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Hayden HGT A20 Combo

Discussion in 'Glowing Bottle Tube Amp Forum' started by HF1600ie, Jun 21, 2017.

  1. HF1600ie

    HF1600ie Tele-Meister

    Age:
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    124
    Sep 26, 2016
    Portugal
    Dear all,

    I have recently purchased a Hayden 20W all-valve combo. I have replaced the stock speaker for a G12M 25w greenback (from my cabinet). Dramatic improvement in tone !

    I am trying to understand the schematic which Hayden has kindly sent to me (I hope I am allowed to share it without issues). I understand some things, but have doubts.
    Amps has :
    - Channel 1 (Bass, Treble, Volume) - Clean
    - Channel 2 (Bass, Mid, Treble, Contour, Gain 1, Master 1) - Crunch
    - Channel 3 (same as above with Gain 2, Master 2) - Lead

    I have a lot of questions. I´m a pain in the ass, probably, but if someone could help me understanding some of them, I can go home and do the homework after.

    1 - The voltage rating of the cathode bypass capacitor of V1B (C2) really has to be 300v ? (usually 25v to 50v is fine.)

    2 - The voltage rating of the cathode bypass capacitor of V2B (C28) really has to be 630v ? As above, usually 25v to 50v is fine).

    3 - V1B is the valve for Channel 1 - Clean. But, in the schematic, the plate capacitor goes either to the right AND to the left ! Does it have any impact on the tone of Channel 2 and 3 ? While playing channel 2 and 3, turning knobs from Channel 1 don´t affect the sound.

    4 - Are Gain 1 and Gain 2 simple gain knobs after signal of V1B ? Like an AC30.

    5 - Close to Gain 1 and Gain 2 there is an "LD" signal that goes close to Master 1 and Master 2 on the right of the schematic. However, Master 1 and Master 2 look like the "volume" knobs on many amps and not like the "typical master", usually a PPIMV. The signal goes from tone stack at the treble knob into the Master 1&2 pots. However, What´s the relation between the Gain and volume here ? Are they the typical Gain and Volume knobs in an amp without PPIMV ?

    6 - What valve amplifies the patch of channel 1? V1B alone ?

    7 - What valves amplify the path of channel 2? V1B + V1A + V2B + V2A ?

    8 - What valves amplify the path of channel 3? Same as above?

    9 - Why V1A, V2B and V2A have such different cathode resistors. The first ones should be around 1K and the last one 5K or 10K. But it´s not the case How can the best tone be achieved?

    10 - What it the purpose of V3A and V3B ?

    11 - Why channel 3 (gain 2) has much more gain than channel 2 (Gain 1)?

    12 - Why channel 2 (Gain 1) has a dark tone and channel 1 or channel 3 (Gain 2) are brighter?

    13 - The Stealth switch (20w - Stage / 3W - Studio) on the back seems like switching between resistors. What exactly is it doing? It works quite well. Is this a real attenuator?

    Thanks everyone. I hope this thread will help the Hayden users of this model as well.
     

    Attached Files:

    Last edited: Jun 21, 2017

  2. haydendude

    haydendude TDPRI Member

    Age:
    26
    10
    Jun 22, 2017
    Australia
    Hello

    I don't own a telecaster but I made an account just to reply to you about this amplifier - I bought one recently second hand, the initial english made version. Bought it on a whim because I thought it sounded excellent, and priced quite well (around the same as some older Marshall DSL combos/vox ac15s etc).

    The cabinet is very nice, and it is very punchy. Seems to be built very well. I am thinking of replacing the speaker like you, going for a vintage 30 or something at some stage - the stock speaker is pretty nice, I just find it has this noise around 2.56k when mic'd up... kind of a papery fizzy thing, no matter what channel. I think I can rectify it with a clearer speaker type. The thing is very deep and loud, through a mic you can't tell it's a combo. I have had issue with combos in the past sounding boxy but this is excellent, and it really fills a room up nicely.

    I like channel II the best, especially when pushed with a mild boost and the master wound up. You can get a really thick old school Sleep style tone with low tunings. The third channel for me seems very, very fizzy especially at low volume, and a bit noisy too - I believe this has the stock shuguang/ruby tubes in it so it could just be a worn 12ax7 (FYI Hayden told me at the time this was made they may have been using Rubys, but since changed to JJs exclusively). I have some new ones on order and will see if it fixes this, at the moment I need the gain turned down and the treble dialed out to use it.

