2359glenn | studio

[Xcalibur255]

It might be pertinent at this point to get the first post of this thread updated with relevant info about the current state of things.

 

[Xcalibur255]

ALSO, hope everybody had happy holidays.

 

[vsrrr]

Posted something about this in the 6AS7G thread by accident, but posting here in case any fellow GOTL owners can share some experience / wisdom when it comes to selecting ideal driver tube and rectifier tube complements to the 5998 power tubes. I'm a new GOTL owner (bought of the classifieds), and can use as much help and guidance as I can get.

But first, I'll share my tube rolling experience so far in case it's useful to anyone else:

I recently picked up a pair of Chatham 5998 power tubes, and my two biggest observations are:
1. The noise level when using 5998's changes pretty dramatically when cycling through different voltage driver tube options. When using 6SN7's, the noise coming out of those 5998's is quite a bit higher than when using 12v or 25v tubes.
- @gibosi has already kindly pointed out that when running 6volt 6SN7 in the GOTL, the heaters use AC current.
When running 12v and 25v, the heaters use DC, which is quieter.
2. Compared to the Sylvania 7236 and Thompson 6080's I've tried so far, the 5998's are delivering the highest resolution I've gotten from a power tube in the GOTL so far. The 5998 has a mostly neutral sound signature with more extended treble and tighter bass - annnnd it accomplishes this without sounding "thin". However, since the 5998 is also a very dynamic and forward sounding tube, I find this can quickly become fatiguing in the GOTL, which is already quite a dynamic and forward sounding amp by nature.

So far, I've tried the following driver tubes:
1. Tung Sol 6SN7GT: very nice combo both tonally and resolution-wise. Perhaps a little light on the bass. BUT, the 6SN7+5998 combo generates too much noise in the GOTL, IMO.
2. Sylvania 12SN7GT Bad Boys: solves the noise floor issue, but since these Sylvanias are quite a dynamic and forward sounding tube, it's like throwing gasoline on the fire of the already dynamic GOTL+5998 combo. Great tube, but not when paired with 5998, IMO.
3. Brimar 13D1: tonally, the Brimar softens the 5998's attack a bit and adds some body to vocals, lower mids, and bass. However, the Brimar is darker, and a step down in resolution compared to the Tung Sol.
4. For me, the ideal driver tube would combine the resolution of the Tung Sol and marry the tonality of the Tung Sol and the Brimar. Any recs?

So far, I've only tried the Raytheon 5CU4 rectifier tube, mainly because of several posts made by @2359glenn earlier in this thread, which I will copy below in italics:

Glenn post #27848
One 6AS7 draws 120ma so two draw 240ma and about 30 for the 6SN7 = 270ma
But it is worse the rectifier has to also recharge the filter capacitors.
When the rectifier turns AC to DC it comes out as pulses when the AC sign wave is at 0 there is nothing
coming out of the rectifier. So the amp is running off the charge on the filter capacitors.
This has to be replaced when the sign wave comes back up.
I can go into a lot of detail on this but most won't understand.
The current will be well over 300ma.

The Amp was designed to run with a 3DG4 or 5AU4 that can handle 350ma. Really the 3DG4 lower voltage drop
I don't know what people think of the SQ of these tubes but the amp was made to run on them.
Most or all other rectifier tubes are being cooked running in this amp when running 6AS7s worse if running 6336.
OK when running 6BX7 or 6BL7 a 5U4 will be OK.

Glenn post #28982 & 28984:
OTL can handle 350ma the 3DG4 has a lower voltage drop:
* 3DG4 voltage drop 25 V @ 350ma
* GZ34 & GZ37 17 V @ 225ma (can handle 250ma but no voltage drop rating at 250ma)
* 5V3 voltage drop 47 V @ 350ma
* The GZ34 & GZ37 is getting pushed hard in this amp.
* Less voltage drop is better but the sound will be different with more. It is really up to the person what sounds better.
* Actually the 5CU4 @ 385ma is the best tube for this amp.

This is me (@vsrrr) speaking again, but these bolded green comments from Glenn are the source of my confusion, and why I've stuck with the 5CU4 rectifier until I figure a few things out.

