Sol 7027 and 7581 in the market still. Some vendors were even stocking both at the same time. I suggest going with the A version.
 
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#4
Wasnex said:
I was under the impression the JJ 7027A does not have a good reputation for reliability in this amp.

I see Tung Sol 7027A and Tung Sol 7581A recommended frequently. However be aware there are older (New Sensor made) Tung Sol 7027 and 7581 in the market still. Some vendors were even stocking both at the same time. I suggest going with the A version.
Click to expand...

I would agree with that statement in regards to the JJ 7027A but I know not everyone does. I have the tung sol reissues in my B25B and a pair for the V2 I’m rebuilding. Haven’t tried them in my V4. The new sensor tung sol tubes I’ve used have been good quality with no issues (12AX7s, 6L6GC, 6SL7, 6V6, 7027A, KT66), but if I recall correctly from our past discussions your experience hasn’t been as positive? I’ve had problems with all of the new sensor gold lion stuff that I’ve tried (12AX7s and KT88s), but that’s a fairly small sample size.
 
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#6
coreyfyfe said:
I would agree with that statement in regards to the JJ 7027A but I know not everyone does. I have the tung sol reissues in my B25B and a pair for the V2 I’m rebuilding. Haven’t tried them in my V4. The new sensor tung sol tubes I’ve used have been good quality with no issues (12AX7s, 6L6GC, 6SL7, 6V6, 7027A, KT66), but if I recall correctly from our past discussions your experience hasn’t been as positive? I’ve had problems with all of the new sensor gold lion stuff that I’ve tried (12AX7s and KT88s), but that’s a fairly small sample size.
Click to expand...

I am practically a JJ KT88 fanboy...that does not mean I think every JJ tube is the best choice ;).

I don't have first hand experience with the JJ 7027A, but my understanding is they do not comply with 7027A specs; the max plate voltage limits is low for the tube type. I have seen quite a few threads that suggest they are not very robust in an amp like the Vintage V4 that runs the plate voltage well over the JJ's published limit. Also I have to suspect there is a reason why Eurotubes does not carry this tube type.

AFAIK New Sensor does not publish actual datasheets for their more recent designs. Instead they republish datasheets for vintage designs, which really have nothing to do with the new designs, other than the name. So we don't have any published datasheets that describes these tubes. But so far the Tung Sol 7027A and 7581A seem to have a decent reputation in the V4. AFAIK JJ and Tung Sol are your only choice for current production 7027A. My understanding is 7027A is essentially a 6L6GC with higher voltage ratings, and a slightly different pin out. AFAIK Tung Sol is the only current production 7581A, and this tube is pretty much a 6L6GC with a higher plate dissipation rating.

It's possible the guts of these two tubes are the same or at least very close. There should at least be some variation in the pinout. It would be interesting to do an AB test to see if they are voiced differently.

upload_2021-11-7_16-25-2.png


The 7581A is $6 cheaper at the Tube Store.
 
#7
JJ's 7027A is the same tube as their 6L6GC. The only difference is the paint. That being said, the original 7027A is basically a 6L6GC that was made to handle higher plate voltage. The performance specs are pretty much identical. Those tubes were spec'ed out 60-70 years ago and none of the original manufacturers of either 6L6GC or 7027A are in the business anymore.

So anything you get is going to be some kind of substitute, regardless of the name on the glass. The internal components are made to match 6L6GC specs. I don't think anyone actually makes a true 7027A to spec. No one.

That being said, a well-built 6L6GC should do fine in a V4 or V4B. In fact, the newer V4B reissues were made to run on 6L6GC (again, regardless of the paint). The V4B is biased to run cool so you are not really pushing them to the specs on the top end of a true 7027A's performance.

tl,dr: A good 6L6GC or a modern 7072A (same tube) will work fine in a V4/V4B. Quality and brand quality will always be a factor. So if they redplate or fail early, blame the manufacturer - not the tube type on any new glass (7072A vs 6L6GC).
 
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#8
Wasnex said:
I am practically a JJ KT88 fanboy...that does not mean I think every JJ tube is the best choice ;).

I don't have first hand experience with the JJ 7027A, but my understanding is they do not comply with 7027A specs; the max plate voltage limits is low for the tube type. I have seen quite a few threads that suggest they are not very robust in an amp like the Vintage V4 that runs the plate voltage well over the JJ's published limit. Also I have to suspect there is a reason why Eurotubes does not carry this tube type.

AFAIK New Sensor does not publish actual datasheets for their more recent designs. Instead they republish datasheets for vintage designs, which really have nothing to do with the new designs, other than the name. So we don't have any published datasheets that describes these tubes. But so far the Tung Sol 7027A and 7581A seem to have a decent reputation in the V4. AFAIK JJ and Tung Sol are your only choice for current production 7027A. My understanding is 7027A is essentially a 6L6GC with higher voltage ratings, and a slightly different pin out. AFAIK Tung Sol is the only current production 7581A, and this tube is pretty much a 6L6GC with a higher plate dissipation rating.

