• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

DIY TUBE PREAMP HELP PLEASE

I'm not sure when it comes to tube amps when it comes to adding a headphone jack, but most SS gear just uses resistors coming off the output transistors to knock down the output. I don't know if the same applies to tubes though.
I just added a tube headphone Amp to my system. My tube preamp has a tape loop. So I just hooked the headphone amp to the tape out. Tape out bypasses the preamp circuit and takes the source right off the selector switch. When using headphones, I don't even have to turn the preamp on unless I'm listening to records since the phono section needs power. You could ask about adding a headphone jack in the tube forum if you don't get a reply here.
Point to point can be a bit challenging if building from scratch. I still struggle with layout myself. I have built a few point to point kits, but they come with instructions and that makes it much easier. I have built a couple preamps and amps from scratch just using a schematic, but layout isn't my best suite.
I posted that simple preamp due to it having a small parts count and being easier to figure out the layout. You want everything in the power supply on one side or end separate from the preamp or amp circuit. No AC wires parallel with signal wires, proper grounding schem, etc. Simple point to point circuits make for a good learning experience when it comes to figuring out routing. I've personally gotten away from star grounds and try to use a ground buss instead. I've just found ground busses easier to help keep things quiet. Starting with input grounds at one end all the way to the power transformer center tap at the other end with the ground bus only being grounded at one end. Inusually use a solid core copper 14ga. bare wire.
 
Califmike33 said:
If the sound is going through the tubes here's what I don't understand she said that amp had no tube sound she said it sounded really clean super clean but it did not have tube sound how can it not have tube sound if the sounds going through the tubes I don't understand that?
Click to expand...
There are numerous factors involved - different tubes sound different, different operating points affect the sound, different circuits sound different, different parts have an influence, etc etc.

I'm no expert, I'm mostly a copy and paste builder, not a designer. But many designers are specifically trying to design tube gear that doesn't sound "tubey". But the term means different things to different people so anytime you try to describe sound there is bound to be confusion.

"Talking about music is like dancing about architecture". Frank Zappa (maybe)

Lavane said:
Some think that tube sound means overly warm. Usually meaning rolled off highs and maybe even rolled off bottom end. If that's the case, something is wrong with the amp. . . . My amps are clean, clear and detailed sounding. . . . I think the biggest difference between SS and tubes is the harmonic distortion. Tubes tend to produce even order harmonics that is pleasing to many peoples ears. . . . Over the years I've just found tube equipment to sound better to my ears. I don't get the ear fatigue I can get from some SS gear.
Click to expand...
^^^ This! ^^^

Many people find that they like some of whatever "it" is that 2nd order distortion brings to the table. And there are varying degrees of "it". It's sometimes hard to really know what someone means because others are not in the room listening to the same gear. Some describe it as "tubey", some as "warm" or "euphonic", some as "less fatiguing".

Whatever you prefer to call it, I seem to prefer tubes. But perhaps there is some tube gear that I wouldn't like if it has a much higher level of 2nd order distortion. I have no way to measure, so I don't know what level that might be. But if the result is bloated and wooly bass and rolled off highs, I'm not a fan.
 
Califmike33 said:
Tubes4hifi from what I've read the SP 14 is a killer amp that hits way above its price point. As I look at their website the sp10 looks like a Conrad Johnson clone it looks like the same thing I see on eBay and AliExpress it looks like the exact same amp but $100 higher am I wrong?
Click to expand...
I don't follow all the commercial offerings very closely, either prebuilt or kits, so I'm not really familiar with the ones you mention. In general, I prefer point to point and simple circuits and commercial designs often take the opposite approach. Sometimes something catches my eye, like that little Nobsound E6. And I did breadboard the FX because I was curious about all the hoopla and I had that preamp breadboard already set up, so why not.