When using a pair of 6AS7G, 6080, 7236, or 5998 power tubes with a 6SN7 driver tube, it seems to me that the very large majority of rectifier tubes that are "compatible" with the GOTL (according to this google doc) are not reallllllly compatible. Instead, they are getting "cooked" as Glenn says.

I know a lot of people prefer the 5U4G, 5U4GB, GZ34, 53KU, and U52, U18/U20 rectifier tubes for various reasons, but wouldn't most of these 200-250 mA rectifiers actually risk arc'ing when used with a pair of 6AS7G, 6080, 7236, or 5998 power tubes and a 6SN7 driver tube?

Lot of questions in here, but hopefully also some useful contextual information and food for thought for my fellow GOTL owners!

Really really appreciate any / all advice!

 

[Monsterzero]

Posted something about this in the 6AS7G thread by accident, but posting here in case any fellow GOTL owners can share some experience / wisdom when it comes to selecting ideal driver tube and rectifier tube complements to the 5998 power tubes. I'm a new GOTL owner (bought of the classifieds), and can use as much help and guidance as I can get.

But first, I'll share my tube rolling experience so far in case it's useful to anyone else:

I recently picked up a pair of Chatham 5998 power tubes, and my two biggest observations are:
1. The noise level when using 5998's changes pretty dramatically when cycling through different voltage driver tube options. When using 6SN7's, the noise coming out of those 5998's is quite a bit higher than when using 12v or 25v tubes.
- @gibosi has already kindly pointed out that when running 6volt 6SN7 in the GOTL, the heaters use AC current.
When running 12v and 25v, the heaters use DC, which is quieter.
2. Compared to the Sylvania 7236 and Thompson 6080's I've tried so far, the 5998's are delivering the highest resolution I've gotten from a power tube in the GOTL so far. The 5998 has a mostly neutral sound signature with more extended treble and tighter bass - annnnd it accomplishes this without sounding "thin". However, since the 5998 is also a very dynamic and forward sounding tube, I find this can quickly become fatiguing in the GOTL, which is already quite a dynamic and forward sounding amp by nature.

So far, I've tried the following driver tubes:
1. Tung Sol 6SN7GT: very nice combo both tonally and resolution-wise. Perhaps a little light on the bass. BUT, the 6SN7+5998 combo generates too much noise in the GOTL, IMO.
2. Sylvania 12SN7GT Bad Boys: solves the noise floor issue, but since these Sylvanias are quite a dynamic and forward sounding tube, it's like throwing gasoline on the fire of the already dynamic GOTL+5998 combo. Great tube, but not when paired with 5998, IMO.
3. Brimar 13D1: tonally, the Brimar softens the 5998's attack a bit and adds some body to vocals, lower mids, and bass. However, the Brimar is darker, and a step down in resolution compared to the Tung Sol.
4. For me, the ideal driver tube would combine the resolution of the Tung Sol and marry the tonality of the Tung Sol and the Brimar. Any recs?

So far, I've only tried the Raytheon 5CU4 rectifier tube, mainly because of several posts made by @2359glenn earlier in this thread, which I will copy below in italics:

Glenn post #27848
One 6AS7 draws 120ma so two draw 240ma and about 30 for the 6SN7 = 270ma
But it is worse the rectifier has to also recharge the filter capacitors.
When the rectifier turns AC to DC it comes out as pulses when the AC sign wave is at 0 there is nothing
coming out of the rectifier. So the amp is running off the charge on the filter capacitors.
This has to be replaced when the sign wave comes back up.
I can go into a lot of detail on this but most won't understand.
The current will be well over 300ma.

The Amp was designed to run with a 3DG4 or 5AU4 that can handle 350ma. Really the 3DG4 lower voltage drop
I don't know what people think of the SQ of these tubes but the amp was made to run on them.
Most or all other rectifier tubes are being cooked running in this amp when running 6AS7s worse if running 6336.
OK when running 6BX7 or 6BL7 a 5U4 will be OK.

Glenn post #28982 & 28984:
OTL can handle 350ma the 3DG4 has a lower voltage drop:
* 3DG4 voltage drop 25 V @ 350ma
* GZ34 & GZ37 17 V @ 225ma (can handle 250ma but no voltage drop rating at 250ma)
* 5V3 voltage drop 47 V @ 350ma
* The GZ34 & GZ37 is getting pushed hard in this amp.
* Less voltage drop is better but the sound will be different with more. It is really up to the person what sounds better.
* Actually the 5CU4 @ 385ma is the best tube for this amp.

