New build Complete: 45W, four 6V6, non-HRM

[jelle]

The old datesheets are guidelines....nothing more than that. Look at Ed Jahns' work.

[talbany]

Jelle
True in the world of audio and especially Guitar amps they were guidelines..In the world of TV's Tube specs were strictly adhered to..
BTW.. Curious where do you draw the line on NOS 6V's

All The Best!!

Tony

[renshen1957]

Steve

For audio work the normal specs of Pa=14W and Pg2=2.2W is valid, i.e. 16.6W in total: This is plate and screen dissipation (in practice we typically keep things a little below design maximum plate dissipation of 14W). I’ve seen several amps like the Deluxe Reverb hit these old tubes with 430V or so and they worked. We also know that tubes are under spec’d for the most part – 400V is most likely OK for the 6v. But, try applying 470 or 550V crank it up and see how long your nice NOS shit lasts……

for grins, I found an old TV schematic that used a 6V6 as a vertical deflection amp and have attached the schematic and voltage chart. Note that the voltages are within design max.



Tony

Hi Tony,

Actually Plate Voltages go down on the amps when you "cranked it up."

The 430V on a Deluxe Reverb is idle plate voltage. When under full load the plate voltages will drop as much as 10% or so, closer to 387 volts in the Deluxe. And the Jim Kelley full load voltages are closer to 423 volts down from 490V (the transformer flyback will be about twice this, but will be of short duration when the tube is off during B part of the AB PP).

Most of the old tubes were rated by design center values (all around compromise as to the usage) rather than design maximums.

In context of the times, Tubes used to be plentiful, very high quality (competition makes for good products), and relatively cheap besides being the only game in town, in the US.

The Tweed Amps, Ampeg's Bass amps which were cathode bias, and the amps in the 1960's were designed around the above factors. Cost cutting (no screen resistors 1950's too low a value on SRs 1960's), designs to squeeze the maximum power (mfgs one up manship) goals were more important than tube life expectancy. In US Guitar Amps, upside down tubes, tubes in close proximity to speakers as in combo amps, tubes operated above or at rated specs (cathode resistors in Ampeg Portaflex or in SE designs like the original Champs, respectively, higher plate voltages.) were the norm.

As to NOS tubes, until recently a NOS tube was a better bet in high voltage amps.

Here is the reason:

The Ruskies (actually the Soviets) started making their own tubes in the 1930s based on US tubes and design center values (guidelines as jelle correctly points out), not on design maximum inherent in the tubes. The Chinese technology comes from the USSR.

Fast forward, US tube mfg stop producing tubes (JAN tubes basically no longer required in quantities to support the mfgs) and West Europe likewise follows suit for economic reasons.

The US consumer (including the US Govt) has to find a source for tubes. What's available? Iron Curtain products designed around the old 1930's guidelines as actual maximums and Chinese tech based on the Russians and pre-war (1937) knowledge of US tubes.

The tubes that were Military issue equivalients to the 6L6 and 5558, and the long life verson of the EL84 are highly reliable,. The USSR version of th EL34 were unreliable (the RFKs from Germany were great), so much so that Marsharll US distributor changes over to 6550 tubes because of the recurrent tube failures.

(The US Govt. actually in violation of US law partnered with a Eastern German company to produce the EL34s, the RFK tubes. These and other USSR tubes are then shipped to the UK and stamped made in England to qualify to be legally sold to the US Gov't and in the US).

All this changes post Iron Curtain falling and the beginning of Chinese trade with the US (more so after Most Favored nation status).

The 6V6, the Russian equivalents weren't used in circuits that challenged the tube past the design values, as best as I can determine (I don't read Russian).

The original Chinese rebranded tubes were not actual 6V6 but a related tube which doesn't have the voltage rating of a 6V6. What the hey, print 6V6 on the tube and let Fender sell it or to Groove tubes. Put it your 68 Deluxe, subsequent tube failures. Start looking for NOS JAN 6V6s!

Today, as much as they are loved or hated New Sensor has pushed to improve the quality and durability of tubes sold as 6V6 under their numerous purchased brand names as well as some original names. However, the major tube buying market isn't Guitar Amps, it's Hi-Fi Audio that drives this market.

The Chinese purchased as much of the old manufacturing equipment from England and elsewhere, and has made effort to improve tube quality. The Chinese are more affluent today and invest more into industry. Shugugang has made tremedous improvements. However, buy Chinese tubes from a reliable source, I would recommend audio hi fi grade products rather than bargains on ebay.

I could apply high voltages on NOS in the proper circuit (Jim Kelly amp has correct values for screen resistors or a Deluxe) with NOS tubes. Many owners still do.

