Headphone Amplification

Finally I was able to acquire an SRA-14S and it has arrived now! No phono equalizer modules however. A previous owner had been cutting copper tracks on the input/switching pcb and added a lot of wires (in different places than the cut traces). Neatly done, but still.... Maybe he had some problem with the switches? So restauration will be a major undertaking without documentation. Can anyone help me with the service manual and/or schematic diagrams? That would be highly appreciated. Paper copy or electronic, everything is welcome. The headphone amp looks at first glance like the circuitry of the SRM-1 (of which I also have no service manual), but the power…

I figured something this rare deserved a thread of its own. Let me introduce the Stax SRA-7S, integrated amp for earspeakers. This was introduced in 1966 for the SR-1 and remained in production into the 70's. With Stax we never really know when they stopped making something but given it's all tube design, it was dead by the mid 70's. This one was missing just one knob but amazingly they are still in current production. A full set has already been sourced... Those RCA's really need to go but pretty clean over all. Pretty much unmolested but somebody decided to remove the fuse holder. Not a good sign... Amp and phono stage on separ…

Hi all, I am hoping you can get me back on the right track in the world of Stax. A while ago I bought from Japan an SRD-7 mk2, a SRM-T1S, a Lambda SR Pro and a Lambda SR Signature Pro headset. The SRD-7 was bought just as an experiment, I did not really expect much from it. Besides I had read that the SRM-T1S should be better. However, from day one I have felt that the SRD7 mk2, coupled to a Pioneer M-22 power amp and a Pioneer C-21 preamp sounds much fuller/dynamic/better lower end compared to the SRM-T1S. The SRM-T1S seems flat or lifeless in comparison. I was sure there was something wrong with it, it is an old amp after all. I tried biasing to no effect. …

The following is what I can understand of the theory behind the diffuse field equalisers Stax produced and an assessment of the sound of one of them. Diffuse Field Equalisation vs Free Field Equalisation. Headphone frequency response measurements, conducted with a microphone in front of the headphone driver, much as speaker measurements were conducted, observed that headphones with a measured flat frequency response did not sound as flat as they measured. Comparing the sound of a flat measured speaker with a flat measured headphone revealed extreme tonal differences that started off a whole lot of investigation into why they sounded different and how a headphone’s fre…

Hi, I recently bought a used SRM-006T to power my SR-404 headphones. The amplifier seems to be working fine and it has the stock 6CF7 tubes. Sometimes I notice slight distortion when listening to fast paced electro music and Souvenir by OMD. I'm not particularly attracted to the idea of tube rolling but I think I should get the SRM-006T serviced soon and I've been offered the Kimik upgrade for £200. This is a lot of money and I'm starting to consider getting a newer SRM-323S or 323II to replace the 006T. I'm not sure whether to service/upgrade the 006T or get a new and cheaper to run solid state 323. I did try SR-407s with a 323S and noticed that the mid range was…

Hi all, I was advised by some head-fi members to inquire about the technical aspects of this amplifier here. Do let me know if I'm failing to follow any rules; just trying to avoid any catastrophes! Here are the photos of my amp: https://imgur.com/a/sshHA7B The amp is an 8FQ7 SRM-007t rated for 100v 50/60hz outlets. I have a step down transformer (PowerBright) rated for 120v to 100v, and my outlets are, I believe, 120v at 60hz (American). The transformer works fine with my Japanese SRM-252S, but the fuse has blown 3 times now when turning on the 007t (always the 2nd time it turns on; the first time seems to be working). I've tried debugging this for a bit, hence…

I have a 007tA that lost the -350V. Looks like the 150ohm filter resistor between the two HV caps is open. There also seem to be something loading the bias voltage. The voltage before the 4.7M resistor in series with the output socket measure 300V after the resistor but 400V before the resistor with nothing connected. Searching thru the forum seems like there is a 007t schematic available somewhere but all the links in previous posts are no longer valid. It would be most helpful if a schematic is available. Would like to find out what causes the 150ohm resistor to open before replacing it. thanks.

Hi there, I've got a strange and somehow annoying problem with my STAX SRM-1 / MK-2 (B Series). Sometimes, in about 3 to 4 cases out of 10 after switching it on in an cold state, I hear a strange clicking / buzzing noise on my Lambda on the left channel only. It's definitely faster or more often to be directly related to 50hz AC noise problems and it sounds more like a "ticktickticktick" kind of noise. This noise doesn't change if I make the amp louder and if it occurs, it's stays for about half an hour and slowly fades out, until the amp is heated up regardless of switching the amp on and off. Sometimes I also get a very distorted left channel which can happen anyt…

I recently got a srm-313 with two pro bias, the voltage is japan 100v, does anybody has experience to convert it to 120v us standard? Thank you very much. The amp is still on the way, I found the internal photo from here,

Two new amps have just been announced: https://stax.co.jp/products/srm-700t/ https://stax.co.jp/products/srm-700s/