This is me (@vsrrr) speaking again, but these bolded green comments from Glenn are the source of my confusion, and why I've stuck with the 5CU4 rectifier until I figure a few things out.

When using a pair of 6AS7G, 6080, 7236, or 5998 power tubes with a 6SN7 driver tube, it seems to me that the very large majority of rectifier tubes that are "compatible" with the GOTL (according to this google doc) are not reallllllly compatible. Instead, they are getting "cooked" as Glenn says.

I know a lot of people prefer the 5U4G, 5U4GB, GZ34, 53KU, and U52, U18/U20 rectifier tubes for various reasons, but wouldn't most of these 200-250 mA rectifiers actually risk arc'ing when used with a pair of 6AS7G, 6080, 7236, or 5998 power tubes and a 6SN7 driver tube?

Lot of questions in here, but hopefully also some useful contextual information and food for thought for my fellow GOTL owners!

Really really appreciate any / all advice!

I'd reach out to @gibosi . He knows all when it comes to the GOTL and rectifiers.

 

[gibosi]

Posted something about this in the 6AS7G thread by accident, but posting here in case any fellow GOTL owners can share some experience / wisdom when it comes to selecting ideal driver tube and rectifier tube complements to the 5998 power tubes. I'm a new GOTL owner (bought of the classifieds), and can use as much help and guidance as I can get.

But first, I'll share my tube rolling experience so far in case it's useful to anyone else:

I recently picked up a pair of Chatham 5998 power tubes, and my two biggest observations are:
1. The noise level when using 5998's changes pretty dramatically when cycling through different voltage driver tube options. When using 6SN7's, the noise coming out of those 5998's is quite a bit higher than when using 12v or 25v tubes.
- @gibosi has already kindly pointed out that when running 6volt 6SN7 in the GOTL, the heaters use AC current.
When running 12v and 25v, the heaters use DC, which is quieter.
2. Compared to the Sylvania 7236 and Thompson 6080's I've tried so far, the 5998's are delivering the highest resolution I've gotten from a power tube in the GOTL so far. The 5998 has a mostly neutral sound signature with more extended treble and tighter bass - annnnd it accomplishes this without sounding "thin". However, since the 5998 is also a very dynamic and forward sounding tube, I find this can quickly become fatiguing in the GOTL, which is already quite a dynamic and forward sounding amp by nature.

So far, I've tried the following driver tubes:
1. Tung Sol 6SN7GT: very nice combo both tonally and resolution-wise. Perhaps a little light on the bass. BUT, the 6SN7+5998 combo generates too much noise in the GOTL, IMO.
2. Sylvania 12SN7GT Bad Boys: solves the noise floor issue, but since these Sylvanias are quite a dynamic and forward sounding tube, it's like throwing gasoline on the fire of the already dynamic GOTL+5998 combo. Great tube, but not when paired with 5998, IMO.
3. Brimar 13D1: tonally, the Brimar softens the 5998's attack a bit and adds some body to vocals, lower mids, and bass. However, the Brimar is darker, and a step down in resolution compared to the Tung Sol.
4. For me, the ideal driver tube would combine the resolution of the Tung Sol and marry the tonality of the Tung Sol and the Brimar. Any recs?

So far, I've only tried the Raytheon 5CU4 rectifier tube, mainly because of several posts made by @2359glenn earlier in this thread, which I will copy below in italics:

Glenn post #27848
One 6AS7 draws 120ma so two draw 240ma and about 30 for the 6SN7 = 270ma
But it is worse the rectifier has to also recharge the filter capacitors.
When the rectifier turns AC to DC it comes out as pulses when the AC sign wave is at 0 there is nothing
coming out of the rectifier. So the amp is running off the charge on the filter capacitors.
This has to be replaced when the sign wave comes back up.
I can go into a lot of detail on this but most won't understand.
The current will be well over 300ma.

The Amp was designed to run with a 3DG4 or 5AU4 that can handle 350ma. Really the 3DG4 lower voltage drop
I don't know what people think of the SQ of these tubes but the amp was made to run on them.
Most or all other rectifier tubes are being cooked running in this amp when running 6AS7s worse if running 6336.
OK when running 6BX7 or 6BL7 a 5U4 will be OK.