I could "cheat" and use rebranded NOS 5992 tubes as 6V6 (military version of the 6V6). The 5992 takes more voltage than any production JJ, EH, or offered higher voltage 6V6 without breaking a sweat. The 5992 will take even more voltage long after current production tube have red-plated. However it was designed, produced, and tested/screened not to fail. No current production tube comes close.
But who is going to shell out $595.00 for a quad of tubes (which however would last very long). The 5992 being more durable doesn't break into 6V6 distortion as easily, which may or may not be what one is looking for.

As to TV sets as mentioned by you in the posts. Unless your TV was the Muntz brand name, there would be up to 3 dozen tubes in the TV set. As reputation of reliability (for those old enough, remember how many US mfg brand names sold TV sets) was paramount the sets circuitry were strictly designed. Old TV sets weren't relagated to the landfill, they became a Bedroom TV and a new set (usually the same brand if found reliable) was purchased. By the time I was 11, we had a living room TV, a TV in the master bedroom, and a TV in the Kitchen, all full size. However, you didn't want to see the TV repair that often.

And if you knew a TV repair man or the DIY like my Dad, he would tell you if one tube failed it could take out many others as well as transformers, etc, or a new tube replacement could stress other tubes resulting in more problems. A good reason for replacing marginal tubes before failure when the TV was acting up (rather than striking it on the side or top as many people did back in the day), work of mouth as to reliable repairmen was better than any advertising. One reason TV repair who came to your home (a TV console is too large and heavy to carry into the shop) had those fishing tackle style tube caddies they carried (even then they knew tube substitutions almost from memory). Check test and replace the tubes before trouble happened again.

A Quad of new production 6V6 should perform well in the circuit, however if this was my build with the OT I would make sure the screen resistors were between 2k7 and 3k3 ohms or not less than 2K2 ohms. I would tweak a cathode capacitor in one of the preamps tubes if necessary to compensate for any tonal changes this might incur.

Best Regards,

Steve

[ToneMerc]

Steve

For audio work the normal specs of Pa=14W and Pg2=2.2W is valid, i.e. 16.6W in total: This is plate and screen dissipation (in practice we typically keep things a little below design maximum plate dissipation of 14W). I’ve seen several amps like the Deluxe Reverb hit these old tubes with 430V or so and they worked. We also know that tubes are under spec’d for the most part – 400V is most likely OK for the 6v. But, try applying 470 or 550V crank it up and see how long your nice NOS shit lasts……

for grins, I found an old TV schematic that used a 6V6 as a vertical deflection amp and have attached the schematic and voltage chart. Note that the voltages are within design max.



Tony

Hi Tony,

Actually Plate Voltages go down on the amps when you "cranked it up."

The 430V on a Deluxe Reverb is idle plate voltage. When under full load the plate voltages will drop as much as 10% or so, closer to 387 volts in the Deluxe. And the Jim Kelley full load voltages are closer to 423 volts down from 490V (the transformer flyback will be about twice this, but will be of short duration when the tube is off during B part of the AB PP).

Most of the old tubes were rated by design center values (all around compromise as to the usage) rather than design maximums.

In context of the times, Tubes used to be plentiful, very high quality (competition makes for good products), and relatively cheap besides being the only game in town, in the US.

The Tweed Amps, Ampeg's Bass amps which were cathode bias, and the amps in the 1960's were designed around the above factors. Cost cutting (no screen resistors 1950's too low a value on SRs 1960's), designs to squeeze the maximum power (mfgs one up manship) goals were more important than tube life expectancy. In US Guitar Amps, upside down tubes, tubes in close proximity to speakers as in combo amps, tubes operated above or at rated specs (cathode resistors in Ampeg Portaflex or in SE designs like the original Champs, respectively, higher plate voltages.) were the norm.

As to NOS tubes, until recently a NOS tube was a better bet in high voltage amps.

Here is the reason:

The Ruskies (actually the Soviets) started making their own tubes in the 1930s based on US tubes and design center values (guidelines as jelle correctly points out), not on design maximum inherent in the tubes. The Chinese technology comes from the USSR.

Fast forward, US tube mfg stop producing tubes (JAN tubes basically no longer required in quantities to support the mfgs) and West Europe likewise follows suit for economic reasons.

The US consumer (including the US Govt) has to find a source for tubes. What's available? Iron Curtain products designed around the old 1930's guidelines as actual maximums and Chinese tech based on the Russians and pre-war (1937) knowledge of US tubes.