    I can't answer most of those questions, but I can have a crack at 10, 11, 12 and 13:


    V3a/b is, if I am correct, the 12ax7 positioned between the power tubes - I believe this is a phase inverter tube, of the "long tail" variety. I am therefore quite confused as to why the amp says on the front panel it is Class A and the promotional stuff says three premap tubes, when this ax7 is physically positioned in the power section. The schematic appears to back me up on this re: the PI function.
    I am just trying to figure out which channels use which preamp tube like you, so I know in future which ones to replace if need be. At the moment I guess I will just replace all three 12ax7s and see if it fixes my channel 3 issue.

    Channel 3 is voiced differently, I read they were going for a more crunchy blues thing with channel II and more of a lead style tone on 3. To me it's almost like a vintage "british" tone on 2, and more of an american high gain on 3. (With humbuckers playing palm muted metal riffs it reminds me of a peavey-style tone) On my particular amp, changing the master setting for channel 2 alters the tone of channel 3 and the published material says this shouldn't be the case? I am starting to not trust the published material haha.

    Channel 2 sounds comparitively dark, but if you dial in some mids and crank it it's a really lovely channel with lots of harmonics, and seems a lot more responsive than channel 3.

    As far as the "stealth" switch goes, I assumed it was a kind of on board attenuator. I am pretty sure (I am not an amp or electronic tech) that most attenuators are resistive types. I believe this is also the way you can run the line out and kill the speaker. Most on board attenuators I have used in the past were terrible but I agree this amplifier sounds wicked cranked on the studio setting. Very usable, and even after 2 or 3 hours operation there are no smells or excess heat.

    I am in the process of recording an album using this amplifier for several guitar tracks. If you are interested, when it is finished, I can message you a link to it if you want to hear some of the different tones I have achieved. Very versatile.

    Cheers
     

  3. haydendude

    haydendude TDPRI Member

    Age:
    26
    10
    Jun 22, 2017
    Australia
    Thanks for the schematic btw it may help me if I need it serviced or repaired in the future
     

  4. HF1600ie

    HF1600ie Tele-Meister

    Age:
    37
    124
    Sep 26, 2016
    Portugal
    Hi,
    Thanks for your reply! Well I actually bought mine 2nd hand from the UK to Portugal. It is an early British version as well.

    I strongly recommended a speaker swap. With a G12M 25W Greenback you won´t believe how better the tone gets !! Trust me... I played the amp for 5 min, twisted the nose and luckly had one in a cabinet to test. Glad I swapped the speaker.

    My valves only say "China". Shuguang? I know the name, but dont know if tone can get better with others. I haven´t changed them.

    V3a+V3b I thought to be the phase inverter as well. Don´t know much about it to be honest...seems not the typical type. I will leave it alone for now.

    V2A seems to be for the tone stack but it is not "cathode follower", but "plate follower" instead. I hope I am not saying anything wrong.

    I am already preparing some 10 or so component modifications for the weekend which I think will do a great improvement in the tone.
    The amp is fine, the box is large and seems well built. The base is great to make it even better.

    Some support of TDPRI gurus on this would be tremenduosly appreciated. I modded an AC50CPH during the past months with the help of a member into a dream amplifier. I am sure I can do the same with the Hayden HGT20w !!

    Cheers
     
    Last edited: Jun 22, 2017

  5. haydendude

    haydendude TDPRI Member

    Age:
    26
    10
    Jun 22, 2017
    Australia
    Yep el84s have a little wing logo in a circle and 12ax7s will just say china. Those are shuguangs which are the same as ruby and groove tubes from memory just unbranded. I have bought the same as replacements as I am not the biggest fan of JJs

    Good luck. The only modification this is going to get is potentially the speaker and a 12at7 as the phase inverter
     

  6. HF1600ie

    HF1600ie Tele-Meister

    Age:
    37
    124
    Sep 26, 2016
    Portugal
    Hi,
    Well, I have JJ´s in poweramp of my Vox AC50CPH and they sound great. Probably others would do fine as well.

    So apparently we have the same valves. I´ll keep them there for now.

    I changed the speaker. Glad I did it, I am very sure you will like it. Celestion G12M 25W greenback work very well and in a few days I can tell you how a G12H 30w greenback will work. Both should sound close to each other.
    To be honest, I think the stock speaker is very bad.

    Why will you use a 12AT7 in the phase inverter ? Having less gain at that stage will give you some benefit ?
     