Glenn post #28982 & 28984:
OTL can handle 350ma the 3DG4 has a lower voltage drop:
* 3DG4 voltage drop 25 V @ 350ma
* GZ34 & GZ37 17 V @ 225ma (can handle 250ma but no voltage drop rating at 250ma)
* 5V3 voltage drop 47 V @ 350ma
* The GZ34 & GZ37 is getting pushed hard in this amp.
* Less voltage drop is better but the sound will be different with more. It is really up to the person what sounds better.
* Actually the 5CU4 @ 385ma is the best tube for this amp.

This is me (@vsrrr) speaking again, but these bolded green comments from Glenn are the source of my confusion, and why I've stuck with the 5CU4 rectifier until I figure a few things out.

When using a pair of 6AS7G, 6080, 7236, or 5998 power tubes with a 6SN7 driver tube, it seems to me that the very large majority of rectifier tubes that are "compatible" with the GOTL (according to this google doc) are not reallllllly compatible. Instead, they are getting "cooked" as Glenn says.

I know a lot of people prefer the 5U4G, 5U4GB, GZ34, 53KU, and U52, U18/U20 rectifier tubes for various reasons, but wouldn't most of these 200-250 mA rectifiers actually risk arc'ing when used with a pair of 6AS7G, 6080, 7236, or 5998 power tubes and a 6SN7 driver tube?

Lot of questions in here, but hopefully also some useful contextual information and food for thought for my fellow GOTL owners!

Really really appreciate any / all advice!

First, I am not an electrical engineer, so I cannot comment on Glenn's guidance. I am sure he is correct.

However, since the beginning of this forum in 2012, to the present, I cannot recall anyone reporting that they had a rectifier fail as a result of being pushed beyond its limits. I've had my OTL since 2015 and I have at least 50 rectifiers. The only rectifier failures I've experienced were used tubes I bought on eBay that failed the first time I plugged them in. That is, "dead on arrival".

So I think you have to decide how much risk you are willing to assume. If you want to be extremely cautious, stick with rectifiers that can provide at least 350ma. If you can handle a small amount of risk, stick with rectifiers that can provide at least 250ma. (And yes, the 5U4G is too wimpy.)

Edit: Oh, if you are going to roll rectifiers in the GOTL, it is good practice to have some extra glass fuses:

3.15 Amp, 5mm x 20mm, Slow Blow, 250 V.

 

[spanyam]

I just purchased this unit and fired it up for the first time after receiving it today (thanks for the excellent and well packaged shipment @blitzpirate!).

The tubes used are:
- 2 x Sylvania 6080 Gold Brand
- 1 x 3DG4 - Shipped from Glenn
- 1 x Ken-Rad Rare 6F8G with included adapter to be used in the 6SN7 Slot

While the clarity, staging, etc are all great, I'm getting quite a bit of hum (sounds a bit electric-ey, like being close to one of those large voltage transformers in countries like India that power entire neighborhoods). That's also accompanied by occasional scratchy sounds on the left side. I think it's a low 60hz hum, and the volume dial does not affect it. Turning the unit off stops the hum, and it only happens as the tubes warm up after powering on.

It's enough that I do notice it even during quiet parts of a track that's playing. Any tips on how to identify which tube(s) are causing it?

It's currently set up like this, with somewhat of a mess of wires behind it. Not sure if any of those would cause the hum, but unplugging the RCA cables doesn't remove the noise for example.

 

[blitzpirate]

I just purchased this unit and fired it up for the first time after receiving it today (thanks for the excellent and well packaged shipment @blitzpirate!).

The tubes used are:
- 2 x Sylvania 6080 Gold Brand
- 1 x 3DG4 - Shipped from Glenn
- 1 x Ken-Rad Rare 6F8G with included adapter to be used in the 6SN7 Slot

While the clarity, staging, etc are all great, I'm getting quite a bit of hum (sounds a bit electric-ey, like being close to one of those large voltage transformers in countries like India that power entire neighborhoods). That's also accompanied by occasional scratchy sounds on the left side. I think it's a low 60hz hum, and the volume dial does not affect it. Turning the unit off stops the hum, and it only happens as the tubes warm up after powering on.