It's possible the guts of these two tubes are the same or at least very close. There should at least be some variation in the pinout. It would be interesting to do an AB test to see if they are voiced differently.

View attachment 4465192

The 7581A is $6 cheaper at the Tube Store.
Click to expand...

They have some limited datasheets for newer tubes available now, or at least redrawn ones. Here is the 7027A

https://shop.ehx.com/catalog/tubes-specs/7027A TS.pdf

And the 7581A

https://shop.ehx.com/catalog/tubes-specs/7581A TS.pdf

But I have seen links and references the old/original datasheets elsewhere for other tube types under their various brands before, and the tung sol website mostly has old datasheets.

Tung-Sol.com:: Tube Specs

While the new datasheets don’t have a rated plate and screen max on these they do have a 35W dissipation rating, which is higher than any of the 6L6GC that new sensor offers.

https://shop.ehx.com/search/6l6/

And, as you mention, outside of the extra pins on the 7027A, they may be the same tube. The specs and curves appear to be the same.
 
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#9
coreyfyfe said:
They have some limited datasheets for newer tubes available now, or at least redrawn ones. Here is the 7027A

https://shop.ehx.com/catalog/tubes-specs/7027A TS.pdf

And the 7581A

https://shop.ehx.com/catalog/tubes-specs/7581A TS.pdf

But I have seen links and references the old/original datasheets elsewhere for other tube types under their various brands before, and the tung sol website mostly has old datasheets.

Tung-Sol.com:: Tube Specs

While the new datasheets don’t have a rated plate and screen max on these they do have a 35W dissipation rating, which is higher than any of the 6L6GC that new sensor offers.

https://shop.ehx.com/search/6l6/

And, as you mention, outside of the extra pins on the 7027A, they may be the same tube. The specs and curves appear to be the same.
Click to expand...

:woot: Wonder when the finally got around to publishing those?


Aside from differences in the pin outs, the only variance I see between the two datasheets is in how they are formatted. All the specs appear identical and even the curve tracer graphs appear identical.
 
#10
Basslice said:
JJ's 7027A is the same tube as their 6L6GC. The only difference is the paint. That being said, the original 7027A is basically a 6L6GC that was made to handle higher plate voltage. The performance specs are pretty much identical. Those tubes were spec'ed out 60-70 years ago and none of the original manufacturers of either 6L6GC or 7027A are in the business anymore.

So anything you get is going to be some kind of substitute, regardless of the name on the glass. The internal components are made to match 6L6GC specs. I don't think anyone actually makes a true 7027A to spec. No one.

That being said, a well-built 6L6GC should do fine in a V4 or V4B. In fact, the newer V4B reissues were made to run on 6L6GC (again, regardless of the paint). The V4B is biased to run cool so you are not really pushing them to the specs on the top end of a true 7027A's performance.

tl,dr: A good 6L6GC or a modern 7072A (same tube) will work fine in a V4/V4B. Quality and brand quality will always be a factor. So if they redplate or fail early, blame the manufacturer - not the tube type on any new glass (7072A vs 6L6GC).
Click to expand...


I found a JJ datasheet that indicates the pin out is different 6L6GC VS 7027A

upload_2021-11-7_18-11-59.png


Compatibility depends on how the tube sockets in the amp are wired. In some amps they function as essentially the same tube. Other amps may work fine with one, but not be able to run the other. This goes for the Tung Sol 7027A and 7581A as well.
 
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#13
Wow - those have a fantastic tone for rock.... truly a great amp for that certain thing they provide, assuming you don't want to go clean and hifi ever.... well that's my recollection anyway.... maybe they are more versatile than I remember. Regardless of my memory, great amp, and I'm excited for ya!
 
#15
baddarryl said:
OMG! I heard this very amp at a friend's show a couple of years ago and nearly creamed myself. Long story short some time later he told me it was at a local shop. I ran over there to pluck it. It wasn't perfect and there was a reason it was there as I talked to the original owner. As I recalled its tone I determined no matter what it took would be worth it. My tech ended up re tubing the 7027A's, replacing the electro catalytic capacitors, and quite a few other things inside at a very reasonable cost. He advised against upgrading it to 6550's for reasons that were beyond me.

At any rate I unplugged my SVT VR and put this into my Heritage 810 at practice Friday and holy smokes! Tube saturation from Heaven!! I have to push the VR with a VT Bass Pedal for that effect, but it's just not the same. Both other guys in the band said that was the best mix we ever had. I was concerned it may not be loud enough and no it won't get there clean, but we like that tube over drive in this band and with that cab I only had to put on about 7. Absolute tonal bliss when pushed with my 2 bands Stingray. What a Rock and Roll combination!!
View attachment 4465038
Click to expand...
100w CL

The new ones are a 100w VR.

The 70s have a CL preamp.

The RIs are channel 1 of a VR.

They're both awesome. Just different flavors.
 
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