  7. haydendude

    haydendude TDPRI Member

    Age:
    26
    10
    Jun 22, 2017
    Australia
    From my limited knowledge of phase inverters I believe there really isn't too much difference until you crank the power. The 12at7 has less gain but can handle many times the current and allegedly lasts longer. Im sure I won't hear a difference at all, but if it makes a tube last a year or two longer why the hell not.

    Also disregard my comments about class a in initial reply, i checked and push pull amps with a PI can indeed still be class a cheers
     

  8. HF1600ie

    HF1600ie Tele-Meister

    Age:
    37
    124
    Sep 26, 2016
    Portugal
    Ok, got it.

    It would be great if forum users like Robrob or Lynxtrap could come over and give to us some comments based on their expertise.

    Yesterday I´ve been playing the Hayden and I think there´s still a lot of room for improvement.
    But, I felt the base of the tone and the base of this circuit are very promising !

    This weekend I´ll be trying some resistor and capacitor mods and I´ll be able to share my results.
     
    Last edited: Jun 23, 2017

  9. HF1600ie

    HF1600ie Tele-Meister

    Age:
    37
    124
    Sep 26, 2016
    Portugal
    Hi,
    Homework done in a Sunday afternoon.

    Important note : I am not responsible for the modifications other people may do, because it is their own responsability and risk. If you can´t do them, take your amp to a tech.

    Here are the current modifications and I will be using this file as a V1.0 :

    upload_2017-6-26_10-29-2.png


    - Channel 1 - Improved cleans. More sparkle and bit more bottom end. This channel doesn´t distort (1 half 12Ax7 only), but the dynamics have changed also a bit. Change was not dramatic, but I liked it.

    - Channel 2 - Improved treble response a lot and totally came alive. Funny, it didn´t loose that much bottom end - if any - when compared to stock. It is now a warm overdriven channel, a bit jangly with plenty of sparkle and bite up there. Also, there´s more drive available now as well. Can be used as a 70s rock sound if gain is pushed or a crunchy Vox sound if gain is rolled back a bit. Cleans up well with guitar volume.

    - Channel 3 - No major changes. Available distortion is more or less the same. This is the hard rock / metal channel. Previously brighter than channel 2, now it sounds a bit darker than channel 2, but it is not a dark channel by any means. I have to check the treble response to match channel 2 better. Also, to see the distortion characteristics as I need a slightly de-compressed feel from it. Cleans up well with guitar volume. Almost there !

    I will be playing along the week before any further mods and see how it feels with different guitars and in different days.

    I can´t forget I´m used to EL-34. This is my first EL-84 amp. Some characteristics will always be different.

    Now answering my own questions (the ones I can) :

    1+2 - 25v/50v should be fine. High voltage ratings have to do with parts availability from manufacturer.

    3 - V1B should be the 1st gain stage of channels 2 and 3. It works in all 3 channels. The path to the right via C3 - coupling capacitor - will go for Channel 1.
    The path to the left via C4 - coupling capacitor - will go for channels 2 and 3.

    4 - They could be. I don´t know how they work. But Gain 1 feeds Gain 2. If you turn Gain 1 (from channel 2) while using Channel 3, you can get a bit more gain and body in the sound. Suble, but it is there. The opposite doesn´t work. Gain 2 doesn´t seem to feed Gain 1.

    5 - Don´t know yet.

    6 - Channel 1 should be amplified by V1B alone + EL84 poweramp. this channel doesn´t distort.

    7 - It should be V1B+V1A+V2B. I think V2A is for the tone stack gain recovery which seems to be of the "plate-follower" type instead of "cathode follower". Need confirmation here...

    8 - Same as above?

    9 - Probably different plate and cathode resistors for each valve, for different shapping of amplification and distortion of the signal along the path. Maybe there´s no rule here.

    10 - Phase inverter valve ?

    11 - Don´t know. Maybe it has to do with different Variable resistors (pots) and the way they´re linked to each other. I am not sure, but it seems that Gain 2 is linked to Gain 1, but, while playing, Gain 1 affects Gain 2, but the opposite doesn´t seem to happen.

    12 - Don´t know, but I have improved it so easily with bleed resistors around Gain 1 and Master 1 and also more gain via smaller R44.

    13 - I have no idea. It slightly changes the tone, but it is subtle. It works very very well !!

    If Robrob or Lynxtrap could come over it would be great !!

    Cheers
     
    Last edited: Jun 26, 2017
    haydendude likes this.

  10. HF1600ie

    HF1600ie Tele-Meister

    Age:
    37
    124
    Sep 26, 2016
    Portugal
    Dancing with myself... oh oh oh....
    I can continue to update the topic on a daily basis, like a diary, but it is too bad no one participates.