It's enough that I do notice it even during quiet parts of a track that's playing. Any tips on how to identify which tube(s) are causing it?

It's currently set up like this, with somewhat of a mess of wires behind it. Not sure if any of those would cause the hum, but unplugging the RCA cables doesn't remove the noise for example.

Wow looks great!! Thanks for the kind words.

 

[Swagsupply]

I just purchased this unit and fired it up for the first time after receiving it today (thanks for the excellent and well packaged shipment @blitzpirate!).

The tubes used are:
- 2 x Sylvania 6080 Gold Brand
- 1 x 3DG4 - Shipped from Glenn
- 1 x Ken-Rad Rare 6F8G with included adapter to be used in the 6SN7 Slot

While the clarity, staging, etc are all great, I'm getting quite a bit of hum (sounds a bit electric-ey, like being close to one of those large voltage transformers in countries like India that power entire neighborhoods). That's also accompanied by occasional scratchy sounds on the left side. I think it's a low 60hz hum, and the volume dial does not affect it. Turning the unit off stops the hum, and it only happens as the tubes warm up after powering on.

It's enough that I do notice it even during quiet parts of a track that's playing. Any tips on how to identify which tube(s) are causing it?

It's currently set up like this, with somewhat of a mess of wires behind it. Not sure if any of those would cause the hum, but unplugging the RCA cables doesn't remove the noise for example.

Try swapping the power tubes first. Those tend to be the most likely culprits. Glenn OTLs are sensitive to picking up noise from the tubes. Langrex sells some nice quiet tubes at a bit of a premium.

If that does not improve the hum then try swapping the rectifier. Usually the rectifier is not the issue but it’s a quick troubleshoot and sourcing a new rectifier is typically cheap and easy.

Last step would be trying a 12 or 25 volt driver and switching the heater voltage at the back of the amp. From what I been told the Glenn runs quieter when using higher voltage drivers. These are not as easy to find as the 6SN7.

 

[spanyam]

Try swapping the power tubes first. Those tend to be the most likely culprits. Glenn OTLs are sensitive to picking up noise from the tubes. Langrex sells some nice quiet tubes at a bit of a premium.

Thanks, I'll start with this one. Should I stick to 6080 or go with something else. The switch in the back is set to 5998, which I think is the right setting for these tubes. For which tubes would I switch it to 6AS7 (other than ones that say 6AS7G, etc.)?

Last step would be trying a 12 or 25 volt driver and switching the heater voltage at the back of the amp. From what I been told the Glenn runs quieter when using higher voltage drivers. These are not as easy to find as the 6SN7.

I could give that a shot if the power tube swap doesn't do it.

 

[Monsterzero]

I just purchased this unit and fired it up for the first time after receiving it today (thanks for the excellent and well packaged shipment @blitzpirate!).

The tubes used are:
- 2 x Sylvania 6080 Gold Brand
- 1 x 3DG4 - Shipped from Glenn
- 1 x Ken-Rad Rare 6F8G with included adapter to be used in the 6SN7 Slot

While the clarity, staging, etc are all great, I'm getting quite a bit of hum (sounds a bit electric-ey, like being close to one of those large voltage transformers in countries like India that power entire neighborhoods). That's also accompanied by occasional scratchy sounds on the left side. I think it's a low 60hz hum, and the volume dial does not affect it. Turning the unit off stops the hum, and it only happens as the tubes warm up after powering on.

It's enough that I do notice it even during quiet parts of a track that's playing. Any tips on how to identify which tube(s) are causing it?

It's currently set up like this, with somewhat of a mess of wires behind it. Not sure if any of those would cause the hum, but unplugging the RCA cables doesn't remove the noise for example.

Congrats on your new amp. Noise and tube amps are a common issue and the cause can be hard to find. Here are a couple ideas:

First and foremost, clean the pins on the tubes. Fine grit sandpaper and rubbing alcohol. If you're unsure on how to do it, there are videos on Youtube. I'd avoid using Deoxit.

Clean the pin sockets- use caution!!!!!!!!!!!!! Unplug amp, use pipecleaner and minimal alcohol. Wait a few hours after cleaning before powering up the amp again.