But, otherwise, I gravitate toward combining various design elements in ways that are somewhat unique and using mostly inexpensive tubes that fly under the radar. The "road less traveled" is kind of my thing.
Califmike33 said:
You know this boogie Factor amp I got to take your word for it then it sounds really good this is probably the one I'm going to end up building and with your help offered that makes me feel a little more easy about it. Charlie any idea cost wise what it would cost me to build that boogie Factor?
Click to expand...
I'm a hobbyist so I just go by what I hear and, like everyone, what I like is subjective. I tried a dozen tube types in this basic circuit and preferred the 1626, others might prefer a different tube. Some of the other tubes I liked are mentioned in the BF thread and they can also be used with only a few minor parts changes, like different resistor values or a different battery to supply a different bias voltage to the grid. It could also be built with a traditional bias resistor. As I pointed out, the preamp that Lavane built with the 12AY7 is essentially the same circuit. It's very versatile.

I never tally up the cost of a build. In the BF thread another person who built it posted a parts list with the Digi-Key parts numbers, so you can enter them into Digi-Key and see their current prices. The most expensive parts for any build (unless you're using exotic tubes or boutique caps) are typically the transformers - in this case the power transformer and choke. The ones I used were parts I had scrounged from old gear. But this is not an expensive build.
 
The SP-14 is an Aikido design. I built one using 12AX7's. I liked it so much I bought an octal version using 6SN7's from Erhard Audio. He sells preamp kits using 12AX7's, both the Aikido and another with tone controls. The finished octal version similar to the SP-14 he doesn't sell anymore. He also sells a finished preamp using 6922's with tone controls along with a finished one using 6SL7's.
 
Lavane said:
When it comes to that "tube" sound, if I come across a tube amp that sounds "tubey", I tend to think something is wrong with it. Some think that tube sound means overly warm. Usually meaning rolled off highs and maybe even rolled off bottom end. If that's the case, something is wrong with the amp. Poor design, not so good output transformers, worn out parts like out of spec caps and resistors, or even worn out tubes. My amps are clean, clear and detailed sounding.
Click to expand...
I agree.
Lavane said:
I think the biggest difference between SS and tubes is the harmonic distortion.
Tubes tend to produce even order harmonics that is pleasing to many peoples ears. While SS I'd odd order harmonics which can come off sounding dry, harsh or analytical to some.
Click to expand...
I don't agree. Tubes and transistors have very similar distortion characteristics - it's the circuit topologies usually employed in tube designs and transistor designs that sound different. It's possible, for example, to design transistor circuits which are very similar to tube circuits, but transistors are very small and cheap compared to tubes so it's easy to use a lot more of them to create constant current sources, current mirrors etc., etc., and have far more gain which allows a ton of negative feedback - so that's what people do. But they don't have to, and in my opinion it's the circuits which make the difference, not any inherent properties of tubes or transistor per se.
Power amps are also completely different from preamps due to the use of output transformers (usually) in tube gear and their absence (usually) in transistor gear.
Anyway, that my opinion (for what it's worth - probably not much).
 
Ian C. said:
Not sure what your expectations are, but I'm doing one of the Marantz 7 clone tube preamps, point-to-point, right now and there is zero documentation. Zero, as in none whatsoever. Way bigger project than I thought I was getting into.
Click to expand...
My suggestion would be to take some time to watch Stephe's build videos. The same basic approach to layout and the mechanical aspects of the build process can be applied to any circuit and any type of tube. Obviously, you need to be able to read and follow a schematic. She has a video about that too, as I recall. Her YT channel is a great resource for DIY newbies.
 
That's what I've been doing today Charlie's watching her channel I think I need to start off with a schematic I need to know every aspect of a schematic that's what I'm going to start studying I'm going to go to her channel and watch that and then go from there.
 
Califmike33 said:
I've never heard a class a single ended tube amp my tube amp is a OTL so is there a big difference between a class a tube amp and an OTL as far as the sound quality?.

One other question . . is there a way to add a headphone jack to an existing tube amp that doesn't have one
Click to expand...
I've never heard an OTL, so I can't say. They seem to be fairly rare compared to the number of traditional amps that use OTs.