    Maybe this topic is not in the right section.

    Should it be moved to " Amp tech Center " ??
    Can someone transfer it to the proper section?
     

  11. haydendude

    haydendude TDPRI Member

    Age:
    26
    10
    Jun 22, 2017
    Australia
    well...

    I retubed the whole thing on a whim recently and the amp came to life, I thought it sounded nice before but now it sounds "good". lovely harmonics, great sustain, punchy etc. Now I feel as though the speaker is really all that's holding it back, so I may follow your lead and put a celestion something in there.

    I used the chinese 12ax7s for V1 and the PI tube again simply because that's what it came with. V2 I used an EHX 12ax7 because I like them, and I thought the third channel previously was too harsh. It smoothed it up a bit.

    EHX el84s for the first time, nice output tubes, very smooth and rounded tone. The factory shuguangs were absolutely knackered, I hadn't pulled the back off and had a proper look until the other day. The labels were burned off, inside the glass envelopes had black burn marks around the top mica plating etc, couldn't believe they still worked.

    Since you have been in your hgt, and I assume it is around the same age as mine (5yrs) - when do you think an amplifier like this would need a service? I don't mean tubes as I can do that any time, I mean dissassembly and new filter caps etc. I know enough to care for a valve amp myself but nothing about actual servicing of this kind.

    Cheers and hope yours is treating you well.
     

  12. HF1600ie

    HF1600ie Tele-Meister

    Age:
    37
    124
    Sep 26, 2016
    Portugal
    Hi Haydendude !
    Actually mine still has the factory El84 and 12AX7. Or at least, it they are replacements already, they´re just like the factory ones saying "China" or something like this. Shuguangs i think.

    I have already thought of replacing all of them soon and save those ones as spare.

    I really recommend that you swap the stock speaker. Really, if you have the chance, just try a Celestion G12M25w (greenback) or a G12H30 (Greenback). I have tried both of them, and currently I have a G12H30 greenback, the one with the heavy magnet.

    You will see immediatly the harshness will be gone and the midrange will improve as well.

    On top of this, I´ve already performed a V2.0 modification to various components and V3.0 should be ready by this or next weekend to fine tune some of them. I am loving the amplifier.

    But, on the other hand, the amp has always "hissed" when I turn it on, even with volume on zero and no guitar cable plugged. There´s always a bit of white noise which Is excessive when compared to other amps I have. It´s not the "high-gain-hiss". It´s an always present background noise, like an old TV.
    Trying to figure this out with support in this forum and from Hayden as well. Hope I can find the cause.
     

  13. haydendude

    haydendude TDPRI Member

    Age:
    26
    10
    Jun 22, 2017
    Australia
    the 12ax7s all still function, although visually the PI looked a bit worn, so i have kept them all as good spares.

    I think I am going to go with a Jensen 12/50 actually, only because I've seen they have amazing low end and for a "sounds-like-a-v30" type speaker it's half the price of the celestion here. I'll give one a go, if I don't like it doesn't matter because I haven't spent much.

    My own hgt is whisper quiet on channel 1 and 2. On startup I get no hissing, once the tubes are warm, at least on the studio switch and even with the volume cranked, you need your ear right next to the speaker to tell it is running at all.

    There is a normal high gain fizz on channel 3, maybe you just have a dying preamp tube or something in your house is causing interference? I know both my valve amps get upset in a certain room when the lights are on, silly things like that. My vox picks up radio waves, phone noises and the like
     

  14. HF1600ie

    HF1600ie Tele-Meister

    Age:
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    124
    Sep 26, 2016
    Portugal
    Well, I actually swapped all three preamp valves to do the testing and the noise didn´t got any worse or better.

    The hissing is absolutely the same regardless of the channel. It doesn´t matter.
    Of course, when I use high-gain, the high-gain-noise is added on top of that hissing. But high-gain noise is quite acceptable in any amplifier and it is easy to identify it.

    I will be reflowing all solder joints of the preamp in a few days and see if the noise is gone.
    I will try bypassing the Fx loop and Reverd connecting preamp to poweramp directly.

    It is really a pitty, because the amp is sounding incredible.

    Let me know how it has improved with the new Jensen speaker !
     

  15. haydendude

    haydendude TDPRI Member

    Age:
    26
    10
    Jun 22, 2017
    Australia
    That's really strange. Like I said my clean channel is almost dead quiet, and channel 2 you need to be close to the amp or have it cranked loud to hear the background hum...