The tubes that were Military issue equivalients to the 6L6 and 5558, and the long life verson of the EL84 are highly reliable,. The USSR version of th EL34 were unreliable (the RFKs from Germany were great), so much so that Marsharll US distributor changes over to 6550 tubes because of the recurrent tube failures.

(The US Govt. actually in violation of US law partnered with a Eastern German company to produce the EL34s, the RFK tubes. These and other USSR tubes are then shipped to the UK and stamped made in England to qualify to be legally sold to the US Gov't and in the US).

All this changes post Iron Curtain falling and the beginning of Chinese trade with the US (more so after Most Favored nation status).

The 6V6, the Russian equivalents weren't used in circuits that challenged the tube past the design values, as best as I can determine (I don't read Russian).

The original Chinese rebranded tubes were not actual 6V6 but a related tube which doesn't have the voltage rating of a 6V6. What the hey, print 6V6 on the tube and let Fender sell it or to Groove tubes. Put it your 68 Deluxe, subsequent tube failures. Start looking for NOS JAN 6V6s!

Today, as much as they are loved or hated New Sensor has pushed to improve the quality and durability of tubes sold as 6V6 under their numerous purchased brand names as well as some original names. However, the major tube buying market isn't Guitar Amps, it's Hi-Fi Audio that drives this market.

The Chinese purchased as much of the old manufacturing equipment from England and elsewhere, and has made effort to improve tube quality. The Chinese are more affluent today and invest more into industry. Shugugang has made tremedous improvements. However, buy Chinese tubes from a reliable source, I would recommend audio hi fi grade products rather than bargains on ebay.

I could apply high voltages on NOS in the proper circuit (Jim Kelly amp has correct values for screen resistors or a Deluxe) with NOS tubes. Many owners still do.

I could "cheat" and use rebranded NOS 5992 tubes as 6V6 (military version of the 6V6). The 5992 takes more voltage than any production JJ, EH, or offered higher voltage 6V6 without breaking a sweat. The 5992 will take even more voltage long after current production tube have red-plated. However it was designed, produced, and tested/screened not to fail. No current production tube comes close.
But who is going to shell out $595.00 for a quad of tubes (which however would last very long). The 5992 being more durable doesn't break into 6V6 distortion as easily, which may or may not be what one is looking for.

As to TV sets as mentioned by you in the posts. Unless your TV was the Muntz brand name, there would be up to 3 dozen tubes in the TV set. As reputation of reliability (for those old enough, remember how many US mfg brand names sold TV sets) was paramount the sets circuitry were strictly designed. Old TV sets weren't relagated to the landfill, they became a Bedroom TV and a new set (usually the same brand if found reliable) was purchased. By the time I was 11, we had a living room TV, a TV in the master bedroom, and a TV in the Kitchen, all full size. However, you didn't want to see the TV repair that often.

And if you knew a TV repair man or the DIY like my Dad, he would tell you if one tube failed it could take out many others as well as transformers, etc, or a new tube replacement could stress other tubes resulting in more problems. A good reason for replacing marginal tubes before failure when the TV was acting up (rather than striking it on the side or top as many people did back in the day), work of mouth as to reliable repairmen was better than any advertising. One reason TV repair who came to your home (a TV console is too large and heavy to carry into the shop) had those fishing tackle style tube caddies they carried (even then they knew tube substitutions almost from memory). Check test and replace the tubes before trouble happened again.

A Quad of new production 6V6 should perform well in the circuit, however if this was my build with the OT I would make sure the screen resistors were between 2k7 and 3k3 ohms or not less than 2K2 ohms. I would tweak a cathode capacitor in one of the preamps tubes if necessary to compensate for any tonal changes this might incur.

Best Regards,

Steve

Talk about thread drifting, this thread has almost a full page of retort about 6V6 design specs and application.


[IMG:150:172]http://www.threadbombing.com/data/media/24/spockorly.gif[/img]

[ToneMerc]

Down to the grid stoppers.
TM

[talbany]

TM
Hey Sorry for the de-rail here but I think this is a fairly important point..

Obviously Steve and I have opposing opinions on how to run 6V's and that's OK.. To be honest I don't really care how he runs his NOS..I do however have a small problem with those who post things like 6V's can take up to 1200v but don't tell you the whole story...
Also come out and say XX designer vastly exceeded manufactures recommended specs in his designs and yet doesn't explain technically how it operated or why he did it or what brand tubes he used or what his screen voltage was or what class/mode the amp is running or if the amp was fixed or cathode biased etc..But he ran his tubes at 490v (once again not telling the whole story) to me in a forum like this can be very misleading to those just starting out rather confusing statements..