For the headphone question, check Stephe's channel. She built a stand alone headphone box that connects to an amp. I'm sure it could be incorporated into a build.
 
I saw her headphone box video actually looked really interesting I sent her a message but she never replied to me I wanted to know if it works with every ohm headphone for instance 32 ohm all the way up to 600 ohm she didn't reply to me so I don't know I may try sending her a message again.
 
It may work but may not sound great depending on the headphone impedance?
My headphone amp has an impedance selector. From 16 ohm to 600 ohm.
My headphones at the moment are 50ohm. If I select an impedance a few settings either way from 50 ohm, I noticed either a roll off of the high end, or the low end. But im useing an all tube headphone amp with output transformers. I'm thinking 220K was a common resistor to use in many old SS receivers?
I dought many payed attention to the impedance when selecting headphones though. I didn't back then. I picked headphones I thought sounded good and just plugged them in.
 
I have the Sennheiser HD 650 which are 300 ohm I've found it takes a good 400 to 500 MW to drive these headphones properly. Of course they sound best with tubes I don't like the sound of them on a solid state amp.

I don't want to have to buy a separate headphone amplifier tube preamp plus an amplifier. I found a very good class AB amp that has an exceptional headphone output that's why I'm looking for a good tube preamp.
 
The 110-120v stayed to power it worries me a bit. A lot of Chinese made tube amps and preamps use 110v primary power transformers. They will work on 120v, but that raises the B+ voltage some, not a huge problem usually, but the 6.3v heater voltage will be higher also. Most likely a little above 7v. That's what I and others have found. This is hard on the heaters. 6.9v is about the max you want. I try to keep it as close to 6v or 6.3v as I can. Think of it as using a 6v bulb in a 8v circuit. It will work, for awhile anyway.
 
Oh so it's not running on 115 volts I don't understand where it says 110 volt-120v so it doesn't run somewhere between there depending on when you plug it on the wall it's going to run on 110?.

Yeah I remember other people telling me about other things unless you get something to reduce the voltage that's coming out of your wall to 110 it can be a problem.

Is there any inexpensive type of device that you can plug into the wall that will reduce the power down to 110? Or do you need to hook up some resistors to reduce the power.
 
Last edited:
I spoke to the seller of this headphone amplifier and they have a version of it that has 115 volts which is close enough to the 120 of the US.
 
Last edited:
Califmike33 said:
I spoke to the seller of this headphone amplifier and they have a version of it that has 115 volts which is close enough to the 120 of the US.
Click to expand...
Maybe I'm being cynical but I find it hard to believe that they have two versions of this with different PT primary voltages. If they did, why wouldn't they show it in the listing? They show choices for different colors, a choice of regular or premium tubes and a no tube option. Nothing about PT primary voltage.

At a minimum, I would ask the seller for pics of the insides of both versions with enough detail to show that the PTs are, in fact, different.

Even with a 115v primary the heater voltage will be too high. Most vintage American gear uses PTs that are rated for 117v and heater voltage is a bit high. It can be dealt with fairly easily but if you just plug and play it will affect tube life.

The easiest way to deal with the issue is to just add a couple of low value wirewound resistors to drop the heater voltage. Pics of the insides will let you see if this mod would be easy to accomplish. While data sheets say it's OK to run as much as 10% higher heater voltage (6.9v) it's best to stay within 5% (6.6v) as tube life drops considerably faster as the voltage increases. Running at or slightly under 6.3v is best.

Some interesting things in the description:

Preamp output impedance: 2v-6v (impedance in not measured in volts, it's measured in ohms)

Distortion degree : 0,001% (for a tube amp?? not likely, not that it matters)

And listed under Tube Amplifier Precautions:

2. Too high or too low power supply voltage does irreversible harm to the amp,preferably less than 5% of the specified voltage. If your mains voltage exceeds this value, often best to use with the AC power supply.