    Yeah jensen arrived. It's transformed the amp - it's taken away some of the noise that the old speaker had at certain frequencies, as well as a slight buzzing. Very defined low end, awesome harmonics, amp sounds a lot better than when I bought it, and when I bought it I thought it sounded great.

    I ran into another problem however - the front of the cabinet is divided into two parts, the baffle and the top section that sits in front of the chassis. I noticed the factory speaker is screwed in with 5 screws, the for usual bolts and one screw at the top into the top part of the cabined. I was initially going to leave it out but I thought it may well have been there for a reason - the improved bass on this jensen has the front of the cabinet rattling like hell against the front of the chassis. No matter how tight I ran that screw it would not rectify it - in the end I jammed the thinnest pick I had into the gap. I think if I ever have the chassis out I will need to line the whole thing with some solid padding
     

  16. HF1600ie

    HF1600ie Tele-Meister

    Age:
    37
    124
    Sep 26, 2016
    Portugal
    I understand your point about the hissing and that´s what´s normal and expectable.

    In my case, no matter where the gain or volume are, there´s ALWAYS a hiss (white noise and a little tiny bit of hum) present.
    In a few days I may have the time to go through the V3.0 of my mods and will re-solder all solder points of the preamp. If it works, great, if not, I will have to jump the preamp directly into the poweramp and isolate the FX loop+reverb to see if the FX board is the culprit.

    I told you. Glad you liked the speaker upgrade. I totally love mine with the G12H30 Greenback. Togheter with the component mods on the capacitors and resistors, it sounds even better.

    My speaker is tight in 4 (I think) bolts. I don´t seem to find the 5th. I only had to slightly "bent" 2 of the bolts so that the speaker wholes could match. Just a very slight bending.
    I think you shouldn´t overtight it to avoid damaging the speaker surrounding.
    If you have extra bass and the Bass knob is not sufficient to cut it, try using the "contour" knob. Even so, maybe you should either upgrade to the Celestion and/or consider some modifications to the circuit, same way I am doing :).
     

  17. haydendude

    haydendude TDPRI Member

    Age:
    26
    10
    Jun 22, 2017
    Australia
    nah I love the low end, haha. It's not excessive, it's just a lot punchier, tighter and more powerful than before. I am thinking the factory speaker was just plain old worn out, I suspect the past owner gigged with it a lot especially due to the test tags on the leads.

    The 5th bolt was a screw mounted at the top of the speaker, it was factory as it's the same type used all over the amp. If you aren't getting vibration, I may just remove the screw completely and see if that fixes it.

    I'm trying to think what might be causing your hissing, hopefully you find the culprit soon
     

  18. haydendude

    haydendude TDPRI Member

    Age:
    26
    10
    Jun 22, 2017
    Australia
    btw that contour knob is a bit strange. I just keep it all the way to the left as it seems the fattest and fullest. In store I assumed it was like a mid-cut type thing as that's what everyone does, but it seems to just dial out the low end and not much else? I guess it could be useful in some cases
     

  19. HF1600ie

    HF1600ie Tele-Meister

    Age:
    37
    124
    Sep 26, 2016
    Portugal
    Hi !!
    The "contour" knob is a "variable slope resistor" of a normal Marshall tone stack. Instead of a fixed resistor, they have it variable. It increases low-mids as you turn it to the left and creates a scoop if you turn it to the right. I usually leave it a bit to the left of right at the middle. For heavier tones, dial it a bit to the right.I checked the schematic and this is what it actually is.

    By the way, I have performed my V3.0 of the schematic and I am truly amazed with the final results (well, I think I won´t really be modding anything else again).

    Believe me : If you have an electronic tech near by, I can give you the modifications which are very simple. I´ll be posting them tomorrow. They have been soooooo worth it.
    This Hayden is now so versatile it is hard to believe. All channels are tonewise compatible right now.
    I should record some sample to show you... :)
     
    Last edited: Jul 20, 2017

  20. HF1600ie

    HF1600ie Tele-Meister

    Age:
    37
    124
    Sep 26, 2016
    Portugal
    Hi everyone,

    Almost there !

    Two questions :

    1 - What is supposed to expect from the "LD" part in the red circle? It has four legs. What is it and what is it doing in there?

    2 - Also, in the green circle, isn´t it strange the "treble peaking circuit" in R39/C22 is a 100ohm/470pf ? What happens if I place 470k/470pf just like the other one in the next stage - R45/C27 ?

    Cheers !


    upload_2017-8-31_10-48-57.png
     

    Attached Files:


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