Tube Selection for Dynakit and Dynaco Amplifiers & Preamps

The information provided here is based on my experience using, buying, testing and selling vacuum tubes over the course of many years now.

I am not a tube expert, I simply know what my experiences have been. Tubes can make a difference in the sound and performance of your equipment. Although I've used many brands of amplifiers and preamplifiers, comments will be limited to the tubes used for Dynakit / Dynaco products that I deal with most often.

I'll cover the vintage US and European makes and a few brands made elsewhere but are noteworthy. I'll also discuss the current production tubes with which I am familiar.

 

Vintage / NOS / Used - Output & Preamp Tubes

I personally love old tubes, especially the Mullard, Amperex and Telefunken brands. The USA had some excellent offerings as well like RCA, GE, Sylvania and Tung-Sol just to name a few. One thing many people are unaware of is that most all of the tube makers, worldwide, made, branded and sold tubes under various names and even for competitive brands. For example, it's not uncommon to find RCA preamp tubes clearly labeled "made in Gt. Britain". RFT was a European maker who actually made tubes for many famous brands like Telefunken.

There are pages upon pages of more detailed information that will help decipher tube manufacturing codes which will usually reveal the actual makers origin and plant location. The codes will also disclose the date of manufacture. I won't get into all that, it's mind boggling.

In a nutshell, most vintage tubes are of great quality and sound excellent. The issues you will encounter are as follows. 

• Were these tubes tested and also auditioned for noise?
• What type of tester was used? Emission or Transconductance?
• How accurate was the tube tester itself?
• Can I trust the seller to give me honest numbers and disclose all issues if any?
• Finding matched pairs or quads can be difficult, what if I need a replacement?

The vintage tubes were made in a time when workplace and consumer safety were in their infancy and in some places simply did not exist. Environmental concerns were minimal. Metallurgy and chemistry related to making tubes was science of another school. Many of the chemicals, techniques and processes cannot be duplicated today, some should probably not be.

From an engineer's viewpoint a tube is supposed to be the same as all other tubes of a particular number. They are designed to operate within very specific parameters. Many will argue that so long as the tubes test the same and are the same number, they cannot sound differently. But most people disagree, strongly. I believe that everyone should listen and decide for themselves, why take someone else's word and make a decision without truly knowing for yourself?

Tube rolling is fine, so long as you are using the correct tube for a particular application. Do not use other numbers than are specified for a location unless you're just wanting the unit to operate differently than it is designed. It can lead to trouble, and trouble can get expensive. It's fun to have antique tubes that operate properly and some even get into collecting them as a hobby. Their value increases over time, they are not making any more old tubes......get em while they're hot!

 

Current Production Tubes - Preamp & Output

Overall my experience with new, current production tubes has been excellent. Reliability has not been an issue. Sound quality has not been an issue. Prices are reasonable, although the Ukrainian conflict caused a rather sharp rise in cost but prices have leveled and most have returned to at or near normal. Most new tubes come from Russia and regions nearby.

I've used about all of the brands and continue to use several of them. I have used experience to make decisions on which ones to sell and supply with my builds. All of my ready-to-ship amps and preamps come with current production tubes selected from my preferred brands. I order them matched and tested, then test them again once they arrive. The brands you see on my site are the brands I have found to be great sounding, reliable and provide value.

I have no hesitation using or selling any of the current production tubes you will find listed on my site. If I don't feel 100% good about them, I don't mess with them. I offer a limited variety that I have found to be trustworthy and can count on for great sounding performance. Occasionally I may locate exceptional NOS or ANOS tubes and offer them for sale. Certain tubes like the 6GH8A, 6U8A, 12X4 and 6AN8A are not available in current production versions as they simply are not being manufactured. These tubes will be NOS, ANOS or test as such (used).

My preferred brand of EL34 in current production is the Mullard. My preferred EL84 tube in current production is also the Mullard. These have proven to be solid tubes, they're great sounding, they have reliable performance, fair pricing, dependable availability and an overall excellent presentation. 

I have had great results too with a few Chinese made tubes. Particularly the NessTone EL34. For about three years it was the "go to" tube for my Dynaco 70 amp builds. I still use these tubes fairly regularly, when I can get them. The tubes are graded (matched) and tested here in the USA, then labeled. These tubes are made at the Shuguang factory in Guangdong, China. They've been in business since about 1965.

NessTone also has an EL84 I like, but it's a European made tube, not Chinese. It is also tested, graded, matched, and labeled in the USA. Supply has become somewhat sketchy for these EL84 NessTone tubes.

I have also had satisfaction from the Psvane EL84 tubes. The people behind Psvane originally worked for Shuguang but now run their company independently. The current Psvane tubes are made by a separate entity called Psvane Audio.  

I have used all of the brands of current production 12AX7 for the Dynaco PAS and they all sound really good. My favorite among these however is the Electro-Harmonix Gold. 

For the 12DW7 / 7247 used in the Dynakit ST-35 the options are limited. Electro-Harmonix and JJ Electronics make this tube. I've used both and cannot discern one from another. 

In the end I strongly suggest starting out with a set of new, current production tubes. Once your comfortable, then if you feel so inclined to embark upon the search for the perfect sounding tubes, just have fun with it. It's part of the hobby.

 

Rectifier Tubes for the Dynaco 70 amplifier and Dynakit PAS preamplifier

I will not contradict the widely shared opinion that the vintage Mullard (and affiliated mfg.) rules the rectifier tube class. The 5AR4 / GZ34 is a hard working and critical tube. These tubes can last for decades so the investment is offset to a degree by that characteristic.

A NOS Mullard or similar 5AR4 / GZ34 will set you back something like $200.00 and up to $500.00 or more depending on its design, style and date code. Brand, cosmetic condition and rarity will definitely be reflected in the asking price too. Again, cross-branding and outsourced manufacturing were common. The Philips umbrella was wide and as far as I know all of their offerings were top notch. One of the little know secrets of getting a Mullard quality 5AR4/GZ34 without the high cost is the Japanese made Matsushita 5AR4 / GZ34. It's a great tube for less money. This tube will have a sutured/seamed top and a hole in the center of its guide pin. It was sold under several brands/labels.

The Marconi-Osram Valve, STC/Brimar and Mazda/Ediswan brands are excellent also but not often found in the US market.

I also have found a few current production rectifiers that have proven themselves reliable and worthy of use. The current production 5AR4 / GZ34 rectifiers I have become reliant on are the Tung-Sol, the Genalex and the Groove-Tubes. These all sound great and can be purchased relatively cheap and replaced easily, they're readily available at all times, so far.

I build a solid state 5AR4 / GZ34 that works in any application calling for the 5AR4 / GZ34. It tightens up the bass response a bit and increases speaker damping some. I love this tube in the ST-70, MK III and MK IV. 

 

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