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List of entry level TUBE amps + mod for less than $300 - Page 2

post #16 of 24
Thread Starter 
Quote:
Originally Posted by scottosan View Post


point taken


Thanks for response anyway~~~ Seems that not many people want to do budget tube, not now it is dominated by SS amps.

I would love to have some woo audios but they are just way too expensive~~

post #17 of 24

Project Ember from garage1217,it's an excellent headphone hybrid amp, very powerful and versatile (can drive the majority of cans, from grado to AKG K1000, from Sennheiser HD800 to Hifiman HE6), you can tune your sound with different settings (output impedance, gain, use of the input capacitors), and change tube without any settings, and it's compatible with a huge amount of tubes (ECC81/12AT7, ECC82/12AU7, ECC83/12AX7, ECC88/6DJ8, ECC86, ECC85, ECC189, E180CC, E80CC, 6BZ7, 6GU7, 12BH7A, 6N1P, 6N2P, 6N23P, 6N27P, etc...), a great amp : http://www.garage1217.com/graphic_design_004.htm

 

for pricing : http://www.garage1217.com/graphic_design_006.htm

post #18 of 24
Quote:
Originally Posted by AlanHell View Post
 


Thanks for response anyway~~~ Seems that not many people want to do budget tube, not now it is dominated by SS amps.

There are numerous budget tube amps but most are NOT designed for low impedance headphones.

OTL (output transformerless amps) are simple and can be inexpensive, depending on the components used and chassis etc. e.g. Bottlehead Crack.

 

This design is great for high impedance cans (HD600/650 etc) does not generate enough current to drive low impedance headphones. To generate the required current a tube amp needs output transformers e.g. WA-6. Good transformers are hand wound and add cost and complication. If you look at Woo WA-3 vs WA-6 the transformers add $140. Woo and Bottlehead both provide info on matching their amps to different headphones.

http://wooaudio.com/docs/wooaudio_amplifier_comparisons.pdf

http://www.bottlehead.com/et/whichheadphoneamp.htm

 

The inexpensive option is a "tube hybrid" e.g. Little Dot 1+ or Project Ember (referred above). These amps combine op-amps (usually) driven by driver tubes to give tube sound with SS output. 

post #19 of 24
Thread Starter 
Quote:
Originally Posted by cheaphifi View Post
 

Project Ember from garage1217,it's an excellent headphone hybrid amp, very powerful and versatile (can drive the majority of cans, from grado to AKG K1000, from Sennheiser HD800 to Hifiman HE6), you can tune your sound with different settings (output impedance, gain, use of the input capacitors), and change tube without any settings, and it's compatible with a huge amount of tubes (ECC81/12AT7, ECC82/12AU7, ECC83/12AX7, ECC88/6DJ8, ECC86, ECC85, ECC189, E180CC, E80CC, 6BZ7, 6GU7, 12BH7A, 6N1P, 6N2P, 6N23P, 6N27P, etc...), a great amp : http://www.garage1217.com/graphic_design_004.htm

 

for pricing : http://www.garage1217.com/graphic_design_006.htm


I gave looked into these like of amps such as project sunrise or other self build amps. Is not like I do not trust the build quality, but I do want a solid metal case outside. Not only for the look, most importantly, provide some shielding against outside noise. I do not like my amp pickup too many things like cell phones or wireless mouse. (I know for most of good designs, they have noise filter built in, but as in the analog world, nothing is as strong as a faraday cage IMO)

 

But, if they do sounds very very good, I might just get one for fun, and used in at my home

post #20 of 24
Thread Starter 
Quote:
Originally Posted by parbaked View Post
 

There are numerous budget tube amps but most are NOT designed for low impedance headphones.

OTL (output transformerless amps) are simple and can be inexpensive, depending on the components used and chassis etc. e.g. Bottlehead Crack.

 

This design is great for high impedance cans (HD600/650 etc) does not generate enough current to drive low impedance headphones. To generate the required current a tube amp needs output transformers e.g. WA-6. Good transformers are hand wound and add cost and complication. If you look at Woo WA-3 vs WA-6 the transformers add $140. Woo and Bottlehead both provide info on matching their amps to different headphones.

http://wooaudio.com/docs/wooaudio_amplifier_comparisons.pdf

http://www.bottlehead.com/et/whichheadphoneamp.htm

 

The inexpensive option is a "tube hybrid" e.g. Little Dot 1+ or Project Ember (referred above). These amps combine op-amps (usually) driven by driver tubes to give tube sound with SS output. 


The hybrid is quiet new and not sure how mature they are right now.  Still deciding how much I am willing to spend on the amp. 