My mains voltage here is typically ~122v, you might want to check yours. I've heard that it runs as high as 125v in some areas. Not sure what "AC power supply" they're referring to. Perhaps they also sell Variacs. If so, they've figured out a way to get even more profit from selling gear with inappropriate transformer voltages.

It goes on to list information about the speaker connections but the item shown does not have speaker outputs.

I think I'd try Stephe's headphone box with an amp that can also power speakers before paying that much for a dedicated headphone amp. If there's an issue with impedance matching to your particular headphones I would think that using alternative parts values would get it dialed in. I haven't looked at her design, though, since I have no interest in headphones.
 
Last edited:
Okay you're right I looked at multiple listings multiple sellers are selling that amplifier.

The distortion level is not possible on a tube amp they're typically about 1% or 0.5% on average.

I later found out after talking to multiple sellers through a messenger on AliExpress that there is no 115-volt version it goes from 110 to 120.

I also saw the speaker listing at the bottom which makes no sense because it doesn't accept speakers.

There are two versions there is the e200 and there are the e400 the e400 has the most power.

Looking at the power ratings for different ohm headphones they couldn't even get that correct she told me it had 900 MW for $ 300-ohm headphones this is on version e200. That turns out to be complete garbage because it said 900 MV, not MW she later comes back and told me it was 250 MW at $300 quite a difference. That made me start looking at the e400 now the e400 has 900 MW for $ 300-ohm headphones which is a ton of power.

It looks like a nice unit it can be used as a preamp to me it looks beautifully made I love the design of it but. The voltage issue I don't like yeah I guess I could put some resistors in it and cut the power. Does look well made like it has some quality parts they just can't seem to put the listing together correctly so you don't know what voltage or what power you're getting I had to talk to multiple sellers to finally settle that part again it's a language barrier.

The only reason I was looking at it is that it would solve my headphone issue and it would give me a preamp then I'd get myself a little class d and I'd be done.

Trying to find an amplifier that will drive speakers, give me tube sound, and has a good headphone jack is not easy; you typically have to buy a separate headphone amp. I think that's why this thing had such appeal to me and it's not ridiculously overpriced it's a reasonable price. I would love to try it the problem is it cost me $300 to ship it back if I didn't like it and that ain't going to happen.

I'm not sold on Steph's headphone box I have repeatedly tried to contact her and she has not responded to me to give me information about it so currently, that's not an option.

Other amps are class tube amps that did have a big thread have a following and I know were solid and have a very good headphone jack built into them the problem is they have speaker outputs but they're only going to put out between five and seven Watts of power which is not much now you have to get very high impedance speakers don't want to go that route.

I'll have to do some more searching on something like her headphone box to see if I can find any information about something like that and how well it works I'm skeptical about that. I have contacted Stephe on her website about the headphone box again and waiting for a reply.

I think the reason I'm looking for something instead of building DIY, is i can't just throw something together in a few days, and bam i have music. I'm going to DIY but practice first and get a feel for it, I'm now studying schematics.
 
Last edited:
Califmike33 said:
Okay you're right I looked at multiple listings there are multiple sellers selling that amplifier.

The distortion level is not possible on a tube amp they're typically about 1% or 0.5% on average.

I later found out after talking to multiple sellers through a messenger on AliExpress there is no 115 volt version it goes from 110 to 120.

I also saw the speaker listing at the bottom which makes no sense because it doesn't accept speakers.

There are two versions there are the e200 and there are the e400 the e400 has the most power.

Looking at the power ratings for different ohm headphones they couldn't even get that correct she told me it had 900 MW for $300 ohm headphone this is on version e200. That turns out to be complete garbage because it said 900 MV not MW she later come back and told me it's 250 MW at $300 quite a difference. That made me start looking at the e400 now the e400 has 900 MW for $300 ohm headphones which is a ton of power.

It looks like a nice unit it can be used as a preamp to me it looks beautifully made I love the design of it but. The voltage issue I don't like yeah I guess I could put some resistors in it and cut the power. Does look well made like it has some quality parts they just can't seem to put the listing together correctly so you don't really know what voltage or what power you're getting I had to talk to multiple sellers to finally settle that part again it's a language barrier.