Back to your build!!

Tony

[ToneMerc]

TM
Hey Sorry for the de-rail here but I think this is a fairly important point..

Obviously Steve and I have opposing opinions on how to run 6V's and that's OK.. To be honest I don't really care how he runs his NOS..I do however have a small problem with those who post things like 6V's can take up to 1200v but don't tell you the whole story...
Also come out and say XX designer vastly exceeded manufactures recommended specs in his designs and yet doesn't explain technically how it operated or why he did it or what brand tubes he used or what his screen voltage was or what class/mode the amp is running or if the amp was fixed or cathode biased etc..But he ran his tubes at 490v (once again not telling the whole story) to me in a forum like this can be very misleading to those just starting out rather confusing statements..

Back to your build!!

Tony

No worries Tony, I knew exactly the point you were trying to make.

TM

[ToneMerc]

It's finally completed and I'm calling it a day. There's one ugly joint on the grid stoppers that I'm going to touch up and then I will power it up tomorrow.

TM

[Structo]

Looks great TM!

How many does this make now for Dumble builds?

I'll be interested in your thoughts and impressions about this amp after you get it dialed in.

[ToneMerc]

Looks great TM!

How many does this make now for Dumble builds?

Thanks Tom

Well, #183 was supposed to last one and you see where that ended.

Brownnote Tweaked D'lite 50W
Brownnote BlueMonkey Reverb HRM 100W
80's high voltage MusicMan supply non-HRM Skyliner 100W
2nd Gen 100W
#183 100W

TM

[renshen1957]

TM
Hey Sorry for the de-rail here but I think this is a fairly important point..


Also come out and say XX designer vastly exceeded manufactures recommended specs in his designs and yet doesn't explain technically how it operated or why he did it or what brand tubes he used or what his screen voltage was or what class/mode the amp is running or if the amp was fixed or cathode biased etc..But he ran his tubes at 490v (once again not telling the whole story) to me in a forum like this can be very misleading to those just starting out rather confusing statements..

Back to your build!!

Tony

Well before Tonemerc goes back to the build.

My apologies for going off on a tangent.

I did try to point that this build with the 3300 ohm transformer would yield power more than 50 Watts rather than the 35Watts. There is a bit more to power amp output design with 6V6 tubes than "Deluxes have 18W clean power with 2 6V6 tubes, ergo 4 would equal 35 Watts.

For more information on the designer and amp that I omitted:

Jim Kelley used Sylvannia 6V6 tubes in a class ab fixed bias amp. Kelley specifically recommended these tubes in his literature, if I recall correctly these were sourced from none other than Groove Tubes as matched sets of tubes. His schematics are online. Kelley's amps were played by Bonnie Raitt, Mark Knopfler, Allan Holdsworth, Ray Parker, Jr., Lee Ritenour, Robben Ford, and Steve Farris to name only a few.

Kelley's design goal was for a non master volume amp, his object was power tube distortion as opposed to preamp distortion or overdrive. Kelley produced one of the earler power attenuators (using a reactive load rather than resistance) to facilitate PA distortion at lower sound levels, a half power switch (60/30), as well as a two channel preamp channel switching amp.

The Jim Kelley amps (either single channel or foot activated channel switchers) came with 4 6V6 and would have the closest power amp to what Tonemerc is building, (the PI is different).

I would recommend 2k ohm or higher screen resistors for 6V6 tubes at least something more than the typical Fender 470 ohms values for tube reliability. (Higher value screen resitors on a 6V6 improves the touch responsiveness of the amp, too).

Again, my apologies to Tonemerc's build thread did not intend to hijack it.

Best Regards,

Steve

[boldaslove6789]

Nice clean build! Should be nice and fat sounding, 4x6V6 D-style amps certainly have they're own distinct character IMO.

[ToneMerc]

Nice! I dig the Sylvania resistors.

Thanks Jelle, I would like to stand over your shoulders.

Mike

[ToneMerc]

Nice clean build! Should be nice and fat sounding, 4x6V6 D-style amps certainly have they're own distinct character IMO.

Thanks, yeah I wanted something a little different.I didn't make as many changes as I first wanted. I figured if I don't like it, it will be easier to tune without so many changes.

TM

[ToneMerc]

Looks great TM!


I'll be interested in your thoughts and impressions about this amp after you get it dialed in.

I went ahead installed the preamps tubes, fused it and lit it.

V1 heater: 6.28VAC
Relay Supply: 5.94VDC, drops to 4.77VDC with both relays activated.
B+: 434.6VDC unloaded @123.2VAC input

TM