If cleaning the pins and sockets doesn't help, you may have to get different tubes. If that doesnt work you might have a grounding issue somewhere, or perhaps something as simple as trying a different electric outlet can help.

Also you shouldn't be listening to headphones when the amp is being powered up or warming up. Unplug headphones before powering on/off amp and allow tubes 15-30 minutes to warm up prior to plugging in headphones and listening.

Keep us posted

 

[Zachik]

The switch in the back is set to 5998, which I think is the right setting for these tubes. For which tubes would I switch it to 6AS7 (other than ones that say 6AS7G, etc.)?

5998 is one tube type that I never bought personally. Mostly, due to cost, but also some issues with them (very prone to arc-ing... )
I would recommend NOT starting there. Get other 6080, or 6AS7, or 6BX7 IMHO.
Also, AFAIK (my GOTL does not have that switch) - the 5998 switch is ONLY for 5998. all other tubes should be on the other position. having said that, Glenn has told me way back then that this switch is not very important, because you can use ALL tubes in either position. This switch is just a (small) optimization for 5998 tubes.

 

[Swagsupply]

Thanks, I'll start with this one. Should I stick to 6080 or go with something else. The switch in the back is set to 5998, which I think is the right setting for these tubes. For which tubes would I switch it to 6AS7 (other than ones that say 6AS7G, etc.)?


I could give that a shot if the power tube swap doesn't do it.

6080 tend to be a bit quieter from personal experience but 6AS7 sound better. I think 6080 just have a more durable robust construction which might help with being less noisy.

Try to find a NOS pair of RCA 6AS7G or some Tungsol6080. 7236 are also a tube type you can look into. I have a quite pair Thompson6080s that I can sell to you. I am going to be letting go of my Glenn OTL and selling off a bunch of tubes including 5998s.

The switch in the back set to 6AS7 unless using 5998 tubes. However, like others have already said, it doesn’t actually do much.

 

[Monsterzero]

Last step would be trying a 12 or 25 volt driver and switching the heater voltage at the back of the amp. From what I been told the Glenn runs quieter when using higher voltage drivers. These are not as easy to find as the 6SN7.

12v sn7s (12sn7) are quite common and can be found for less $ usually than the 6v version. The 25v tube OTOH are rare. Only a few out there AFAIK.

 

[spanyam]

Congrats on your new amp. Noise and tube amps are a common issue and the cause can be hard to find. Here are a couple ideas:

First and foremost, clean the pins on the tubes. Fine grit sandpaper and rubbing alcohol. If you're unsure on how to do it, there are videos on Youtube. I'd avoid using Deoxit.

Clean the pin sockets- use caution!!!!!!!!!!!!! Unplug amp, use pipecleaner and minimal alcohol. Wait a few hours after cleaning before powering up the amp again.

Hey man, glad to hear from you. I think you were the one who put me onto thinking about a Glenn a couple of years back (on the Headphones forum). I'll try the pin cleaning (and maybe the socket cleaning too) and see if that helps before jumping into tube rolling.

Also you shouldn't be listening to headphones when the amp is being powered up or warming up. Unplug headphones before powering on/off amp and allow tubes 15-30 minutes to warm up prior to plugging in headphones and listening.

Oh whoops. Noted.

5998 is one tube type that I never bought personally. Mostly, due to cost, but also some issues with them (very prone to arc-ing... )
I would recommend NOT starting there. Get other 6080, or 6AS7, or 6BX7 IMHO.
Also, AFAIK (my GOTL does not have that switch) - the 5998 switch is ONLY for 5998. all other tubes should be on the other position. having said that, Glenn has told me way back then that this switch is not very important, because you can use ALL tubes in either position. This switch is just a (small) optimization for 5998 tubes.

Good to know, thanks! I'll focus on the 6080 or 6AS7 for now.

 

[spanyam]

First and foremost, clean the pins on the tubes. Fine grit sandpaper and rubbing alcohol. If you're unsure on how to do it, there are videos on Youtube. I'd avoid using Deoxit.

Clean the pin sockets- use caution!!!!!!!!!!!!! Unplug amp, use pipecleaner and minimal alcohol. Wait a few hours after cleaning before powering up the amp again.

Does this methodology work:

Exacto knife + QD, then using the tube pins to coated in the stuff to clean the socket.