Hello to all, I'm fairly new to this forum and untill now I have read a lot of posts to get a bit acquainted. For normal bias phones, I use a SRM-1/Mk2 which I would like to upgrade (actualy a P.P., but I fitted 1 normal bias socket). I have read about swapping out the power transistors for 2SC5466 units, currently used in Stax amps. However, in a SRM-323 thread I read that 2SC3675 transistors are to be preferred over the 2sc5466 units. Why is that and which transistors are best for the SRM-1/Mk2 (p.p.)? For pro bias phones, I use a SRM-727II on which I want to perform the "spitzer mod". What resistors are to be used? metal film, carbon film, others? Are 1/2 Watt…

Has anyone heard or experience reliability issues with any of these amps. I saw a reference on StereoWOW about the 717 having issues. StereoWOW

I just got an SRM-T1 (my first Stax amp) to go with 404LE (my first Stax headphones). I see there is an earthing terminal. Under what circumstances should I use this, and how should I use it? (Balanced cable specially made up?) TIA Nic

Hello Everyone This is my first post here. I have done some research about T1 troubles here and didn't find any topic about hot trafo. In my opinion this trafo is too hot but I don't have another SRM-T1 to check. I have removed tubes and then trafo is only warm - seems ok. Picture shows where I put temp sensor (blue wire). Did anyone had similar problems? P.S. I have just bought SR-Omega with Mk1 driver and SRM-T1 - amazing sound My previous system was SRM-727 and SR-507 and it wasn't so good.

A friend of mine has asked me to look at his vintage SRM-T1. The caps are all vintage so I will be replacing them. I count 10 electrolytic caps in there. 4x 400V 100uF 2x 10V 220uF 2x 35V 47uF 2x 50V 10uF The left channel has very weak sound. You can barely hear it when the volume knob is turned up all the way. The right channel is perfectly fine however. I'm not sure where to start troubleshooting this one. Unfortunately, I do not have another pair of electrostatic headphones to try. The left channel has worked before but it seems to work intermittently. I adjusted the offset and balance when he first purchased the amp a few months ago. Am…

I thought the King of all headphone amps would deserve his own thread. This is a beast of epic proportions, 11 power supplies, an overload of CCS and it draws close to 300W from the wall. I'll be updating this post later on with more specs about this monster. Well, here are some pics for your viewing pleasure. They are huge so may take a while to load.

So my birthday present is finally here, the SRM-T8000. I just quickly plucked it into my computer rig with the Denafrips Ares as a source: Here I can compare directly against the Carbon CC and the as yet unrealesed new KGSSHV, budget edition. Think of this one as the 727 if Stax had any sense. Anyway, back to the T8000. The packaging is classic Stax and no complaints there. I do have some complaints about the casework though, the front panel looks awesome but who decided what to do with the rest of it? Seriously that sparckly silver paint is just horrible. Reminds me of some super cheap Chinese amps. Yeah... not great. I had a quick peek inside to…

Hello all, I have this unit, but it stopped working so I opened it up. It seems that in right channel are shorted mosfets on output stage. But LEDs are not lit on both channel so I need to check it more. I started drawing schematic from the board. Since this is only one sided pcb, it was easy. But there is one thing I don't really understand. It is the cascode pair of 2SA1699. It should be that emitter is connected to the drain of the 2sj109 and output is at collector. But there it is connected differently. Or there is something I don't see. If we look on the board, there is drain of the 2sj109 and it is connected to the base of 2sa1699 according to …

Hi ! I get this unit, but I'm confusing with offset voltage - I measured the output offset voltage and it is far from 0V - I do not know if these stax amplifiers have that, but mine has, respectively: 8.8V, 5.4V, 12V and -0.6V? Electrostats are rather new to me, but here the DC voltage at the output should be close to 0V, as in conventional amplifiers? Is it not damaged? Does anyone have a list of the correct voltages in this model?

Dear All Due to sudden voltage spike last night - my stax vaccume tube amp srm007TA diode burnt out. Can you guide through the process to fix this issue? I have attached the images below for reference. Hopefully the PCB seems to be intact. But i am not a expert and any advise is highly appreciated Thank you

why all the agro? stax didn't make two seperate designed boxes i know this can be done to eliminate the stepup blue cube and run a us ul power cord the rca plugs can be changed to new ones. other mods are also possible

Does anyone have a schematic for the SRM323? I can't seem to find one through Google. @Spritzer: I assume it's possible to do a balanced input on it? At least that's what I inferred and seen from other designs - the STAX amps are inherently balanced.

Hi stax experts, I measured my t1w bias voltage, the pro bias port is 420v and normal bias is about 150v, is this normal or something needs to be replaced? Thank you.

Here's Step 4 of my 12-Step Plan: How To Stop People From Laughing At Your Amplification. Step 1 was simple: Join the head-case forum. Be polite and humble. Try not to cry too much when people laugh at you and post mean things. :'( Step 2 was to refrain from posting too much at head-case, in case someone points out your inadequate amplification. Sure, it's good, clean entertainment for everyone but you don't want to be the butt of the jokes all the time. You can continue posting at Head-Fi as much as you want, your posts will blend in nicely with all the other idiot posts there. Step 3 was to divert attention from your amps by posting exclusively about headphone…

Do you like stepped attenuators in your amps? I had one in my Corda HA-2 MKII SE which I've since sold, and find myself missing it. I never really had the problem of finding the "right" volume level that other listeners have. Right now, I think I will definitely have one in my next amp. So, what is it for you?