 

Just a very very silly question:

 

Is it possible to add an resistive load on the output and use the OTL amp for IEMs? I use to DIY some connectors for putting my HD800 aside with my T1 to compare sound in HDVD800 balance output. Not sure they will make the OTL tube sounds better on IEM though.

post #21 of 24

The hybrid tube technology has been around and is well tested, even in higher end gear such as the Peachtree or PAthos amps. If you like to try one that is better shielded get the Little Dot 1+ for $120 or Antique Sound LAbs makes on that's $350 but has a separate power supply ASL HB-1:

CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), quality = 100

post #22 of 24
Thread Starter 
Quote:
Originally Posted by parbaked View Post
 

The hybrid tube technology has been around and is well tested, even in higher end gear such as the Peachtree or PAthos amps. If you like to try one that is better shielded get the Little Dot 1+ for $120 or Antique Sound LAbs makes on that's $350 but has a separate power supply ASL HB-1:

CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), quality = 100


This one looks much better than the Little dot 1 I think~~ It is in the similar price range of the Schiit. I also saw some comment about the little dot is very easy to pick on noise from the environment like a cell phone signal. So, if $50 more I got a better isolated PSU, I think I am willing to pay for it.

Do they they share the same tube socket? For what I see, you either have the bigger tube (what normal balance desktop tube amp use), or you have these smaller thinner tubes.

 

I hate to brother you with entry level questions. So, if you know any link that have good comprehensive introduction about tube amps, I will be happy to read them before I raise any newbie questions here~~~ It is actually very hard to find a good guid in headfi since all the ppl that roll tubes seems either be super rich and experienced, or just want something very specific. It is hard to get a overview for the industry here~~~

post #23 of 24
Quote:
Originally Posted by AlanHell View Post
 
Quote:
Originally Posted by parbaked View Post
 

There are numerous budget tube amps but most are NOT designed for low impedance headphones.

OTL (output transformerless amps) are simple and can be inexpensive, depending on the components used and chassis etc. e.g. Bottlehead Crack.

 

This design is great for high impedance cans (HD600/650 etc) does not generate enough current to drive low impedance headphones. To generate the required current a tube amp needs output transformers e.g. WA-6. Good transformers are hand wound and add cost and complication. If you look at Woo WA-3 vs WA-6 the transformers add $140. Woo and Bottlehead both provide info on matching their amps to different headphones.

http://wooaudio.com/docs/wooaudio_amplifier_comparisons.pdf

http://www.bottlehead.com/et/whichheadphoneamp.htm

 

The inexpensive option is a "tube hybrid" e.g. Little Dot 1+ or Project Ember (referred above). These amps combine op-amps (usually) driven by driver tubes to give tube sound with SS output.


The hybrid is quiet new and not sure how mature they are right now.  Still deciding how much I am willing to spend on the amp.

 

Just a very very silly question:

 

Is it possible to add an resistive load on the output and use the OTL amp for IEMs? I use to DIY some connectors for putting my HD800 aside with my T1 to compare sound in HDVD800 balance output. Not sure they will make the OTL tube sounds better on IEM though.

There's more of a problem with OTL amps and low impedances than just lack of current.  OTL amps must use output coupling capacitors to filter out the DC high voltage.  Unfortunately, the impedance of a headphone load combined with the output coupling capacitors form what's known in electronic theory as an RC circuit (Resistance-Capacitance circuit).  This type of circuit is frequency-dependent on whether it allows current to flow.  IOW, for given ratings of the capacitors and the impedance of the headphones, the circuit will filter out the bass frequencies.

 

OTL amps usually have output coupling capacitors that are sized (~220uf) to keep the bass frequencies unharmed for 300-ohm headphones, not 32-ohm.  With typical 16-ohm IEMs, expect to start losing bass at 200-400 Hz.  By the time you hit 20 Hz, response will be down by 7-8 dB.


Edited by tomb - 11/25/13 at 3:58pm
post #24 of 24
Thread Starter 
Quote:
Originally Posted by tomb View Post
 

There's more of a problem with OTL amps and low impedances than just lack of current.  OTL amps must use output coupling capacitors to filter out the DC high voltage.  Unfortunately, the impedance of a headphone load combined with the output coupling capacitors form what's known in electronic theory as an RC circuit (Resistance-Capacitance circuit).  This type of circuit is frequency-dependent on whether it allows current to flow.  IOW, for given ratings of the capacitors and the impedance of the headphones, the circuit will filter out the bass frequencies.

 

OTL amps usually have output coupling capacitors that are sized (~220uf) to keep the bass frequencies unharmed for 300-ohm headphones, not 32-ohm.  With typical 16-ohm IEMs, expect to start losing bass at 200-400 Hz.  By the time you hit 20 Hz, response will be down by 7-8 dB.


thanks, that clears out a lot of questions I have. basically you are saying is that the amp's output stage acts as a first order band pass filter, right? 

 

that also gives me the second question, can this be solved by put an gain switch in the amp so they will at least have coupling for typical resistive load (16, 300 and 600) ~~ Or, can the output stage been tuned by switching to different types of tubes?

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