The only reason I was looking at it is because it would solve my headphone issue and it would give me a preamp then I'd get myself a little class d and I'd be done.

Trying to find an amplifier that will drive speakers give me tube sound and has a good headphone jack is not easy in fact it's very difficult you typically have to end up buying a separate headphone amp. I think that's why this thing had such appeal to me and it's not ridiculously overpriced it's a reasonable price. I would love to try it the problem is it cost me $300 to ship it back if I didn't like it and that ain't going to happen.

I'm not sold on Steph's headphone box I have repeatedly tried to contact her and she has not responded to me to give me information about it so currently that's not an option.

There are other amps that are class a tube amps did have a big thread have a following and I know where solid and have a very good headphone jack built into them the problem is they have speaker outputs but they're only going to put out between five and seven Watts of power which is not much now you have to get very high impedance speakers don't really want to go that route.

I'll have to do some more searching on something like her headphone box see if I can find any information out about something like that and how well it works I'm skeptical about that.
Click to expand...
When they say 110v to 120v they aren't talking about two different transformers, they're just claiming that your wall voltage can be in that range. In the US 120v is the "nominal" but actual voltage is almost always higher.

Headphones are extremely sensitive and only require amps with mW output levels. A single 6V6 will put out between ~2w or so in triode to maybe 5w in pentode. Lots of tubes can be used to power headphones.

Most Chinese gear looks great. It's the electrical elements of the design and the parts and build quality that are problematic. Lots of sellers offer the same product and very very few of them know anything about technical details. So don't count on getting informed answers.

If they sent you pics please post them.

As for using speakers, the power needed is probably much less than you might think. Lots of us use low power amps with speakers that aren't crazy efficient. Obviously, there are lots of factors that should be taken into account - size of room, type of music, how loud you listen, etc.

Most of the tube amps I listen to regularly are under 10 wpc. The Bugle 45 SET that I've mentioned is about 2 wpc or so. My most recent DIY build, the Nuance iSET, is about 4 wpc. The reason the 1626 became somewhat well known is because it was used in a DIY design called the Darling amp, which was made to power speakers. In that amp it only puts out 0.75w / 750mW.

Most of us are only actually using 1w or less in most situations, depending on how loud you listen and the efficiency of your speakers. I've only read a few posts but here's a thread on General about listening levels. Even inefficient speakers are probably around 84db/w/m.

https://www.audiokarma.org/forums/index.php?threads/how-loud-do-you-listen-to-music.1024063/

Remember, the volume / power output relationship is not linear. Doubling the power will not give you twice the volume. It takes 2x the power to create a 3db increase in sound. That's the equivalent of moving 39" closer to your speakers. Subjectively, for something to sound "twice as loud" takes 10x the power.

How are you trying to contact @StepheK ? Send her a private message (start a conversation at the Inbox tab). She is not on here every day. I think she gets so many messages on her YT and website that she might get overwhelmed sometimes. Be patient.

Though I've never used them, some of my vintage amps have headphone jacks. Scott and Fisher come to mind. Very . . . well, more common on older gear.
 
Last edited:
Sent her a message on her video on headphone box and on her website under contact me, no reply.

Thank you Charlie for your input. I was very worried about having under 7 watts to drive speakers in a 12x12 room, so used to 50w or more. Now people have tried to convince me thats its enough, now your saying it again. This amp, i was on and goiing to buy, gets great review, there are threads on it, good headphone output and has 6.5 watts output and there are mod threads. Its build well with good parts and looks like a deal. Maybe solve all my desires. On the other hand some say its best to pair tubes with a seperate amp, so tube pre amp, and maybe class d amp, thats where i get confused.

https://www.bing.com/ck/a?!&&p=2e77...wcm9kdWN0L3Byb2R1Y3QmcHJvZHVjdF9pZD01NA&ntb=1
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom